A MULTIPLE TEST BATTERY APPROACH OF PATIENTS WITH MULTIPLE SCLEROSIS

A MULTIPLE TEST BATTERY APPROACH OF PATIENTS WITH MULTIPLE SCLEROSIS
A MULTIPLE TEST BATTERY APPROACH
DURING THE ASSESSMENT OF THE AUDITORY NERVOUS SYSTEM
OF PATIENTS WITH MULTIPLE SCLEROSIS
In partial fiJ11illmentof the requirements
for the degree M Communication Pathology
at the Department of Communication Pathology,
Faculty of Humanities, University of Pretoria, South Africa
© University of Pretoria
•
Prof Rene Hugo for numerous hours spent on lengthy drafts and her patient
guidance.
•
Dr Dunay Schmulian for her assistance with the practical aspects of the study as
well as her positive outlook on research and for being such a gift of
encouragement.
•
Chrisna Vermeulen for numerous hours spent on the language editing, graphics
and final typing of the dissertation.
•
My parents and brothers who persevered in believing that I could meet this
challenge.
•
The subjects and the South African MS Society for their willingness to partake
in the study.
•
The staff at the University of Pretoria's library for obtaining research articles on
this topic.
A MULTIPLE TEST BATTERY APPROACH
DURING THE ASSESSMENT OF THE AUDITORY NERVOUS SYSTEM
OF PATIENTS WITH MULTIPLE SCLEROSIS
SUPERVISOR
: Prof. S.R. Hugo
CO-SUPERVISOR
: Dr. D. Schmulian
DEPARTMENT
Communication Pathology,
University of Pretoria,
South Africa
M Communication Pathology
Audiologists are challenged with various neurological diseases, such as Muhiple
Sclerosis.
nervous
This disease causes demyelination of the white matter in the central
system resulting in desynchronisation of neural impulses.
Despite
controversy in the literature many studies illustrated some degree of auditory
involvement associated with this disease.
The auditory brainstem response has
dominated the field during the assessment of the auditory system of patients with
Muhiple Sclerosis.
Ahhough this objective test procedure is useful during the
assessment of the auditory nerve on a brainstem leve~ it reveals its own set of
limitations when used in isolation as a single test procedure. A multiple test battery
approach has shown promise in addressing the limitations of any single test
procedure. This appr()aqhaipls to assess the auditory nervous system of patients with
Multiple Sclerosis on different levels (sensory and neural). The aim of the current
study was to determine the effectiveness of a clinically appropriate battery of test
procedures during the assessment of the auditory nervous system of 25 aduh subjects
with Muhiple Sclerosis.
The subjects were divided into two groups: Group 1
consisted of fifteen (15) subjects without a history of noise exposure, whereas the
ten (10) subjects in Group 2 had previously been exposed to noise.
A combined experimental-descriptive research design was selected in order to
describe both the qualitative and quantitative resuhs obtained during the study. The
following test procedures were included in the test battery:
.:. A self-assessment questionnaire allowing subjects to report on hearing
abilities,
related
auditory-vestibular
symptoms
and
communicative
competence during every day life;
.:. Puretone audiometry, distortion product otoacoustic emissions as well as the
cochlear microphonic; and
.:. Auditory brainstem response recordings using both the tarefaction and
condensation click polarities consecutively.
The results indicated that a high percentage of subjects experienced vestibular
symptoms such as dizziness and vertigo by the time the study was conducted. The
presence of tinnitus and hearing difficuhies were uncommon among subjects. Despite
this, more than half of the subjects experienced difficuhy with communication in the
presence of background noise. Puretone audiometry demonstrated that some of the
subjects presented with mild high-frequency hearing losses.
However other
configurations with impaired hearing thresholds were also observed.
Most of the
subjects' auditory brainstem response recordings displayed abnormalities using either
the rarefaction or condensation click polarity.
The use of the condensation click
polarity displayed more ABR abnormalities compared to the rarefaction click polarity.
Several subjects displayed additional
cochlear involvement while a smaller
percentage of subjects presented only with neural involvement.
This study demonstrated that a single audiometric test procedure would not be
effective in detecting auditory involvement in subjects with Multiple Sclerosis, and a
multiple· test battery approach is needed to assess the auditory nervous system at
several levels. It is essential that quantitative (objective) data must be supplemented
with qualitative (descriptive) data. The study led to a better understanding of this
degenerative disease and the effect that it can have on the auditory nervous system of
patients with Multiple Sclerosis.
Key words: Multiple Sclerosis, battery of test procedures, multiple test battery approach,
self-assessment
questionnaire,
puretone
audiometry,
distortion
product
otoacoustic
emissions, cochlear microphonic, auditory brainstem response, rarefaction & condensation
click polarities, auditory-vestibular symptoms.
L
'N TOETSBATTERY BENADERING
TYDENS DIE EVALUERING VAN DIE OUDITIEWE SISTEEM
VAN PASIeNTE MET VEEL VULDIGE SKLEROSE
STUDIELEIER
: Prof. S.R. Hugo
MEDE-STUDIELEIER
: Dr. D. SchmuHan
DEPARTEMENT
: Kommunikasie Patalogie,
Universiteit van Pretoria, Suid Afrika
: M Kommunikasie Patalogie
Verskeie neurologiese toestande, soos Veelvuldige Sklerose, bied 'n uitdaging aan
oudioloe.
Hierdie toe stand word veroorsaak deur demielinisering van die witstof in
die sentrale senuwee stelsel en lei tot desinkronisasie van neurale impulse. Ten spyte
van teenstrydighede in die literatuur is ouditiewe betrokkenheid gedemonstreer tydens
verskeie studies. Die uitvoering van ouditiewe breinstamrespons prosedures is tot op
hede hoofsaaklik tydens die evaluering van die ouditiewe sisteem van pasiente met
Veelvuldige Sklerose gebruik. Alhoewel hierdie objektiewe toetsprosedure sensitief
is vir abnormaliteite op 'n ouditiewe breinstam vlak, het daar ook sekere beperkinge
navore gekom indien dit in isolasie as 'n enkel toetsprosedure gebruik word. 'n
Toetsbattery benadering voorkom die beperkinge van 'n enkel toetsprosedure.
Hierdie benadering se doel is om die ouditiewe sisteem op verkeie vlakke (sensories
en neuraal) te evalueer.
Tydens hierdie navorsingstudie is daar gepoog om die
kliniese bydrae van 'n toetsbattery benadering vas te stel, tydens die evaluering van
die ouditiewe sisteem van 25 volwasse proefPersone met Veelvuldige Sklerose. Die
proefPersone was opgedeel in twee groepe: Groep I het bestaan uit vyftien (15)
proefPersone wat nie voorheen aan hoe geraasvlakke blootgestel was nie, terwyl
Groep 2 betaan het uit tien (10) proefpersone wat wel 'n geskiedenis gehad het van
geraasblootstelling.
'n Eksperimenteel-beskrywende navorsingsontwerp was geselekteer om beide die
kwalitatiewe en kwantitatiewe data wat verkry was gedurende die studie te beskryf.
Die volgende toetsprosedures het deel uitgemaak van die toetsbattery:
.:. In Self-evalueringsvraelys wat geleentheid bied vir die beskrywing van
algehele gehoorvermoens, ouditief-vestibulere simptome en kommunikasie
vaardighede gedurende alledaagse luistersituasies;
.:. Suiwertoonoudiometrie, distorsie produk oto-akoestiese emmissies asook die
teenwoordigheid van die koglieremikrofoon potensiaa1;en
.:. Ouditiewe
breinstamrespons
metings, waar beide
die rarefraksie en
kondensasie polariteite afsonderlik aangebied word.
Die resultate het aangedui dat 'n groot hoeveelheid van die proefpersone vestibulere
simptome van duiseligheid en vertigo gerapporteer het tydens die studie, terwyl die
voorkoms van tinnitus en gehoorprobleme deur 'n beperkte aantal proefpersone
aangedui is. Ten spyte hiervan het meer as helfte van die proefpersone probleme
ondervind tydens kommunikasie in die teenwoordigheid van agtergrondsgeraas.
Suiwertoonoudiometrie
het aangedui dat sommige proefpersone geringe hoe
frekwensie geho~rverliese gehad het, maar ander oudiogram konfigurasies was ook
waargeneem.. Verder het die meerderheid van die proefpersone ook ouditiewe
breinstamrespons abnormaliteite vertoon wanneer die rarefraksie of kondensasie
polariteit gebruik was.
Meer breinstamrespons abnormaliteite was waargeneem
tydens die aanbieding van die kondensasie kliek stimulus. Sommige proefpersone het
gepresenteer met bykomende kogliere skade, terwyl slegs neurale ouditiewe
betrokkenheid teenwoordig was in Inklein aantal van die proefpersone.
Die resultate het aangedui dat 'n enkel toetsprosedure nie effektiefwas om ouditiewe
betrokkenheid by proefpersone met Veelvuldige Sklerose te identifiseer nie.
'n
Toetsbattery benadering, wat beide sensoriese en neurale afwykings kan identifiseer,
moet toegepas word.
Dit is belangrik dat kwalitatiewe (beskrywende) data,
. kwantitatiewe (objektiewe) data moet aanvul. Hierdie studie het nie net gelei tot In
beter begrip van hierdie neurologiese degeneratiewe siektetoestand nie, maar ook tot
inligting aangaande die ouditiewe betrokkenheid wat kan voorkom.
Sleutelterme:
evalueringsvraelys,
Veelvuldige Slderose, toetsbattery, 'n toetsbattery benadering, selfsuiwertoonoudiometrie,
distorsie produk oto-akoestiese emmissies,
koglieremikrojoon potensiaal, ouditie-rvebreinstamresPOns.rarefraksie & kondensasie /diek
stimulus, ouditiej-vestibulere simptome.
TABLE OF CONTENTS
SIGNS AND SYMPTOMS OF AUDITORYINVOLVEMENT
ASSOCIATED WITH MULTIPLE SCLEROSIS
11
2.3 Assessment of patients with Multiple Sclerosis using the basic
audiometric test battery
15
TABLE OF CONTENTS (continued)
2.4 Assessment of patients with Multiple Sclerosis using auditory
evoked responses
18
2.5 Assessment of the central auditory nervous system (CANS)
of patients with Multiple Sclerosis
28
2.6 A multiple test battery approach used in patients with Multiple
Sclerosis
30
2.8 Summary of Chapter 2
36
TABLE OF CONTENTS (continued)
CHAPTER 3
RESEARCH
METHODOLOGY
37
3.1 Introduction
37
3.2 Aims of the study
38
3.2.1 Main aim of the study
38
3.2.2 Sub-aims
38
3.3 Research design
39
3.4 Research subjects
40
3.4.1 Subjects
40
3.4.1.1 Criteria for subject selection
40
3.4.1.2 Subject selection procedures
44
3.4.1.3 Description of subjects
45
3.4.1.4 Rating panel
49
3.5 Material and apparatus
49
3.5.1 Subject selection material and apparatus
49
3.5.2 Data collection material
50
3.5.3 Data collection apparatus
52
TABLE OF CONTENTS (continued)
3.6.1.1 Determination of the suitability of the self-assessment
questionnaire
53
3.6.1.2 Determination of optimal stimulus and configuration
parameters for DPOAEs
54
3.6.1.3 Determination of optimal stimulus and acquisition
parameters for ABRs
55
3.6.1.4 Determination of the time required to complete all
measurements
59
3.6.2 Data collection and recording procedures conducted during
thesm~
59
3.6.3.2 Analysis of data obtained from the self-assessment
questionnaire
62
TABLE OF CONTENTS (continued)
3.7 Summary of Chapter 3
4.2.1 Reported initial MS-related symptoms prior to the actual
diagnosis ofMS
74
4.2.2 Reported auditory-vestibular symptoms during the time of the
study
75
TABLE OF CONTENTS (continued)
4.4.7 Discrepancies and similarities of different types of ABR
abnormalities when reversing the click polarity
TABLE OF CONTENTS (continued)
5.2.3 The contribution ofDPOAEs and the CM in conjunction with
puretone audiometry
125
5.2.5 The contribution of ABRs using both the Rand C click
pohuities
130
TABLE OF CONTENTS (continued)
APPENDIX B: THE COURSE OF MULTIPLE SCLEROSIS
SYMPTOMS
APPENDIX C: COVER LETTER, CONSENT FORM, GENERAL
INSTRUCTIONS AND QUESTIONNAIRE
DEKBRIEF, TOESTEMMINGSVORM,
INSTRUKSIES EN VRAELYS
ALGEMENE
LIST OF TABLES
Table 2.1: Reported ABR abnormalities
26
Table 3.2: Collection of data using a self-assessment
questionnaire
51
Table 3.5: DPOAE protocol setting for the current study
55
Table 3.8: Approximate time required for the assessment of one
participant
59
Table 3.12: Examples of ABR abnormality
69
Table 4.1: Self-assessment of communicative competence
80
Table 4.2: Comparing hearing difficulties with other MS-related
symptoms and the affect on quality of life
82
Table 4.3: Results of pure tone audiometry, DPOAEs and CMs of
Group 1
84
Table 4.4: Results of puretone audiometry, DPOAEs and CMs of
Group 2
89
LIST OF TABLES (continued)
Table 4.5: Distribution of absent and doubtful waves according to
both click polarities for both groups
96
Table 4.6: Distribution of waves with poor repeatability
according to both click polarities for both groups
99
TableA.7: Distribution of waves with abnormal absolute latency
according to both click polarities for both groups
100
Table 4.8: Distribution of waves with abnormal interpeak
latency according to both click polarities for both
groups
101
Table 4.9: Distribution of subjects with abnormal interaural
latency difference of Wave V according to both click
polarities for both groups
102
Table 4.10: Distribution of abnormal amplitude ratios of
Wave VII according to both click polarities for both
groups
104
Table 4.11: The presence and absence of waves when reversing
the click polarity
106
Table 4.12: Repeatability of waves when reversing the click
polarity
107
Table 4.13: Absolute latency of waves when reversing the click
polarity
108
Table 4.14: Interpeak latency of waves when reversing the click
polarity
109
Table 4.15: ABR abnormalities of both groups using both click
polarities
112
Table 4.16: Summary of results for Group 1 and 2
115
LIST OF FIGURES
Figure 2.1: The absence of Wave V using R clicks
23
Figure 3.1: Age and gender distribution of subjects
47
Figure 3.2: Time lapse between the medical diagnosis and the
current study
47
Figure 3.3: Time lapse between fIrst experienced MS-related
sYmptoms and the medical diagnosis
48
Figure 4.2: Auditory-vestibular symptoms reported during the
current study
75
Figure 4.3: Configuration of audiograms
94
Figure 4.4: Results of puretone audiometry and DPOAEs
95
Figure 5.1: Concluding fmdings ofDPOAEs and CMs in
conjunction with the results of puretone audiometry
126
Figure 5.2: Concluding findings of ABRs (using the R click
polarity) in conjunction with DPOAEs
128
Figure 5.3: Concluding fmdings of ABRs (using the C click
polarity) in conjunction with DPOAEs
129
ABBREVIA nONS
A
Alternating click polarity
Al
Left Ear Electrode
A2
Right Ear Electrode
ABR
Auditory Brainstem Response
ABRs
Auditory Brainstem Responses
AL
Absolute Latency
ALs
Absolute Latencies
ANSI
American National Standards Institute
AP
Action Potential
AR
Acoustic Reflex
C
Condensation
CANS
Central Auditory Nervous System
CAP
Central Auditory Processing
CM
Cochlear Microphonic
CMs
Cochlear Microphonics
em
3
Cubic centimeter
CNS
Central Nervous System
COM-C
Communication Complaint List
CT
Computed Tomography
Cz
Vertex Electrode
daPa
decaPascal
dB
Decibel
DP
Distortion Product
DPgram
Distortion Product "Audiogram"
ABBREVIATIONS (continued)
DPOAE
Distortion Product Otoacoustic Emission
DPOAEs
Distortion Product Otoacoustic Emissions
EcochG
ElectrocochJeognaphy
EEG
Electroencephalography
EMG
Electromyography
ENG
Electronystagmography
f1
Lower Frequency
f2
Higher Frequency
Fz
Forehead Electrode
GSI
Grason Stadler Instrument
Hz
Hertz
ILD
Interaural Latency Difference
IPL
Interpeak Latency
IPLs
Interpeak latencies
kHz
Kilo Hertz
L1
Intensity Level of f1
L2
Intensity Level off2
LVR
Late Vertex Response
MLD
Masking Level Difference
MLR
Middle Latency Response
MRI
Magnetic Resonance Imaging
MS
Multiple Sclerosis
millisecond
J.LV
microvoh
NF
Noise Floor
nHL
Normal Hearing Level
NR
No Response
ABBREVIATIONS (continued)
DAB
Otoacoustic Emission
DABs
Otoacoustic Emissions
PB
PP
Phonemically Balanced
R
Rarefaction
RR
Relapsing-remitting
RSEE
Rating Scale for Each Ear
SABS
South African Bureau of Standards
SD
Standard Deviation
SPL
Sound Pressure Level
SRT
Speech Reception Thresholds
Primary Progressive
How can you look so good and be ill?
I really cannot understand it still
How is it one day you feel so fine,
And another you seem like you're losing your mind?
This US thing is a mystery it's true,
Did you say you feel dizzy and wobbly and blue?
Do you always get tiredfrom a walk around town?
I told you I'm up and then I am down
Terri (unknown)
Multiple Sclerosis (MS) remains a mystery both to patients suffering from it, and the
medical profession and audiologists concerned with the assessment thereof
This is one
of the most common types of demyelinating diseases in aduh neurological impairment,
excluding the
geriatric
population
(Hall, 1992). Muhiple Sclerosis is a chronic
inflammatory disease of unknown origin, unpredictable course and prognosis, as well as
high variability regarding the pathology and the symptom pattern (see Appendix A for a
comprehensive description of the disease).
Symptoms are also likely to be multiple,
whether they are temporary or persistent, and are determined by the pathways that are
demyelinated.
Multiple areas in the central nervous system (CNS), especially the white
matter surrounding the ventricular system of the cerebral hemispheres, the brainstem,
cerebellum, optic nerves and spinal cord, can be affected by demyelination (Lechtenberg,
1995). Since the brainstem is the site of frequent demyelination according to McAlphine
et al. (1972) and Lechtenberg (1995), researchers have assessed the auditory pathways in
this small compact area to determine the extent of auditory and vestibular involvement
since 1977 (Elidan et al., 1982; Hall, 1992). Some auditory and vestibular involvement
can be expected in patients suffering from Multiple Sclerosis.
This chapter
procedure,
wiD provide an overview on the sbortcomings of using a single test
or only the basic audiometric
nervous
system
implementing
auditory
of patients
with
test battery, when assessing the auditory
Multiple
Sclerosis.
The
importance
of
a multiple test battery approach for assessing the sensory and neural
nervous system will be discussed.
The need to include the assessment of
cochlear function, as well as the self-assessment of bearing ability, related auditoryvestibular
outlined.
symptoms and communicative
competence during every day life, will be
This delineates the purpose of the study: to determine whether a clinically
appropriate
multiple test battery approach
wiD be able to determine the auditory
involvement present in patients with Multiple Sclerosis.
Certainly not all, but a considerable number of patients with Multiple Sclerosis, have
some type of auditory deficit (Musiek et al., 1994).
The incidence of auditory
abnormalities and hearing difficulties in the MS population is underestimated (Musiek et
al., 1994).
Furthermore related symptoms such as auditory-vestibular involvement are
often overlooked.
These symptoms include balance disorders, vertigo, dizziness and
tinnitus, and are associated with MS in more than 80 % of sufferers (Daugherty et al.,
1983).
The MS population poses a challenge to researchers, since the disease can
manifest in many different areas of the auditory nervous system.
In the auditory
pathway, the disease generally has its primary site in the brainstem (proximal balf) and
auditory abnormalities are mostly described as retrocochlear in nature (McAlphine et al.,
1972).
Demyelinating lesions have also been reported at the root of the cranial VIIIth
nerve (distal half) in 10 % of the cases (Jacobson et al., 1987).
Literature abounds with controversy on whether or not MS is associated with some
particular characteristic form of auditory involvement (Stach et ai, 1990). As such, the
opinions on the number and quality of hearing loss in MS vary considerably (Grenman,
1985).
This may partly be due to the diverse nature of the disease, but can also be
attributed to the audiometric test procedures selected to assess the auditory nervous
system.
WIthin the MS population an audiologist can encounter an individual with
normal hearing
sensitivity, normal speech understanding, subjective complaints of
hearing difficulty and no measurable auditory brainstem response (ABR), whereas
another may present with normal ABR recordings and hearing sensitivity, but reduced
speech understanding ability. The forms of auditory involvement may include subjective
complaints of difficulty with hearing and/or hearing impairment of varying degrees,
audiometric configurations
and/or neural auditory involvement.
Hearing impairment
resulting from MS has been described either as unilateral or bilateral; sudden or
insidious; acute or chronic; mild to severe; and high-frequency, "dome-shaped," or lowfrequency in configuration (Dayal et aL, 1970; Cohen & Rudge, 1984). Although reports
of acute hearing loss with the onset or exacerbation ofMS symptoms have been received,
it remains a rare phenomenon (Hall, 1992; OzUnln et aL, 1998). In these cases sudden
sensory-neural hearing loss is often temporary and in some studies it was found that
hearing sensitivity did return to normal. Furman et aL (1989) believe that hearing defects
in MS might be missed due to their temporary nature.
Accurate large-scale statistics on the incidence of hearing loss specifically due to MS are
not available.
Reported
incidence of hearing loss in patients with Multiple Sclerosis
varies markedly, mnging from as low as 1 % to as high as 86 % (Hall, 1992). The very
low percentage can perhaps be explained by the following:
.:. A low percentage of patients report hearing difficulties (MUller, 1949; Grenman,
1985). This finding correlated with a study performed in South Africa where only
23 % of the patients reported difficulty with hearing. The patients rated their
hearing problems as insignificant when compared to other MS-related symptoms
(Klugman,
2000).
Hearing deficits are not typically the most debilitating
symptoms
experienced
and
patients
with
Multiple
Sclerosis
are
often
overwhelmed by more invalidating and disabling symptoms (Daugherty et al.,
1983; Rappaport et al., 1994). Therefore, they are more likely to report major
symptoms and, if not questioned, may fail to mention hearing difficulties or
associated symptoms.
.:. The type of hearing defect is often a mild high-frequency unilateral hearing loss
and could go unnoticed by the patients themselves, and is often not detected
during a routine physical examination by medical practitioners or during the use
of tuning forks (Furman et al., 1989; Hall, 1992).
•:. Subtle
auditory
problems,
in the absence of any clinical indications of
abnormality may exist but go undetected (Mustillo, 1984). Testing of auditory
function may be perfunctory
or omitted completely from the neurological
examination. If patients with Multiple Sclerosis do undergo a hearing assessment,
it often involves only the basic battery of tests and auditory deficits associated
with higher auditory pathways often remain undetected.
This explains why difficulty with hearing or mild hearing losses may remain a hidden
handicap.
On the other hand the high percentage reported in some studies is more
difficuh to explain.
It is possible that the battery of test procedures selected in those
studies could have played a role in the higher number of abnormalities found.
Hicks (1982), reported on the shortcomings of using only the basic audiometric test
battery when assessing patients with Multiple Sclerosis. The puretone audiogram and/or
word discrimination scores lack test sensitivity regarding the neuro-otological deficits
related to the demyelinating process.
(1983) and Grenman (1985).
This finding was supported by J?augherty et al
For instance the determination of speech reception
thresholds (SRT) has been considered to be a relatively poor indicator of the central
lesions caused by MS in the auditory pathways (Noffsinger et al, 1972). When the effect
of age, sex and other factors not related to MS are excluded, the results of the basic test
battery, like puretone thresholds and speech understanding in a quiet test environment,
are very often within normal limits.
In addition to this, the results of the basic
audiometric test battery provided limited to no information on whether or not a patient is
experiencing hearing difficulty during daily communication (Alphiner, 1982).
When
labels such as "slight", "mild" or ''moderate'' hearing loss are used, they should always be
supplemented with further information descnbing communicative competence (Yantis,
1994). Due to the shortcomings of the basic audiometric test battery, it cannot be used in
isolation and should be used in conjunction with other audiometric test procedures, such
as auditory evoked potentials.
Many researchers have shifted their attention to the use of auditory evoked potentiak
such as the ABR
ABRs have been extensively used since the 1970s to evaluate the
integrity of the auditory nerve in patients with Multiple Sclerosis (Jerger et al., 1986).
However the sensitivity of ABR in detecting abnormalities in MS varies, ranging from as
low as 0 % to as high as 93 % (Weldon et al., 1983). The high degree of ABR variability
and discrepancies between studies can be attnbuted to several factors, such as:
.:. procedural
differences, such as whether ipsi- or contralateral recordings were
performed and/or slow or fast repetition rates were presented;
.:. wave interpretation, such as the presence of Wave V, interpeak latencies (IPL)
and/or Wave VII amplitude ratios as criteria for ABR abnormality;
.:. disease status either being possible, probable or definite MS, and the site and
number of myelinated plaques formed on the auditory pathway; and
.:. statistical measurements using either ± 2, 2,5 or 3 standard deviations (SD) from
the mean (Jacobson et al., 1987).
Several studies conducting ABRs did not routinely include puretone audiometry, and
nonnal hearing sensitivity was predicted on the assumption that subjects could hear
o
dBnHL while listening to a click stimuli This could have resulted in low-frequency
hearing losses going undetected
Although conflicting results on the number of ABR abnormalities remains a problem, this
does not justifY the exclusion of ABR from the test battery. ABR is an objective tool for
assessing VIIIth nerve and brainstem abnormalities in MS (Hosford-Dmm, 1985).
Only a limited number of studies have examined the cochlear function of patients with
Multiple Sclerosis by using auditory
evoked responses.
According to some reports,
involvement of the auditory neIVOUSsystem originates in the retro-labyrinthine area or
brainstem region and hearing impairment in this disease has retrocochlear features
(Furman et al., 1989). This may explain why procedures such as otoacoustic emissions
(OABs) and Electrocochleography
(EcochG) were not included during the assessment of
the auditory nervous system in patients with Multiple Sclerosis (Nishida et aL, 1995).
Furthermore OABs have only been used in the field of diagnostic audiology since the mid
1990s (Martin et at, 1990). OABs and EcochG were used in the 1990s in single case
studies of sudden deafuess, as a tool for differential diagnosis between cochlear and
retrocochlear
lesions.
Clearly, more information regarding the cochlear function of
patients with Multiple Sclerosis is needed.
Therefore, an examination of the cochlear
function, to determine whether or not the hearing impairment in this disease is only of
retro-labyrinthine origin and causes no damage to the hair cells of the cochlea, should
still be performed.
Several studies were performed without addressing the self-assessment of hearing
abilities, associated auditory symptoms and communicative competence during every day
life of patients with Multiple Sclerosis.
Only a limited number of research studies
assessed subjective auditory complaints and associated auditory-vestibular symptoms
such as tinnitus, dizziness and vertigo.
The reason for this may be that researchers
concluded that difficulty with hearing was one of the less significant symptoms of the
disease; or that if a hearing loss occurred, it was of a mild degree not having a negative
impact on communicative
competence. Furthermore studies including patients' own
perception of their hearing abilities and related auditory symptoms, only used a limited
number of questions to address this matter (Musiek et al., 1989; Protti-Patteron & Young,
1985). Yet, despite the lack of in-depth questions, the percentage of patients reporting
difficulty with hearing was found to be higher than in other studies (Musiek et al., 1989).
More than 40 % of subjects with normal hearing sensitivity presented with subjective
complaints of hearing difficulties in either simple or complex listening situations.
subjective complaints
Thus
of hearing difficulty may not always correlate with puretone
thresholds. Musiek et al. (1989) indicated that the hearing complaints were related to
brainstem dysfunction, which was also confirmed by the presence of ABR abnormalities.
The fact that researchers did not include self-assessment of hearing complaints as part of
the battery of test procedures may be related to the fact that this type of assessment has
several shortcomings.
Firstly, reported hearing difficulties do not enable researchers to
ascertain a possible site of lesion and secondly some hearing difficuhies may not be
reported, since MS often silently affects the central auditory nervous system (CANS).
From the above discussion it is clear that discrepancies exist among the audiometric
findings of di1furent studies, contributing to the controversy on whether or not MS could
be associated with auditory abnormalities or whether a characteristic form of auditory
involvement is present. In spite of these controversies Jerger et al. (1986) and Musiek et
al. (1989) concluded that there was a relatively high incidence of auditory abnormalities
in their subjects with Muhiple Sclerosis that could only be discovered through the use of
appropriate test procedures.
Appropriate audiometric test procedures should assess the auditory nervous system at
several levels (sensory and neural), especially when taking the pathophysiological nature
of the disease into account.
These procedures should be sensitive not only to lesions in
the brainstem, but also include the patients' subjective perception of hearing abilities,
associated auditory-vestibular
symptoms and communicative competence during every
day life.
The discussed limitations and existing controversies led to this study.
The need to
implement a clinically appropriate battery of test procedures to assess several levels of
the auditory nervous system in patients with Muhiple Sclerosis has been identified. For
the purpose of this study it was decided to implement a selt:assessment questionnaire,
puretone
audiometry,
distortion product otoacoustic emissions (DPOAEs), cochlear
microphonics (CMs) and ABRs.
The research question is whether a clinically appropriate battery of test procedures
will be able to effectively describe the auditory involvement of patients with
Multiple Sclerosis.
In order to prevent misinterpretation the following key concepts used in the current study
were defined by the researcher as follows:
.:. Auditory-vestibular
symptoms:
This includes symptoms such as tinnitus, vertigo,
dizziness and a feeling of being off-balance .
•:. Sensory
hearing loss or involvement:
Hearing impairment due to sensory,
specifically cochlear involvement .
•:. Neural hearing loss or involvement: Involvement of the neural auditory nervous
system ranging from distal (auditory nerve) to proximal (brainstem) .
•:. Basic audiometric test battery: This includes procedures determining puretone
thresholds, speech reception thresholds and discrimination scores in a quiet test
environment, as well as immittance measurements .
•:. Participants:
Those patients who volunteered to be part of the study, but still
have to meet the selection criteria developed.
Those patients included in the
preliminary study are also described as participants .
•:. Subjects:
Those patients who met the selection criteria developed for the study,
and ultimately formed part of the sample.
The purpose of this chapter is to identifY a specific research problem related to the
auditory involvement of patients with Multiple Sclerosis and to provide a rationale for
the current study. This chapter includes the research question and definitions of the
terminology that will be used during the current study.
.:. Chapter two: Signs and symptoms of auditory involvement associated with
Multiple Sclerosis
This chapter will discuss and evaluate the audiometric test procedures commonly
used in studies on patients with Multiple Sclerosis. Procedures including the basic
test battery, evoked responses and central auditory processing measurements will be
discussed.
A critical evaluation of the results will be supplied and limitations will be
discussed.
This will be followed by a critical discussion of studies that have
implemented a multiple test battery approach. The worth of such an approach as the
appropriate procedure to assess the auditory nervous system of patients with Multiple
Sclerosis will be substantiated.
This chapter will describe the operational framework implemented to conduct the
empirical research.
Reference to the main aim and sub-aim of the study, research
design, procedures
for subject selection, selection criteria, material and apparatus,
compilation
of the assessment battery, data collection and recording, and the
statistical analysis of data will be supplied.
This chapter will present the resuhs obtained dwing the statistical analysis. Results
will be presented according to the sub-aims stipulated in Chapter three. After each
presentation of results, an interpretation and discussion of its value and implications
in relation to the literature will be discussed.
This chapter will consist of a critical evaluation of the study. Conclusions of the
findings will be provided in conjunction with the theoretical and clinical implications.
Implications
for the medical profession and MS population will be discussed.
Recommendations for clinical use and future research will be made, followed by the
:finalcomments.
This chapter aimed to provide relevant background information in order to elucidate the
topic of the study and to create a broad perspective on the importance of the rationale for
this research study. Patients with Multiple Sclerosis may display auditory and vestibular·
symptoms.
Controversy
however exists regarding the specific nature of auditory
symptoms and the incidence of hearing impairment in MS.
auditory
nervous
The assessment of the
system of patients with Multiple Sclerosis cannot be performed
effectively by using a single test procedure, and due to the diverse nature of the disease a
muhiple test battery approach assessing several levels of the auditory nervous system
should be implemented.
Attention was drawn to the need for assessing the cochlear
function of patients with Muhiple Sclerosis and also to include their subjective perception
of their hearing abilities, related auditory-vestibular symptoms and communicative
competence during every day life. The putpose and variations of ABR recordings were
discussed, being the most common objective test procedure used in the MS population.
The implementation of a clinically appropriate multiple test battery was recommended.
SIGNS AND SYMPTOMS OF AUDITORY INVOLVEMENT
ASSOCIATED
WITH MULTIPLE SCLEROSIS
Hearing loss is considered a non-typical symptom ofMS (Hall, 1992). This may partially
be as a resuh of other more invalidating symptoms, causing hearing loss to go unnoticed.
Furthermore mild unilateral hearing losses often tend to go undetected by patients with
Multiple Sclerosis.
Questions regarding hearing abilities, associated auditory-vestibular
symptoms (such as tinnitus, vertigo and dizziness) and communicative competence during
every day life, may be omitted during the routine clinical evaluation leading to these
symptoms not being easily identified.
In this regard Jerger et al. (1986) found that
auditory dysfunctions in MS are a frequent occurrence, but these are usually sub-clinical
(silent) and mild.
It has also been found that the resuhs of the basic audiometric test battery, including
puretone thresholds, speech reception threshold and speech discrimination abilities in a
quiet test environment, are often within normal limits, although variability has been found
(Grenman, 1985; Noffsinger et al., 1972 & Daugherty et al., 1983). Furthermore, MS
lesions appear to be largely silent and not easily detected using auditory tests, such as
puretone audiometry, speech discrimination, masking level differences and interaurallevel
discrimination.
The common feature of all these test procedures is that there is no
requirement for precise neural synchrony. In order to detect the presence of a sound, the
CANS is only required to detect an increased level of neural activity in the auditory
afferent pathway during the interval over which the tone is presented, typically a period of
several seconds.
Whether a nerve impulse arrives a few milliseconds late in response to
the tone, will probably not affect the decision about whether the tone has been detected or
not (Levine et al., 1994). Antonelli et al. (1987) concluded that central lesions, as might
be present with MS, do not substantially affect the audiometric threshold leveL This may
also account for the low percentage of abnormal hearing sensitivity found in patient~ with
Multiple Sclerosis.
Despite these preceding comments, reports of MS-related hearing loss have appeared in
the literature since the early 1890s. Since then, the literature abounded with controversy
on whether or not MS is associated with a particular form of auditory dysfunction.
The purpose of this chapter is to provide a theoretical framework for the empirical
research through a critical evaluation and interpretation
wiD be achieved
Furthermore
by discussing
previously
of relevant literature.
possible sites of auditory
implemented
audiometric
involvement
tests procedures
This
in MS.
during
the
assessment of the auditory nervous system of patients with Multiple Sclerosis wiD be
evaluated in terms of their contributions
and/or timitations.
Firstly, an overView of existing knowledge regarding the auditory involvement found in
patients with Multiple Sclerosis willbe provided. The cochlea, VInth nerve and brainstem
will be included in the discussion.
This overview of what is currently known about the
auditory nervous system of patients with Muhiple Sclerosis, and the problems and issues
surrounding it, will provide a base of information from which the method of this study can
be established and resuhs discussed and explained.
Secondly, the published research results on audiometric issues will be presented in the
following order: basic audiometric test battery, auditory evoked responses and results of
central auditory processing assessment procedures.
The relationship between MS and
impaired hearing sensitivity will also be reviewed, since this is a controversial issue that
needs to be considered during research on the auditory system of patients with Multiple
Sclerosis.
The existing high variability between the number of ABR abnormalities in
patients with Multiple Sclerosis, and possible reasons, will be discussed. Finally the need
for further assessment of cochlear function will be outlined.
The elements of a multiple test battery approach: case history information, basic
audiometric test battery and site-of-Iesion testing, will be supplied.
Studies using a
multiple test battery approach will be investigated, including diverse studies on related
auditory-vestibular
symptoms.
The self-assessment of a patient's hearing ability and
communication competence during every day life will be summarised. These theoretical
foundations play an important organisational role in establishing terminology, selecting
and formulating research aims, and providing a framework for the interpretation of the
resuhs of the current study.
2.2 AUDITORY INVOLVEMENT ASSOCIATED WITH MULTIPLE
SCLEROSIS
Patients with Multiple Sclerosis are known to have eNS lesions and when the cortical or
brainstem auditory pathways are involved, a central auditory disorder can be present
(Silman & Silverman, 1991).
Of all the neurological systems, the auditory system (at
brainstem level) is probably the system most dependent upon precision in neural timing,
and for this reason assessing this system shows great promise for identifying the
physiological changes as a resuh of MS, both for research as well as diagnostic and
therapeutic purposes (Levine et al, 1994).
The MS population is a particularly interesting group to study, as the demyelinating nature
of the disease essentially results in a disruption of neural timing due to the filet that the
transmission of signals is delayed or blocked completely. Therefore demyelination in the
CNS may desynchronise or reduce the neural activity, either traveling toward (sensory
pathway) or away (motor pathway) from the brain, ultimately decreasing or totally
blocking the conduction of the a.frected neurons (Jacobson & Jacobson, 1990). These
phenomena of desynchronisation and slowing of neural conduction can also be present in
the VIIIth nerve.
Hearing is a perception that is intimately related to sensation in time. Mustillo (1984)
stated that a contnbuting factor for patients' hearing difficulties could be a deficit in
temporal processing, presumably related to delays of signal transmission within the
auditory pathways.
One of the characteristic features of MS is the presence of silent
lesions, i.e. regions of disease involvement for which no corresponding neurological sign
or symptoms can be detected. This characteristic has made it difficult to follow the course
of the disease by neurological examination, since the site oflesions may fluctuate without
any associated signs or symptoms.
Any portion of this system may be affected, as the distal part of the auditory nerve is
covered with peripheral myelin and the central part with central myelin (Verma & Lynn,
1985). Demyelination can result in pre-neural and/or neural involvement, and therefore
needs to be assessed with audiometric test procedures sensitive to lesions in these parts.
Despite these recommendations, many studies have restricted their assessment to either
preneural (outer ear, middle ear and cochlea) or neural (VIIfh nerve and brainstem) sites.
One reason for this
is the di:ff~g
aims of the studies conducted; for example: Antonelli et
al. (1988) aimed to compare the presence ofbrainstem lesions by using ABR recordings
and contrasting it with MRI findings. Thus only the neural structures of patients with
Multiple Sclerosis were assessed. The time frame also determined which test procedures
were readily available at that stage, for example Musiek et a1. (1989) implemented seven
different test procedures, without including DPOAEs, possible due to its unavailability.
Until recently, the effects of MS were thought to be restricted to the CANS. However,
evidence has shown segmental demyelination (pollack et aL, 1977) and abnormal
refractory periods (Hopf & Eysholdt, 1978) in the peripheral nerves of patients with
Multiple Sclerosis. While recording ABR and EcochG to confirm the presense of Wave I,
Hopf and Maurer (1983) tested 71 patients with Multiple Sclerosis and found that 11 %
exhibited prolonged
Wave I latencies.
They attnbuted peripheral involvement to
segmental demyelination of the distal part of the acoustic nerve. There appears to be
anatomical support for their conclusion.
However, the extent of peripheral involvement
caused by MS, is still poorly defined despite numerous investigations (Grenman, 1985).
Parving et a1 (1981) investigated the use ofEcochG and emphasised the need for methods
to assess the cochlear function of patients with Multiple Sclerosis, as it is evident that the
literature is lacking information in this area. The relatively recent development of OAB
measurements provides a useful tool to efficiently and objectively assess the cochlear
function of patients. A further advantage of applying this measurement is that it plays an
important role in the differential diagnosis between cochlear and neural involvement, when
used in combination with ABR
It is apparent
that auditory involvement is present in the MS population, but due to
the diverse nature of the disease, a clear pattern of involvement cannot be identified.
Assessment
needs to be comprehensive
nature of auditory
involvement
in order to determine
the presence and
in each individual patient with Multiple Sclerosis.
This is an ongoing process, as the course of the disease fluctuates.
2.3 ASSESSMENT
OF PATIENTS WITH MULTIPLE SCLEROSIS USING THE
BASIC AUDIOMETRIC
TEST BATIERY
Most, but not all studies, used puretone audiometry to determine the hearing sensitivity of
patients with Multiple Sclerosis. Earlier studies noted that 59,1 % ofa group of patients
with Multiple Sclerosis demonstrated puretone losses, as compared to 27,3 % in a closely
matched control group (Dayal & Swisher, 1967). High-frequency hearing losses were the
most common configuration found during that study. It was concluded that there was a
small and definite number in the MS group, where puretone hearing losses were secondary
to the demyelinating process.
Unilateral or bilateral mild, high-frequency hearing losses
were reported by Musiek et al. (1989) and Rappaport et at (1994), although a profound
hearing loss was documented in research conducted by Shea and Brackmann (1987) and
Marangos, (1996).
Dayal et al. (1970) also concluded a descending curve to be the most
often observed configuration illustrated in 67 % of cases, followed by a flat configuration
(17 %) and low-frequency hearing losses (4 %). No dome-shaped configurations were
reported.
The study concluded that the abovementioned descending puretone losses
represented VIIIth nerve involvement and that the pathology was in the ne~
structures of
the auditory system. On the contrary Cohen & Rudge (1984) reported that patients with
definite Muhiple Sclerosis presented with thresholds within normal limits, but auditory
acuity at some of the low frequencies was found to be significantly worse in more than
half of the patients. Simpkins (1961) also confirmed that low frequencies were specifically
affected in patients with Muhiple Sclerosis.
Luxon (1980) found that 58 % of patients with brainstem lesions due to MS had
significant hearing losses, but no consistent audiometric pattern was identified. Weldon et
al. (1983) also stated that approximately 50 % of patients with Multiple Sclerosis
presented with mild puretone losses at various frequencies.
OzUn1u et at (1998) provided the following valuable predictions of puretone findings in
patients with Multiple Sclerosis:
.:. If the demyelinating lesions encroach upon or occur at the root of the VllIth nerve,
it may result in a high-frequency hearing loss in a way similar to the effects of
cochlear nerve tumors .
•:. If the demyelinating lesions occur in the auditory brainstem, it may resuh in a lowfrequency hearing loss of a type similar to the effects of other forms of brainstem
lesions .
•:. If oedema occurs in the tissue surrounding the demyelinating lesion, it may resuh
in a sudden loss of hearing.
improvement,
These patients' hearing loss may show rapid
probably due to the resuh of decreasing acute and extensive
demyelination and/or resorption of oedema in the auditory pathways.
As early as 1975 Colletti already found that speech audiometry was of minimal value
during the clinical assessment of patients with Muhiple Sclerosis. Dirks (1978) found that
the CANS of patients with Multiple Sclerosis was resistant to hearing loss as measured by
puretone audiometry and simple speech stimuli.
Supporting these findings, Keith and
Jacobson (1985) stated that the findings of conventional speech audiometry have not
contributed
significantly toward the assessment of auditory deficits in patients with
Multiple Sclerosis.
The understanding of single syllable phonemically balanced (PB)
words, measured in a quiet test environment, is usually normal in cases of MS (Stach et
al., 1990; LeZak & Selhub, 1966; Grenman & Salmivalli, 1982; Jacobson et al., 1983).
Some researchers have reported PB word score abnormality, but these percentages were
low, ranging from 3 % (Grenman, 1985) to 7 % (Noffsinger et al., 1972).
The literature
does
differentiate between speech audiometric results measured
in
background noise or competition, and those measured in a quiet test environment. Some
speech audiometric results were found to be abnormal in patients with Multiple Sclerosis,
when measured with a competing signal.
As a rule, tests performed in the presence of a
competing signal are generally sensitive to
vrnth nerve or auditory brainstem
disorders.
Musiek et al. (1989) illustrated that the analysis of reflex thresholds, detennining its
presence or absence and the use of reflex decay measurements, are less sensitive to lesions
caused by MS.
abnormal acoustic
However, Jerger et al. (1986) demonstrated a high percentage of
reflexes (AR) in patients with Multiple Sclerosis when applying
advanced reflex analysis procedures.
analysing suprathreshold
The acoustic reflex results were examined by
amplitude and latency characteristics, in a large group of
patients. Abnormality was observed in 75 % of the study population and acoustic reflexes
were altered as a result of retrocochlear auditory disorders, so :frequently associated with
MS.
The results of puretone audiometry provides information on the degree and type of
hearing loss (normal vs. abnormal, conductive, sensory-neural or mixed), but only limited
information concerning
communicative competence during every day life and/or the
site-of-lesion.
This limitation is partly addressed by supra-threshold speech audiometry.
Results of speech audiometry provide data in assessing the validity of puretone thresholds
(Roeser et al., 2000). However the results of speech audiometry performed in a quiet test
environment
was often within normal limits for patients possibly due to the high
redundancy of information found in speech signals (Sanders, 1971). When the speech
signal is presented with a competing signal, diagnostic information regarding the site-oflesion can be obtained (Roeser et al., 2000). Acoustic reflexes were useful during the
assessment of patients with Multiple Sclerosis, but only when using advanced amlysis
procedures, which were not available during the current study.
Although puretone and speech audiometry fonn the foundation of the basic test
battery, it is clear that it should not be used in isolationwhen assessingpatients with
Multiple Sclerosis. Due to the diverse nature of the disease,the basic battery of tests
needs to be supplemented with other audiometric site-of-Iesion test procedures
(assessing the neural system), in order to ditJerentiate between pre-neural and/or
neural involvement.
2.4 ASSESSMENT OF PATIENTS WITH MULITPLE SCLEROSIS USING
AUDITORY EVOKED RESPONSES
The use of evoked responses such as EcochG and OABs have been applied minimally in
MS studies as tools for the assessing the cochlear :function. Parving et al. (1981) applied
EcochG and observed intensity-dependent prolongations of the action potential (AP)
latencies and decreased AP amplitudes in nine patients with Multiple Sclerosis, despite
normal or near-normal puretone thresholds at 2000Hz.
The authors presented these
findings as evidence of cochlear involvement. Suggested mechanisms causing this deviant
findings were entirely hypothetical and included:
altered synaptic transmission in the
cochlear-eighth nerve region, plaques in the neuroglial part of the VII~ nerve, and
efferent innervation of the cochlea.
Lesions causing an altered activity in the efferent
nerve fibres originating in the brainstem, might result in a dysfunction of the peripheral
sensory structures.
Nishida et al. (1995) used OAEs and EcochG to assess the cochlear function of patients
with Multiple Sclerosis displaying unilateral sudden loss of hearing. Both tests indicated
normal responses, suggesting normal cochlear function. Cevette et al. (1995), Robinette
and Facer (1991) as well as Yamasoba et al. (1997), reported case studies of patients with
Multiple Sclerosis presenting with sudden unilateral hearing losses.
Due to normal
OAEs, cochlear pathology was ruled out as a possible cause of these sudden sensoryneural hearing losses, and the abnormalities were descnbed as retrocochlear in nature.
Sudden hearing losses are not a common occurrence associated with MS (being reported
in approximately 1 % of patients), and cochlear pathology does not seem to be the cause.
Brainstem auditory evoked responses, also known as ABRs, have become a useful clinical
tool during the assessment of patients with demyelinating diseases, such as MS, because of
its sensitivity to disruption of nuclei and pathways in the deep pons. This procedure is so
sensitive that it could pick up a delay of just a fraction of a millisecond, if such a delay is
present in the specific brainstem pathway tested (Nuwer, 1990).
The aim of performing ABRs in patients with Multiple Sclerosis is firstly to demonstrate
involvement of the auditory pathways in the pons and the midbrain (VIIIth nerve lesions)
and secondly to detect silent lesions.
These lesions can also be identified by magnetic
resonance imaging (MRI), for which corresponding :functionaldeficits have not yet been
found. ABRs are sensitive in detecting physiological changes that are not accompanied by
physical
signs of localising problems,
or so called silent lesions (Nuwer,
1990;
Lechtenberg, 1995). Detection of these silent lesions can assist in the diagnosis ofMS by
providing evidence of a second or third lesion in early clinicalMS.
Numerous studies extensively investigated the application of ABRs in patients with
Multiple Sclerosis, since the late 1970s. Earlier studies by Robinson and Rudge (1975),
Shanon et al. (1979), Starr and- Achor (1975), and Lynn et al. (1980) indicated that a
substantial number of patients with Multiple Sclerosis demonstrated ABR abnormalities.
Estimates of abnormalities ranged from 34 % (Chiappa & Norwood, 1977) to 73 %
(Robinson & Rudge, 1975). The overall percentage of abnormalities is the summation of
patient subgroups classified as definite, probable, or possible MS.
More recently, the
reported rates of ABR abnormality in MS has ranged from 0 to 93 %, with an average of
61 % across 16 studies (Jerger et al., 1986).
The incidence and types of ABR
abnormalities vary significantly between studies, due to the following:
.:. Different classifications (possible, probable, definite) in which patients'
symptoms
were categorised.
Patients with definite or confirmed Multiple
Sclerosis display symptoms of at least two separate CNS lesions, and a history of
exacerbations
Multiple
and remission, whereas patients with possible and probable
Sclerosis
exacerbations
display a presence
of one or more lesions, without
and remission of symptoms (Quaranta et al., 1986).
Different
classifications can account for the difficulty in comparing the results of various
studies with one another.
abnormalities
For example Lynn et al. (1980) found ABR
in 75 % of patients diagnosed with definite MS, 33 % when
classified as probable MS, and 29 % when the symptoms were possibly due to
MS. The highest number of ABR abnormalities found by Chiappa et al. (1980),
was also in a group of patients diagnosed with definite MS. The physical severity
of the disease
(also descnDed as the amount of disability the patient is
experiencing) and the duration of the disease did not emerge as important :factors
in relation to the prevalence of ABR abnormalities (Jerger et al., 1986; Grenman,
1985) .
•:. The occurrence of disseminated lesions at several levels of the brainstem
(Keith & Jacobson, 1985). An increased number of ABR abnormalities have been
associated with patients diagnosed with clinical and neurological (MRI) evidence
of brainstem involvement.
Robinson and Rudge (1977) demonstrated ABR
abnormalities in 79 % of patients with definite evidence of brainstem lesions and
only 51 % abnormalities in those without clinical signs of brainstem disease.
Chiappa et al. (1980) recorded similar findings.
Due to advanced technology and the availability ofMRI, other investigators have
compared the occurrence ofbrainstem lesions involving the auditory pathway (as
detected by MRI) and the presence of ABR abnormalities. Levine et al. (1994)
demonstrated
ABR abnormalities in all of their patients displaying brainstem
lesions in the auditory brainstem pathway.
In a study performed by Antonelli et
al. (1988) the ABRs of32 patients with definite Multiple Sclerosis were contrasted
with the brainstem anatomic lesions identified by MRI, and with neurological signs
and symptoms of brainstem involvement found during the clinical examination
Twenty-one
corresponded
(65,5 %) of the 32 patients bad abnormal ABR findings, which
well with patients demonstrating abnormal MRI and/or signs of
brainstem involvement.
These results stress the need for combined neurological,
ABR and MR.I assessment ofbrainstem lesions in patients with Multiple Sclerosis,
especially in cases where the disease is in an early stage. A correlation between
findings of the ABR, MRI and that of the neurological examination can be drawn,
when all these tests are performed concurrently .
•:. Variations in the criteria used to describe ABR abnormality.
variations ranged from the mean
(Hall, 1992).
±2/
These
2,5 / 3 standard deviation from the norm
Such differences can have a substantial effect on the estimated
prevalence of ABR abnormalities .
•:. DitTerentprocedures foDowedduring the recordingof ABRs. This includes,
different stimulus (also described as technical parameters) and acquisition (also
descn"bed as procedural parameters) parameters.
r'
Ib 4130_~9
bl~5S-04.u4-
The effect of using different stimulus parameters (repetition rate and stimulus
polarity) will be discussed according to reports in the literature:
•
Stimulus repetition rates
Some investigators suggested that ABR recordings were more sensitive to lesions
caused by MS if the stimulus rates were increased (Antonelli et al., 1988;
Jacobson et al., 1987; Musiek et al., 1989), although there was also evidence to
the contrary (Jacobson & Newman, 1989; Cbiappa et al., 1980).
Due to
demyelination, an increase in stimulus rate can adversely affect the central
auditory synaptic function and neural refractoriness, thus altering the ABR results
(Shanon et ai, 1981). Jacobson et al. (1987) determined that faster repetition
rates yielded an increased number of abnonnal ABR latency measurements
(absolute latency of Wave V and I-V interpeak latency), when compared to
slower rates. They concluded that the number of abnormal ABRs increased as a
function of increased stimulus rate and individual wave peak detection.
It was
found that a 67 per second stimulus rate produced the largest percentage of
abnormal ABR recordings.
As expected, wave peaks became more difficult to
identifY with increasing stimulus rates. Even though it was expected that
alternation
in stimulus rates would expose pathology, this manoeuvre only
aggravated pathologies already apparent at slow stimulus rates
(Elidan et al.,
1982). Chiappa et al. (1980) also reported an insignificant difference in relative
latency values between presentation rates of 10 and 70 clicks per second.
Significant ABR changes did not appear at increased repetition rates. Jacobson
and Newman (1989) reported similar :findingswhen the effect of the interactions
between stimulus rate and polarity was studied. These authors failed to show
Wave I-V latency abnormality for rapid versus slow rates, using rare:fuction
polarity click stimuli.
Increased stimulus rates also tended to reduce the clarity
and the repeatability of recordings, therefore hampering interpretation.
On the other hand, Soudant et al. (1978) and Antonelli et al. (1986) observed a
''less abnormal" ABR recording at increased repetition rates in some cases.
Better synchronisation of the nerve at increased stimulus rates was given as a
possible explanation for this phenomenon.
Despite these findings, stimulus
repetition rates are less reliable in determining ABR abnormality than absolute
latency (Hood, 1998).
•
Stimulus polarities
In most ABR studies performed on patients with Multiple Sclerosis, only one
click polarity was used (Jacobson et al., 1987; Jerger et al., 1986; Parving et al.,
1981). The three alternatives during click polarity selection are rarefaction (R),
condensation (C) and alternating (A) click polarities. The R click polarity was
most frequently utilised, although the separate application of both R and C click
polarities has generally been recommended (Hammond et al., 1986; Emerson et
al., 1982; Maurer, 1985). Studies where bOth R and C click polarities were used,
illustrated interesting findiiigs. See Figure 2.1 for changes in ABR recordings
when using the R click polarity.
Figure 2.1: The absence of Wave V using R clicks (Chiappa, 1990:255)
23
Although
Maurer
(1985) reported
nineteen ears with identical patterns of
abnormality using either the R or C click polarity, twenty-one of the ears gave rise
to different wave abnormalities dependent on the polarity of the stimulus. This
indicated that there were patients with normal ABRs using one click polarity and
pathological waves in the other. Hammond et al. (1986) reported an equal number
of ABR abnormalities between both R and C click polarities, but different types of
abnormalities were found in 40 % of the patients.
Interpeak prolongation of
waves, absence of Waves III and V as well as the absence of Wave V with the
preservation of earlier waves, was found using both R and C click polarities.
Similar findings were reported by Emerson et al (1982); Sand (199lb) and
Hammond et al (1986).
It was concluded that the two polarities could result in
two different abnormal wave patterns, indicating different levels of lesions in the
CANS.
It was recommended by Sand (1991 a) that both the R and C click recordings did
not have to be abnormal for the ABRs to be interpreted as abnormal, but rather
that only ABR recordings using one polarity needed to be abnormal for such an
interpretation to be made.
By expecting recordings using both R and C click
polarities to be abnormal may be more specific, but reduces the sensitivity of the
test. These findings stress the importance of using both stimulus polarities
consecutively, particularly if the initial ABR recording in one click polarity was
normal.
Another contributing factor leading to discrepancies between ABR studies, was
the technique used in acquiring ABR recordings.
Controversy exists in the
literature on whether contralateral recordings are helpful in patients with Multiple
Sclerosis.
Contralateral ABR recordings increased the percentage of abnormality
from 74 % (ipsilateral recordings) to 89 % (Quaranta et al, 1986). According to
this study, contralateral recordings reproduced the abnormalities already present
during ipsilateral recordings, and also demonstrated that in a certain number of
patients with normal ipsilateral ABRs it was possible to observe pathological
contralateral responses.
It was concluded that using the contralateral parameter
increased the sensitivity of ABR recordings in terms of the detection of pathology.
On the contrary Barajas (1982) did not find increased ABR abnormalities when
using the contralateral parameter and Hammond and Yiannikas (1987) found that
contralateral recordings were not especially helpful when performing ABRs on
patients with Muhiple Sclerosis.
The use of contralateral recordings to detect
ABR abnormality in MS has not been sufficiently conclusive to warrant use by all
investigators (Jacobson & Jacobson, 1990).
The
abovementioned
factors
have influenced the incidence and types of ABR
abnormalities found between studies. Due to the high variability in ABR abnormalities
reported, clinicians should not expect to find a homogeneous pattern of results in a patient
population displaying such a varied distribution of lesions (Keith & Jacobson, 1985) with
the auditory pathway being involved at several levels (Yamasoba et al., 1997). The ABR
findings include response abnormalities of prolonged interpeak (I-III, ill-V, I-V) latencies,
decreased amplitudes (especially of wave V), poor morphology of later wave components;
poor repeatability; total absence of one or more recognisable wave components after
Wave I or II (most often Wave V); and occasional absence or prolongation of Wave I.
The disparity between these different types of abnormalities is not easily explained by
merely considering the known conduction deficits in demyelinated axons, such as slow
conduction across the demyelinated segment in the increased refractory period (Chiappa,
1990).
In
some
patients,
absolute
and
interpeak latencies
were
statistically
indistinguishable (deviates by four standard points) from the mean normal value.
The
pathophysiological implication is that the ABR recording can be normal in a given patient,
if MS does not involve the auditory brainstem pathway. However even a small plaque in
the auditory brainstem is enough to radically alter the neural conduction along the
pathway
(Hall, 1992; Chiappa,
1990).
abnormalities reported in the literature.
Table 2.1 summarises the different ABR
THE ABSOLUTE LATENCIES
Normal Wave I latency
Oziinlii et al. (1998)
Hausler & Levine (1980)
Delayed Wave I latency
(2 to 10 % of cases)
MS does not usually affect the peripheral
portion of the auditory nerve where the
myelin sheath is formed by Schwann cells
rather than Iial cells.
Possible demyelination of the cochlear nerve
causing abnormal transmission of auditory
in ut at the eri h
In some MS cases the auditory nerve, even at
its most distal sent,
ma be involved.
No possible reason was provided.
Anatomically, the presumed brainstem
generators of Wave V are more likely to be
compromised in patients with Multiple
Sclerosis than those of Wave I (cochlear
nerve.
THE PRESENCE OF WAYES
Absent Wave III
(25 % of patients)
Wave V abnormalities
(absent, low amplitude
in 87 % of cases)
Absent Wave V
15,4 % of ears
AMPUTUDES
Musiek et al. (1989)
Chiappa et al. (1980)
Musiek et al. (1989)
OF WAVES
Abnormal VII amplitude
ratios (21 % of cases)
Musiek et al. (1989)
Robinson & Rudge (1975)
Starr & Anchor (1975)
It was suggested that amplitude ratio may be
a valuable measure and may be a worthwhile
inclusion criteria during the determination of
ABR abnormalities.
The amplitudes oflater waves are expected to
be affected, as they are highly sensitive to
brain stem atholo .
INTERWAJlELATENClES
I - III (11,1 %)
III- V (l4,3 %)
1- V (25,6 %)
Musiek et al. (1989)
The high incidence of prolonged Wave I - V
could relate to the high incidence of absent
Wave III. More patients displayed III-V than
I-III interpeak latency shifts, suggesting
greater involvement of the central pontine
pathways than the VIIIth nerve or peripheral
onto-medull
areas.
The majority of conduction abnormalities
were found to occur between the generators
of Wave I (superior olivary complex) and
Wave III (inferior colliculus), as would be
expected, since this is the longest segment of
white matter in the athwa bein tested.
While the ABR reflects activity of the
vrnth
cranial nerve and auditory brainstem, the
middle-latency response (MLR) and late vertex response (LVR) reflect higher-level
subcortical and cortical activity. The MLR and LVR have been used in col1iuoction with
the ABR to assess higher levels of CANS function. In general it was found that the MLR
and LVR are less likely to be abnormal when compared to the AB~ due to sclerotic
lesions being relatively uncommon in the CANS (Stach & Hudson, 1990). The extent of
cortical and high-level subcortical dysfunction, due to MS is not yet well defined (Stach &
Hudson, 1990).
In spite of these uncertainties, evidence is mounting that MLR and LVR can in fact be
abnormal as a result of MS.
Robinson and Rudge reported abnormal MLR and LVR
results as being 45 % and 5 % respectively, as far back as 1977. Abnonnal MLRs were
found in 40 % of patients diagnosed with Multiple Sclerosis in a study performed by
Speershneider et al. (1986).
Later a study was conducted by' Stach and Hudson (1990)
using AB~ MLR and LVR on 118 patients with definite Multiple Sclerosis .. They found
that at least one of the three evoked potentials was abnormal in 74 % of the patients
tested
ABR was abnormal in 58 %, MLR in 47 % and LVR in 20 % of patients. The
combination of ABR and MLR yielded the highest sensitivity to auditory involvement in
patients with Muhiple Sclerosis, while the LVR was fOlmdto be less sensitive.
There are many variables that need to be controlled during the recording of MLR and
LVR
The patient's attention state and medication, which especially produces a central
suppression of bmin activity such as barbituates and chloral hydrate, will significantly
influence and usually diminish the MLR and LVR (McPherson & Ballachanda, 2000).
These variables can however be controlled when assessing adults with Multiple Sclerosis.
Another influencing factor is that an abnormal MLR may simply be a reflection of the
disordered lower brainstem (abnormal ABR) through which nerve impulses must pass.
Thus the absence of an MLR may not be the result of a disorder at the generator site of
the MLR, but rather be the consequence of dysynchrony imposed by MS at a more
peripheral (brainstem) site.
2.5 ASSESSMENT
OF THE CENTRAL AUDITORY NERVOUS SYSTEM
(CANS) OF PATIENTS WITH MULTIPLE
SCLEROSIS
In an age of such sophisticated diagnostic tools such as computed tomography (CT)
scanning and MRI, the need for neuro-audiological tests for the detection of CANS
lesions can be questioned.
describe the functional
However, audiometric test Procedures are being used to
status of the auditory nervous system in patients with Multiple
Sclerosis, while the radiological tools would yield data only on the anatomical changes of
the CNS system..
Furthermore, costs and availability of radiological or neurological
procedures may be a :factor, making central auditory assessment an appropriate choice.
Although silent lesions are detectable with current radiological or magnetic imaging
techniques, audiometric test procedures
such as AR and ABR are also sensitive in
detecting these lesions.
Another area where the audiometric assessment of the CANS is providing valuable
information is during the monitoring of the neurological and auditory status of patients. In
addition to this, CANS assessment can help document auditory :function in patients with
known CNS damage, ifan auditory problem is suspected (Musiek & Lamb, 1994).
In the following section the findings of audiometric test procedures used during the
assessment the CANS of patients with Multiple Sclerosis will be discussed.
CAP test procedures assess different anatomic regions and processes of the brain, which
might be affected by the MS degenerative process. Rappaport etal. (1994) studied the
temporal resolution capacity of 16 patients with Muhiple Sclerosis, examining their
performances in gap detection and speech recognition in continuous and interrupted
background
noise.
discriminate
as separate
1997:199).
Temporal resolution is defined as ''the ability to perceive or
events,
sound segments spaced closely in time" (Stach,
The role of temporal resolution in understanding speech in the presence of
background noise is being recognised and studied increasingly in the field of audiology.
Most patients with Multiple Sclerosis performed within normal limits, at all stimulus
intensities during the gap detection testing. However, these patients displayed significant
abnormalities under the interrupted masker of the speech-in-noise paradigm, confirming a
temporal processing deficit.
These performances suggested the predominant role of
forebrain pathways in mediating auditory temporal resolution.
In 1990, Hendler
psychophysical tasks:
tests.
et al. studied
15 patients with Multiple Sclerosis using two
the monaural gap detection and binaural masking level detection
The authors concluded that demyelinating lesions could cause deficits in temporal
processing in the central auditory pathways, independent of the peripheral hearing status.
Inferences were made that abnomialities at different levels of the auditory system could
disrupt different types of temporal processing. Specifically, the gap detection performance,
was the least affected by the demyelinating lesions.
Musiek et al. (1989) used a battery of CAP tests on 27 patients with Multiple Sclerosis.
The two most sensitive tests were: masking level differences (50 %), which is known for
its sensitivity to lower brainstem/pontine lesions often present in patients with Multiple
Sclerosis, and the dichotic digits test (33 %), which measures brainstem and cerebral
auditory fimction. Other tests demonstrated less sensitivity:frequency pattern test (26 %),
followed by the staggered spondaic words test (22 %), and only 7 % abnormality on the
low-pass filtered speech test.
The above findings allude to the fact that only some CAP tests are more sensitive to
lesions caused by MS and should be selected as part of the battery of test procedures.
Musiek et al.'s (1989) study indicated that an extensive CAP test battery may not be
necessary, and recommended the inclusion of two or three CAP tests (such as the masking
level differences and dichotic digits test) which are sensitive in detecting central auditory
processing disorders (CAPD) in the MS population.
Although these tests are appropriate and efficient for assessing the CANS of patients with
Multiple Sclerosis, there are certain limitations. One contnbuting fuctor is the complexity
of the system under consideration (Musiek & Lamb, 1994). Even now the anatomy and
physiology ofthe CANS is not completely understood, nor has its many different functions
adequately been defined.
Another factor is that MS frequently affects the peripheral
brainstem structures, and sclerotic lesions with more central loci are relatively uncommon
(Stach & Hudson, 1990). Finally there are only a limited number of standardised CAP
tests available for clinical use in South Africa. Subsequently CAP tests were not included
in the current study.
2.6 A MULTIPLE TEST BATTERY APPROACH USED IN PATIENTS WITH
MULTIPLE SCLEROSIS
As discussed, many audiometric test procedures have been performed on patients with
Multiple Sclerosis, but not without controversy and limitations. Some but not all of the
limitations can be reduced if the auditory nervous system of patients with Muhiple
Sclerosis is assessed using a multiple test battery approach, selecting each test procedure
to focus on a particular level of function (Hannley, 1986).
In many instances auditory
manifestations are so entwined that is difficult to separate the different areas using current
test procedures.
understandable
When considering the complexity of the auditory nervous system, it is
that only a limited number of tests are site-specific, although also
dependent on the integration of other parts of the auditory nervous system. For example
DPOAEs are dependent on the conductive mechanism and CAP tests are dependent on the
conductive and sensory-neural mechanism of the ear. Therefore the existing lack of
agreement in the literature regarding the definitions of sensory-neural, retrocochlear and
neural disorders is understandable.
This emphasises the fact that a muhiple test battery
approach that assesses all the components of the auditory nervous system is essential.
When using a multiple test battery approach to assess the auditory nervous system of
patients with Multiple Sclerosis, the test battery needs to conform to several requirements.
The battery of test procedures must be accountable during the interpretation of results,
identifying auditory dysfunction on several levels and understanding the way in which the
dysfunction affects the patient's hearing ability (Hannley, 1986).
The importance of obtaining a case history has been indicated by Silman and Silverman
(1991) as well as Grenman (1985).
The case history provides the audiologist and/or
medical practitioner with information regarding MS-related symptoms that the patient is
experiencing on a subjective level
According to the literature the case history should
include at least two components (Grenman, 1985; Daugherty et at, 1983). Firstly, the
auditory symptoms associated with MS consisting of the patients' subjective perception of
their hearing difficulties and communicative competence during every day life should be
.
assessed.
.
Questions regarding the presence of tinnitus should routinely be included.
Secondly, the vestibular symptoms such as the presence of nystagmus, vertigo, balance
disorders, and dizziness should be fully understood.
Each component will be discussed in
some detail.
Studies that included the patients' subjective perception of their hearing abilities illustrated
discrepancies with their puretone findings.
Grenman (1985) found a good correlation
between patients' complaints of subjective hearing difficulty, and their impaired puretone
thresholds. However, other studies reported that only 20 - 40 % of patients with impaired
hearing thresholds
Bentzen et at,
Rappaport
complained of hearing difficulties (Yon Leden & Horton, 1948;
1951; Von Preibisch-EfIenberger,
1963).
In a study performed by
et al. (1994) patients reported minimal complaints when listening in the
presence of background
noise.
No correlation was found between these patients'
complaints and their puretone thresholds.
It has been documented that central and even
VIUth nerve auditory deficits can exist with little or no compromise in puretone sensitivity.
Musiek et al (1989) also found a poor correlation between more than 40 % of patients
presenting with subjective complaints of hearing difficulties, all had normal hearing
sensitivity (thresholds equal or better than 25 dB HL, from 250 - 4 000 Hz). This:finding
may indicate that the patients' auditory symptoms were related to CNS dysfunction
(specifically CANS dysfunction) and it was concluded that the patients' subjective
perception of their hearing abilities provided information on the nature of their auditory
problems.
Not all patients with Muhiple Sclerosis mention a history of hearing difficulties although
audiometric test procedures may confirm the presence of a hearing loss (Grenman, 1985).
This indicates that patients' subjective perception of their hearing and communicative
competence should be assessed in coJ1junctionwith a battery of other test procedures.
Due to the filct that hearing impairment is rarely an initial or prominent symptom of MS
one can assume that tinnitus is not a common complaint often reported by patients. The
occurrence of hearing loss with accompanying tinnitus, as an initial manifestation or during
the course ofMS is estimated to be less than 10 % (Fischer et al., 1985). Grenman (1985)
found that 8,5 % of patients with Multiple Sclerosis complained of tinnitus and suggested
that noise-induced hearing loss and presbyacusis may also have been the cause.
Only limited attention has been paid to vestibular symptoms even though these symptoms
are associated with MS in more than 80 % of patients (OzOn1ti, 1998). It is therefore
important to include questions regarding these symptoms as part of the case history.
During the first formal description ofMS, nystagmus was recognised as a salient feature
of the disease (Charcot, 1877). Nystagmus is a rhythmic horizontal or rarely, vertical
movements of the eyeballs that results from the anatomical connection between the
vestibular and ocular systems (Hall, 1992; Stach, 1997). Nystagmus has been identified in
16 % to 70 % of afrected patients (Gr6nman, 1985; Schweitzer & Shepard, 1989).
MS causes a variety of abnormal nystagmus including: spontaneous, lateral gaze and
positional
nystagmus;
preponderance.
unilateral
or
bilateral
caloric weakness
and
directional
These eleetronystagmography (ENG) findings were demonstrated within
both the CNS and peripheral vestibular systems, as a result of plaques within the nerve
root, where peripheral nerves contain CNS myelin (Keith & Jacobson, 1985).
These
lesions can also result in disequilibrium, ataxia and vertigo.
Vertigo has been reported as an initial SYlllptomin only 5 - 12 % of patients with Multiple
Sclerosis, with approximately 50 % of patients reporting vertigo during the course of their
disease (Schweitzer & Shepard, 1989). Vertigo is a symptom resulting from brainstem
and/or cerebellar lesions (Grenman, 1985). Lechtenberg (1995) fuund that vertigo is an
uncommon sYmptom during the exacerbation of MS symptoms, and is more likely to
develop in conjuction with a problem in the vestIbular system of the inner ear than with a
problem in the brain or brainstem.
However, Grenman (1985) fuund that 51 % of the
patients reported vertigo.
Another vestibular SYlllptomrelated to MS, is the occurrence of diDiness.
Lechtenberg
(1995) found that dizziness is a firirly common symptom during a flare-up or exacerbation
ofMS SYlllptoms. In contrast to this, Grenman (1985) found that only 7 % ofhis patients
complained of dizziness and a fulling tendency was reported by 21 % of the patients.
Walking difficulty can De attnbuted to dizziness that can be described as a feeling of
postural
unsteadiness
or light-headedness,
but usually arises from problems with
co-ordinating limb movements, namely ataxia. Unsteadiness, dizziness and vertigo have
been found to be among the most common complaints during the course of the disease
(V on Leden & Horton, 1948).
After obtaining a comprehensive case history, the second phase of the multiple test battery
approach is performing the basic audiometric test battery.
approach must include the elements of the basic test procedures.
A muhiple test battery
Puretone audiometry serves as the foundation of every audiometric assessment and is an
essential part of the battery of tests (Hall, 1992). The basic test battery also includes
speech audiometry and immittance measurements, and the findings during the assessment
of patients with Multiple Sclerosis were supplied in Section 2.3. These findings of the
basic test battery guide the audiologist in terms of patient management, such as medical
referral, referral
for speech-language
testing, hearing aid evaluation, site-of-Iesion
assessment and counseling.
Due to the fact that a peripheral hearing impairment can confound the interpretation of
ABR recordings used in neuro-otological assessment, it is vitally important to obtain a
puretone audiogram before ABR testing.
It was found that very few studies used
puretone audiometry before recording ABRs. Since confident and accurate interpretation
of any auditory evoked responses, such as ABR, usually requires at least some knowledge
of middle ear and inner ear status, the basic test battery should be included during the
assessment of patients with Multiple Sclerosis.
A multiple test battery approach has been effectively applied by researchers, such as Jerger
et al. (1986) and Musiek et al. (1989) despite the diversity of the disease, uncertainties
regarding symptom patterns, variations among patients, the complexity of the auditory
nervous system, and the fact that MS can affect any part of the CNS. They concluded that
no single test procedure
was adequate during. the assessment of neuro-otological
disorders, such as MS. The resuhs obtained from Musiek et al.'s (1989) study, suggested
cortical or higher brainstem involvement and lower brainstem dysfunction (as assessed by
ABRs and CAP test procedures).
However the researchers concluded that the sensitivity
of any combination of test procedures would be reduced, especially if the MS lesions did
not affect the auditory pathway.
One of the most significant findings of Jerger et al.'s
(1986) study was the relatively high prevalence of auditory abnormalities found in patients
with Multiple Sclerosis, and it was concluded that auditory testing was sensitive to the
presence of MS. They did however not expand on the possible site-of-Iesion involvement.
From the preceding overview on the nature of auditory involvement in patients with
Multiple Sclerosis, certain implications for research can be deduced and implemented in
the current study.
Firstly, it was confirmed that MS could effect any portion of the
auditory nervous system. An accurate description of the auditory function of patients with
Multiple Sclerosis is dependent on a comprehensive assessment procedure.
A multiple
test battery approach assessing different levels of the auditory nervous system should be
the focus of research.
This multiple test battery approach has been applied in some of the
research studies, and only Partially in others.
In the light of the unresolved debate on the number of ABR abnormalities, further
evaluation of several ABR parameters and recordings is necessary. The implementation of
other test procedures, such as the self-assessment of patient's hearing abilities, associated
auditory-vestibular
symptoms and communication competence during every day life has
also been Partially assessed. The use ofOAEs and eMs to assess the hair cell function of
the cochlea is needed to determine whether Pre-neural auditory involvement exists.
Further research on audiometric test procedures, such as puretone audiometry, DPOAEs,
ABRs, and patients' subjective perception of their hearing abilities are necessary and can
be conducted based on the knowledge that is presented in Chapter one and two. These
audiometric test procedures should be used in combination in order to supplement each
other.
The multiple test battery should supply the researcher with sufficient information
regarding the auditory functioning of patients with Multiple Sclerosis.
The assessment of the auditory nervous system and the treatment of hearing difficulties
should be of growing interest in the field of audiology and neurology.
Audiologists
dealing with patients with Multiple Sclerosis must understand the nature of the disease and
the rationale behind implementing a multiple test battery approach.
Furthermore they
must form part ofmuhi-disciplinary team during the management of these patients.
The goal of this chapter was to descnbe and discuss the signs and symptoms of auditory
involvement associated
with MS.
This was followed by published results of test
procedures used to assess the auditory nervous system of patients with Multiple Sclerosis.
The elements of a multiple test battery approach were explained and research studies that
have followed this approach were outlined.
It is evident from the previous two chapters that the nature and incidence of auditory
involvement in patients with Multiple Sclerosis is influenced by various factors that are
not yet clearly defined. It was illustrated that the disease is diverse in nature, resulting in
a variety of audiometric patterns.
also outlined.
The limitations of using a single test procedure were
It has been theoretically suggested that a multiple test battery approach
would be the most effective, during the assessment of the auditory nervous systems of
patients with Multiple Sclerosis.
Although studies were conducted using a multiple test
battery approach, certain limitations were identified.
The purpose of this chapter is to describe the research method implemented during
the current study. The research method was compiled to meet the theoretical and
clinical needs previously identified as essential during the audiometric assessment
of patients with Multiple Sclerosis. The focus was on designing a battery of tests
procedures sensitive in detecting sensory and neural auditory involvement.
A
practical and clinically appropriate battery of test procedures was selected for the
assessment of the auditory nervous system of patients with Multiple Sclerosis.
The main of this study was to determine the clinical effectiveness of the selected battery
of test procedures during the audiometric assessment ofa group of adults with Multiple
Sclerosis .
•:. Sub-aim 1
To describe the contribution of a self-assessment questionnaire in order to obtain
information regarding the subjects' perception of their hearing abilities, auditoryvestibular symptoms and communicative competence during every day life .
•:. Sub-aim 2
To determine the contribution of pure tone audiometry, DPOAEs and CMs to the
multiple test battery, in order to describe the degree of hearing impairment (as
assessed by puretone audiometry), as well as the type of hearing impairment in
terms of sensory involvement (as assessed by DPOAEs and CMs).
To determine the contribution
polarities consecutively.
of ABR recordings using both R and C click
Leedy (1993: 139) stated that:
"The nature of the data and the problem for research
dictate the research methodology.
If the data is verbal, the methodology is qualitative, if
it is numerical the methodology
is quantitative".
Due to the nature of the selected
audiometric test procedures, both qualitative and quantitative research methodologies
were utilised during the current study. Qualitative and quantitative data are compatible
and can co-exist in a single study. Subjects were individually assessed using a multiple
battery of test procedures and their audiometric results were described both quantitatively
and qualitatively.
A combined experimental-descriptive
research design was selected for the gathering of
quantitative and qualitative data (Ventry & Schiavetti, 1980). "This research design often
involves a within-subjects experimental study of the effect of an independent variable on
a dependent
1980:105).
variable with two different types of subjects" (Ventry & Schiavetti,
The research was partly descriptive due to the fact the researcher selected
subjects who fell into a pre-existing pathology.
independent
variable.
These subjects were described as the
Although all of the subjects had Multiple Sclerosis, they were
divided into two groups.
The experimental aspect of the study was the researcher's
ability to select the audiometric
test procedures
(also described as the dependent
variable), which included:
.:. the self-assessment questionnaire;
.:. puretone audiometry;
.:. DPOAEs including the CM; and
.:. ABR recordings using both R and C click polarities.
The following constant variables could be controlled, and were therefore excluded from
the current study:
.:. presbycusis;
.:. poor co-operation;
.:. abnormal middle ear functioning and/or conductive hearing losses;
.:. evidence of middle ear surgery;
.:. use of ototoxic drugs; and
.:. history of trauma to head and/or ears.
Non-probability sampling, specifically convenience/accidental sampling, was selected fur
the current study.
complicated
The advantage of non-probability sampling is that it is much less
and expensive
than probability sampling.
Another advantage of this
sampling procedure is that it can be implemented on a spur-of-the-moment basis to take
advantage of available participants, without the statistical complexity of probability
sampling (Baily, 1994).
Furthermore this type of sampling is indicated when only a
small group of participants will suit the requirements of the study. The disadvantage of
non-probability
sampling
is that the researcher cannot claim that the sample is
representative of the larger population and generalisation of findings beyond the sample
cannot be made (Leedy & Onnrod, 2001).
Subjects with definite Multiple Sclerosis were the focus of this study. Subjects were
recruited from the South African National Multiple Sclerosis Society as well as from a
neurologist. A notice concerning the research project was published in the South African
MS Society's newsletter, asking members to participate in the study. Despite this, most
of the subjects were obtained via word of mouth. All volunteering participants who met
the inclusion criteria for subject selection formed part of the sample. The study's mting
panel consisted
of two additional audiologists
selected by virtue of their clinical
experience in diagnostic assessment.
Subjects were required to meet the following criteria (as confirmed by audiometric
testing and/or self-reporting in the administered self-assessment questionnaire), in order
to be included in the study:
All subjects had to be diagnosed by their physician or neurologist with definite
Multiple Sclerosis, prior to the study. The diagnosis requires that the patient be ofan
appropriate age and experienced at least two episodes of neurological disturbance
implicating two distinct sites of involvement in the CNS (McDonald & Silberberg,
1986).
Subjects were required to be between 20 and 50 years of age, as the study focused on
adults with Multiple Sclerosis. The reason for this is firstly, because MS typically
begins in the second or third decade oflife, and is rarely diagnosed in children under
the age of 15 or in adults over the age of 55 (Noseworthyet al., 2000). In order to
assess hearing impairment exclusively caused by MS, normal deterioration of hearing
sensitivity as a function of age, needed to be ruled out.
All subjects were required to be proficient in English or Afrikaans, since the selfassessment questionnaire and instructions during the actual testing were presented in
either of these two languages.
Competence
in either of the two languages was
required in order to minirnise misinterpretation ofinfurmation.
Only subjects who were able to co-operate for approximately two and a half hours
were included in the study. Due to the fact that patients with Multiple Sclerosis often
experience
futigue, sensitivity to heat, spasticity as well as bowel and bladder
problems, resting periods were given during the assessment. If a subject seemed to be
in an acute exacerbation
(relapse) phase during the audiometric testing causing
discomfort and/or inattentiveness, he or she was excluded from the study.
Gender was not a selection criterion, due to several reasons.
MS has a female
predominance of approximately 2:1 (Noseworthyet al., 2000). Therefore an unequal
number of female and male subjects were acceptable.
Gender effects on DPOAEs
are apparently limited to minor differences in DPOAE amplitudes and thresholds
(Lonsbury-Martin et al., 1990). Although small differences have been found between
the ABR findings of females and males, the clinical importance of this fact is
generally minimal due to the substantial normal variability (Hall, 1992).
The
published norms for ABR findings used in the current study were developed from a
population that included both males and females (Bio-Logic System Corporation
Evoked Potential User's Manual, 1993).
Due to the fact that any conduction problem caused by a middle ear pathology would
influence the accuracy of the puretone thresholds, DPOAEs and ABR recordings,
normal middle ear functioning was required.
Normal middle ear functioning was
determined by performing an otoscopic examination and tympanometry.
Otoscopic examination of the external auditory meatus was important to determine
if the ear canals were not occluded with excessive cerumen or debris. This can affect
the puretone thresholds and block the otoacoustic emission microphone, preventing
the accurate measurement of the DPOAEs. The second aspect investigated was the
tympanic membrane.
The absence of perforations and the presence of a light
reflection on the tympanic
membrane were viewed as indicative of a healthy
tympanic membrane (Hall & Chandler, 1994).
A subject's tympanometry
results had to be within the following specifications for
inclusion in the study:
A Type A tympanogram was one of the criteria indicating normal middle ear
functioning.
Jerger's (1970) classification system for single-component, low probe-
tone frequency (226 Hz) tympanograms was used. A Type A tympanogram has a
peak (point of maximum admittance) near normal atmospheric pressure, within the
range of 0 to -100 daPa. The peak can actually be slightly positive, for example,
+ 25 daPa. Normal static immittance values, whenmeasuredat 226 Hz and described
as compliance of an equivalent volume of air, range approximately from
0.30 - 1.60 cm3• Normal ear-eanal volumes as determinedfor adults, range from 0.65
- 1.75 cm3 (Hall & Chandler, 1994).
In order to ensure that hearing impairment and auditory-vestibularsymptoms were
related specifically to MS, participants' using drugsthat are ototoxic to the cochlea
and vestibular system, were excluded from the study. Drugs that are ototoxic to the
ear and can cause a hearing impairment, include certain antibiotics, salicylates,
quinine, cis-platin,um, aminoglycosides (including gentamycin, streptomycin and
tobramycin), selected diuretics (furosemides), analgesics(aspirin), antihypertensives
(reserpine) and antiarrhythmics (quinidine) (Ginsberg& White, 1994). Medications
that have been reported to produce symptoms of tinnitus in isolation or in
combination with hearing impairment include agentssuch as erythromycin, lidocaine,
reserpine, furosemide and lithium (Stach, 1997). Participants using any of these
listed drugs when the case history information was obtained and/or during the
administration of audiometric test procedures wereexcluded from the study.
Participants were excluded from the study if they reported a history of trauma to the
head and/or ear/(s) and/or middle ear surgery seeingas this can result in the presence
of a sensory-neural and/or conductive hearing loss. On the other hand, participants
who were exposed to single episodes or continuous high levels of noise either using
hearing protectors or not, were included in the study. Noise exposure was not
controlled as one of the constant variables since the sample size was already
relatively·smal1 and excluding these subjects wouldhave resulted in an even smaller
sample.
Furthermore audiologists are bound to assess patients with Multiple
Sclerosis who have a history of noise exposure. Probablyan audiologist will seldom
encounter a patient with symptoms and auditory involvement exclusively due to
Multiple Sclerosis. *The results of these subjects were presented separately.
The procedure through which subjects were:finally selected consisted of the information
obtained from the self-assessment questionnaire (see Appendix C), followed by an
otoscopic examination of the external meatus and tympanic membrane, as well as
tympanometry.
The self:.assessment questionnaires were mailed to all participants who volunteered
telephonically to participate in the study. A cover letter explaining the purpose of the
study and what the study would involve accompanied the questionnaire. General
instructions for the completion of the questionnaire were included (see Appendix C).
Participants had to complete a consent form and return it to the researcher with the
completed questionnaire. The information obtained fromthe questionnaire was used to
determine whether participants met the inclusion criteria developed for the study and to
confirm their candidacy. Sections A and B of the questionnaire were designed to yield
biogmphical and case history information about the participants and their disease.
Questions regarding age, time of diagnosis, MS classificationand medication currently in
use were contained in these sections. Questions regardingnoise exposure, head and/or
ear trauma, etc. were answered in Section C. All variables, other than the diagnosis of
MS that could negatively affect participants' hearing sensitivitywere identified and those
participants were excluded from the study.
*It can be expected that these subjects would demonstrate impaired hearing sensitivity, subjective
complaints of difficulty with hearing and cochlear involvement. Most of the subjects demonstrated
abnormal puretone thresholds due to cochlear involvement, but did not complain of hearing difficulties.
The hearing losses were of a mild degree and not steep and 1he expected ABR abnormalities fuund wi1h
high-frequency hearing losses were not often observed. Thus the fact that these subjects were exposed to
noise prior to the study could explain cochlear involvement, but not necessarily neural involvement
Those participants, who met the criteria for inclusion in the study, were informed
telephonically.
An audiometric assessment was then scheduled. During the scheduled
assessment the answers provided in the self-assessment questionnaire were discussed and
elaborated on to ensure that all data provided was accurate and that the questions were
clearly understood.
Subsequently
the otoscopic examination and tympanometry were
performed.
The final sample consisted of25 subjects (50 ears) with Multiple Sclerosis, 17 females
and 8 males, which correlated with the female predominance of2:1 (Noseworthy, 2000).
Their ages ranged from 31 to 49 years, with a mean age of 41,6 years. One participant
was excluded from the study as he presented with a congenital hearing impairment.
high incidence of relapsing-remitting
correlated
The
MS, compared to other courses of the disease
with the literature (Noseworthy,
individualised description of the sample.
et al., 2000).
See Table 3.1 for an
NO
YEAR
OF
DIAGNOSIS
SEX
AGE
Male
I
Female
YEAR
OF
INITIAL
SYMPTOMS
COURSE OF
SYMPTOMS
RACE
ORIGIN
GROUP 1
1
46
X
1999
1996
RR
W
SA
4
43
X
1995
1995
RR
W
SA
5
39
X
1981
1980
SP
W
SA
6
39
X
1999
1999
RR
W
SA
8
36
X
1988
1983
RR
W
SA
9
34
2001
2000
U
W
SA
11
39
X
1996
1978
U
W
SA
15
48
X
1986
1969
B
W
SA
16
39
X
1991
1979
SP
W
SA
17
39
1994
1993
RR
C
SA
18
37
X
1988
1980
RR
W
SA
19
49
X
1989
1987
RR
W
SA
20
31
X
1997
1996
SP
W
I
22
45
X
1992
1985
U
W
SA
25
46
X
1986
1982
SP
W
SA
X
X
GROUP 2
2
48
X
1994
1994
U
W
SA
3
46
X
1992
1986
RR
W
I
7
39
X
1990
1985
PP
W
SA
12
43
X
1987
1987
RR
W
SA
13
41
X
1998
1993
RR
W
SA
14
46
X
1990
1982
RR
W
SA
21
46
X
U
1980
U
W
I
23
41
X
1990
1983
U
W
SA
24
48
X
2000
1997
U
W
SA
26
34
1998
1997
RR
W
I
X
Course of Symptoms
(See Appendix B)
RR
SP
PP
B
U
=
=
=
=
=
Relapsing-remitting
Secondary progressive
Primary progressive
Benign
Uncertain
Race
Origin
W
C
SA
I
=
=
=
=
White
Coloured
South African
Immigrant
Figure 3.1 illustrates the age and gender distribution of the subjects across
SIX
age
intervals of five years each.
9
8
tl
•..'"
.....=
:E'
•..•..
.&>
e
7
6
5
Q
=
Z
10
4
3
Femme
Male
I
2
1
0
The subjects were categorised into two groups.
Group 1 consisted of 15 subjects (30
ears) with Multiple Sclerosis who had no history of exposure to high levels of noise.
Group 2 consisted of 10 subjects (20 ears) with Multiple Sclerosis, who had at some time
been exposed to single episodes or continuous high levels of noise. Only two of the ten
subjects made use of hearing protectors.
Figure 3.2 illustrates the time lapse between the medical diagnosis ofMS and the current
study across five intervals of five years each.
10
9
tl
~
:E'
..=
8
7
'c
6
5
~
4
~
Z
3
2
1
o
Both groups' time of diagnosis ranged from the same year when the study was performed
to 20 years before the study, with a mean range being 8 years, 2 months prior to the
current study.
Figure 3.3 illustrates the time lapse between first experiencing MS related symptoms and
the medical diagnosis across five intervals of five years each.
~
~ 10
:E'
•...~ 8
Q
i;
..c
6
§ 4
Z
0-4
5-9
10-14
15+
Uncertain
Age interval (years)
Figure 3.3: Time lapse between first experienced MS-related
symptoms and
the medical diagnosis
Most of the subjects noticed their MS related symptoms several years before the
diagnosis.
For some subjects, MS related symptoms were experienced up to 18 years
before diagnosis.
The mean time lapse between initial MS related symptoms and time of
diagnosis was 5,3 years for Group 1; 3,8 years for Group 2, and 4,7 years across both
groups.
No Indian or Black subjects formed part of the study, which correlated with the low
prevalence ofMS in these ethnic groups (Rivera, 1990). Four subjects were born outside
the Republic of South Africa and immigrated before the age of 15 years.
Immigrants
moving from a high-risk to a low-risk area (such as from England to South Africa) carry
with them the risk factor for increased MS prevalence provided they immigrated over the
age 15 years (Rivera, 1990). Seeing as the four subjects in the current study immigrated
to South Africa before the age of 15 years, the high-risk factor can be excluded.
It was interesting to note that in this relatively small group of subjects, six reported
family member/(s) with Multiple Sclerosis. Although there is no conclusive evidence
that MS is directly inherited, it has been found to develop 12 to 15 times more readily in
relatives of affected individualsthan in the population at large (Rivera, 1990).
The material and apparatus used for this study can be categorised in three sections,
namely:
subject selection material and apparatus; data collection material and data
collection apparatus.
•:. The self-assessment questionnaire was sent to the subjects prior to the actual
audiometric assessment and included questions to determine whether
participants met the criteria for subject selection. See paragraph 3.5.2, Table
3.2 and Appendix C for a description of the self-assessmentquestionnaire.
•:. A Welch Allyn 2.5 model otoscope was used to examine the external meatus
and tympanic membrane of each subject.
•:. A Grason Stadler Instrument TympStar version 2 Middle Ear Analyser that is
calibrated annuallywas used for tympanometry.
.:. Several questions were included in the self-assessment questionnaire for the
purpose of data collection. The data obtained included the subjects' perception of
their
hearing abilities, auditory-vestibular symptoms and communicative
competence during every day life. Different questions and response formats were
included in the questionnaire:
Open-ended
questions
were added and had to be completed with written
answers. Coding errors can however occur when the researcher misinterprets
open-ended responses.
Therefore answers provided were verified during the
interview.
A list of likely answers was provided in the closed-ended response format and
participants were instructed to indicate which of the answers applied to them.
The advantages of closed-ended questions are that they reduce the number of
vague or ambiguous answers that might be given, and respondents can usually
answer these items quickly (Breakwell et al., 1997). The disadvantage of this
format is that it can create artificially forced choices and rule out unexpected
responses. Therefore, the choices of all the closed-ended response questions were
reviewed by two participants during the preliminary study. The following closedended response formats were included in the self-assessmentquestionnaire:
Categorical response format, where participants could indicate only one
possible answer, was used particularly for the collection of biographical
information.
Multiple-response items, where participants were expected to select the
appropriate answer from approximately three possibilities, for example "yes",
Rating scales were included and participants had to mark three- and four-step
rating scales for example the Rating Scale for Each Ear (RSEE) and
Communication Complaint List (COM-C).
The specific areas and aims of the self-assessment questionnaire is summarised in
Table 3.2.
~.~
..
~
...
~
1'8.Su.r•~~
.
Q_S'l10.~ •••.
lascJtJPnON
OJ
AND
~S
SUBJECT SELECTION
Section A,
Question 7;
Section B,
Questions 12,16 and 17;
Section C,
Question 19.
SELF-ASSESSMENT OF
RELATED MS SYMPTOMS
Section B,
Question 15
-Initial MS related symptoms
-Auditory-vestibular symptoms
SELF-ASSESSMENT OF
HEARING ABll..ITY
-Unilateral and bilateral
-The nature and onset of the
hearing difficulties
Section C,
Questions 20-23
Section D,
Questions 24-27
Section E,
Question 31 (10 items)
SELF-ASSESSMENT OF
COMMUNICATIVE
COMPETENCE
COMPARING
HEARING DIFFICULTY
WITH OTHER MS
RELATED SYMPTOMS
AND THE EFFECT ON
QUALITY OF LIFE
MOTIVATION
SOUltCU
To determine whether participants
met the inclusion criteria.
Most of the questions were
derived from Silman &
Silverman's (1991) case history
information format.
To compare the presence of
hearing difficulties, tinnitus and
vertigo as part of the initial MS
related symptoms, to those
reported during the study. To
determine the presence oftinnitus,
dizziness and vertigo during the
study (Daugherty et aI., 1983).
The information obtained from
the RSEE (Schein et aI., 1970)
was used to compare subject's
self-perception of their hearing
abilities with their puretone
findings as well as the results
from other audiometric test
procedures.
Communication Complaint List
(COM-C), Schowet ai. (1990).
Two items were added:
"Do your fumily and/or
friends say you have a
hearing problem?"; and
"Do you experience difficulty
localising the direction of
sound?"
Section E,
Question 32 and 33
To determine how subjects rated
their hearing difficulties as
compared to other MS related
symptoms as well as the effect on
their quality of life (Klugman,
2000).
.:. Puretone audiometry was performed in a soundproof booth, within a sound treated
room suitable for threshold determination.
The soundproof booth met the
SABS:0182 specifications for background noise levels. The test signal was
delivered with a Grason Stadler Instrument Clinical Audiometer (OSI 61) and
transduced in a set ofTDH-50P supra-aural headphones and Radioear B-71 bone
vibrator. The audiometer is calibrated annually in accordance with the SABS
0154-1:1996 specifications.
•:. The Bio-Iogic System Brainstem Auditory Evoked Potential was used for the
ABR recordings. These recordings were performed in a soundproof booth with
the subjects lying on a bed.
The stimuli were presented through Etymotic
Research ER-3 insert earphones. A Hewlett Packard LaserJet 6L was used for
printing purposes.
•:. The measurement of DPOAEs was conducted with a Grason Stadler Instrument
(OSI 60) Distortion Product Emissions. The probe was calibrated for a quiet
room in September 2001, in accordance with the SABS 0154-1:1996
specifications.
Puretone audiometry and ABR recordings were performed in the same soundproof booth,
while DPOAEs were conducted separately in a sound treated room.
.:. The procedures followed during the preliminarystudy.
•:. The procedures followed during the collection and recording of data.
•:. The procedures followed during the analysisof data.
•:. The procedures followed during the processing of data.
Two participants with definite Multiple Sclerosis (of relapsing-remitting
progressive course) volunteered to be part of the preliminary study.
and primary
Both participants
met the criteria developed for subject selection.
.:. Evaluate the suitability of the self-assessment questionnaire .
•:. To determine stimulus and configuration parameters ofDPOAEs .
•:. To determine the stimulus and acquisition parameters of ABRs .
•:. To determine the required time for the completion of all the test procedures for a
single participant, in order to plan the data collection procedures.
Two participants were given trial self-assessment questionnaires to obtain feedback on
the length, format, ease of answering questions,
level of complexity and general
instructions
and answers were given to one
of the questionnaire.
The questions
participant orally, because he was blind .
•:. "Bladder problems" was included in the list of associated symptoms of MS in
Section B, Question 15.
•:. A column
for ''reason
for usmg medication"
was provided
next
to
"medication" listed at Section B, Question 17.
•:. A space was provided after each item at Section C, Question 19 for subjects to
provide particulars, if they answered "yes" .
•:. Several options for possible answers were provided in Section C, Question 26,
instead of requesting the date or time when difficulties with hearing had first
been noticed.
3.6.1.2 Detennination of optimal stimulus and configuration parameters for
DPOAEs
Two distortion product "audiograms" (DPgrams) were obtained for each ear in order to
determine the repeatability of the responses. The normative database, Vanderbilt 65/55
sample ofNonnal
Ranges was selected (Hornsby et al., 1996). This nOlDlative DPOAE
data was originally collected from young, normal hearing adults (hearing levels of
15dB HL or better from 250 - 8 000 Hz, and Type A tympanograms) in a quiet, but not
sound-treated room. The amplitude of the distortion product was plotted as a function of
the f2 frequency.
The same stimulus and configuration protocols as developed for the Vanderbilt 65/55
Nonnal Ranges were used during the preliminary study.
See Tables 3.3 and 3.4 for
further details.
Table 3.3: DPQAE stiumlus protocol
U=65
dB SPL
562 - 6250Hz
4
6
1.2
32000 Hz
Table 3.4: DPOAE configuration protocol
Single-frame noise level: absolure noise> 35 dB SPL
U or L2 out of tolerance: ± 5 dB SPL
Test time: ~ 400 frames
Noise level exceeded: ~ 50 frames
U out of tolerance: ~ 20 frames
L2 out of tolerance: ~ 20 frames
Minimum accepted frames: ~ 10 dB SPL
Absolure average noise: S; -6 dB SPL
DP amplitude - average noise floor: ~ 10 dB SPL
Average absolute noise: S; -12 dB SPL
Sourced from: Hornsby et al. (1996:44)
During the preliminary study the stimulus and configuration protocols were slightly
varied, in order to determine their applicability and practicality for the current study. The
following changes were made:
6 DP points per octave
(amounts to 22 frequency
pairs)
3 DP points per octave
(amounts to 12 frequency
pairs)
DP amplitude minus average DP amplitude minus
noise floor ~ 10 dB SPL
noise floor ~ 5 dB SPL
Decreased test time and
sufficient information
regarding DPOAE presence
between test frequencies.
The DP amplitude must
exceed the noise floor (NF)
by at least 5 dB SPL for a
DP point to be considered
as present (Hall. 2000).
The stimulus and configuration protocols that were adapted for the current study were
accepted as being sufficient for the purpose of assessing the subjects' cochlear function.
Due to the significant variability of abnonnal ABRs found in patients with Multiple
Sclerosis,
special attention
was paid to the selection of stimulus and acquisition
parameters, since these fuctors could influence the outcome of ABR recordings (Hood,
1998). The adult ABR normative data published in the Bio-Logic System Corporation
Evoked Potential User's Manual, developed at the Boys Town National Institute for
Communication Disorders was used during the preliminary study, since published norms
were not yet available at the current place of assessment (University of Pretoria) at the
time of the study. When using published nonnative ranges, Hood (1998) recommended
the use of the same stimulus and acquisition parameters as those implemented to establish
the normative values.
Subsequently,
the same stimulus and acquisition parameters
applied to develop the Boys Town ABR nonnative data were used during the preliminary
study. The only exception was that one-channel, instead of two -channel recordings were
used since contralateral recordings during the detection of ABR abnormality in MS has
not been sufficiently conclusive to justify use by all researchers (Jacobson & Jacobson,
1990). See Table 3.6 for a full description.
t
S11Ml1l •.OS •••••••••
Type
Click
Duration
Rate
100 msec
Polarity
Rarefaction
Intensity
80 dBnHL
Transducer
Beyer DT48
13/sec
ACQ.mO"p~1'DS
Amplif"lCation
100,000
Electrodes
Fz-to-ipsi lateral mastoid, with non-test ear as ground
Filter settings
100
Notch f"lIter
None
Filter slopes
6 dB/octave
Analysis period
10,24 or 15,36 msec
Number of sweeps
I 024; two replications
- 3 000 Hz
Sourced from: User Manual of Bio-Logic System Corporation Evoked Potential
(1993:E3)
.:. The ABR recordings of the first participant displayed poor wave morphology and
waves were difficult to identify in the right ear at 80 dBnHL with a stimulus rate
of 13 per second. The intensity level was increased to 90 dBnHL, but even poorer
wave morphology was present.
Thereafter the stimuli were presented at a rate of
67.7 per second at 80dBnHL, but waves could still not be identified.
No
repeatable waves could be obtained from the left ear due to increased artifacts.
Even though the participant was sleeping, the electromyography (EMG) was high
and reliable recordings could not be obtained. Patients with Multiple Sclerosis
experience muscle spasms especially in their legs, which may influence the
amount of artifacts measured.
According to Hood (1998) patients with Multiple
Sclerosis may also display spontaneous nystagmus, even when their eyes are
closed. Nystagmus could result in high EMG activity during ABR recordings .
•:. The ABR click stimuli for the second participant was presented at 80dBnlll.-, also
at a low stimulus rate of 13 per second. Reliable tracings of Waves I and II were
recorded at 80 dBnHL and 90 dBnlll.-. However, no reliable tracings of later
waves could be obtained in the right ear due to high artifacts caused by EMG
activity. The participant was instructed to open his eyes, but this only increased
the number of artifacts.
After a rest period of 15 minutes recording was
discontinued as the artifacts continued to accumulate.
After conducting
the preliminary
study the following suggestions were made and
implemented for the current study:
.:. More time should be scheduled for ABR recordings. Testing should be paused
when arti:fu.ctsaccumulate and the researcher must wait for the EMG activity to
reduce before continuing the recordings .
•) If increasingly high artifacts are present, subjects should be instructed once again
to lie still and not move their bodies, eyes or jaws. If nystagmus is suspected,
subjects should be advised to open their eyes and fixate on an object .
•:. When no reliable ABR recordings can be obtained due to increasingly high
artifacts, this should be recorded as a no response (NR).
On the basis of the results of the preliminary study and recommendations
from the
literature, stimulus and acquisition parameter adjustments were made. Parameters such
as the intensity, stimulus polarity, transducer, electrode placement, number of sweeps and
replications were adjusted.
See Table 3.7 for a summary and discussion of the stimulus and acquisition parameters
utilised during the current study.
Rarefaction
and
Condensation
1024;
two repetitions
dBnffi,
Insert
earphones
(ER-3)
The use of insert earphones is recommended due to the fact that Wave I
is easier to iden.tify(stimulus artifact is separated from the onset of1he
response) in most instances, ear collapse is prevented and interaural
attenuation is increased. Insert earphones are more comfortable for
longer periods of time, which may assist in reducing the artifacts (Hood,
1998).
2000;
two to three
repetitions
100-
300 -
3000Hz
3000 Hz
Cz-to-ipsilateral
mastoid with
forehead as
ground
(2-channel
montage)
When the POlaritY (R and C) of the click phase is reversed, the waves
also invert resulting in the presence of the cochlear microphonic (CM).
The presence of the CM assists the researcher in the identification of
Wave I. especially when the stimulus artifact is enlarged. The p-esence
of 1he CM (prior to Wave 1) in 1he absence of waves can be indicative
of auditory neuropalhy (Hood, 1998).
During 1he application of ABRs for neurological purposes 1he elide
stimuli need to be presented at an intensity level wen above 1hreshold,
usually between 70 and 80 dBnffi, (Hood, 1998). The first ABR
recording will be obtained at 80 dBnffi,. If a clear response is not
obtained, 1he intensity will be increased to 90 dBnffi,. If a clear
response is still not obtained, the stimuli will be decreased to 70 dBnHL.
80,90& 70
Headphones
(Beyer DT48)
The type of stimulus polarity influences the shape and normalcy of the
ABR recordings (Tackmann & Voge~ 1987). Due to the discrepancies
fuund when reversing the click polarity it is recommended that both
R and C click polarities be presented consecutively (Sand, 1991 b;
Maurer, 1985; Emerson et ai, 1982).
F z-to-ipsi1atera1
mastoid with
non-test ear
as ground
(l-channel
montage)
Due to an inaeasingly high number of artifacts found in the preliminary
study, it was decided to inaease the number of sweeps to 2 000. As the
number of sweeps is increased, the background noise (caused by EMG,
EEG activity and 50 Hz noise) deaeases, making the ABR waves more
visible (Hood, 1998). When two recordings are repeatable 1esting will
be discontinued. If repeatability cannot be fuund after two recordings a
third recording will be obtained using 2000 sweeps. Up to 1hree
recordings of2 000 sweeps each will be allowed.
Increasing 1he high-pass filter setting usually eliminates low-frequency
eleclrical and electrophysiological noise, including EEG (Hood, 1998).
Ipsilateral recordings were most often used in the clinical setting where
the study was performed. There are many controversies in the li1crature
whether contralateral recordings in patients with Muhiple Scleros~
yields more information than ipsilateral recordings. BanYas (1982)
illustrated that the number of ABR abnormalities did not inaease using
contralateral recordings, but only redefined those abnormalities present
when using ipsilateralrecordings.
In order to schedule appointments with future subjects the test battery was performed
during the preliminary study to determine the amount of time that will be required for the
assessment of each subject. As seen in Table 3.8 the complete assessment lasted for
approximately two and a halfhours for each participant. More time was required in some
instances, especially when ears demonstrated hearing impairment and puretone bone
conduction thresholds had to be obtained. In the presence of increased artifucts extended
testing time was required due to increased averaging, in order to obtain repeatable
tracings.
Table 3.8: Approximate
time required for the assessment of one participant
15 minutes
10 minutes
15 minutes
15 minutes
1 hour, 30 minutes
In order to describe the audiometric findings of future subjects it was necessary to collect
data from the self-assessment questionnaire, puretone audiometry, DPOAEs and ABRs
(including the presence of the eM).
As mentioned
in paragraph 3.5.1 the self-assessment questionnaire, cover letter and
consent form were mailed to every participant who volunteered to be part of the study,
prior to the actual audiometric assessment.
questionnaire.
An instruction sheet was included with the
The participants were reminded telephonically in cases where questionnaires had not
been returned within three weeks after they had been sent. Despite the fact that five
participants did not return the questionnaire, the return rate was higher than 80 %.
Each subject was seated in a soundproof booth and was given the following instructions:
"I will now place the earphones on your ears. You will hear pulsing tones, :first in the
right ear and then in the left ear. Please press the button every time you hear the tone,
even ifit is very soft."
If subjects presented with impaired air-conduction thresholds, only those subjects with
sensory-neural hearing losses (no gap between air and bone conduction thresholds) were
accepted for the study. Puretone thresholds were detennined according to the preferred
technique
based on the Carhart-Jerger modified Hughson-Westlake method (Hall &
Mueller, 1997; GSI 61 User Manual, 1996). Thresholds for air and bone conduction
puretone audiometry were plotted on an audiogram for each ear separately. The standard
symbol system for audiograms developed by the American Speech-Language-Hearing
Association (Roeser et aI., 2000) was used.
DPOAEs were performed directly after the completion ofpuretone audiometry. Subjects
were seated facing the GSI 60 DPOAE system and the procedure was explained briefly
by making a statement such as: "For this test I'm going to place a soft tip into your ear
canal. Once it is in place, you'll hear some tones. They won't be loud. Pay no attention
to these sounds.
You don't have to tell me that you hear the sounds. This test should
only take a minute or two for each ear. Please just sit still and relax during this time. rll
let you know as soon as the test is completed."
First, the stimulus and configuration protocol was selected and subsequently a new file
was opened for each subject. Thereafter the probe was inserted into the external meatus
assuring a snug fit within the ear canal.
During the recording of the DPgrams the noise floor levels were monitored visually on
the computer screen.
prescribed norm.
DPgrams were repeated if the noise floor levels were above the
The DPgrams were repeated at least twice for each ear to increase
reliability. Hall (2000) recommended that the absolute distortion product (DP) amplitude
values should be reasonably similar from one DPgram to the next (e.g. ± 2, 3, 5 dB).
Before performing a second DPgram the probe tip was removed from the ear canal and
replaced.
This once again ensures a proper fit (Hall, 2000). The two DPgrams were
superimposed
for rapid evaluation of repeatability.
Every DPgram consisted of twelve
:frequency pairs and every :frequency pair consisted of two puretones, f1 and :f2, presented
to each ear simultaneously.
The twelve :frequency pairs were presented in sweeps, one at
a time, starting with the low :frequencies and ending with the high :frequencies. The
stimulus mtio between the two :frequencies (f2/f1) was 1,20. Four DPgrams were saved
for each subject.
One-channel recordings, using a three-electrode montage, were used for recording ABRs.
The forehead electrode (FJ was positioned in the midline on the forehead approximately
at the hairline.
Electrodes were also positioned on the mastoids of each ear. The left
electrode site is referred to as Al and the right electrode site as A2• The non-test ear's
electrode served as the ground electrode. The wave tracings were plotted in the vertexpositive direction, with the vertex upward.
The following instructions were given to each subject once they were lying on the bed in
the sound proofbooth:
"You will hear loud clicking sounds, first in the one ear and then
in the other, but you do not have to respond".
Subjects were encouraged to relax and
even sleep.
Electrodes were applied by first cleaning the surface of the skin where the electrodes
were to be placed.
The forehead and mastoids were scrubbed with a commercial
prepping solution and wiped offwith an alcohol-soaked gauze pad. The electrode discs
were filled with conductive paste and applied to the prepared sites. Silver-plated disc
electrodes were securely attached with tape.
After a file had been opened for each
subject the electrode impedance was measured. Impedance should be below 5 000 ohms
for all electrodes
electrodes
combined,
and fairly equal (within about 2 000 ohms) between
sites (Hood, 1998).
Electrode impedance was checked after the insert
earphones had been positioned for testing and also periodically during testing, as any
changes in impedance could affect the quality of the recordings.
First, the stimuli consisting ofR clicks (100 msec dumtion) were presented monaurally
through a pair of insert earphones at a rate of 13 per second at 80dBnIll... White noise for
masking the contralateral ear was presented at 60dBnIll.. if an asymmetrical hearing
impairment was present during puretone audiometry.
sweeps were required.
presenting
The same collection procedure was followed during the
of C click stimuli.
average-response
In an average response 2 000
computer.
times at each intensity level.
Responses were recorded and analysed by using an
All responses were repeated twice or, if necessary three
This would increase the consistency of the recordings.
Responses were amplified 100 000 times and the band-pass filters were set at 300 Hz for
the high-frequency noise and at 3 000 Hz for the low-frequency noise at 6 dB per octave.
Responses were averaged by using a 10,24 msec analysis window.
The audiograms,
ABR recordings
and DPgrams together with the Spreadsheets on
Microsoft Excel were handed over to the panel of audiologists. These audiologists are
familiar with the analysis of the selected test procedures. The interpretation of results
was verified and consensus between both audiologists represented a positiv~ criterion.
During the development
of the self-assessment questionnaire a coding information
column "For office use" was included.
A respondent number was allocated to each
subject's completed questionnaire and a variable number was allocated to each data item
or question.
Every answer supplied at each variable was coded in the information area.
The coded information was supplied to the data analyser for computer analysis.
The commercially
available rating scale (RSEE) and questionnaire
(COM-C) were
analysed as follows:
.:. To determine how the subjects rated their hearing abilities in both ears the
prescribed analysis format for the RSEE was used (Schow et al., 1990). The four
item rating scales for each ear were scored as follows:
1 = "good hearing";
2 = "little trouble hearing";
3
= "a lot of trouble
hearing"; or
4 = "1 am deaf'.
Ratings from both ears were combined in the following arrangement:
1 & 1 = 1;
1 & 2 = 2; 1 & 3 = 3; 1 & 4 = 4; 2 & 2 = 5; 2 & 3 = 6; 2 & 4 = 7; 3 & 3 = 8;
3 & 4 = 9, and 4 & 4 = 10. A combined score of 1 or 2 on the RSEE constituted
a pass. A combined score greater than 2 constituted a fiill.
•:. No prescribed method for the analysis of data gathered from the COM-C could be
obtained from the literature.
The researcher developed a method for analysing
this data. Three out of twelve items (one, two and four of Section E, Question 31)
were selected to determine the extent of subjects' communicative competence
during every day life.
Answers "yes" or "sometimes" were interpreted as
indicative of communication difficulties.
The results obtained during puretone audiometry were used to make the initial diagnosis
of normal or abnormal hearing sensitivity. For the putpose of this study, normal hearing
sensitivity
frequencies
was described as thresholds within the 0 - 20 dB HL range, across all
tested (125 - 8 000 Hz) (Jerger & Jerger, 1980).
Abnormal hearing
sensitivity was defined as any threshold below 20 dB HL, at any given frequency tested.
63
It should be noted that the average threshold level (determined according the ANSI-1989
method) was not calculated.
Determining an averaged puretone threshold may result in
some ears being interpreted as displaying normal hearing sensitivity, while the thresholds
in the very low and/or high-frequency range may be elevated.
The abnormal audiograms were categorised according to the configurations illustrated in
Table 3.9.
:m..
A hearing loss greater than 20 dB
across
the frequency range 250 - 4 000 Hz, and
thresholds at each :frequency are within 5 to
10 dB :m.. from each other.
As the frequency increases, the degree of
hearing loss increases. It is characterised by
hearing losses greater than 10 dB
in the
higher frequencies, compared to the low
:frequencies.
:m..
As the frequency increases, the degree of
hearing loss decreases. Thresholds are better
in the higher frequencies. The hearing loss is
at least 10 dB :m.. or more in the low
:frequencies, compared to the high
:frequencies.
The greatest hearing loss is in the low and
high frequencies, and hearing sensitivity is
better in the mid frequencies.
The hearing loss is limited to the high
:frequencies ranging from 4 000 to 8 000 Hz.
If the audiometric configuration could not be
categorised according to the above
mentioned, it was categorised and descnbed
as "other".
After puretone thresholds were analysed the quantitative data was organised, and entered
into the Microsoft Excel Spreadsheet to simplify later processing of data.
Once a valid and reliable DPgram was obtained for each ear the analysis was performed.
At this stage in the clinical development ofDPOAEs there is no ''preferred method" for
analysis (Hall, 2000).
Guidelines developed by Hall (2000) were used for DPOAE
analysis and are displayed in Table 3.10.
Take advantage of the frequency specificity offered by
DPOAEs.
DP amplitude must exceed the noise floor (NF) to be
considered present. Minimal criterion set for the study is
a DP - NF difference ~ 5 dB. This does not imply that the
DP is normal, onI that it is detectable.
If the DP amplitude (ignoring the NF) exceeds some
minimum limit, such as > -10 dB, it is probably not due to
physiological activity from the cochlea. but rather noise
from either the environment or the OAE device.
The DP amplitude values should be reasonably similar
from one DPgram to the next (e.g. ± 2 dB or 3 dB):
There are no
ted idelines for DP reliab·· .
DPOAE interpretation must be performed with reference to
an appropriate normative database. The Vanderbilt 65/55
normative database was selected for the current study.
The DPOAE will be recorded with a protocol similar to the
Vanderbilt 65/55 normative data. DPOAE data versus
normative data was interpreted as a function of stimulus
frequency.
During the analysis of the DPgrams the three DP points per octave, in each of the four
octaves (0.5 - 1 kHz; 1 - 2 kHz; 2 - 4 kHz and 4 - 8 kHz) were analysed separately.
According to Hall (2000) the analysis of DPOAEs will lead to one of three general
outcomes, implemented as follows during the current study:
.:. Outcome one: The DPOAEs were entirely normal.
If one DP point per octave (3 points per octave) fell below the accepted level the
DPgram was still analysed as normal.
.:. Outcome two: The DPOAEs are reduced or abnormal.
No distinction was made between a DP point being reduced or absent. Both of
these findings were analysed as abnormal.
For a DPgram to be analysed as
abnormal, two or three DP points per octave, in all four octaves had to be below
the normal range .
•:. Outcome three: This outcome is a combination of the first two.
lf two or more DP points in a specific octave fell outside the normal range, that
octave was analysed and described as being abnormal.
The results of the DPOAEs were analysed according to the above outcomes and the data
was entered into the Microsoft Excel Spreadsheet.
ABR waveforms
consecutively.
were recorded
for each ear, using both polarities
(R and C)
The waveforms were analysed according to several parameters:
.:. Waves I, ill and V were defined as individual waves being present, which meant
it could be easily identified between other waves. Reduced amplitudes resulted in
waves being analysed as doubtful .
•:. The repeatability of Waves I, III and V was analysed as either acceptable or poor.
Acceptable repeatability of waves meant that two out of the three tracings of that
particular wave were repeatable, as rated by the panel of audiologists .
•:. Absolute latency of Waves I, ill and V was calculated in msec fiom the onset of
stimulus to the peak of the wave .
•:. Interpeak: latency Wave I-III, ill-V and I-V was measured between wave peaks .
•:. Interaural Wave V latency difference refers to the difference of the absolute
latencies of Wave V between the two ears.
.:. The cochlear microphonic is an inverted response prior to Wave 1,when the click
polarity is reversed. The CM was analysed either as being present or absent. It
was described as being present when the potential inverted in all of the traces (in
the same ear) and as absent when no inversion was found after reversing the click
polarity .
•:. The Wave VII amplitude mtio was calculated by dividing the amplitude of
Wave V by the amplitude of Wave 1, and if the mtio was less than 1,0 JlV it was
analysed as abnormal (Hood, 1998). The amplitudes of both Wave I and V was
measured from the peak to the trough of each wave. The mtios of both the R and
C click polarities were recorded.
The absolute and interpeak latencies were classified as abnormal if they were not within
the limits of the following published normative data.
±2,5SD
0,12 ms
1,24 -1,82 ms
0,11 ms
0,10ms
3,44 - 3,94 ms
0,12 ms
3,37 - 3,67 ms
0,19ms
5,07 - 6,01 ms
0,22 ms
4,97 - 6,07 ms
2,14 ms
0,23 ms
1,57-2,71ms
0,14ms
1,78- 2,48 ms
1,86 ms
0,14ms
0,20 ms
1,51- 2,21 ms
0,17ms
1,43- 2,27 ms
3,5 -4,5 ms
0,19 ms
3,51 - 4,45 ms
4,00ms
Sourced from:
(1993:E8)
User Manual of Bio-Logic
System Corporation Evoked Potential
The ABR recordings were analysed as abnormal when one or both ears (using either the
R or C click polarity consecutively) displayed one or more of the following:
k7~~
"~~
The CM is one of two cochlear potentials evoked by sound. It is an alternating current
potential arising mainly from outer hair cells, although there may be limited inner hair
cell contribution
(Hall, 2000).
Dallos and Cheatham (1976) stated that CMs were
potentials generated by activation of both inner and outer hair cells, and their absence is
indicative with impaired hair cell function. Mechanisms underlying the production of the
CM are may involve velocity or acceleration of hair cell movement and displacement of
the basilar membrane.
Withnell (2001) found that the CM was recorded from the round
window and is dominated by cellular generators located at the base of the cochlea.
The presence or absence of the CM was compared to that of the DPOAEs. One might
question the need for including both DPOAEs and the CM in the multiple test battery, as
both of these measurements determine the cochlear hair cell activity. In the current study
the CM was not analysed as part of the EcochG, but rather as part of the ABR recordings.
The analysis of the CM was valuable when used in cohesion with a battery of other test
procedures
since ABR abnormality in the presence of observable DPOAEs, and CMs
were indicative of auditory nerve involvement in the presence of normal cochlear hair
cell function (Starr et al., 2001).
t
0.9 ms delay
After the ABR waveforms for both ears were recorded the pre-programmed Graph
Master (protocol
1) was used during the analysis and interpretation of latencies in
comparison to normative data boundaries.
The GraphMaster is a time saving tool for
data interpretation and its curves represent a range of ± 2.5 standard
evoked-potential
deviation from the mean.
To increase the reliability of data analysis and interpretation, all of the ABR waveforms
were handed over to two clinicians familiar with the interpretation of ABR measurements
when using different click polarities.
All the ABR recordings,
using both polarities consecutively, were categorised and
presented in figures or tables for each group according to the aforementioned examples.
The data was entered into the Microsoft Excel Spreadsheet for analysis.
The coded information of the self-assessment
questionnaire was captured utilising a
computer package (Statistical Analysis System). The printed information was given to
the researcher to locate any errors. Errors were corrected and checked by the researcher
for a second time.
The data was statistically analysed to obtain frequency distribution
presented in forthcoming figures or tables.
All the prepared
data organised on the Spreadsheets was converted statistically to
recognise trends and patterns in the results.
representations
This was illustrated by using graphic
and frequency tables. Correlations between test scores were calculated.
No statistical tests, for example, the ''t-test'', were justified.
This chapter provided a thorough description of the procedures implemented in the
research methodology to acquire the data according to the sub-aims, in order to address
the main aim of the study. The need to determine the contribution of a multiple test
battery approach in a group of adults with Multiple Sclerosis, in order to determine the
clinical usefulness of these test procedures was the driving force behind this research.
The research design was outlined followed by the selection criteria and description of
subjects used in the current study. The material and apparatus used for the selection of
subjects and the collection of data was subsequently discussed, followed by the
procedures for data collection and recording as well as analysisprocedures utilised during
the realisation of the three sub-aims. The chapter was concluded by an overview of the
data processing procedures implementedduring the current study.
CHAPTER 4
RESULTS AND DISCUSSION
The results will be discussed based on the maIn aim of the study, describing and
examining the results obtained from a selected battery of test procedures performed on a
group of adults with Multiple Sclerosis, in order to determine the clinical appropriateness
of the multiple test battery. These results were addressed through the realisation of three
closely related sub-aims.
The purpose of the first sub-aim was to determine the
contribution of a self-assessment questionnaire as part of the multiple test battery. The
second sub-aim was to determine the puretone thresholds as well as cochlear function,
and its contribution as part of the multiple test battery. The third sub-aim was to examine
the contribution of ABR recordings using R and C click polarities consecutively. This
sub-aim was followed by a description of the discrepancies and similarities of different
types of ABR abnormalitieswhen reversing the click polarity.
The purpose of this chapter is to present the results of this study according to the
three sub-aims, in order to address the main aim of the study.
presented
and discussed by integrating
the current
The results are
body of knowledge, and
extracting the significance of results obtained. The results for each sub-aim will be
presented, followed by an interpretation and discussion alongside current literature.
In the final section of this chapter a summary of results as obtained from the
multiple test battery, in realisation of the main aim, will be supplied.
To determine the contribution of a self-assessment questionnaire developed to obtain
i1iformation regarding the subjects' perception
of their hearing abilities, auditory-
vestibular symptoms and communicative competence during every day life.
Results will be discussed in terms of subjects' reported initial MS-related symptoms prior
to their diagnosis as well as, and opposed to, the self-assessment of related hearing
abilities, auditory-vestibular symptoms and communicative competence during every day
life, at the time of the current study.
Subjects reported the following symptoms as part of their initial MS-related symptoms
prior to the actual diagnosis ofMS:
70%
60%
60%
40%
• Paralysis of the anns, legs
and/or trunk
• Vertigo
30%
20%
10%
0%
II Pain in the anns, legs
and/or trunk
Compared to the other related symptoms of MS, tinnitus
were reported by a relatively small number of subjects.
that patients
and difficulty with hearing
Daugherty et al. (1983) found
do not complain of hearing difficulties possibly due to other more
invalidating MS-related symptoms.
Four subjects who reported the presence of tinnitus and/or difficulty with hearing had
also been exposed to single episodes and/or continuous noise, thus MS might not have
been the only cause of these symptoms.
Only a small percentage of subjects reported vertigo as one of their initial MS related
symptoms, as also noted by McAphine et al. (1972).
These numbers can be expected to
increase during the course of the disease due to increased involvement of the peripheral
nerve, cerebellum and/or vestibular nuclei as the disease progresses (Grenman, 1985).
It was concluded
that loss of hearing
and related
auditory-vestibular
symptoms
were not clinically significant as part of the initial MS- related symptoms.
The prevalence of symptoms such as tinnitus, vertigo, dizziness and difficulty with
hearing during the time of the current study were reported as follows:
80%
70%
60%
50%
40%
30%
20%
10%
0%
C Difficulty
ears)
with hearing (both
A high percentage
headedness.
(72 %) of subjects experienced dizziness
or a feeling of light-
Most of the subjects described their dizziness as a balance disturbance and a
feeling of being unsteady.
This may be a form of weakness or co-ordination problem
resulting from cerebellum lesions.
However dizziness may also attribute to balance
disturbances
Other descriptions obtained were "feeling dizzy"
(Lechtenberg,
1995).
during a MS relapse, or experiencing a "floating feeling".
Some subjects reported that
their dizziness occurred when their activity level increased or during exposure to heat. It
is a known fact that MS symptoms will worsen during exposure to heat (Lechtenberg,
1995). The percentage of subjects who reported the presence of dizziness was similar to
that found by Muller (1949), where 78 % of patients experienced balance abnormalities
and 32 % a feeling of giddiness.
According to McAlpine et al. (1972) "giddiness" or
"dizziness" is as common as "true vertigo" in patients with Multiple Sclerosis.
The prevalence of reported vertigo increased during the course of the disease (from 25 %
to 60 %). Grenman (1985) found this to be a typical symptom related to MS. According
to Keith and Jacobson (1985) approximately 50 % of patients report vertigo at some time
during the course of the disease, whereas Martin (1981) found that vertigo can occur in as
many as 75 % of patients.
The reason for this might be related to the specific area of
pathology caused by MS.
True vertigo possibly has its origin in the labyrinth, VIIIth
nerve (vestibular portion), or vestibular nucleus (Barbour, 1985). Less common causes
of vertigo include lesions of the cerebral cortex, cerebellum and the oculomotor apparatus
(Barbour, 1985). It is well known that the vestibular nerve (Ylikoski & House, 1981), as
well as the vestibular afferent pathways (Robinson & Rudge, 1977) can be involved in
the demyelinating process resulting in vertigo. Yon Leden and Horton (1948) also found
that reported symptoms such as unsteadiness, dizziness and vertigo are among the most
common
complaints
during
pathophysiological background.
Due to the high percentage
the
course
of
the
disease,
irrespective
of
the
This was also the case in the current study.
of subjects who experienced
dizziness and vertigo at a
later stage of the disease, and the fact that these vestibular
result of VIUtb nerve involvement,
it can be concluded
these symptoms need to be included in the self-assessment
symptoms may be the
that questions
questionnaire.
regarding
The prevalence of tinnitus experienced before the diagnosis of MS was low, but the
percentage increased to 24 % during the current study.
More subjects belonging to
Group 1 (not exposed to noise) reported the presence of tinnitus.
According to the
literature tinnitus is a rather uncommon complaint in patients with Multiple Sclerosis
(Grenman, 1985).
Nishida et al. (1995) reported that the frequency of tinnitus as an
initial symptom or during the course of the disease has been estimated to be less than
10 %.
Grenman (1985) found that only 8,5 % of patients (including those previously
exposed to high levels of noise) complained of tinnitus while an even lower percentage
was reported by Klugman (2000) and Kahana et al. (1973). These low percentages were
interesting to note since this auditory symptom has been associated with demyelinating
diseases (Lechtenberg & Shulman, 1984).
However, a higher percentage was present
during the current study. Tinnitus is most often caused by a dysfunction of the cochlear
apparatus, but may also be as a result of a dysfunction in the cochlear nucleus or more
central auditory pathways (Barbour, 1985). The two subjects in Group 2 who reported
tinnitus had been exposed to high levels of noise, thus complicating the isolation of the
cause.
Although most of the subjects in both groups rated their hearing abilities as good in both
ears, a small percentage (24 %) of subjects indicated that they experienced little trouble
with hearing in both ears.
groups.
This percentage was equally distributed between the two
Thus exposure to noise could only be a possible contributing factor in half of
these cases.
The six subjects (both groups) who rated their hearing abilities as affected to some
degree, for both ears, made the following statements regarding the onset of the hearing
loss:
.:. three subjects were of the opinion that the onset of their hearing loss was gradual;
.:. two were uncertain; and
.:. one subject reported a sudden loss of hearing.
The latter subject presented with a unilateral mild to moderate sensory-neural hearing
loss. Although sudden loss of hearing sensitivity has been reported in the literature, this
77
finding is rare (in about 1 % of patients) (Bergamaschi et aI., 1997). Furthermore it must
be kept in mind that the presence of MS does not preclude the likelihood of a sudden
hearing loss resulting from other causes (Stach et aI., 1990).
The six subjects who experienced some degree of hearing difficulty described the nature
of the hearing loss as follows:
.:. one subject was of the opinion that the hearing loss remained constant;
.:. one was of the opinion that the hearing loss was progressive;
.:. two observed fluctuating hearing losses; and
.:. two were uncertain.
Despite the above mentioned subjects commenting on the onset and nature of the hearing
losses, another two subjects who rated their hearing abilities as good in both ears, made
the following statements:
.:. one subject believed that the hearing abilities had gradually worsened over the
past 2 years and a fluctuating hearing loss was in fact perceived; and
.:. the other subject experienced difficulty with hearing at a later stage during the
course of the disease.
These two subjects were not included in the percentage as illustrated in Figure 4.2,
because they provided conflicting information.
According to the literature, difficulty with hearing is not a common or prominent
complaint in patients with Multiple Sclerosis (McAlpine et aI., 1972). However the
percentage of subjects rating some degree of hearing difficulty in the current study was
higher than Milller's (1949) 4 % and Noffsinger et aI.'s (1972) finding of approximately
7 % of patients.
Rappaport et aI. (1994) reported that none of their patients had
significant hearing complaints, despite the fact that some of these patients demonstrated
mild high-frequency hearing losses when tested. Grenman (1985) found that only six
patients reported impaired hearing ability in both ears (including patients being exposed
to noise).
However Klugman (2000) reported that 23,3 % of patients experienced
difficulty with hearing in both ears, which correlates with the findings of the current
study.
The relatively low prevalence of both tinnitus and hearing difficulties seemed to be
consistent with the literature accumulated over the last 55 years. These symptoms
are dependent on the site oflesion/(s) and may in some instances not be perceived by
the patients themselves, but may only be identified through appropriate audiometric
testing. Subjects' self-perception of the auditory symptoms should be included as
part of the self-assessment questionnaire considering that it can provide valuable
information, but should not be used in isolation.
The following section will discuss subjects' self-assessment of their communication
competence during every day life, as experienced at the time of the current study. As
stated in Chapter 3, items no. 1,2 & 3 were pre-selected for analysispurposes.
Number of subjects (percentage)
Types of communication
complaints
Group 1 = 15 subjects
Group 2
= 10 subjects
1. People mumble
10 (66,66 %)
6 (60 %)
2. Asking for repetition
11 (73,33 %)
6 (60 %)
4 (26,66 %)
3 (30 %)
11 (73,33 %)
7 (70 %)
8 (53,33 %)
7 (70 %)
6. Difficulty hearing when face not visible
6 (40 %)
6 (60 %)
7. Not hearing the ringing of telephone
3 (20 %)
2 (20 %)
8. Need to turn up volume of TV/ radio
8 (53,33 %)
5 (50 %)
9. Difficulty hearing while using the telephone
4 (26,66 %)
2 (20 %)
1(6,66 %)
3 (30 %)
2 (13,33 %)
0(0 %)
12. Difficulty localising the sound source
8 (32 %)
3 (30 %)
Analysis of items no 1, 2 and 4
(71,06 %)
(63,3 %)
3. Hearing words, but not understanding
4. Difficulty hearing in background noise
5. Difficulty hearing from another room
10. Family noticed hearing problem
I 1. A voids social events
Despite the fact that a high percentage of subjects rated their hearing abilities as good in
both ears, a relatively high percentage of subjects (both groups) were of the opinion that
they often had to ask for repetition, experienced difficulty hearing in the presence of
background noise, and that other people seemed to mumble. Very few subjects reported
difficulty hearing the telephone ringing or when following a conversation
telephone.
over the
It seemed that when the sound source was close to the subjects' ears, they did
not experience difficulty hearing, however when the sound source was further away, like
the television or radio, approximately half of the subjects needed to turn up the volume.
It is interesting to note that although a high percentage of subjects were experiencing
difficulty hearing in the presence of background noise, only a limited number of these
subjects avoid social events where background noise is present. It seemed that difficulty
with hearing did not necessary lead to the perception of a hearing handicap. Musiek et al.
(1989) also found that 40 % of patients with normal puretone thresholds experienced
difficulty with hearing in the presence of background noise while Rappaport et al. (1994)
demonstrated an even lower percentage of only 25 %. However, during the current study
hearing difficulties in the presence of background noise were reported in 73,33 % of the
subjects in Group 1 and 70 % of the subjects in Group 2.
The discussion of the hearing difficulties and communication difficulties during every
day life should be evaluated in the light of two additional findings obtained from the selfassessment questionnaire. These findings are illustrated in Table 4.2.
Table 4.2: Comparing hearing difficulties with other MS-related symptoms and the
affect on quality of life
2. Rating hearing problems as compared to other MSrelated problems:
0(0 %)
1 (10 %)
1 (6,66 %)
0(0 %)
7 (46,66 %)
4 (40 %)
7 (46,66 %)
5 (50 %)
Although most of the subjects experienced difficultywith hearing in scenarios depicted in
items 1, 2 and 4 (Table 4.1), it is evident from Table 4.2 that their quality of life was not
negatively affected. Klugman (2000) reported similar results.
Since general, mental
health and vitality plays a significant role in patients' quality of life (Rothwell et al.,
1997), it is understandable that such a small percentage of subjects were of the opinion
that their quality of life was affected by their hearing difficulties. Most of the subjects
perceived their hearing difficulties as less significant when compared to other MS related
problems. Hearing difficulties were rated as not applicable in 48 % of the cases due to
the fact that a large percentage of the subjects were of the opinion that they had good
hearing abilities.
Klugman's (2000) patients also rated their hearing difficulties as
insignificantwhen compared to other MS-related problems.
Descriptions of scenarios where subjects experienced difficulty with communication
were
obtained
understanding
and
enabled
the
of their communicative
researcher
to
develop
a
comprehensive
competence during every day life.
The
inclusion of a questionnaire, in this case the COM-C (Schow et aL, 1990) was useful,
and should be included in the self-assessment questionnaire.
To determine the contribution of puretone audiometry, DPOAEs and CMs to the multiple
test battery, in order to describe the degree of hearing impairment (as assessed by
puretone audiometry), as well as the type of hearing impairment in terms of sensory
involvement (as assessed by DPOAEs and CMs).
As stated in Chapter 3, puretone thresholds between 0 - 20 dB HL, over the frequency
range 125 - 8 000 Hz were analysed as being within normal limits. A threshold/(s) worse
than 20 dB HL at any given frequency was analysed as abnormal (Jerger & Jerger, 1980).
None of the subjects displayed abnormal thresholds at only one test frequency, but rather
at two or more frequencies.
The DPOAEs were analysed as abnormal according to the
preset Vanderbilt 65/55 Normative Range in the four octaves.
The CM was analysed as
either being present or absent when reversing the click polarity.
The following section will provide the results of the two groups.
First the results of
puretone audiometry, DPOAEs and the CM (as seen during the ABR recordings) of
Group 1 will be provided.
;SUbject
L
R
L
R
L
R
absent
present
abN
N
DomesIBped
2-8 kHz
present
present
abN
abN
abN
4-8 kHz
present
present
N
N
N
abN
4-8 kHz
present
present
abN
abN
Hi~
High-
frequ:n;:y
frequency
8
N
N
present
present
abN
N
frequency
9
abN
abN
1-8 kHz
present
present
N
abN
11
abN
N
4-8 kHz
present
present
abN
N
15
N
N
absent
absent
N
N
16
abN
N
5-2 kHz
present
present
N
N
17
abN
abN
4-8 kHz
present
absent
abN
N
18
N
N
present
present
N
N
19
N
N
present
present
N
N
20
N
N
absent
absent
N
N
22
N
N
present
present
N
N
25
N
N
absent
absent
N
N
R
L
N
N
4
abN
abN
5
N
6
number
10ean
(33;J3%) .
R=Rightear
L= Left ear
N=normal
abN = abnormal
R
4-8 kHz
L
1-8 kHz
4-8 kHz
Sears
(23,33%)
9ears
(30%)
Hi~
Sloping
frequ:n;:y
High-
Notch
Notch
Highfrequency
Normal puretone thresholds across the frequency range (125 - 8000Hz)
in 70 % of the ears.
were illustrated
Eight subjects presented with bilateral normal puretone thresholds
and 5 subjects had normal puretone thresholds in one ear.
Verma and Lynn
(1985)
found 72,5 % of their patients with definite Multiple Sclerosis had normal puretone
thresholds, which corresponds with the findings ofthe current study.
Nine ears (30 %) presented with thresholds outside normal limits.
Two subjects had
bilateral hearing losses and the remaining five presented with unilateral hearing losses.
This finding of a higher prevalence of unilateral hearing losses corroborates
with the
literature, stating that unilateral hearing losses were most often found in patients with
Multiple Sclerosis (Noffsinger et aI., 1972; Citron et al., 1963; Dayal & Swisher, 1967;
Luxon, 1980).
The percentage of ears with abnormal puretone thresholds found in the
current study corresponds
with Dayal et al.'s (1966) study where 35 % of the ears
displayed hearing impairment.
Dayal and Swisher (1967) as well as Von Leden and
Horton (1948) reported higher percentages of 59 % and 43 % of the ears with some
degree of hearing impairment respectively, whereas Mustillo (1984) reported a much
lower percentage of only 7 %.
Although other configurations were also present, those ears with hearing impairment
most often displayed high-frequency hearing losses.
audiometric
configurations,
Studies have shown a variety of
including rising, high-frequency,
dome-shaped
and flat.
Musiek et al. (1989) and Grenman (1985) also noted high-frequency losses to be the most
common configuration
found in patients with hearing losses.
Stach et al. (1990)
predicted that demyelinating lesions that encroach upon or occur at the root of the VIIIth
nerve might cause high-frequency hearing loss in a way similar to the effects of cochlear
nerve tumors.
The abovementioned results suggested that abnormal puretone thresholds were present,
but only in a small percentage
of ears.
It is also suggested that the audiometric
configuration was likely to be as variable as the site-of-lesion, and despite the fact that no
single pattern adequately characterised the hearing impairment associated with MS, high-
frequency audiometric configurations were more apparent. It was predicted that highfrequency hearing losses could be the result of lesions upon or at the root of the VIIIth
When comparing the results of puretone audiometry with those ofDPOAEs (across the
frequency range of 625 - 7 625 Hz) and the CM, the following trends were present:
.:. Normal puretone thresholds and DPOAEs
Seventeen (56.66 %) ears presented with normal puretone thresholds as well as
normal DPOAEs. The presence of normal DPOAEs indicates that the preneural
cochlear receptor mechanism was able to respond to sound in a normal fashion.
However, six ears demonstrated absent CMs, which could have been the result of
inner hair cell damage. Thus only eleven ears displayed no cochlear or sensory
involvement.
•:. Normal puretone thresholds with abnormal DPOAEs
Four ears presented with abnormal DPOAEs despite normal puretone thresholds.
This finding may indicate subtle cochlear involvement that is not detected by the
less sensitive audiogram (Hall, 2000).
However, three of these ears had
measurable CMs, which did not correlate with abnormal DPOAEs. The CM may
be recorded in the absence of DPOAEs if receptor potentials remained intact, yet
the complex mechanisms involved in active processing (motility) were disrupted
(Hall, 2000).
This can indicate that the inner hair cells of the cochlea were
probably intact. Although hearing sensitivity was described as being normal if
thresholds were in the 0 - 20 dB HL range, DPOAEs are likely to be abnormal if
the hearing loss exceeds 15 dB HL (Hall, 2000). Parving et al. (1981) illustrated
cochlear involvement in patients with definite Multiple Sclerosis displaying
normal to near-normal audiometric thresholds using EcochG measurements. The
finding of cochlear involvement in the presence of normal puretone thresholds
have been illustrated by Parving et al. (1981) and also in the current study.
.:. Abnormal puretone thresholds with abnormal DPOAEs
Six ears presented with abnormal puretone thresholds as well as abnormal
DPOAEs. It can be concluded that this indicated outer hair cell damage resulting
in cochlear hearing losses since no middle ear involvement was detected using
either puretone thresholds and/or tympanometry. However, all of these ears
presented with CMs, which can be recorded in the absence of DPOAEs. Withnell
(2001) also found the CM to be present in ears with outer hair cell pathology and
stated that the presence of a CM in the absence of an otoacoustic emission should
not be construed as indicative of normal outer hair cell function.
•:. Abnormal puretone thresholds with normal DPOAEs
Three subjects displayed abnormal puretone thresholds in the right ear despite
normal DPOAEs in those ears. In two of these ears the CM was present. Hall
(2000) provided a possible explanation for the finding of abnormal puretone
thresholds with normal DPOAEs. If the DPOAE amplitudes are entirely normal
despite hearing thresholds exceeding 15 dB HL, one must suspect either invalid
puretone findings or, far less likely, neural (retrocochlear) auditory dysfunction.
The researcher can confirm reliable puretone findings. The fact that MS is a
disease affecting the CNS and that the CM was present may suggest retrocochlear
auditory involvement.
During a further analysis of the abovementioned results, the DPgram was compared with
the configuration of the affected audiograms. This was possible due to the fact that the
frequency of the DPOAE stimulus was aligned with the audiometric frequency and the
DPOAE reflects the integrity of the cochlea at the f2 frequency (Hall, 2000).
The
following results were obtained. As seen in Table 4.3, the high-frequency configurations
corresponded with the DPgrams in the following manner:
.:. three ears presented with abnormal DPgrams in the corresponding high-frequency
octave (4-8 kHz), and the remaining two ears had normal DPgrams in this octave.
However these puretone thresholds were not worse than 30 dB HL at either 6 000
or 8000 Hz);
.:. two audiograms with notch configurations demonstrated corresponding DPgrams;
.:. one ear's audiogram
with a sloping configuration, also displayed abnormal
DPgrams in octaves 2 "-4 and 4 - 8 kHz; and
.:. one ear's audiogram with a dome-shaped configuration (puretone thresholds were
not worse than 25 dB HL or 30 dB HL in the low and
high :frequencies
respectively) also displayed normal DPgrams. These puretone thresholds could
however still produce normal DPgrams (Hall, 2000).
A large percentage of subjects presented with normal puretone thresholds, DPOAEs
and present eMs indicating that no sensory involvement was present. The DPgrams
imitated the audiometric configurations of the affected audiograms in most cases.
The following section will describe the results of puretone audiometry, DPOAEs as well
as the eM (as seen during ABR recordings) of Group 2.
Group2
(n=20
ears)
DPOAEs
(625 - 7 625 Hz)
Octaves affected
Cochlear
microphonic
Puretone
thresholds
(125 - 8 000 Hz)
Configurations
(in case of abN
puretone thresholds)
Subject
number
R
L
R
L
R
L
R
L
R
L
2
N
abN
-
4-8 kHz
present
absent
abN
abN
Highfrequency
Highfrequency
3
abN
abN
4-8 kHz
4-8 kHz
present
absent
N
abN
-
Notch
7
N
N
-
-
present
present
N
abN
-
Highfrequency
12
abN
abN
2-8 kHz
1-4 kHz
present
present
abN
abN
Highfrequency
Other
13
abN
abN
4-8 kHz
4-8 kHz
present
present
abN
abN
Highfrequency
Highfrequency
14
abN
abN
4-8 kHz
4-8 kHz
absent
absent
abN
abN
Highfrequency
Domeshaped
21
abN
abN
1-8 kHz
1-8 kHz
present
present
N
abN
-
Rising
23
N
N
-
-
present
absent
N
N
-
-
24
abN
abN
1-2 kHz
4-8 kHz
1-8 kHz
present
absent
abN
abN
Highfrequency
Highfrequency
26
abN
abN
4-8 kHz
4-8 kHz
present
present
abN
abN
Highfrequency
Highfrequency
Total
abN
R= Right ear
L = Left ear
N=normal
abN = abnormal
15 ears
(75 %)
6 ears
(30 %)
15 ears
(75 %)
Due to the fact that the subjects of this group were exposed to single episodes (for
example subjects no. 7, 12, 13, 14,21 & 26) or continuous levels of noise (for example
subjects no. 2, 3, 23 & 24), the following findings were probably the result of two
pathologies:
(l) cochlear pathology due to noise exposure and/or (2) brainstem
pathology due to MS. Thus the following results of Group 2 may not be exclusively
related to MS:
.:. More ears presented with impaired puretone thresholds than Group 1.
•:. More bilateral than unilateral hearing losses were found.
•:. The affected audiograms consisted of high-frequency configurations (55 %),
characterised by a gradual slope at 6 and 8 kHz and/or 4 kHz. Other audiometric
configurations, such as notch, rising, dome-shaped and other were observed to a
limited extend. Despite this group's history of noise exposure the characteristic
notch configuration was only observed in one ear. However, if subjects were
exposed to noise over several years, the notch can be eXPectedto widen and all
the high frequencies will subsequently be affected (Jorden & Roland, 2000).
According to Ginsberg and White (1994) the threshold at 4 000 Hz will
deteriorate as the damage extends to other high frequencies.
This was not
observed in these audiograms during the current study, as the thresholds were
mostly affected at 8 000 Hz and not at 4 000 Hz. Whether these high-frequency
configurations could be solely attributed to noise-induced hearing losses remains
uncertain, since MS can also affect the puretone thresholds in the high frequencies
(Stach et al., 1990). Furthermore, high-frequency configurations are most often
present in presbycusis, which can't be excluded as a possible cause as subject's
ages ranged from 20 to 50 years and presbycusis can occur from as early as 40
years (Brant & Fozard, 1990).
A high percentage of subjects presented with abnormal high-frequency puretone
audiograms. As discussed this finding cannot be contributed to MS exclusively, since
noise-induced hearing losses and presbycusis cannot be excluded.
When comparing the results of puretone audiometry with those of DPOAEs (across
the frequency range of 625 - 7 625 Hz) and the CM, the following trends were
present:
.:. Normal puretone thresholds and DPOAEs
Although most of the ears in Group 2 displayed outer hair cell damage in the
cochlea, there were three ears, that presented with both normal puretone
thresholds and DPOAEs across all frequencies tested.
Two of the three ears
showed evidence of present CMs, and normal hearing sensitivitywas found.
•:. Normal puretone thresholds with abnormal DPOAEs
Abnormal DPOAEs were present in two ears that displayed both normal puretone
thresholds and present CMs, which again proves that DPOAEs are sensitive in the
detection of outer hair cell damage before it is visible on the audiogram. Hall
(2000) described reduced DPOAE amplitudes even though the audiogram was
still within the normal clinicalregion in patients with a history of exposure to high
levels of noise. The presence of the CM in the absence of the DPOAEs can
possibly be indicative of normal inner hair cell function.
•:. Abnormal puretone thresholds with abnormal DPOAEs
Thirteen ears (65 %) with abnormal puretone thresholds also presented with
abnormal DPOAEs.
This is indicative of outer hair cell damage resulting in
affected thresholds. Only five of these ears had absent CMs and the remaining
eight ears showed evidence of present CMs. These results proved that the CM
could be present in the absence of DPOAEs, which corresponded with Hall's
(2000) findings.
•:. Abnormal puretone thresholds with normal DPOAEs
An additional two ears' DPOAEs were interpreted as normal (only one DP point
in the octave was affected). After closer examination the amplitude of the DP
frequency 7 625 Hz was abnormal, which corresponds well with impaired hearing
sensitivity at 6 000 and 8 000 Hz. These two ears presented with very highfrequency cochlear damage, and thus sensory involvement.
The DPOAE amplitudes were plotted as a function of f2 and are expected to agree with
the
audiogram
configurations
(Hall, 2000).
Due to DPOAEs being frequency
specific, the
of the DPgrams were compared to the puretone audiograms.
The
following results were found:
.:. In those
ears
corresponded
displaying
high-frequency
hearing
losses,
the
audiogram
with the abnormal DPgrams found in the high frequency octave.
Six ears with high-frequency
hearing losses also presented with abnormal
DPgrams in the high-frequency octave (4 - 8 kHz). Of the remaining five ears,
two presented with abnormal DPgrams in octaves 1 - 2, 2 - 4 and 4 - 8 kHz, and
another one with abnormal DPgrams in octaves 2 - 4 and 4 - 8 kHz.
The
remaining two ears had normal DPgrams .
•:. The audiogram of the ear with a rising configuration did not correspond with the
abnormal DPgrams found at octaves 1 - 2 and 4 - 8 kHz .
•:. The
audiogram
of the
ear with
a dome-shaped
configuration
partially
corresponded with abnormal DPgrams found in octave 4 - 8 kHz .
•:. One ears' audiogram could not be categorised and was described under the other
configuration.
The abnormal DPgram in octaves 1 - 2 and 2 - 4 kHz imitated the
audiometric configuration.
A large number of the subjects displayed abnonnal puretone thresholds as well as
abnormal DPOAEs, indicating cochlear involvement. Once again most of the DPgrams
correlated with the audiometric configurations of the affected audiograms.
The inclusion of puretone audiometry
of hearing
audiometry
impairment
contributed
and the configurations
information regarding the degree
of affected audiograms.
Puretone
remaiDS the foundation of every audiometric test battery, but should not
be used in isolation during the assessment of patients with Multiple Sclerosis.
In addition the inclusion of DPOAEs enabled the researcher to objectively assess
those ears displaying normal and abnormal puretone thresholds, to determine
whether sensory and/or cochlear involvement was present. DPOAEs proved to be a
useful tool in identifying those subjects who presented with definite cochlear or
early cochlear damage.
The measurement of an absent CM in the presence of abnormal DPOAEs
contributed to the confirmation of cochlear involvement. However, a present CM in
the presence of abnormal DPOAEs was possibly the result of normal inner hair cell
function.
Furthermore an absent CM in the presence of normal DPOAEs can
possibly be the result of inner hair cell damage and/or impaired synaptic
transmission of the inner hair cells to the dendrites of the auditory nerve fibres
(Withnell, 2001). Thus the CM provided more detailed information regarding the
cochlear function of subjects with Multiple Sclerosis.
The following observations were made when reviewing the results of both groups for
sub-aim two:
.:. Degree of hearing loss
Although not calculated, it was evident that most of the hearing losses were of a mild
degree (20 - 40 dB HL), very few of a moderate degree (55 - 70 dB HL) and only
one ear presented with a puretone threshold of75 dB HL at 6 000 Hz (severe hearing
loss at one frequency). Some investigators generally agreed that when loss of hearing
sensitivity exists, it is of a mild degree and less than 35 dB HL (Luxon, 1980;
Noffsinger et aI., 1972). In fact, profound hearing losses appear not to be typical in
most patients suffering from Multiple Sclerosis (Daugherty et aI., 1983).
.:. Configuration of affected audiograms
The following configurations were observed in the 48 % of ears with abnormal
puretone thresholds:
• Normal
o High-frequency
D Dome-shaped
Notch
OSloping
o Rising
o other
o Ski-slope
o Flat
Slightly more than half of the subjects demonstrated normal puretone audio grams,
with high-frequency hearing losses being the most frequent configuration present.
.:. Puretone audiometry and DPOAEs
The results·ofpuretone
audiometry in conjuction with DPOAEs were as follows:
• Normal puretones &
DPOAEs
DAbnormal
DPOAEs
puretones &
• Normal puretones &
Abnormal DPOAEs
DAbnormal puretones &
Normal DPOAEs
•
No ears presented with abnormal DPOAEs in all four octaves (outcome 2).
•
Thirteen ears (26 %) displayed normal puretone thresholds, normal DPOAEs as
well as observable CMs indicating normal hair cell function, and thus no sensory
involvement.
Twenty ears (40 %) presented with normal puretone thresholds and
normal DPOAEs indicating normal outer hair cell function.
As expected 32 %
and 6 % of these ears belonged to Group 1 and 2 respectively.
•
Twenty-one
ears (42 %) presented
corresponding
with abnormal puretone thresholds with
abnormal DPOAEs in the same ear, of which 12 % and 30 %
belonged to Group I and 2 respectively.
Only five of these ears had absent CMs
and the results were indicative of definite outer hair cell involvement.
•
The remaining 18 % of the ears displayed either abnormal puretone thresholds or
abnormal DPOAEs.
Twelve percent of these ears demonstrated subtle cochlear
involvement without affecting thresholds beyond 20 dB HL. Only 6 % of the ears
presented
with abnormal puretone
indicating retrocochlear involvement.
thresholds
and normal DPOAEs possibly
To determine the contribution of ABRs in subjects with Multiple Sclerosis using both
Rand C click polarities consecutively.
The criteria, possible reasons and examples for ABR abnormality were outlined in
Chapter 3, Table 3.12. A comparison between the two groups and the two polarities will
be provided.
Table 4.5: Distribution of absent and doubtful waves according to both click
polarities for both groups
Wave I (alone)
Wave
m (alone)
I ear doubtful*
I ear
3 ears doubtful
I ear
I ear doubtful
I ear
I ear doubtful
I ear doubtful
3 ears
2 ears doubtful
I ear
2 ears doubtful
I ear
2 ears doubtful
I ear
7 ears
(23,33 %)
R
C
10 ean
(33,33 %)
8 ears
(40 %)
4 ears
(20 %)
= Rarefaction
=
click polarity
Condensation click polarity
*Poor morphology and reduced amplitudes necessitated that the presence of some waves had to be analysed
as doubtful.
Most of the ears in both groups displayed waves that could be described as present. Ears
belonging to Group 2 illustrated a higher percentage of absent and doubtful waves using
the R, compared to the C click polarity.
In both groups the most frequent abnormality observed was an absent or doubtful
Wave ~ with the preservation of earlier waves using the R or C click polarity. The
absence of Wave V with the preservation of earlier waves has not been associated with
high-frequency
cochlear hearing losses in the literature (Hood, 1998; Hall & Mueller
1997). This finding, especially in Group 2, could not been the result of noise-induced
hearing loss.
According to the literature, an absent Wave V with the preservation of
earlier waves was the most common abnormality in patients with Multiple Sclerosis
(Jerger et al., 1986; Chiappa, 1990). The presumed generators of Wave V are the lateral
lemniscus as the auditory nerve enters the inferior colliculus (Hall & Mueller, 1997). The
presence of lesions at these locations and even rostral to the lesions can eliminate
Wave V (Arnold, 2000).
Thereafter, especially the ears of Group 1 demonstrated an absent or doubtful Wave III
with the preservation of Waves I and V. The presumed anatomic generators of Wave m
are structures such as the trapezoid body and superior olivary complex within the
auditory pathways of the pons (Hall & Mueller, 1997). According to Hall and Mueller
(1997) Wave ill is absent either due to a hearing loss or brainstem dysfunction.
Since
most of the ears belonging to Group 1 presented with normal hearing sensitivity, a
brainstem dysfunction is most probably the cause of this finding.
Absent and doubtful Waves III and V with the preservation of Wave I, were found in
only three ears.
This indicates auditory involvement of the acoustic nerve, or at least to
the proximal part of it, seeing as Wave I is generated by the distal part of the acoustic
nerve (Hall & Mueller, 1997). The low percentage of ears presenting with absent waves
after Wave I did not correlate with Jerger et al.'s (1986) findings, where a higher
percentage of ears presented with a loss of all waves after Wave I. However, this finding
was clinically valuable in the current study and can be associated with MS.
Although high-frequency cochlear hearing losses could result in a small or absent Wave I
(Hall & Mueller, 1997), a similar number of ears with an absent and doubtful Wave I
were found between the two groups.
Other possible explanations for this abnormality
could be related to the following:
.:. The high-pass filter of300 Hz could have resulted in a small or absent Wave I due
to an increase in filter distortion resulting in wave alterations (Hall & Mueller,
1997). This filter setting was selected due to the high amount of artifacts found
during the preliminary study .
•:. Although the absence of Wave I was previously reported in patients with Multiple
Sclerosis (Chiappa et al., 1980; Daugherty et aI., 1983; Russolo & Polio 1983;
Verma & Lynn, 1985) this abnormality is uncommon, ranging from 2 - 10 % of
patients
(Bergamaschi
et
aI., 1997).
Evidence
has
linked
segmental
demyelination and abnormal refractory periods to the peripheral nerves of patients
with Multiple Sclerosis (Hopf & Eysholdt, 1978).
The researcher endorsed the possibility that the effects of the central demyelinating
process extend distally, involving the peripheral myelin of the ~
nerve based on the
absence of Wave I (Verma & Lynn, 1985). These results support the contention that
peripheral nerve involvement may occur concomitantly with central lesions and the ABR
was capable of detecting these subclinical lesions (Jacobson & Jacobson, 1990).
The percentages
of both groups using both click polarities were combined.
ABR
abnormality was present in 29 % of the ears during the analysis of the presence of waves
and should therefore be included as one of the criteria to determine ABR abnormality.
Due the fact that the judgment of repeatability is subjective in nature, repeatability was
defined as waveforms being reproduced with at least two repetitions of recordings
performed using identical stimulus and acquisition parameters (Arnold, 2000). The
presentation
of the R and C click polarities consecutively revealed the following
abnormalities in the two groups.
Table 4.6: Distribution
of waves with poor repeatability
according to both click
polarities for both groups
2/20
(10 %)
1/30
(3,3 %)
1/18
(5,5 %)
1/19
(5,2 %)
1/28
(3,5 %)
2/26
(7,6 %)
3/29
(10,3 %)
2/28
(7,1 %)
4/20
(20 %)
5 ears
(5,74 %)
4ears
(7,4 %)
6ears
(15 %)
2 ears
(5,4 %)
R = Rarefaction click polarity
C = Condensation click polarity
Most of the ears in both groups demonstrated repeatable waves. Poor repeatability of
Wave V when using the R click polarity compared to the C click polarity seemed to be
the most :frequent abnormality
observed.
The percentage
of waves with poor
repeatability in the current study was lower than those reported in the literature.
Poor
waveform morphology and trace repeatability are common findings in patients with
Multiple Sclerosis.
abnormalities
Desynchronisation
of neural impulses produced by conduction
associated with MS, are thought to be the major cause of poor ABR
waveform response stability (Drulovic et aI., 1993).
Repeatability of waves is not
dependent on the type of click polarity used, but presumably due to desynchronisation
resulting from neural plaque formation (prasher & Gibson, 1980; Robinson & Rudge,
1980; Jacobson & Jacobson, 1990). However a high number of abnormalities, regarding
the repeatability of waves, were not present despite using both click polarities.
The AL was calculated for waves analysed as being either present or doubtful. Despite
the poor repeatability of waves found in 11 ears (using the R click polarity) and 6 ears
(using the C click polarity) in the two groups, the AL of these waves was still calculated.
The AL of certain waves could be not be analysed using either the R or C click polarity
due to the:
.:. Absence of Wave I in two ears using the C click polarity;
.:. Absence of Wave ill in two ears (R click polarity) and in five ears (C click
polarity); and
.:. Absence of Wave V in one ear (R click polarity) and in three ears (C click
polarity).
Table 4.7: Distribution
of waves with abnormal absolute latency according to both
click polarities for both groups
1/28
(3,6 %)
1/26
(3,8 %)
2/20
(10 %)
1/19
(5,2 %)
1ear
(3,8 %)
2 ears
(10 %)
1ear
(5,2 %)
1/29
(3,4 %)
2 ears
(3,5 %)
R = Rarefuction click polarity
C = Condensation click polarity
Most of the ears displayed waves with normal AL using either the R or C click polarity.
Prolonged latency o/Wave III was the most frequent abnormality in both groups. The
percentages found in the current study were much lower than those in the literature.
Musiek et al. (1989) reported 35 % of 52 ears with abnormal Wave ill latencies using the
R click polarity. Hannley et al. (1983) also found a high percentage of ears with delayed
Wave ill and V latencies in patients with confirmed Multiple Sclerosis and other
investigators such as Robinson and Rudge (1975), Robinson and Rudge (1977), Stockard
. et aI. (1977) and Thorton et aI. (1978) reported a delayed Wave V as the predominant
feature.
The IPL of the following waves could not be analysed using either the R or C click
polarities, due to absent waves:
.:. Wave I-ill and ill-V in two ears (R click polarity) and in six ears (C click
polarity); and
.:. Wave I-V in one ear (R click polarity) and in four ears (C click polarity);
Table 4.8: Distribution of waves with abnormal interpeak latency according to both
click polarities for both groups
1/28
(3,5 %)
R
C
= Rarefaction click polarity
= Condensation click polarity
1/20
(5 %)
1/18
(5,2 %)
1/28
(3,5 %)
5/25
(20 %)
1/20
(5 %)
3/19
(15,7 %)
1/29
(3,4 %)
2/28
(7,1 %)
1/20
(5 %)
1/18
(5,5 %)
3 ears
(3,5 %)
7 ears
(13,2 %)
3ean
(5%)
5 ears
(9%)
The analysis ofIPL did not yield clinically significant results, as most of the ears in both
groups demonstrated normal IPL using either the R or C click polarity. When comparing
the number
demonstrated
of abnormalities
using both polarities,
a larger percentage
abnormal IPL using the C click polarity.
of ears
The Wave III-V interval
prolongation (especially after the presentation of the C click polarity) was most often
observed. This correlated with findings ofChiappa (1990); Lynn et al. (1980); Shanon et
al. (1981) and Hammond et al. (1986), where the Wave ill-V interval was most often
affected.
However, some investigators reported conflicting findings.
Shanon et al.
(1981) and Hannley et al. (1983) found the Wave I-ill interval to be more frequently
affected than the Wave ill-V interval. Abnormal Wave I-V intervals were reported in a
small percentage of patients by Chiappa et al. (1980), which correlates with the current
study's findings.
Abnormal IPL can indicate a deficit in the conduction of neural
impulses from the various generators of the auditory brainstem (Drulovic et al., 1993),
due to demyelinated areas.
The ILD could not be analysed when Wave V was absent in one or both ears. The results
will be provided according to the number ofsubjects, as this is an interaural measurement
between two ears.
The ILD of both groups could not be measured in:
.:. three subjects (C click polarity); and
.:. one subject (R click polarity).
Table 4.9: Distribution of subjects with abnormal interaurallatency
ditJerence of
Wave V according to both click polarities for both groups
4/14
(28,6%)
R = Rarefaction click polarity
C = Condensation click polarity
3/13
(23 %)
3110
(30 %)
2/9
(22,22 %)
The lLD of Wave V was abnormal in a relatively high percentage (26 %) of subjects,
using both click polarities.
The percentage of subjects displaying abnormal ILD of
Wave V was similar for both groups. A slightly increased number of subjects illustrated
abnormal lLD of Wave V using the R click polarity compared to the C click polarity.
The findings of the current study correlated with the 33 % of patients who demonstrated
abnormal lLD of Wave V, using the R click polarity, during a study performed by
Jerger et al. (1986).
The researcher agrees with Arnold's (2000) statement that the ILD of Wave V in the
general population may be a more sensitive measure than the AL of Wave V, due to the
fact that Wave V can be prolonged in one ear relative to the other (but still be outside the
normal range). False positive results could be obtained when a unilateral or asymmetrical
hearing loss is present
The Wave V AL may be significantly prolonged in one ear
simply due to the hearing loss and not as a result of retrocochlear pathology (Arnold,
2000). Owing to the fact that a multiple battery of test procedures was used in the current
study, the presence of mIse positive results was unlikely.
subjects with abnormallLD
Despite the :fact that four
of Wave V also displayed asymmetrical hearing losses (of
which two had bilateral abnormal DPOAEs), the Wave V AL was not significantly
prolonged.
Only one subject presented with prolonged Wave V AL in one ear even
though the puretone thresholds were within normal limits bilaterally.
The lLD is highly sensitive and specific for vJWh nerve tumor detection, however the
literature is scarce on the effect that brainstem lesions (as caused in MS) have on the lLD
of Wave V (Musiek et al., 1994). According to Musiek et al. (1989) the sensitivity of
lLD of Wave V measured in patients with Multiple Sclerosis is lower than is seen in
patients with
vn:rth
nerve tumors.
Brainstem lesions may affect both ipsilateral and
contralateral brainstem auditory pathways, causing similar latency delays of Wave V for
each ear. The met that the aD of Wave V was the only abnormal ABR measure in 4
subjects (using either the R or C click polarity) makes this measure sensitive in detecting
brainstem lesions.
The amplitude ratios of Wave VII were measured and will be discussed in the following
section.
The Wave VII amplitude ratios could not be measured due to the absence of Wave I
and/or V in:
.:. one ear (R click polarity); and
.:. four ears (C click polarity).
When the presence of Waves I and V was described as doubtful, these waves were still
included during the analysis of amplitude ratios.
Table 4.10: Distribution of abnormal amplitude ratios of Wave VII according to
both click polarities for both groups
Polarity
R
Amplitude ratio
of Wave VII
R
C
=
=
Group 2
(0=20 ears)
Group 1
(0=30 ears)
9/29
(31 %)
C
R
C
11/28
(39,28 %)
7/20
12/18
(35 %)
(66,66 %)
Rarefaction click polarity
Condensation click polarity
In determining abnormal ABRs, the amplitude ratio of Wave VII yielded the highest
percentage of abnormality in both groups, using either the R or C click polarity, to such
an extent that in 15 ears (7 ears in Group 1 and 8 ears in Group 2) the amplitude ratio of
Wave VII was the only abnormal ABR parameter.
The amplitude of Wave V was more
reduced than that the amplitude of Wave I. Reduced amplitudes of later ABR waves
have been reported in other ABR studies (Chiappa et aI., 1980; Robinson & Rudge,
1975). No abnormally increased Wave I amplitudes were recorded in the current study.
The following explanations for these findings were supplied in the literature:
.:. Reduced Wave V amplitudes could be the result of poor temporal synchrony of
the auditory nerve (Starr et al., 2001) possibly due to incomplete myelination of
nerve fibres, which is common in patients with Multiple Sclerosis (Elidan et al.
1982) .
•:. Starr and Achor (1975); Hall and Mueller (1997) stated that the amplitude oflater
ABR waves are highly sensitive to brainstem pathology, which resulted in
reduced amplitudes.
This finding was substantiated by Arnold (2000) .
•:. Musiek et al. (1989) stated that the presumed brainstem generators of Wave V
are more likely to be affected in patients with Multiple Sclerosis than those of
Wave I (cochlear nerve) .
•:. According to Hall and Mueller (1997) a Wave I with reduced amplitude could be
present in high-frequency
cochlear hearing losses.
High-frequency cochlear
hearing losses were identified in the current study, which could have contributed
to abnormal Wave VII amplitude ratios.
This could account for the higher
percentage of abnormal amplitude ratios that were present in ears belonging to
Group 2.
In both groups the C click polarity yielded the highest percentage of abnormality. This
could not be related to the specific click polarity since Hughes et al. (1981); Sand and
Sulg (1984) did not find significant differences between the amplitude ratios of Wave VII
when using different click polarities.
A possible explanation for this finding can be
related to auditory nerve fatigue, since the C click polarity was always presented after the
recording of ABRs using the R click polarity.
4.4.7
Discrepancies
and similarities of different types of ABR abnormalities
when reversing the click polarity
ABR recordings were elicited after the presentation of the R and C click polarities and
interesting findings were observed in some of the subjects.
abnormalities
Discrepancies in ABR
were present, even in the same ear, when reversing the click polarity.
Maurer (1985) also described these discrepancies as dependent on the phase of the
stimulus.
More specifically, Wave ill was absent using one click polarity and present using the
reverse polarity in the same ear (under the same recording conditions). This phenomenon
is not present in persons with normal hearing sensitivity or in patients with other
peripheral hearing disorders (Chiappa, 1990).
These findings can have diagnostic
implications for the recording and analysis of ABRs in patients with Multiple Sclerosis.
The following section will describe the discrepancies and similarities of different types of
ABR abnormalities demonstrated in some subjects, as observed during the presentation of
both the Rand C click polarity.
Present V
Doubtful V
Discrepancy
Present III
Doubtful III
Doubtful III
Doubtful V
Absent III
Similarity
Doubtful V
Doubtful V
Discrepancy
Doubtful V
Absent V
Discrepancy
Present III
Douibtful III
Discrepancy
Present III
Absent III
Present V
Similarity
Absent III
Absent V
Doubtful I
Absent III
Similarity
Absent III
Absent III
Discrepancy
Absent V
Present V
Discrepancy
Present I
Absent I
GroupZ
Present I
Present III
Present V
R
C
Absent I
Absent III
Absent V
= Rarefaction click polarity
= Condensation click polarity
As illustrated, 10 ears presented with discrepancies of ABR abnormalities indicating that
an ear displayed present waves in the one phase and absent waves in the other phase.
Similar results were reported by Maurer (1985) and Emerson et at. (1982). Emerson et
al. (1982 did not observe a polarity-dependent
disappearance of Wave V in normal
hearing subjects, and concluded that either an abnonnality or an infrequently occurring
normal variant was the cause.
Only subject no. 25 demonstrated an absent Wave III in both ears using both click
polarities, although Wave V was absent in the left ear when using the R click polarity and
present when using the C click polarity. In subject no. 5 the left ear presented with a
doubtful Wave V using both click polarities.
Repeatable V
Poor ill
R
C
=
=
Poor V
Absent ill
Absent V
Poor I
Repeatable I
Rarefaction click polarity
Condensation click polarity
Discrepancy
Repeatable ill
Poor ill
Similarity
Poor V
Poor V
Discrepancy
Repeatable ill
Poor ill
Repeatable V
Discrepancy
Repeatable V
Discrepancy
Discrepancy
Repeatable V
Poor V
Poor I
Repeatable V
Repeatable I
Discrepancies
in ABR abnormalities
were found in 12 ears.
This indicated poor
repeatability of some waves when using one click polarity, and not when using the other
click polarity. Only subject no. 5 demonstrated poor repeatability of Wave V in the left
ear when using both click polarities.
R
C
= Rarefaction
=
click polarity
Condensation click polarity
Four ears demonstrated normal AL using one phase and prolonged AL when using the
other phase.
Two ears displayed prolonged Wave ill AL using the R click polarity
compared to normal Wave ill AL when using the C click polarity.
Only one ear
presented with prolonged AL of Wave ill when using both click polarities.
According to Hood (1998) different click polarities yielded different AL of waves, for
example:
.:. When using the R click polarity the AL of Wave I and ill is decreased;
.:. The Wave I and ill AL may be prolonged when using the C click polarity; but
.:. There is an insignificant difference in the Wave V AL using either the R or C
click polarity for normal individuals (Hood, 1998).
A
±
2,5 SD :from the mean was applied during the analysis of the AL and thus these
decreased latencies (using the R click polarity) and prolonged latencies (using the C click
polarity) could not have affected the high percentage of different ABR abnormalities
found in the current study.
Prolonged I-III
Discrepancy
Discrepancy
Discrepancy
Dsierepancy
R
C
Normal III-V
Normal I-V
Prolonged I-III
Prolonged I-V
Discrepancy
Normal III-V
Prolonged III-V
Discrepancy
Normal III-V
Prolonged III-V
Similarity
Discrepancy
Prolonged III-V
Prolonged I-V
Prolonged III-V
Normal I-V
Discrepancy
Discrepancy
Discrepancy
Normal III-V
Normal I-V
Normal III-V
Prolonged III-V
Prolonged I-V
Prolonged III-V
Normal I-III
Prolonged III-V
Prolonged I-V
Normal I-III
Normal I-V
= Rarefaction
=
click polarity
Condensation click polarity
Subjects no. 7, 9 and 19 displayed prolonged IPL of Wave ill-V and I-V when using the
C click polarity, but normal IPL of these waves when using the R click polarity (in the
same ear). Subject no. 13 demonstrated prolonged IPL of Wave I-ill and Wave I-V when
using the R click polarity, with normal IPL of these waves when using the C click
polarity.
According to Hammond et al. (1986) significant differences of the IPL in control groups,
in relation to either click polarity or gender, were not present.
However, during the
recording and analysis ofIPL of the current study, 12 ears presented with discrepancies
after reversing the click polarity. Only subject no. 5 demonstrated prolonged Wave ill-V
IPL in the left ear when using both polarities.
The literature suggests that identical abnormalities should occur in both ears, despite the
type of click polarity used (Hammond et· al., 1986). Maurer (1985) found identical
patterns of abnormality in 30 % of ears, but only 4 ears (8 %) displayed identical ABR
abnormalities in the current study when using the two click polarities.
The cases in which ABR recordings were normal using one click polarity and abnormal
when using the reverse polarity, are of particular clinical interest. Whether these ABR
recordings should be regarded as abnormal remains disputed. Hammond et al. (1986)
claimed that this constitutes abnormality, since the absence of similar occurrences was
not reported in control groups. It was also suggested that all patients should be evaluated
using both click polarities consecutively.
Sand (1991b) was of the opinion the ABR
recordings with R versus C discrepancies should be interpreted with more caution as
opposed to those responses where similarity was observed, at least until results from
longitudinal studies are available.
Two explanations were provided, by several researchers for these discrepancies between
ABR abnormalities in the same ear, using the two click polarities:
.:. brainstem pathologies caused by demyelination affecting the auditory nerve at
different levels (Maurer, 1985; Sand, 1991b; Hammond et al., 1986); and
.:. diffuse central conduction abnormality (Chiappa, 1990; Coats & Martin, 1977).
The influence
discrepancies
of cochlear
is uncertain.
pathology
and high-frequency
hearing loss in these
The fact that these discrepancies were also observed in
Group 1 (with less cochlear pathology and/or high-frequency hearing loss), led to the
conclusion
that lesions in the auditory brainstem pathway could have caused these
findings.
ABR recordings were useful in the detection of neural involvement in the subjects,
considering that ABR abnormalities were present in 68 % and 84 % of the subjects, using
the R and C click polarities respectively.
Several researchers only utilised one click
polarity during ABR recordings, and yet the results of the current study indicated that the
C click polarity yielded the highest percentage of ABR abnormality and should therefore
be included during the recording of ABRs. A possible explanation for this finding was
provided by Sand (1991b:296):
"The less synchronized C click evoked neural volley,
may be more sensitive to central demyelination than the R click evoked volley". Both the
R and C click polarity should be presented
consecutively.
More bilateral ABR
abnormalities (indicating bilateral brainstem dysfunction) were illustr:ated, regardless of
the polarity used, which corresponded
with Chiappa et al. (1980) and Jerger et al.'s
(1986) finding of a higher number of bilateral ABR abnormalities. Table 4.15 illustrates
the percentages of abnormal ABRs according to each criterion in both groups using both
click polarities.
17 ears
(28,33 %)
12 ears
(30 %)
9 ears
(6,57 %)
8 ears
(10,2 %)
3 ears
(3,7 %)
3 ears
(7,6 %)
10 ears
(8,4 %)
8 ears
(7%)
25,8%
of subjects
26,1 %
of subjects
20 ears
(35 %)
19 ears
(50 %)
Prolonged absolute latency
ofwaves
The C click polarity yielded the
highest percentage of abnormality
for Group 1.
The R click polarity yielded the
highest percentage of abnormality
forGrou 2.
More ears demonstrated
abnormality when using the
R click polarity in both groups.
Slightly more ears demonstrated
abnormal AL when using the
R click polarity.
More ears demonstrated
abnormality when using the
C click polarity.
The highest percentage of
abnormality was illustrated when
using the R click polarity.
More ears demonstrated
abnormality when using the
C click polarity.
Based on the preceding results, the following criteria for ABR abnormality were found to
be clinically useful during the analysis of ABR recordings:
.:. The presence of waves;
.:. The ILD of Wave V;
.:. The amplitude ratio of Wave V/I;
.:. Reversing the click polarities;
.:. The IPL of waves should be included as the Wave ill-V interval is likely to be
prolonged.
The area between the suspected anatomic generators (the superior
olivary complex and the inferior colliculus) is the longest tract of white matter in"
the eNS, and therefore the most susceptible to the effects of demyelinating
disease (Keith & Jacobson, 1995).
The following criteria for ABR abnonnality were not found to be clinically significant
during the analysis of ABR recordings:
.:. The repeatability of waves; and
.:. The AL of waves.
The purpose of the summary is to combine all the previous results discussed, in order to
provide a quantitative and qualitative description of the effectiveness of a multiple test
battery approach.
Firstly, all the results of sub-aim one, two and three will be tabulated
for each group separately.
The ABR abnormalities will be tabulated for both ears, since
the ILD of Wave V was analysed between two ears. All waves described as doubtful
were included and interpreted as abnormal.
As illustrated in Table 4.16 the :first test procedure was the self-assessment questionnaire
consisting of information
regarding the presence of tinnitus, vertigo and dizziness,
followed by the rated hearing abilities (RSEE), and finally communicative competence
(COM-C) during every day life.
The second test procedure was puretone audiometry.
Thirdly the DPOAEs were performed. This was followed by the absence of the CM as
seen during the ABR recording. The final test procedure was ABRs using both the R and
C click polarities consecutively.
Table 4.16 consists
of eight areas, and every subject's bilateral performance, was
indicated by an "X" for each of the following:
.:. When either the presence of tinnitus, dizziness or vertigo was indicated on the
self-assessment
questionnaire;
.:. When some degree of hearing difficulty was reported by subjects;
.:. When subjects experienced communication difficulties during every day life;
.:. When either ear presented with abnormal puretone thresholds;
.:. When either ear presented with abnormal DPOAEs;
.:. When either ear presented with an absent CM;
.:. Ifeither ear displayed abnormal ABR using the R click polarity; and
.)
If either ear displayed abnormal ABR using the C click polarity .
•:. Subjects who scored either 0/8, 1/8 or 2/8 passed the test battery, and significant
auditory-vestibular symptoms andlor auditory involvement were not present;
.:. Subjects who scored with a total of 3/8, 4/8 or 5/8 will be discussed as the
intermediate group; and
.:. Subjects who scored a total of 6/8, 7/8 or 8/8, firlledthe test battery.
Self-assessment questionnaire
Subject
number
Tinnitus,
Dizziness,
and/or
Vertil!O
Some
degree of
hearing
difficulty
Puretone
DPOAEs
eM
(ontcome3)
ABR
(R)
ABR
Either
ear
Either
ear
-
X
X
X
X
X
X
(C)
Total
COM-C
R
L
R
L
R
X
L
Group 1
15 subjects = 30 ears
X
X
X
X
X
X
X
-
1
4
5
6
8
9
11
15
16
17
18
19
20
22
25
X
X
X
X
Total
13
X
X
-
-
-
-
-
X
X
-
-
X
X
X
-
X
X
X
X
X
X
X
X
X
-
-
-
X
X
X
X
-
-
-
-
-
X
X
-
-
X
-
-
-
X
X
X
X
4
11
X
X
X
-
-
X
-
-
-
X
X
X
-
-
-
-
-
-
-
-
-
X
X
-
-
-
-
-
7
X
X
X
X
-
X
X
-
-
-
7
X
X
X
-
X
X
X
X
X
-
X
X
-
-
-
X
X
X
X
X
4
4
9
11
X
X
X
X
X
X
X
X
X
X
-
X
X
X
X
X
X
X
X
X
X
8
10
5/8
6/8
5/8
6/8
6/8
5/8
5/8
2/8
4/8
7/8
0/8
3/8
4/8
4/8
5/8
Group 2
10 subjects = 20 ears
-
-
-
X
X
X
X
-
-
-
2
3
7
12
13
14
21
23
24
26
X
X
X
X
Total
6
X
R
L
(R)
(C)
X
-
X
X
X
-
X
X
X
X
X
X
X
X
X
X
-
X
X
X
-
-
X
X
X
X
X
X
X
X
X
-
-
-
-
-
-
X
X
X
X
X
X
X
X
X
X
2
6
= failed the test procedure
= Right ear
= Left ear
= Rarefaction click polarity
= Condensation click polarity
9
8
X
X
X
X
1
5
5/8
8/8
3/8
5/8
6/8
5/8
6/8
5/8
6/8
5/8
.:. Two subjects from Group 1 passed the battery oftest procedures;
.:. Another eight subjects failed the battery of test procedures, and were equally
distributed between the two groups .
•:. Fifteen subjects were described as the intermediate group of whom 9 subjects
belonged to Group 1.
Those subjects (no. 15 & 18) who passed the battery of test procedures did not
experienced
clinically
and/or communication
significant
auditory-vestibular
symptoms, hearing difficulties
difficulties during every day life. Only subject no. 15 presented
with bilateral absence of the
using the R click polarity.
eM and
unilateral abnormal amplitude ratio of Wave VII.,
The fuct that a multiple test battery was used to assess these
subjects' auditory nervous system provided a more comprehensive understanding of their
auditory abilities.
Those subjects who failed the battery of test procedures displayed auditory involvement
of either a cochlear and/or neural nature, with corresponding hearing complaints and
related symptoms.
It was expected that more subjects in Group 2, with a risk for noise-
induced hearing loss, would fail the test battery, but this was however not the case.
The intermediate group illustrated the complexity and high variability of different types
of auditory-vestibular
symptoms, cochlear and/or neural involvement between subjects
and once again stressed the importance a of a multiple test battery approach. This group
of subjects'
auditory nervous system should be assessed on a regular basis using a
multiple test battery approach to detect any changes during the course of the disease.
When comparing the findings of all the tests procedures, more subjects from Group 1
reported hearing difficulties, the presence of related auditory-vestibular symptoms and
communication difficulties during every day life. In Group 2 more subjects demonstrated
impaired puretone thresholds and abnormal DPOAEs, indicating a high percentage of
cochlear involvement
in this group, possibly due to a history of noise exposure.
Furthermore all of the subjects in Group 2 displayed ABR abnormality using the C click
polarity indicating additional neural involvement.
The multiple test battery approach was sensitive in detennining the nature and degree of
auditory involvement
in subjects with Multiple Sclerosis.
This approach was also
specific in identifYing those subjects without any obvious symptoms and auditory
involvement.
The use of a multiple
test battery contributed towards forming a
comprehensive
view of the auditory-vestibular
symptoms and auditory involvement of
subjects with Multiple Sclerosis, and should include the following .
•:. presence of tinnitus; since the number of subjects who reported this auditory
related symptom increased during the course of the disease.
Hearing loss is
reported to be the primary risk factor for subjective tinnitus (Chung et al., 1984).
The researcher concluded that the presence of tinnitus was the result of outer hair
cell damage (in most of the cases). However, some of the subjects also displayed
ABR abnormalities (using either the R or C click polarity), and the question
whether brainstem abnormalities
also contributed to the presence of tinnitus
remains unsolved .
•:. subjective perception of hearing
experienced
abilities; since the number of subjects who
hearing difficulties as an initial MS-related symptom increased
during the course of the disease.
Whether subjects' perception of hearing
difficulties was solely due to cochlear hearing loss remains uncertain, since some
subjects also demonstrated ABR abnormalities (using both polarities) and the
perception
of hearing
difficulties
could be attributed
to neural
auditory
involvement.
.:. perception
of communicative
competence
during every day life; since this
would also describe the various scenarios where communication difficulties were
experienced
during every day life.
In most cases sensory involvement was
present in subjects who reported communication difficulties, although a small
number of subjects only presented with neural involvement, despite complaining
of communication difficulties.
The multiple test battery should also include procedures to assess the degree of auditory
involvement and procedures to determine whether this involvement is the result of
cochlear damage and/or neural involvement.
•:. Pw-etone
audiometry
was included to determine the extent of hearing
impairment and the configurations of affected audiogram.s. Although this test
procedure does not supply information regarding the site-of-lesion, it was
valuable when u.sedin combination with other test procedures.
•:. The analysis of the eM as seen during ABR recordings was applied to determine
hair cell involvement.
In some cases the absence of the CM and abnormal
DPOAEs resulted in the diagnosis 'of definite cochlear involvement, although
most of the ears demonstrated the presence of the CMin the absence of some DP
points.
The effectiveness of the CM (applied in isolation from the DPOAE
findings) in the differential diagnosis of inner ear/auditory nerve disorders was
not found to be clinically significant during the current study. When used in
combination with the DPOAE findings, it resulted in the conclusion that inner
hair cell activity could have contributed to the presence of the CM in some ears
with abnormal DPOAEs.
•:. The DPOAE is an objective test procedure to detect outer hair cell involvement
and should therefore be included as part of the multiple test battery. Even
subjects who were not exposed to high levels of noise presented with cochlear
involvement, indicating that the perception ofMS, as being a disease that only
affects the brainstem structures, could be questioned. The CM and DPOAE
alternations found in subjects in the current studyprovided a strong presumption
that cochlear functions can be involved in this disease. This finding was verified
by a study on auditory neuropathy by Starr et al. (2001). They were however
unable to distinguish whether the alternations of cochlear hair cell functions were
a cause or a consequence of disordered auditorynerve activity considering that
auditory nerve function could also be impaired if the site of the lesion was the
inner, outer hair cells and/or the synapse between the inner hair cells and the
V~
nerve dendrite (Harrison, 1998). Due to this uncertainty, ABR recordings
should be included in the test battery.
•:. One might question the effectiveness of ABR recordings used on subjects with
hearing impairment since the degree and configuration of the audiograms can
influence the ABR recordings. This was however not the case in the current
study. Most of the high-frequency hearing losseswere not steep and ofa mild to
moderate degree.
Hood (1998) stated that if the hearing loss is less than
60 dB m.., and cochlear in origin, then normal ABRs to high-intensity clicks are
the expected result. The expected ABR abnormalitiesin conjuction with highfrequency hearing losses are that of prolonged or absent Wave 1, or sometimes
reduced Wave I-V IPL.
These expected abnormalities were addressed by
adjusting the stimulus and acquisition parameters such as, presenting a slow
stimulus mte, increasing the stimulus intensity and using insert earphones.
Although absent and poor repeatability of Wave I was found in some ears, no
prolonged Wave I or reduced Wave I-V IPL were observed. As mentioned
previously, the degree of high-frequency hearingloss, could not have contributed
to the abnormalities of Wave I, as was previously observed in the literature
regarding MS. Abnormalities of Wave I have been interpreted as involvement of
the distal vIJth nerve.
The ABR recordings, using both the R and C clickpolarities consecutively, were
especially effective in the current study consideringthat the use of a single click
polarity did not detect abnormality in some cases. It was also possible to detect
the eM after reversing the click polarities and a high number of discrepancies
between different types of ABR abnormalitywereobserved, even in the same ear.
The ABR was also specific in identifYingtwo subjects with bilateral normal
ABRs using both the R and C click polarities. When comparing the ABR
recordings with the results of puretone audiometry and DPOAEs, it was found
that the ABR recordings were sensitive in the detectionof six subjects' displaying
only auditory brainstem involvement, possibly dueto their disease. In these cases
lesions in the brainstem have not yet resulted in impairedpuretone thresholds and
cochlear involvement. Thus a certain level of synchronisation was sufficient for
the perception of puretones, but not for the formationof waveforms (OzOnluet aI,
1998). Dirks' (1978) statement that the CANS is resistant to hearing loss of the
type measured by puretone audiometry was confirmed. It was interesting to note
that five of these subjects were of the opinion that they experienced some degree
of hearing impairment and/or reported communication difficulties during every
day life. These results were also demonstrated in a single case study performed
by James et al. (1983).
In five subjects, ABRs were effective in detecting abnormalities associated with
possible sensory involvement.
The presence of sensory involvement was
uncertain, considering that either unilateral abnormal DPOAEs or unilateral
impaired puretone thresholds were found. Outerhair cells receive a rich efferent
innervation from the CNS and the interaction of DPOAEs with external
stimulation reflects the influence of the CNS on the operation of the cochlear
biomechanical system (Robinette & Glattke, 2000).
Therefore abnormal
DPOAEs could be measured in the presence ofCNS abnormality. Hall (2000)
reported retrocochlear auditory dysfunction with concomitant cochlear deficits
associated with different types, sizes and locationsof tumors. Ohlms et al. (1990)
noted mildly reduced DPOAEs in patients with retrocochlear lesions.
The
researcher could however not trace any studies regarding the effects of
demyelinating disease on the cochlear function, thus the results of abnormal
ABRs as well as DPOAEs, are difficult to explain. The only studies measuring
DPOAEs in patients with Multiple Sclerosis were performed during single case
studies with sudden loss of hearing. Normal DPOAEswere found in the presence
of abnormal ABRs (Robinette & Facer, 1991; Nishida et al., 1995; Cevette et al.,
1995). Considering that four of these subjects presented with bilateral CMs, led
the researcher
to conclude
that abnormal unilateral DPOAEs or impaired
unilateral puretone thresholds, might have been the result of neural involvement.
The multiple test battery approach was also effective in confirming the presence of silent
or subclinical lesions in the auditory pathways of subjects with Multiple Sclerosis. This
implies that the ABRs should detect auditory brainstem involvement in the absence of
clinical findings or reported auditory-vestibular symptoms (Jacobson & Jacobson, 1990).
Three
subjects
reported
no tinnitus,
vertigo,
dizziness,
hearing
complaints
or
communication difficulties but presented with abnormal ABR recordings using either the
R or C click polarity.
A clinically
appropriate
assessment of the auditory
battery
of test procedures
was effective
Due to the
of findings between the subjects, the diverse nature of the disease,
the complexity of the auditory
encounter
the
nervous system of subjects with Multiple Sclerosis. Even
in Group 1, no single pattern of auditory involvement could be observed.
high variability
during
nenrous system and the fact that an audiologist can
patients with Multiple Sclerosis who have been exposed to high levels of
noise, a multiple test battery approach should be implemented.
In this chapter the results obtained in the current study were discussed according to the
three specified sub-aims. These sub-aims were selected in an attempt to answer the main
aim of the study. Each sub-aim provided results that were discussed and integrated with
current literature to ascertain the validity thereof
A summary of results was compiled
from the findings obtained in each sub-aim, and supplied at the end of the chapter. The
results provided the empirical study with some clinical implications for future research
and applications in the clinical setting.
The main aim of the current study was to examine the contribution of a multiple test
battery approach, in order to determine the clinical appropriateness of such a test battery.
The multiple test battery assessed the subjects' self-perception of their hearing abilities,
associated auditory-vestibular symptoms, communicative competence during every day
life as well as the sensory and neural auditory nervous system. Conclusions drawn from
each test procedure, including the implications of the results obtained will be discussed.
This will be followed by a critical evaluation of the research method used in the current
study. A discussion of the major clinical and theoretical implications will be provided.
General aspects regarding the auditory system of patients with Multiple Sclerosis that
emerged from the auditory assessment during the current study, as well as previous
studies, will then be discussed. This will be followed by recommendations for future
research. Despite the discussion of results in Chapter 4, three additional figures were
included in Chapter 5.
One of the most significant findings of the current study was the relatively high
prevalence of auditory and vestibular involvement found in subjects with Multiple
Sclerosis, which could be conclusively identified with a multiple test battery approach.
The findings of the multiple test battery demonstrated that 96 % of the subjects reported
auditory-vestibular symptoms and/or presented with sensory and/or neural auditory
involvementwhen tested with several audiometric test procedures.
The battery of test procedures selected for the current study proved to be effective
and sensitive in detecting auditory involvement during the assessment of the
auditory nervous system of subjects with Multiple Sclerosis. The results provided
support for the application of a multiple test battery approach.
The following information provides a general overview of the results obtained during the
application of the multiple test battery approach.
It is important to draw some
conclusions on the contributions of each test procedure, not necessarily related to the
statistical significancethereof
One of the positive contributions of the self-assessment questionnaire was that it offered
the opportunity to actively involve the subjects during the audiometric assessment. The
subjects reported on their auditory-vestibular symptoms as well as their hearing abilities
and communication competence during every day life.
•:. Initial auditory-vestibular symptoms. Although the prevalence of vertigo, hearing
difficulties and tinnitus were rarely reported as part of the subjects' initial MSrelated symptoms, these numbers seemed to increase by the time of the current
study. Since the symptoms of the disease can fluctuate and are progressive in
nature, it is important to continuously assess these symptoms during the course of
the disease.
•:. Auditory-vestibular symptoms reported during the current study. Most of the
subjects reported the presence of dizziness and vertigo at the time of the current
study. These symptoms can be indicative of VIIIth nerve involvement warranting
the assessment of the vestibular system by using ENG measurements. In the
current study only a few subjects reported the presence of tinnitus, which can be a
symptom of cochlear, VI11thnerve and/or central auditory involvement. Although
Nishida et al. (1995) reported the prevalence of tinnitus to be less than 10 % in
patients with Multiple Sclerosis, it has preciously been associated with
demyelinating diseases (Lechtenberg & Shulman, 1984). The presence oftinnitus
warrants further audiometric assessment to determine the possible site-of-lesion .
•:. Subjective perception o/hearing
abilities. A high percentage of subjects were of
the opinion that their hearing abilities were good in both ears even though other
test procedures indicated cochlear and/or neural involvement. Hearing difficulties
were experienced as insignificant when compared to other MS-related symptoms,
and subjects did not feel that it affected their quality of life. Due to the presence
of mild unilateral hearing impairment and silent lesions without corresponding
hearing complaints, many subjects might have been unaware of impaired hearing
sensitivity.
It is important that patients undergo a comprehensive
hearing
assessment since silent lesions and mild hearing impairment can be detected
during the audiometric assessment, as was the case in the current study .
•:. Communicative competence during every day life. Despite the low percentage of
subjects reporting hearing difficulties in both ears, many subjects experienced
communication
difficulties during every day life. This possibly underlines the
subjects' lack of awareness regarding the relationship between hearing loss and
communication
competence.
It is important for audiologists to include a rating
scale and/or ask specific questions regarding communicative competence during
every day life as part of the audiometric assessment.
The descriptions obtained
did not enable the researcher to ascertain a possible site-of-lesion, but when used
in combination with other differential diagnostic test procedures, it provided a
more comprehensive view of each subject's auditory functioning.
Other audiometric test procedures should not be excluded when ears present with normal
puretone thresholds (as was the case in six subjects displaying bilateral normal puretone
thresholds), since some of these ears presented neural involvement. On the other hand all
of these subjects reported the presence of tinnitus, vertigo, dizziness, some degree of
hearing difficulty and/or communication difficulties during every day life. Therefore the
presence of any subjective complaint, despite normal hearing sensitivity, necessitates
further assessment using site-of-Iesion test procedures.
Despite the low percentage of subjects displaying abnoImal puretone thresholds (30 % of
subjects in Group 1), the presence of a hearing loss raises an interesting theoretical
question. Does MS cause the audiometric deficit or were the obseIVed hearing losses due
to other unrelated factors such as aging, noise trauma and ototoxic drugs? The problem is
complicated by the fact that many different audiometric configurations were observed in
the puretone thresholds
of patients with Multiple Sclerosis.
Care was exercised in
controlling the contaminating effects of these unrelated factors during the current study.
It can be concluded that MS was the cause of at least some, ifnot most, of the commonly
observed high-frequency hearing losses, especially the unilateral hearing losses and rising
configurations found in Group 1.
5.2.3 The contribution of DPOAEs and the
eM in conjunction with
puretone
audiometry
The inclusion of DPOAEs and CMs as part of the multiple test battery provided the
researcher with the opportunity to assess the subjects' cochlear function, an aspect not
:frequently included in previous studies. Figure 5.1 illustrates the results ofDPOAEs and
CMs in conjunction with the findings of pure tone audiometry.
• Normal DPOAEs &
Puretone with CM
o Normal DPOAEs &
Puretone without CM
• Normal DPOAEs &
Abnormal Puretone
II Abnormal DPOAEs &
Normal Puretone
IlIIAbnormal DPOAEs &
Puretone with CM
III Abnormal DPOAEs &
Puretone without CM
Figure 5.1: Concluding fmdings ofDPOAEs and eMs in conjunction with the
results of pure tone audiometry
.:. Normal DPOAEs and puretone thresholds with an obsenrable
CM were
present in 26 % of ears, indicating the absence of sensory involvement .
•:. Normal DPOAEs and puretone thresholds without an obsenrable CM were
present in 14 % of ears, indicating normal outer hair cell function, but possibly
some inner hair cell involvement and thus sensory involvement of some kind .
•:. Normal DPOAEs and abnormal puretone thresholds were present in 10 % of
ears, indicating normal outer hair cell function. This finding could have been the
result of neural involvement.
The CM was absent in only one ear and some
degree of cochlear involvement could be argued .
•:. Abnormal.DPOAEs
and normal puretone thresholds were present in 12 % of
ears, indicating subtle cochlear. involvement without affecting the puretone
thresholds.
involvement.
The CM was absent in one ear due to outer and/or inner hair cell
DPOAE measurement was more sensitive in detecting outer hair
cell involvement than the analysis ofCMs, in these ears.
.:. Abnormal DPOAEs and puretone thresholds with an observable
eM
were
present in 28 % of ears, specifically indicating outer hair cell involvement.
.:. Abnormal DPOAEs and puretone thresholds without an observable CM were
present in 10 % of ears, indicating sensory involvement.
Twenty-six percent of the ears that displayed abnormal DPOAEs and puretone thresholds
belonged to Group 2, and the hearing impairment could also have been the result of noise
exposure.
However, a percentage of these abnormal findings could also be the result of
MS.
The CM was present in 46 % of ears in conjunction with abnormal puretone thresholds
and/or DPOAEs.
Hall (2000) also reported this finding, especially if the receptor
potentials remained intact, while the complex mechanisms involved in active processes
(motility) were disrupted.
Additionally, the fact that the CM generation is not entirely
dependent on outer hair cell functioning, but also due to some inner hair cell contribution,
the CM in the absence of some DPOAEs may indicate normal inner hair cell function.
The analysis of the CM in the current study was useful, but cannot be effectively applied
and interpreted without including DPOAEs.
Figure 5.2: Concluding findings of ABRs (using the R click polarity) in conjunction
with DPOAEs
By performing an objective test procedure such as ABR in conjunction with DPOAEs, a
differential
diagnosis
could
involvement (Hall, 2000).
be made between
cochlear
and retrocochlear/neural
It was concluded that the highest number of ears (32 %)
displayed both cochlear and retrocochlear involvement (as determined by abnormal
ABRs and DPOAEs), whereas fourteen ears presented only with neural/retrocochlear
involvement.
Ten of the ears (20 %) displaying both cochlear and retrocochlear
involvement belonged to Group 2.
Figure 5.3: Concluding findings of ABRs (using the C click polarity) in conjunction
with DPOAEs
An equal number of ears (28 %) displayed either only retrocochlear/neural involvement
or both cochlear and retrocochlear involvement.
Figure 5.2 when using the R click polarity.
Similar numbers were illustrated in
Eleven ears demonstrated both normal
DPOAEs and ABRs using the C click polarity, and these ears presented with normal
cochlear and neural functioning. Only eleven ears (22 %) presented with only outer hair
cell involvement, since DPOAEs abnormality was found in 4 ears from Group 1 and 7
ears from Group 2, in the presence of normal ABRs. The inclusion of ABR recordings
and DPOAEs were valuable during the assessment of subjects with Multiple Sclerosis.
The criterion for ABR abnormality that yielded the highest percentage of abnormality
(using either of the click polarities) was the amplitude ratios of Wave VII, followed by
the absence of waves and the ILD of Wave V. The C click polarity yielded the highest
percentage
of unilateral
Additionally,
reversing
or bilateral auditory
the click polarities
involvement on a brainstem
illustrated valuable findings.
level.
A high
percentage of ears illustrated R versus C click polarity discrepancies between different
types of ABR abnormalities.
This can be indicative oflesions at different levels of the
auditory pathway. A small number of ears demonstrated similar abnormalities using both
click polarities.
It was concluded that all the test procedures selected as part of the multiple test battery
approach were effective when used in combination with each other, but not in isolation.
The results of the current findings also demonstrated that the test procedures were
sensitive to both sensory and neuml auditory involvement in a group of adults with
Multiple Sclerosis.
the disease,
This study provided a framework towards better understanding of
and the effect it has on the auditory nervous system.
Audiologists
performing diagnostic measurements need to understand the usefulness and importance
of applying a multiple test battery approach during the assessment of the auditory
nervous system of patients with Multiple Sclerosis. These results can supplement other
assessments
involving evoked potentials and clinical neurological evaluations.
The
audiometric assessment of a patient with Multiple Sclerosis can also provide guidelines
for assistance with auditory problems, for example: assistive listening devices, as well as
monitoring the changing effects of the disease.
The research question was whether a clinically appropriate battery of test procedures
would be able to effectively describe the auditory involvement of patients with Multiple
Sclerosis.
In other words the multiple test battery should accurately identifY those
patients with auditory involvement and not those without. In answering this question the
primary criteria are based on the re6ability and va6dity of the test procedures (Roeser et
al.2000).
Reliability refers to consistency (Roeser et al., 2000): to what extent will the test results
correlate if the test procedures are administered, and then repeated at a differenttime by
the same or different individual.
as effective.
The reliability of a test must be high for it to be viewed
The reliability can be controlled and maintained at a high level by
standardising test administration, ensuring proper equipment calibration, and controlling
patient variables (Roeser et al., 2000) .
•:. The reliability of the self-assessment questionnaire was high since this test
procedure assessed the subjects' perceptions of hearing difficulties, auditoryvestibular
symptoms
and communicative
Several cross-checked
questions
competence during every day life.
were added and answers were confirmed
verbally to determine accuracy before the onset of the audiometric assessment.
.:. Puretone audiometry
participation is required.
is subjective in nature due to the fact that patient
Reliability was increased by preparing each subject for
the testing, ensuring that instructions were understood (Roeser et al., 2000).
Effective co-operation was received from all of the subjects.
responses were observed during threshold determination.
No false positive
.:. Gaskill and Brown (1990) found DPOAE measurements to be extremely stable
over time, and in the current study DPOAEs were only analysed when at least two
DPgrams were repeatable. Therefore DPOAEs seem to be reliable measurement .
•:. According
to Hall (1992) ABR recordings are reliable if the tracings are
repeatable.
However, poor morphology
and repeatability of waves made
identification of waves difficult in some cases. Furthermore Garza et al. (1982);
Prasher and Gibson (1980) and Robinson and Rudge (1980) found the test-retest
reliability of ABR recordings to be poor in patients with Multiple Sclerosis.
The last aspect that also played a role in the reliability of the current study was human
error during data preparation, analysis, and processing.
where possible by electronic preparation,
analysis
of ABR recordings,
Human errors were reduced
analysis and processing of data. However, the
such as the presence of waves, and especially the
repeatability of waves, remains a subjective analysis. Due to this, the results of all the
audiometric test procedures were analysed by a panel of audiologists. All test procedures
implemented were measured as accurately as technology currently allows on calibrated
equipment.
Not only must the test procedures and results be reliable, it must also identify the problem
for which it is being conducted.
The test procedures should be a valid measure of the
disorder for which it was designed. The validity oftest procedures and the results should
correctly identify subjects with disorders (sensitivity), and not those without (specificity)
(Roeser et aI., 2000) .
•:. The self-assessment questionnaire was sensitive to communication difficulties
during every day life and vestibular
symptoms experienced by the subjects.
Furthermore the specificity was high for rating their hearing abilities and auditory
symptoms such as tinnitus.
.:. Puretone audiometry was a valid test procedure for determining if the hearing
sensitivity of subjects was affected, as well as supplying information on the
degree, configuration and type of hearing impairment .
•:. OAEs are a valid auditory measurement with high sensitivity in detecting even
subtle cochlear dysfunction involving the outer hair cells. No reference was made
regarding the specificity ofDPOAEs (Hall, 2000) .
•:. Jerger and Jerger (1983) and Musiek et al. (1983) reported that ABR recordings
had unusually
high sensitivity and specificity rates.
The criteria for ABR
abnormality in the current study were defined as abnormalities found using either
the R or C click polarities (and not both), and this resulted in higher sensitivity but
lower specificity.
Valid ABR recordings are dependent on the hearing sensitivity
and audiometric configuration (Arnold, 2000). The high-frequency hearing losses
found in the current study was of a mild degree, and the configurations of the
affected audiograms were not steep, thus not affecting the validity of the ABR
recordings.
Subjects were recruited by accidental sampling. Additionally a notice was published in
the South African MS Society' newsletter. This method could be viewed as biased if only
subjects with hearing difficulties responded to the notice. However, this was not the case
seeing that only three of the twelve subjects who responded to this notice were of the
opinion that they experienced hearing difficulties.
Information on whether subjects were smoking was not included as one of the criteria for
subject selection. Smoking is related to hearing loss and indirectly affects the prevalence
of tinnitus (Chung et al., 1984). Therefore, it is suggested that subjects who smoke be
excluded in future research studies.
Although
the sample was representative
convenience/accidental
of both sexes and a wide range of ages,
sampling does not allow for generalisations and inferences of
results to the MS population.
Although all the subjects were diagnosed with Multiple Sclerosis, the number and sites of
brainstem lesions, as well as involvement of the auditory pathway were not known to the
researcher.
neurologists.
It would have been possible to obtain this information from subjects'
However, this information would not have been reliable owing to the
following reasons:
.:. some of the subjects did not attend their annual neurological examinations;
.:. others received a MRI by the time of diagnosis, a mean range of 4, 7 years before
the current study;
.:. the course of the disease varies over time;
.:. the symptoms vary from one patient to another; and
.:. MS is progressive in nature.
The fact that the medical history of the subjects was not known implies that no
correlation can be drawn between the findings of the current study, and the number of
known or suspected brainstem lesions. This can be viewed as a limitation of the current
study.
No differentiation
was made between the different severities of MS.
Some of the
subjects experience no difficulty with walking, whereas others used walking sticks and
some were wheelchair bound. Although some reports found a correlation between the
number of auditory abnormalities and the severity of the disease, it could have been
useful to compare the number of auditory abnormalities found in the current study with
the physical severity of the disease.
The test procedures that were selected as part of the multiple test battery for the current
study are available at most universities and educational hospitals, but only in some
audiology
practices.
The necessary referrals ensuring the implementation
of the
suggested multiple battery of test procedures can however minimise this problem during
the assessment ofthe auditory nervous system of patients with Multiple Sclerosis .
•:. The rating scales applied in the self-assessment questionnaire were easy to
complete
ensuring reliable results.
A self-assessment questionnaire
can be
completed during the neurologist clinical examination, and the necessary referrals
made. Only 19 % of the subjects in the current study had previously been referred
for a complete audiometric assessment.
This low percentage proves that there is
as of yet no effective team approach in place between neurologists, general
practitioners and audiologists .
•:. Puretone audiometry forms the foundation of every audiometric test battery, and
although
valuable
information regarding hearing sensitivity was obtained it
should not be used in isolation during the assessment of patients with Multiple
Sclerosis .
•:. By including DPOAEs and CMs, an objective cross-check measurement of the
cochlear function in subjects with Multiple Sclerosis were provided. The results
of the DPOAEs and eMs were compared to abnormal puretone thresholds to
confirm sensory involvement.
Furthermore a correlation was found when the
affected octaves of the DPgram were compared to the configurations of the
affected audio grams.
.:. Except for ABR recordings, no other test procedures were selected to provide a
powerful cross-check on localisation of auditory function and dysfunction within
the brainstem.
Jerger et al. (1986) found that the ABR receives no special
advantage above other measurements such as AR, speech audiometry and MLD.
A high percentage of abnormality, using sophisticated analysis of AR waveforms,
was illustrated.
Hannley et al. (1983) stated that the ABR and MLD had an
equally high rate of identification accuracy, and according to Lynn et al. (1980)
the MLD offered a test instrument not only sensitive to retrocochlear disorders,
but it also offers specificity.
discrimination
Levine et al. (1994) found interaural time
for high-frequency sounds to be the most sensitive in detecting
brainstem lesions when compared to other tests procedures.
Much of the disagreement among previous investigators regarding the prevalence of a
given auditory abnormality can be traced to variation in criteria of abnormality.
To
determine abnormal hearing sensitivity, several criteria can be used:
.:. Northern and Downs (1991) classified normal hearing sensitivity for adults, when
puretone thresholds are between 0 - 25 dB HL, which would have resulted in less
subjects displaying abnormal puretone thresholds .
•:. Martin and Champlin (2000) proposed that 15 dB HL, rather than 25 dB HL must
be considered as the upper limit of normal hearing sensitivity considering that so
many people with hearing thresholds worse than 15 dB HL experienced difficulty
with hearing.
Using this classification system in the current study would have
resulted in an increased number of ears with slight hearing losses, explaining the
high number of subjects experiencing difficulty with communication during every
day life .
•:. During the current study puretone thresholds were expected to be between
o - 20
dB HL to be considered as normal, and may not be sensitive enough in
detecting slight hearing losses.
Differences in ABR analysis may have a substantial effect on the estimated prevalence of
abnormality, especially for ABR absolute latencies. During ABR analysis investigators
used a:
.:. 95 percent criterion (i.e., a result is abnormal when it exceeds the mean ± 2 SD
from the normative data); or a
.:. 99 percent criterion (Le., a result is abnormal when it exceeds the mean ± 3 SD
from the normative data) .
•:. For the current study a
than 0.4
IDS
± 2,5
SD from the mean, an interaurallatency
of greater
for Wave V and the VII amplitude ratio below 1.0 mV was
considered to be abnormal. More ears would have presented with AL and IPL
abnormalities
if a ± 2 SD from the mean had been used to determine ABR
latencies.
The ABR recordings and DPOAEs measurements were analysed according to norms
established
at other facilities, since norms were not available at the facility were test
procedures were performed. The published norms used for the analysis ofDPOAEs and
ABR recordings
were however developed for the same instruments used during the
current study.
5.5 IMPLICATIONS
FOR THE MEDICAL PROFESSION AND THE MS
POPULATION
The current study provided several theoretical and clinical implications for audiologists,
as well as for the medical profession, and the MS population as a whole.
The MS
population, support groups and medical profession, especially neurologists and general
practitioners,
should be aware of the fact that the disease can affect the auditory nervous
system at several levels.
Questions regarding hearing abilities, auditory-vestibular
symptoms and communicative
competence
during every day life should routinely be
included during the medical evaluation of patients with Multiple Sclerosis.
Patients
should be encouraged to report any change in their hearing abilities and related auditoryvestibular
symptoms such as tinnitus, vertigo and dizziness during the course of the
disease.
Increased
patient awareness regarding hearing abilities, auditory-vestibular
symptoms and communicative competence during every day life will result in the referral
of patients
to
comprehensive
audiologists
and ear-, nose-
and throat
specialists,
ensuring
a
assessment and management. This could ultimately increase quality of
life and improve the overall well-being of patients with Multiple Sclerosis.
5.6 RECOMMENDATIONS
FOR CLINICAL USE (CLINICAL
IMPLICATIONS)
.:. A multiple
test battery approach should be followed during the audiometric
assessment of patients with Multiple Sclerosis .
•:. The multiple
subjective
test battery should include infonnation regarding the patients'
perception
communicative
of hearing abilities, auditory-vestibular
competence
during every day life.
symptoms and
This information can be
obtained through the use of a self-assessment questionnaire
and/or personal
interview .
•:. Test procedures
should assess the auditory nervous system on several levels by
including puretone audiometry, DPOAEs, the CM and ABRs .
•:. The presence of a
eM as seen
during ABR recordings does not exclude DPOAEs
from the battery of test procedures since it may reflect the function of the inner
hair cells while DPOAEs can supply information on the outer hair cell function.
Abnormal DPOAEs can be found despite the presence of the CM .
•:. The R click polarity was most often used in studies utilising ABR recordings. As
seen in the current study only a limited number of ABR abnormalities were
observed during the presentation of R click polarity, while the
yielded a higher percentage of abnormality.
Furthennore
.c click
polarity
R versus C click
polarity discrepancies would not have been detected with only the use of one click
polarity.
Due to the high variability of abnonnalities found between the results
obtained, by using the R or C click polarity, ABR recordings should include both
of these polarities performed consecutively.
.:. A high percentage of abnormal Wave VII amplitude ratios were present during
ABR recordings in the current study. The inclusion of this criterion to determine
ABR abnormality
should be considered during other clinical investigations.
Musiek et al. (1989) have also concluded that this parameter should be included
during the determination of ABR abnormality .
•:. Improved comparisons
involvement
between the auditory findings and the level of CNS
will result from knowledge regarding the presence of clinical or
radiological evidence ofbrainstem involvement.
.:. Due to the nature of the disease, any abnormal audiometric pattern may result and
this pattern can be expected to change during the course of the disease .
•:. Several clinical implications need to be considered by the audiologist in the
management of patients with Multiple Sclerosis. Patients with combined cochlear
and neural involvement could be fitted with non-linear hearing instruments, while
the use of FM-systems
are recommended
for those patients with neural
involvement, as well as those experiencing communication difficulties during
every day life.
Several significant aspects requiring further investigation were revealed by the results
obtained,
and conclusions
recommendations
drawn from the current study.
The following specific
apply to future research:
.:. The current study can be repeated using a similar multiple test battery approach
for the assessment of changes due to increased duration and severity of symptoms
(longitudinal tracking) .
•:. Due to the lack of available normative values for DPOAE and ABR recordings, it
is advisable to use a control group of similar gender and age as the sample group .
•:. Patients with Multiple
Sclerosis could seIVe as a pathology group to study
particular aspects of processing, such as OAB suppression .
•:. A wider spectrum of audiometric test procedures to assess different aspects of the
hearing phenomenon in patients with Multiple Sclerosis should be added to the
current battery of test procedures.
This will increase the validity of test results.
For example: electrophysiological tests such as AR, MLR, LVR and EcochG can
be used in future research. The MLR and the LVR will provide more information
on the central auditory system, and specifically the auditory cortex. The P300
Oate or long auditory evoked potential) could be implemented to assess auditory
subcortical brain structures of patients. These test procedures should be used in
cohesion with neurological findings .
•:. Most patients with Multiple Sclerosis experienced vestibular symptoms such as
dizziness, vertigo and balance disturbances during the course of the disease. ENG
measurements could assess these symptoms to determine whether it is related to a
peripheml
or central vestibular disorder.
Due to the pathophysiology
of the
disease, a more central vestibular lesion may account for these symptoms .
•:. A similar study can be performed on patients who are newly diagnosed with
Multiple Sclerosis. Not only will the MRI findings be available, but the site-oflesions (caused by plaques), will also be known. This will allow for comparison
between mdiological and audiometric test results. Conclusions regarding the
reliability
and valid.ity of audiometric
test procedures used on patients with
Multiple Sclerosis can be determined .
•:. Since the ABR amplitude measures vary considerably (Musiek et al., 1989),
further investigation of this parameter should be performed .
•:. More audiological
disorders
research is required
on patients with other degenerative
such as Charcot-Marie- Tooth disease, Alzheimer as well as other
neurological diseases, such as Parkinson's disease and Neurofibrosis.
The ultimate goal of audiological assessment should be to perform a cost-effective and
clinically
effective
battery of test procedures,
in order to ensure comprehensive
assessment of the auditory nervous system ofpatients with Multiple Sclerosis at several
levels.
The effective management of patients with Multiple Sclerosis should include
regular monitoring
of their auditory nervous system and resulting rehabilitation needs.
These needs may vary and should be individualised according to specific needs. Only
through continuous research of neurological diseases like MS, can the most appropriate
multiple test battery approach be identified, and management guidelines be developed
and refined.
"A test battery is the. foundation of responsible and effective auditory
assessment" (Hannley, 1986:1).
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230: 161-170.
The purpose of Appendix A is to provide a description of the neurological disease known
as Multiple Sclerosis.
The name "Multiple Sclerosis" refers to the two features of the
disease:
The first feature is that scattered (multiple) areas in the central nervous system (eNS),
especially
the white matter
surrounding
the ventricular system of the cerebral
hemispheres, the brainstem, cerebellum, optic nerves and the spinal cord, are affected by
demyelination
(Lechtenberg,
1995).
Demyelination is the process during which the
myelin sheaths are damaged or stripped from the nerve fibres. Nerve fibres that are
covered with an insulating myelin sheath are described as myelinated, and this insulation
is as vital to the transmission of information -carrying signals as the fibre itself. It allows
for faster conduction of impulses along the nerve fibre, as well as improved transmission
of closely spaced impulses. Demyelination slows down or blocks the neuro-transmission
of impulses by the nerve.
The second feature of the disease refers to the appearance of hardened (sclerotic) patches
in the involved (or demyelinated) areas of the brain and spinal cord. These sclerosed
patches are called plaques (Lechtenberg, 1995).
Approximately
70 % of patients affected by Multiple Sclerosis are between 20 and 40
years of age at the onset (Grenman, 1985), and there is a predilection for females of about
2 to 1 (Lechtenberg,
1995).
Differences in the prevalence rates for people living at
different altitudes have been well established (Knight, 1992). Temperate zones more
remote from the equator are higher risk zones than those closer to the equator
(Lechtenberg,
1995).
Individuals growing up in tropical regions, such as equatorial
Africa or South America, usually do not develop MS. In the northern part of the United
States, Northern Europe and Canada, the prevalence is about 30-80/100 000. Dean
(1967) reported that the prevalence for white Afrikaans speaking natives was 3/100 000,
and for white English speaking natives it was 11/100000.
It was also found that most
patients with Multiple Sclerosis in South Africa were immigrants from Europe, with a
prevalence of 50/1 00 000. This rate is equivalent to that found in their country of origin.
The diagnosis ofMS is still clinical in nature, aided by laboratory investigations such as
evoked potential measurements, cerebrospinal fluid assay, blood tests, computerised
tomography (CT) and magnetic resonance imaging (MRI) (Hallpike, 1983). In order for
MS to be diagnosed the patient must be of an appropriate age, and must have experienced
at least two remitting episodes of neurological disturbances, implicating two distinct sites
of involvement in the CNS (McDonald & Silberberg, 1986). The typical clinical course
of the disease is one of relapses and remissions, yet usually progressive. Episodes of
acute symptoms are followed by periods of improvement, sometimes with complete
remission, or with residual symptoms or deficits. In some cases the disease takes a
chronic progressive course without remissions (Grenman. 1985). The pathology and
symptom pattern ofMS is highly variable, and thus it should come as no swprise that the
course and prognosis for the disease is equally unpredictable (Knight, 1992).
Pathological studies demonstrated the presence of clinically "silent" demyelinating
lesions. Silent lesions are those that do not result in apparent symptoms, but can be
identified by radiological or electrophysiological studies (Riviera, 1990). The symptoms
of patients with Multiple Sclerosis may vary greatly from patient to patient, as well as
over time in each individual (Lechtenberg, 1995). As the disease progresses, an
increased number of symptoms may emerge. The multiplicityof the overall symptoms
associated with MS is indicated in Table 1.
Table 1: Frequency of related MS symptoms
BIihUlc:e,abn().r'nl8lities'
",'"
,'.
..
.,
- _.
,
;;
"
~'"
-
-,,~:.-.','.
.-,;.
. ".-'
'".
40%
"
32o/c
18o/c
15%
5%
M°tlOP~~
"
A:taxia<>fliri:rbs' ',
""."Di:plopia'
".1Inp()~c:e
'
H~.1OSS'
TicdoUloureaux ,',
5%
4%
2%
Sourced from: Muller (1949:10)
The most :frequently encountered symptom (from an otological point of view) was
disturbances in balance (78 %), whereas hearing loss was a rare complaint associated
with MS (4 %).
The aim of Appendix B is to provide a description of the different courses that the disease
can follow. Noseworthyet
al. (2001) described four courses ofMS:
.:. The relapsing-remitting
(RR) course:
Each flare-up (exacerbation or relapse)
ofa patient's symptoms is a sign that inflammation or demyelination is occurring.
The site of demyelination
in the eNS and the extent thereof determines the
symptoms produced, for example: if demyelination occurs in the optic nerve, the
patient experiences visual disturbances.
When the patient enters a period free of
evolving symptoms, he or she is said to be in remission.
The recovery (or
improvement) after each episode is complete (Lechtenberg, 1995). The relapses
are severe and occur frequently. Following the first attack of the disease, relapses
can occur after months or years. They involve either the re-emergence of old
symptoms or the appearance of new deficits, or both .
•:. The secondary
progressive
course (SP):
In some patients the course of the
disease is initially RR in nature, but develops progressively. In this course of the
disease the related symptoms fiill to remit completely and deterioration becomes
progressive .
•:. The chronic progressive/primary
progressive (PP) course: One symptom after
another appears with no apparent or significant respite from the disease. In this
course of the disease, severe disability increases over time .
•:. Benign course (B): Some patients experience only a few episodes of abruptly
appearing symptoms that resolve quickly and leave no permanent disabilities
(Lechtenberg,
1995). Only after several years the disease will progress and lead
to disability (Knight, 1992).
COVER LETTER, CONSENT FORM,
GENERAL INSTRUCTIONS AND QUESTIONNAIRE
DEKBRIEF, TOESTEMMINGSVORM,
ALGEMENE INSTRUKSIES EN VRAELYS
University of Pretoria
Pretoria 0002 Republic of South Africa Tel (012) 420-23571
420-2816
Fax (012) 420-3517
http://www.up.ac.za
Department of Communication Pathology
Speech, Voice and Hearing Clinic
I am currently studying towards a Masters degree in Audiology at the Department of
Communication Pathology of the University of Pretoria. My field of interest is persons
with Multiple Sclerosis, their hearing abilities and the testing thereof.
WHAT AM I INVESTIGATING?
.:. Multiple Sclerosis can have an effect on the auditory system, either from the ear to
.the brain, or only the au~ory
part Qf the brain. Through simple and advanced
hearing tests this can be investigated.
•:. In addition, I will want to determine your subjective perception of your hearing
abilities, and other related symptoms during the time that you have bad MS.
•:. Many studies about hearing and the testing thereof have been performed overseas.
However, a few studies involving MS (in general) have been performed in SouthAfrica.
The information now obtained could be used to assist audiologists in
eValuatingan individualwith MS more effectively.
WHAT WILL TIllS INVOLVE?
.:. I will need you to fill in the questionnaire and post it back to me. If you meet the
selection criteria that have been ·designed for the study, you will be informed
telephonically. A date and time will be scheduled ~t your convenience for hearing
tests .
•:. I will need to confirm some of your medical information with your neurologist.
(. I will need you to come to the University of Pretoria (Hatfield), Department of
~~._C0IllJ!luni~ation Pathology for your ~aring to be tested.
The testiIlg will take
about two hours. The results will be given to you. Of course there will be no
charge!
WHAT HAPPENS TO THE INFORMATION GATHERED IN THE STUDY?
.:. The researcher (myself), supervisor and co-supervisor involved in this project are
qualified audiologists who will deal with all information in strict confidence.
•:. The information from. the questionnaire and hearing tests will be statistically
evaluated.
•:. You will remain anonymous when I report our findings.
•:. The findings of the study will be made available to you after its completion, if you
so wish.
WHAT HAPPENS IF YOU DON'T MEET THE SELECTION CRITERIA?
.:. Unfortunately, you will not be able to undergo the hearing test .
•:. The information provided in the questionnaire will still be used in the study.
•:. You will be referred to an audiologist in your area if you are interested in
undergoing hearing testing. .
WHAT HAPPENS IF YOU CHANGE YOUR MIND DURING THE STUDY?
.:. You will be able to withdraw at any time.
•:. The study is completely voluntary .
•:. If you change your mind, any benefits that I have offered to you in terms of
information will still be available.
WHAT
IF THE
RESULTS
GENERATE
A NEED
FOR
FURTHER
TREATMENT?
You will be referred to an audiologist in your area for rehabilitation. Your results
may be handed to him or her with your permission.
I wish to thank you in anticipation for your kind cooperation.
Yours sincerely
Rene Hornby
AUDIOLOGIST
Professor Hugo
SUPERVISOR AND HEAD OF
COMMUNICATION
PATHOLOGY DEPARTMENT
If you would like to participate in this study, please complete and sign the consent
form, complete the questionnaire and return both the questionnaire and the form to me
by 30 November 2001, or fax it to (012) 331-4469.
If you have any questions, you
may phone me at (012) 331-4469 (office hours) or 083 701 6618 (after hours).
I,
, am willing to participate
in the study. I hereby give permission that my medical history be provided to you by
my neurologist.
1. Instructions for the answering of questions are provided in ,t~lics at t?e end of
each question. The appropriate answer must be marked with an "x" or be written
in the space provided.
2. It would be appreciated if you could answer the questions as carefully as possible.
The success of this questionnaire depends on the honesty and comprehensiveness
of your answers.
3. The questionnaire consists of eight pages. Completion of the questionnaire should
take about 15 minutes.
5. A stamped envelope is enclosed.
completion.
NOTE:
Please send the questionnaire
to me after
I would appreciate it reaching me by 30 November 2001 at the latest.
The abbreviation
Multiple Sclerosis
MS that is used in the questionnaire
stands for
Respondent number
For office use
VI
CD
1-2
Instr uetions:
Mark the appropriate answer with X. Blank spaces must be written in.
TIONA
Surname and names:
Postal address:
Code:
Telephone number:
(W)
(H):
Cellular
Name of current neurologist(s)?
DrIP rof.
Where is/are he or she located?
Telephone number of neurologist?:
Date of birth:
(year)
(day)_(month)
V2
Age:
Are you male or female?
Were you born in South Africa?
I
I
I
I
I~
10
V3
FEMALE
YES
I~
V4
MALE
NO
10
If not South African, how old were you on immigrating to
South Africa?
Age:
What is your race?
1
Black
2
White
3
Coloured
4
34
-
5
CD
V609
V5
Asian
00
0
06
7-8
12. When were you diagnosed with Multiple Sclerosis?
V7DDDD
(year)
10-13
13. At present, is your MS classified as ... ?
(Please mark the appropriate block with X)
Benign
multiple
sclerosis
1
MS
2
Relapsing/remitting
Secondary
Primary
progressive
progressive
3
MS
4
MS
5
Uncertain
14. When did you first notice symptoms,
V8
D
14
related to MS?
(year)
V9DDDD15-18
15. Which of the following symptoms were some of your initial
symptoms? (You may mark more than one item.)
BAbnormal sensations", for example: feelings of heat, cold,
tingling, pins and needles, crawling, itching in hands/arms/legs
1
Visual disturbances
2
Heaviness or weakness in armsltrunklleas
3
Pain in arms, legs and or trunk
4
Difficulty with hearing
5
Tinnitus (sounds/noiselbuzzina
in ears or head)
V10
1----1 19
6
Vertigo (feeling of spinning or beina drunk)
7
Bladder problems
8
OTHER SYMPTOMS:
(Specify)
V18
1----1---.1 27 -28
V19
1----1---1
V20
V21
~-4---1
1---4---1
29-30
31-32
33 - 34
19. Have you experienced any of the following?
(JPlease answer all questions)
YES
NO
Recurrent or chronic middle ear infections?
Specify:
1
2
V38
Previous ear surgery?
Specify:
1
2
V39
Accidents and/or injuries to ear and/or head?
Specify:
1
2
V40
Exposure to high levels of noise e.g. military,
mining, industrial, hobbies?
Specify:
1
2
V41
(If you answered "yesj were/are hearing
protectors used?
Specify:
1
2
V42
Difficulty with hearina before the onset of MS?
Specify:
1
2
V43
Is there a family history of hearing impairment?
Specify:
1
2
V44
D
D
D
58
D
60
D
D
D
Are you currently aware of a "ringing" or "bUZZing" sound or noise
(tinnitus) in your ear(s) and/or head?
(Please mark one)
YES (DAilY)
1
SOMETIMES
2
NO (NEVER)
3
(If you answered "no", ignore Question 21)
V45
D
57
59
61
62
63
21. Do you notice the "ringing" or "hissing" or other sound or noise
(tinnitus) in your ... (Marl< one)
HEAD
1
BOTH EARS
2
RIGHT EAR
3
LEFT EAR
4
UNSURE OF LOCATION
5
22. Do you ever experience a feeling of dizziness
Iightheadedness?
(Mark one)
V46
D
or
V47
D
1---+----1 69-70
23. Do you ever experience a feeling of movement
yourself or objects (vertigo)? (Mark one)
or spinning
of
V53
24. Mark the option which best describes your hearing in each ear with
x.. If you use a hearing aides), please describe the way you hear
without the hearing aides)
D
LEFT EAR
RIGHT EAR
1
1
2
2
3
3
4
4
MY HEARING IS GOOD
LITTLE TROUBLE HEARING
v54D
v55D
LOTS OF TROUBLE HEARING
I AM DEAF/CANNOT
HEAR
(If your hearing is "good in both ears", ignore Questions 25,26 and 27
and carry on with Question 28)
26.
GRADUAL
1
SUDDEN
2
UNSURE
3
v56D
When, for the first time, did you become aware of difficulty with
hearing?
1
BEFORE YOUR INITIAL (FIRSn SYMPTOMS OF MS
DURING THE TIME YOU EXPERIENCED SYMPTOMS
OFMS
2
ONLY AT A LATER STAGE OF MS
3
OTHER (SPECIFY)
4
V60
STABLE (REMAINS THE SAME)
1
V58
PROGRESSIVE
2
FLUCTUATING
(GETTING WORSE)
(BETTER, WORSE, BETTER)
D
3
4
UNSURE
28.
[==r=J
Have you been referred to an ear, nose and throat specialist,
Audiologist or hearing-aid acoustican for a hearing test during the
time of MS?
~0
~L=J
V59
D
87
84-85
29.
Did that hearing test indicate a hearing loss?
NO
V60
D
88
V61
D
89
2
~
30. Are you currently using a hearing aid or hearin
aids?
YES
NO
SECTION E
.tE
31. Do you experience any of the following hearing problems?
(Please describe the way you usually hear with both
ears. If you use a hearing aides), please describe how you
hear without the aides). Mark YES, SOMETIMES,
or NO for each question. Do not skip a question.)
YES
Have you noticed that people seem
to mumble?
Do you find yourself asking people
to repeat?
Do you hear words but don't
Understand them?
Do you find it difficult to hear in the
presence of background noise, e.g.,
parties or groups?
Do you have diffiCUlty hearing when
someone speaks to you from another
room?
Do you have difficulty hearing when
a speaker's face is not visible?
Have you been told that you have
Missed the ringing of the telephone?
Do you need to turn up the volume of
the TV and/or radio to understand
clearly?
Do you find it difficult to hear while
using the telephone?
Do your family and/or friends say you
have a hearing problem?
Do you avoid social events because
Ivou have difficultv with hearing?
Do you experience difficulty localizing
the direction of sound?
SOMETIMES
NO
1
2
3
V62
90
1
2
3
V63
91
1
2
3
V64
92
1
2
3
V65
93
1
2
3
V66
94
1
2
3
V67
95
1
2
3
V68
96
1
2
3
V69
97
1
2
3
V70
98
1
2
3
V71
99
1
2
3
V72
100
1
2
3
V73
101
32. Do the above-mentioned
of your life? (Mark one)
hearing difficulties affect the quality
YES
1
NO
2
NOT APPLICABLE
3
33. Do you experience your hearing
(Mark one answer only)
problem(s)
0102
as ... ?
o
103
34. Any other comments about your hearing and hearing
problems?
1--.-4f----l
1---4f---4
1---4r----;
1---4r----;
104-105
106-107
108-109
110-111
University of Pretoria
Pretoria 0002 Republic of South Africa Tel (012) 4204111
Fax (012) 362-5190 1362-5168
http://www.up.8C.Z8
Ek is tans
-.
besig met my Meestersgraad
Kommunikasiepatologieaan
In Oudiologie
die Universiteit van Pretoria.
by die Departement
Ek stel belang in persone
met Veelvuldige Sklerose, hul gehoorvermoens en die toetsing daarvan .
•:. Veelvuldige Sklerose kan die gehoorsisteem affekteer, vanaf die binne-oor tot by
die brein. Deur middel van eenvoudige en gesofistikeerde gehoortoetsing kan dit
. geevalueer word .
•:. Ook wil ek graag u
subjektiewe belewenis van u gehoorvermoens
en ander
addisionele simptome wat u mag ondervind gedurende die tydperk wat u MS het,
ondersoek.
.:. Verskeie studies aangaande gehoor en die toetsing daarvan is al oorsee uitgevoer,
maar slegs enkele studies oor MS (in die algemeen) is al in Suid-Afrika uitgevoer .
•
Die inligting wat deur middel van hierdie studie ingewin word, sal oudioloe kan
help om persone met MS meer effektiefte evalueer .
•:. U moet die vraelys invul en aan my terugstuur.
Indien u voldoen aan die seleksie-
kriteria wat vir die studie ontwikkel is, sal ek u telefonies in kennis stel. 'n Datum
en tyd wat vir u gerieflik is, sal vir gehoortoetsing geskeduleer word .
•:. Sommige van u mediese inligting sal deur u neuroloog bevestig moet word.
.:. U moet na die Universiteit van Pretoria (Hatfield), Departement Kommunikasiepatologie, kom vir die gehoortoetse.
Die toetse sal ongeveer twee ure duur. Die
resultate daarvan sal aan u verduidelik word. Dit is natuurlik gratis!
WAT GEBEUR MET DIE INLIGTING WAT VANUIT DIE STUDIE VEKRY
WORD?
.:. Die navorser (ekself), leier en medeleier is almal gekwalifiseerde
oudioloe wat
aIle inligting as vertroulik sal hanteer .
•:. Die inligting wat uit die vraelys en gehoortoetsresultate
verkry is, word statisties
verwerk.
.:. U bly anoniem wanneer resultate in verslagformaat uiteengesit word .
•:. Na die voltooiing van die studie sal die bevindinge aan u beskikbaar gestel word.
WAT GEBEUR INDIEN U NJE AAN DIE SELEKSIEKRITERIA
VOLDOEN
NJE?
.:. Ongelukkig sal u nie die gehoortoetse kan ondergaan nie .
•:. Die inligting wat u in die vraelys verstrek het, kan steeds in die studie gebruik
word .
•:. As u gehoortoetse willaat
ondergaan, kan ek u na 'n oudioloog in u omgewing
verwys.
WAT
GEBEUR
INDIEN
U GEDURENDE
DIE
STUDIE
VAN PLAN
VERANDER?
.:. U mag enige tyd onttrek.
.:. Die studie is heeltemal vrywillig .
•:. Indien u besluit om nie meer betrokke te wees nie, sal at die voordele wat ek in
terme van inligting belowe het, steeds geld.
WAT GEBEUR
AANTOON
INDIEN DIE mSLAG
DAT
VERDERE
VAN DIE GEHOORTOETSE
OUDIOLOGIESE
BEHANDELING
NOODSAAKLIK IS?
.:. U sal na 'n oudioloog in u omgewing verwys word vir verdere rehabilitasie.
uislag van u gehoortoetse kan met u toestemming aan horn ofhaar verskafword.
Die
Rene Homby
OUDIOLOOG
ProfessorH
STUDIELEIER EN
DEP ARTEMENTSHOOF
KO~SrnPATOLOGIE
VAN
Vul asseblief die toestemmingsvorm
in indien u aan die studie wi! deelneem en stuur
dit voor 30 November 2001 saam met die ingevulde vraelys terug aan my, offaks dit
aan (012) 331-4469.
(kantoorure),ofby
As u enige vrae het, kan u my gerus skakel by (012) 331-4469
083 701 6618 (na-ure)
Ek,
, is bereid om aan die studie
deel te neem.
geskiedenis
Hiermee
aan u verkaf.
gee ek toestemming
dat my neuroloog
my mediese
1. Instruksies vir die beantwoording van vrae word aan die einde van elke vraag in
kursief aangedui. Die toepaslike antwoord moet met 'n "X" gemerk word, of die
spasie wat verskafword, moet ingevul word.
2. Ek sal dit waardeer as u die vrae so noukeurig moontlik beantwoord. Die sukses
van die vraelys hang van die eerlikheid en volledigheid van u antwoorde af
3. Die vraelys bestaan uit agt bladsye en behoort ongeveer 15 minute te neem om in
te vul.
5. 'n Gefrankeerde koevert is hierby ingesluit.
Stuur die vraelys asseblief terug
nadat u dit ingevul het. Ek sal dit waardeer indien ek dit teen 30 November 2001
kan ontvang vir die verwerking daarvan.
NEEM KENNIS: Die afkorting MS wat in die vraelys gebruik word, staan vir.
MiiItiple-Saero-SiSorveelvularge-sJaerOse~
Respondentnommer
Vir kantoorgebruik
VI
Instr uksies:
Merk die toepaslike
word
[IJ
1-2
antwoord met X. Oop spasies moet ingevul
ELiNG A
Van en voomaam:
Posadres:
Kode:
elefoonnommer:
0JV)
(H):
Selluler
Wie is tans u neuroloogl?
DrlProf
Waar praktiseer hy of sy?
Neuroloog se telefoonnommer?:
Geboortedatum:
(dag)__
(maand)
Oaar)
V2
Ouderdom:
Is u manlik of vroulik?
I
I
Is u in Suid-Afrika
gebore?
I
I
MANLIK
1[2]
VROULIK
10
JA
1[2]
NEE
10
V3
V4
00
0
34
-
5
Os
Indien u nie in Suid-Afrika gebore is nie, hoe oud was u tydens
immigrasie na Suid-Afrika?
Ouderdom:
Aan watter rassegroep behoort u?
V5
Indier
1
Swart
2
Blank
3
Kleurling
4
vs
[I]
09
7-8
V7DDDD1~13
13. In watter kategorie is u MS tans geklassifiseer?
(Merk die toepaslike blokkie asseblief met X)
Benigne
Relaps/remitting
Sekondere
Primere
Onseker
1
MS
2
MS
3
progressiewe
progressiewe
MS
4
5
D
V9DDDD15-18
V8
14
15. Watter van die volgende geassosieerde simptome van MS het u
die eerste opgemerk? (U mag meer as een merk.)
"Abnormale sensasies" by. gevoel van hitte, koue, tintelling,
naalde en spelde. beweging, jukkerigheid in arms/bene/bolyf
1-----1
25
ANDER SIMPTOME:
(Spesifiseer')
1---+----1
27 -28
Gebruik u tans enige medikasie (behalwe vitamines)?
I
I
JA
NEE
I
1
I
I
2
I
0·37
(Indien u -nee" geantwoord het, ignoreer Vraag 17 en gaan
aan met Vraag 18)
Naam van die medikasie wat tans gebruik word:
NAAM VAN MEDIKASIE
WAARVOOR
GEBRUIK WORD
~-+--;
~-~---;
~-+--;
~-~---;
Het u 'n familielid wat ook met MS gediagnoseer
I
I
Indien
u "ja" geantwoord
is?
JA
NEE
I
I
1
2
I
I
V29
het, wat is die verwantskap?
(Merk asseblief die toepaslike blokkie)
Ouer
1
Grootouer
2
Broer
3
Suster
4
Dom
5
Tannie
6
NeeflNiggie
7
Kind
8
048
38- 39
40 - 41
42-43
44-45
19. Watter van die volgende het u al ondervind?
(.'Aile vrae moet beantwoord word)
JA
NEE
Gereelde of kroniese middeloorinfeksies?
Spesifiseer:
1
2
V38
Eniae oorchiruraie?
Spesifiseer:
1
2
V39
Ongelukke en/of beserings aan kop en/of ore?
Spesifiseer:
1
2
V40
1
2
V41
Indien u "ja" geantwoord het op vorige vraag, het
u gehoorbeskermers gedra?
Spesifiseer:
1
2
V42
Enige probleme met gehoor voor die aanvang
van MS?
Spesifiseer:
1
2
V43
Is daar 'n familiegeskiedenis
gehoorprobleme?
Spesifiseer:
1
2
V44
Blootstelling aan hoe geraasvlakke,
industriE!le of stokperdjiegeraas?
Spesifiseer:
by. militere,
van
D
D
D
D
D
D
D
Is u tans bewus van 'n "suising" of fluitgeluid" of k1ank (tinnitus)
in u oor/ore of kop?
(Indien u "nee" geantwoord
JA (DAAGLlKS)
1
SOMTYDS
2
NEE (NOOln
3
het, ignoreer Vraag 21)
V45
D
57
58
59
60
61
62
63
21. Is h'erdie
·suising" of "fIuitgeluid" of ander geluid in u ....?
I
Merkeen)
~
KOP
1
BEIDEORE
2
REGTEROOR
3
L1NKEROOR
4
ONSEKER VAN PLEK
5
Ondervind u ooit duiseligeheid
V46·D·
65
of 'n gevoel van Iighoofdigheid?
JA (DAAGLlKS)
1
SOMTYDS
2
NEE (NOOln
3
V47
D
ESKRYF ASSEBLlEF:
1---1-----1
Ondervind u 'n gevoel van beweging
ander voorwerpe (vertigo)?
of draaiing
van useIf of
JA (DAAGLlKS)
1
SOMTYDS
2
NEE (NOOln
3
ELiNG D
Merk die opsie wat u gehoorvermoe in elke oor die beste beskryf
met X Indien u 'n gehoorapparaat of -apparate dra, beskryf
asseblief hoe u daarsonder hoor,
V53
D
71-72
L1NKEROOR
1
REGTEROOR
1
2
1
2
1
2
MY GEHOOR IS GOED
EK HET GERINGE
GEHOORPROBLEME
EKHETBAIE
GEHOORPROBLEME
EK IS DOOF/KAN NIE HOOR
NIE
::8 ::
2
(Indien u "gehoor goed is in beide ore", ignoreer Vrae 25, 26 en 27
en gaan voort met Vraag 28)
GELEIDELIK
1
SKIELIK
2
ONSEKER
3
V56
D
26. Wanneer was u vir die eerste keer bewus van probleme met
gehoor?
VOOR U EERSTE M5-SIMPTOME
1
SAAM MET U EERSTE M5-SIMPTOME
2
EERS IN 'N LATERE STADIUM VAN U MS
3
ANDER (SPESIFISEER)
27. Beskryf u gehoorvermoens.
PROGRESSIEF
FLUKTUEER
ORDSWAKKER
ERBETER,VERSLEG,VERBETER
ONSEKER
28.
V60
1
V58
o=J
Dit ... (Merk. een)
BLY DIESELFDE
VERSLEG
4
D
2
3
4
Is u al verwys na 'n oor-, neus- en keelspesialis, oudioloog of
gehoorapparaathandelaar
vir gehoortoetsing in die tydperk wat
u MS het?
59
D
86
84-85
29.
30.
Is 'n gehoorverlies
ge·identifiseer tydens die gehoortoetsing?
tffifE
D
Dra u lans 'n gehoorapparaal of gehooraplral::E
V61
D
89
AFDELING E
31. Ondervind u enige van die volgende gehoorproblerne?
(Dui aan hoe u gewoonlik met beide ore hoor. Indien u 'n
gehoorapparaat dra, dui aan hoe u daarsonder hoor.
Mer/< JA, SOMTYDS of NEE vir elke vraag. Beantwoord
al die vrae).
JA
SOMTYDS
NEE
1
2
3
V62
90
1
2
3
V63
91
1
2
3
V64
92
1
2
3
V65
93
1
2
3
V66
94
1
2
3
V67
95
1
2
3
V68
96
1
2
3
V69
97
1
2
3
V70
98
1
2
3
V71
99
1
2
3
V72
100
1
2
3
V73
101
Korn dit vir u voor asof rnense mornoel?
Moet u 'n spreker vra om te herhaal wat
hy/sy gese het?
Kan u woorde hoor, maar dit nie
verstaan nie?
Ondervind u probleme om te hoor in die
teenwoordigheid van agtergrondlawaai,
bv. partvtiies of tussen croeDe.
Het u probleme om te hoor wanneer
iemand vanuit 'n ander vertrek met u
praat?
Ondervind u probleme om te hoor as die
speker se gesig nie sigbaar is nie?
Het u al die lui van die telefoon nie
gehoor nie?
Moet u die volume van die TV of radio
harder stet om ooed te k.an hoor?
Ondervind u probleme om 'n gesprek te
vololte hoor oor die telefoon?
Is u familie en/of vriende van mening
dat u gehoorprobleme het?
Vermy u sosiale byeenkomste a.g.v.
probleme met gehoor?
Is dit vir u moeilik om te bepaal uit
watter rigting klank kom?
JA
1
NEE
2
NIE VAN TOEPASSING
NIE
3
0102
Een van die meer betekenisvolle robleme van MS
V75,
D
103
Gel kstaande aan die ander robleme van MS
Een van die minder betekenisvolle robleme van MS
V76
1---+---1
V77
1---+---1
V78
1---+---1
V79
...--;---;
V80
104-105
106-107
108-109
110-111
112-113
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