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An audio-vestibular study of 128 children presenting to a specializedpaediatric audio-vestibular clinic: Should every child withhearing impairment have vestibular function assessed?
EWA RAGLAN1,2, PAUL RADOMSKIJ1, JOHN VENESS2 & KAUKAB RAJPUT2
1Department of Audiological Medicine, St. George’s Healthcare NHS Trust, London, and 2Department of Audiological
Medicine, Great Ormond Street Hospital for Sick Children, London, UK
AbstractThis is a study of the vestibular function of 128 children with a varying degree/type and cause of hearing impairmentpresenting to a specialized paediatric vestibular service. It shows that there are some syndromic and non-syndromicconditions that may be associated with vestibular dysfunction. Due to the relatively small cohort of children tested with alesser degree of hearing impairment, the study is unable to confirm the proportional dependence of the presence ofvestibular dysfunction with the degree of hearing impairment but it confirms such a trend. However, it supports earlierfindings that profound hearing loss due to autosomal recessive inheritance associated with mutation in the Connexin 26gene is not associated with vestibular dysfunction of the lateral semicircular canal. It further shows that children withprofound hearing loss and lack of vestibular function present with a history of gross motor developmental delay. It arguesthat the referral of a child for vestibular assessment should be based on the knowledge of syndromic/non-syndromicconditions associated frequently with inner ear anomalies as well as the knowledge of the noxious factors that may lead tovestibular dysfunction and also hearing impairment such as meningitis, rubella, birth risk factors and ototoxicity.
Key words: children, hearing impairment, vestibular dysfunction, Connexin 26
Introduction
Several factors such as anatomical proximity, com-
mon developmental processes, possible susceptibility
to the effects of the same developmental or other
noxious factors all lead to the understanding that
there is a high probability of hearing disorders being
associated with vestibular disorders.
Indeed, this correlation has been documented by a
number of authors (1�3). With the increasing pre-
valence of permanent hearing impairment associated
with increasing age in children (4,5), it is reasonable
to conclude that prevalence of vestibular disorders
should also increase. The prevalence of vestibular
disorders in children in the community is not well
known, although some studies (6) indicate that there
may be an increased prevalence with age. Moreover,
the prevalence of vestibular disorders in children
with hearing impairment ranges between 30% and
40% in different studies, with an increased preva-
lence in children with profound hearing loss (7). It
has been reported that about 30% of children with
congenital autosomal dominant deafness would have
either a unilateral or bilateral vestibular disorder
(8,9). Children with autosomal recessive conditions
(10) and those with progressive mixed hearing loss
were also found to have vestibular abnormalities
(11,12).
Methods
Subjects
One hundred and twenty-eight children of both
sexes with hearing impairment, ranging from 11
months to 18 years of age (mean age, 8�10 years)
were referred to the specialized (third level of care)
paediatric vestibular clinic and studied.
The children with hearing impairments were
referred to the clinic because of symptoms of
dizziness, imbalance or as part of assessment for
pre-cochlear implantation.
Each child had a detailed clinical history taken
(inclusive of motor development status (13)), eye
movement examination, gait and stance tests
on hard floor and on thick padded foam as well as
Correspondence: Ewa Raglan, Great Ormond Street Hospital for Sick Children, Great Ormond Street, London WC1, UK. Tel: �44 207 813 8430.
Fax: �0207 829 7877. E-mail: [email protected]
Audiological Medicine. 2009; 7: 143�147
ISSN 1651-386X print/ISSN 1651-3835 online # 2009 Informa UK Ltd. (Informa Healthcare, Taylor & Francis As)
DOI: 10.1080/16513860903205683
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the head thrust test (14) performed. The audio-
vestibular assessment was followed by aetiological
studies in accordance with the established BAAP
protocol (15) for patients presenting with hearing
impairment. The diagnosis of a child’s medical
condition was made on the basis of the clinical
history, examination and results of the aetiological
tests.
Audiometric assessment
We performed audiometric assessment inclusive of
age appropriate behavioural hearing tests (16),
which was supported by auditory electrophysiologi-
cal results (ABR) where appropriate, and further
complemented by standard measures of middle ear
function and tympanometry (17). From this we were
able to establish not only the presence or absence of
hearing impairment but also its type � conductive,
sensorineural or mixed � as well as the degree of loss,
being mild, moderate, severe or profound, as pre-
sented in Table I (4).
Vestibular assessment
All children had objective vestibular assessments
carried out with eye movements measured using
electro-nystagmography (ENG); in older children
video-nystagmography (VNG) and caloric testing
was also preformed.
The computerized vestibular laboratory (Neuro-
kinetics, Inc.) was able to run a full range of tests,
but the final choice of tests was dependent upon the
child’s maturational age. However, all children were
tested using the rotational techniques, using impul-
sive stimuli at a velocity of 60 s�1 and if possible also
at 90 s�1 and 120 s�1, as well as the sinusoidal
stimuli at a frequency of 0.04, 0.08 and 0.16 Hz with
a peak velocity of 60 s�1.
Depending upon the child’s cooperation, further
tests were carried out such as pursuit, saccades, full-
field optokinetic response as well as subjective visual
vertical and visual horizontal. Where appropriate,
caloric testing was carried out using the Fitzgerald-
Hallpike (18) method of binaural stimulation; re-
sultant data were analysed according to Jongkee’s
(19) formula.
It is important to note that these data relate only
to the function of the lateral semicircular canal,
which is the subject of testing using this battery
approach. Saccular or utricular function was not
tested in this study. The objective test results were
considered to be complementary to the clinical
vestibular assessment.
The obtained results were compared with norma-
tive data for our laboratory (for older children, aged
8�10 years), where abnormal rotational impulsive
response at velocity stimulation of 60o/s is more than
17% and the results of caloric testing are abnormal
when canal paresis is more than 20% and the
directional preponderance is also worse than 20%.
Considering jointly the results of the ENG/VNG
recording and the caloric testing, the vestibular
function was classified as:
. normal;
. hypo-function, where there was a presence of a
spontaneous nystagmus without optic fixation
on gaze testing, a significant directional pre-
ponderance on rotational tests and partial canal
paresis found on caloric testing;
. absent, where there was no response on rota-
tional as well as caloric testing with supporting
clinical history and tests. The diagnosis of
absence of vestibular function bilaterally in
profound hearing impairment was also made
on the basis of combined information from the
positive history of unbalance, especially in
certain situations such as darkness, history of
delayed motor development and the results
of clinical and neurootological assessment
inclusive of a positive Halmagyi response,
abnormalities of gait testing (veering off on
the straight-line walk, widening of the gait
base with eyes closed or blindfolded when
walking or standing, falling on the foam pad
with eyes closed as well as no response on the
rotational and caloric tests described above).
Results
In the studied group there were four children with
various degrees of conductive hearing loss: a child
with dysmorphic features had absent vestibular
function, a child who had vestibular hypofunction
had Down’s syndrome and two children had
CHARGE association (Table II) (20).
There were seven children with a mild degree of
sensorineural hearing loss and totally normal vestib-
ular function and those children had the following
conditions: epilepsy, Arnold-Chiari malformation,
labyrinthine concussion after a head injury, Meniere’s
Table I. Classification of hearing impairment. The level of the
thresholds measured in the better hearing ear at: 0.5, 1, 2, 4
kHz�average hearing level (4).
Mild 20�39dB HL
Moderate 40�69dB HL
Severe 70�94dB HL
Profound ��95dB HL
144 E. Raglan et al.
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disease and three children where diagnosis of the
condition was unknown (see Table III).
There were 20 children with moderate/severe
hearing impairment. In this group thirteen children
had normal vestibular function, inclusive of 10
children with migraine, one with X-linked deafness,
one with global developmental delay and birth
asphyxia. Six children presented with vestibular
hypofunction: three with a large vestibular aqueduct,
one with branchio-oto-renal syndrome, one with
CHARGE association, one with Gaucher’s syn-
drome, and child with CMV had an absent vestib-
ular function (see Table IV).
The largest group studied was that with bilateral
profound hearing impairment. The majority of those
children were assessed pre-cochlear implantation. In
our unit those children undergo a lengthy assessment
process comprising not only audiovestibular and
radiological testing but also a thorough aetiological
evaluation looking for the possible cause of the
hearing impairment. The protocol embraces genetic
testing that consists not only of later genetic coun-
selling but above all routine genetic blood sample
testing for the Connexin 26 mutation (21). In this
large group of 97 children with profound hearing
loss, 40 had normal vestibular function, 36 suffered
with hypo-function and 21 had absent vestibular
function (Table V, Table VI and Figure 1).
Table VI shows the vestibular status of children
with profound hearing impairment due to a variety
of medical conditions (hereditary with different
modes of inheritance, acquired, syndromic). The
striking observation is the result of normal vestibular
function in all children (16) who were shown to be
Connexin 26 positive. All children with absent
vestibular function presented with gross motor
developmental delay.
Of the five children with CHARGE association,
none had normal vestibular function, 3 had absent
vertibular function and 2 presented with a hypo-
function not correlating with the degree or type of
hearing impairment. Seventeen cases were studied
with meningitis with profound hearing loss. Among
those only three had normal vestibular function,
three had hypo-function and 11 had absent vestib-
ular function with a clinical presentation of delayed
gross motor skills.
Conclusions
There are several observations that could be drawn
from this study. Children with profound hearing
impairment and absent vestibular function present
with gross motor developmental delay. Patients who
show profound hearing loss due to the Connexin 26
mutation generally have normal vestibular function
(on testing lateral semicircular canal function).
However, the rate and degree of vestibular dysfunc-
tion in severe/profound hearing loss is generally
higher than in a milder degree of hearing impairment
with the exception of Connexin 26 pathology.
However, some patients have vestibular hypo-
function or absent vestibular function and yet pre-
sent with a varying degree and type of hearing
impairment like CHARGE association and congeni-
tal CMV. The presence or absence of vestibular
dysfunction in patients with hearing impairment
Table II. Conductive hearing loss versus vestibular status (n�4).
Condition Vestibular status
Dysmorphic 1 Absent
CHARGE assoc. �2 Hypo-function
Down’s syndrome �1 Hypo-function
Table III. Degree of SNHL versus vestibular status (n�7) (mild
hearing impairment).
Epilepsy 1 Normal
Arnold-Chiari 1 Normal
Lab Concuss. Post head 1 Normal
Meniere’s disease 1 Normal
Unknown 3 Normal
Table IV. Moderate/severe hearing loss and status of vestibular
system.
Category
Number
(total�20)
Status of
vestibular system
Migraine 10 Normal
CMV 1 Absent
LVA 3 Hypo-function
BOR 1 Hypo-function
X-linked deaf. 1 Normal
CHARGE
assoc.
1 Hypo-function
Gaucher’s
syndrome
1 Hypo-function
Birth asphyxia 1 Normal
Global dev.
delay
1 Normal
Table V. Profound SNHL and vestibular function (n�97).
Normal 40 (41%)
Hypo-function 36 (37%)
Absent 21 (22%)
Audio-vestibular study of children: need for vestibular function assessment 145
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depends upon the nature of the medical condition.
There are some syndromic conditions presenting
with anatomical anomalies of the inner ear where,
regardless of the degree and type of hearing impair-
ment, the vestibular function will be affected such as
in CHARGE association. There will be other
syndromic and non-syndromic conditions that are
not associated with congenital anatomical anomalies
of the inner ear and which will have the vestibular
dysfunction, such as the Usher syndromes or con-
genital cytomegalovirus infection.
Therefore, the decision regarding whether or not
the child should be referred for vestibular assessment
should be based on knowledge of the syndromic and
non-syndromic conditions that may present with or
without inner ear anomalies associated with the
vestibular dysfunction, as well as the knowledge of
the noxious factors that may lead to vestibular
dysfunction such as meningitis, rubella, birth risk
factors and ototoxicity.
A clinical presentation including a history of
dizziness, imbalance or delayed motor development
and profound hearing loss is also an indication for
vestibular assessment.
Discussion
There are a number of reasons why most children
with permanent sensorineural hearing impairment
should have vestibular assessment performed. Not
only does assessment help to confirm the syndromic
diagnosis (Usher syndrome) and provide a more
comprehensive phenotypic picture for the genetic
diagnosis to be made, but also in some cases of
profound hearing loss it may explain the reasons for
the gross motor developmental delay.
Delayed gross motor development observed in
small children with absent vestibular function in-
dicates the importance of these structures in the
normal development of equilibrium. Such children
who have a normal functioning central nervous
system (CNS) will compensate for their loss well
and eventually, by the time they become adolescents,
will have normal balancing function but will need to
be aware of the need to recognize dangerous
environmental situations, such as being in total
darkness (22). Such a situation may lead to disor-
ientation of the vestibular, visual and proprioceptive
input with grave consequences for their well-being.
This study presents a large group of patients with
profound prelingual hearing loss and normal vestib-
ular function (vestibular ocular reflex of the lateral
semicircular canal) who suffer with autosomal
recessive deafness due to a Connexin 26 mutation.
This study corresponds to the results of work of Todt
et al. (23), who reported a normal lateral canal as
well as utricular function in patients with Connexin
26 mutations but abnormal function of the saccule
as tested using VEMPs. Unfortunately this test was
not available for our study at the time.
Table VI. Profound SNHL and vestibular data.
Vestibular function
Category No. Normal
Hypo-
function Absent
Connexin 26 16 16
Auto-dominant 5 3 2
Auto-recessive 10 6 4
Waardenburg
syndrome
6 4 2
Prematurity 2 2
Craniosynostosis 1 1
Maternal rubella 1 1
Pearson’s syndrome 1 1
Head injury 1 1
Auditory neuropathy 1 1
Large vestibular
aqueduct
4 1 3
Mondini defect 1 1
Secondary
endolymphatic
hydrops
1 1
Meningitis 17 3 3 11
Congenital CMV 4 1 0 3
Pendred syndrome 2 2
Usher syndrome 3 2 1
CHARGE
association
5 2 3 1
Moebius syndrome 1 1
Embro
rhabdomysarcoma
1 1
Gentomicin
ototoxicity
1 1
Unknown 13 5 4 4
0
2
4
6
8
10
12
14
16
Connexin26
Auto Rec Auto Dom LVA Meningitis CMV cong Waarden Charge
No
of P
atie
nts
normal
hypo
absent
Figure 1. Profound Hearing Loss versus Vestibular Status.
146 E. Raglan et al.
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The relatively small number of children presenting
with lesser degrees of hearing impairment where
vestibular function was studied does not confirm the
assumption that the increased degree of hearing
impairment is accompanied by an increased rate of
vestibular dysfunction. However, this study shows a
trend between degree of hearing impairment and
presence of vestibular dysfunction. This notion has
been supported by a number of authors (8,9).
At present the needs of this population of patients
are not met adequately and there is unknown
demand for a service. The results of this study
indicate the implication for development of paedia-
tric services inclusive of networked care, need for
development of the vestibular screening battery and
further refinement of qualitative and quantitative
vestibular assessment in children.
Early diagnosis of vestibular dysfunction in
those children and their subsequent management
through appropriate physiotherapy programmes
should lead to potentially better clinical outcomes.
Vestibular assessment should be an integral part of
the evaluation of children with sensorineural hearing
impairment and this view is supported by other
authors (22,24�26).
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