Download Large Vestibular Aqueduct Syndrome: A Case Study

J Am Acad Audiol 16:822–828 (2005)
Large Vestibular Aqueduct Syndrome:
A Case Study
Jackie L. Clark*
Ross J. Roeser*
Abstract
A 23-month-old female was referred for hearing aid fitting after failing newborn
hearing screening and being diagnosed with significant hearing loss through
subsequent diagnostic testing. Auditory brainstem response (ABR) and
behavioral testing revealed a moderate-to-severe bilateral mixed hearing loss.
Prior to the hearing aid evaluation, tympanostomy tubes had been placed
bilaterally with little or no apparent change in hearing sensitivity. Initial testing
during the hearing aid fitting confirmed earlier findings, but abnormal middle
ear results were observed, requiring referral for additional otologic management.
Following medical clearance, binaural digital programmable hearing aids were
fit using Desired Sensation Level parameters. Behavioral testing and probe
microphone measures showed significant improvements in audibility. Decrease
in hearing sensitivity was observed six months following hearing aid fitting.
Radiological studies, ordered due to the mixed component and decreased
hearing sensitivity, revealed large vestibular aqueduct syndrome (LVAS). Based
on the diagnosis of LVAS, a cochlear implant was placed on the right ear; almost
immediate speech-language gains were observed.
Key Words: Amplification, aural habilitation, cochlear implantation, large
vestibular aqueduct syndrome, pediatric audiology
Abbreviations: BKB = Bamford-Kowal-Bench; DSL = Desired Sensation
Level; LVAS = large vestibular aqueduct syndrome; MRL = minimal response
levels; SOPCHL = sudden onset or progressive childhood hearing loss; WDRC
= wide dynamic range compression
Sumario
Una niña de 23 meses de edad fue referida para adaptación de audífonos
luego de fallar una prueba de tamizaje auditivo para recién nacidos, y de
establecerse que era portadora de una hipoacusia significativa con el uso de
pruebas diagnósticas subsecuentes. Las respuestas evocadas de tallo cerebral (ABR) y las pruebas audiométricas conductuales demostraron una
hipoacusia mixta bilateral de grado moderado a severo. Previo a la evaluación
para adaptar auxiliares auditivos se le colocaron tubos timpánicos sin cambio
aparente su sensibilidad auditiva. Las pruebas iniciales durante la adaptación
de los auxiliares auditivos confirmaron los hallazgos iniciales, pero se observaron resultados anormales en la función del oído medio que requirieron una
referencia para manejo otológico. Cuándo fue dada de alta médicamente, se
le adaptaron auxiliares auditivos digitalmente programables en forma binaural utilizando parámetros de Nivel Deseado de Sensación. Las pruebas
conductuales y las medidas de micrófono de sonda mostraron un incremento
significativo en la audibilidad. Una disminución en la sensibilidad auditiva se
observó seis meses después de la adaptación de los audífonos. Los estudios
radiológicos, ordenados debido al componente mixto y a la disminución en la
sensibilidad auditiva, revelaron un síndrome de acueducto vestibular grande
(LVAS). Basados en el diagnóstico de LVAS se colocó un implante coclear en
el oído derecho, y casi de inmediato, se observó una mejoría en el hablalenguaje.
*UT Dallas/Callier Center for Communication Disorders
Jackie Clark, Ph.D., UT Dallas/Callier Center, 1966 Inwood Road, Dallas, TX 75235; Phone: 214-905-3031; E-mail:
[email protected]
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Large Vestibular Aqueduct Syndrome/Clark and Roeser
Palabras Clave: Amplificación, habilitación aural, implante coclear, síndrome
de acueducto vestibular grande, audiología pediátrica
Abreviaturas: BKB = Bamford-Kowal-Bench; DSL = Nivel Deseado de
Sensación; LVAS = síndrome de acueducto vestibular grande; MRL = niveles
de respuesta mínima; SOPCHL = Hipoacusia de inicio súbito o progresiva de
la infancia; WDRC = compresión de rango dinámico amplio
D
etermining etiology, prognosis, and
management for sudden onset or
progressive childhood hearing loss
(SOPCHL) remains somewhat controversial
and unknown. Retrospective studies using
sequential audiograms suggest that it is
impossible to analyze critical variables with
any degree of validity. However, two possible
prognostic elements are audiogram
morphology and the degree of initial hearing
loss (Molini et al, 1998). While there are
multiple etiologies associated with SOPCHL,
the single most prevalent is Large Vestibular
Aqueduct Syndrome (LVAS), accounting for
15–20% of the cases (Emmett, 1985; Arcand
et al, 1991).
Valvassori and Clemis (1978) first
described radiographic observations for 50
patients with LVAS and documented the size
of the aqueduct in these patients ranging
from 1.5–8.0 mm in diameter (normal
diameter is defined as less than 1.5 mm),
with bilateral involvement being twice as
prevalent. In children, LVAS is associated
with asymmetrical, sudden, or progressive
mixed or sensorineural hearing loss, typically
with onset within the first few years of life.
Children with LVAS often experience
decreased hearing following minor trauma,
infection, or activities involving a Valsalva
maneuver (Goeverts et al, 1999; Can et al,
2004). LVAS is more prevalent in females
than males and is often associated with inner
ear anomalies such as hypoplastic cochlea,
congenital disorders (e.g., CHARGE, Alagille
syndrome, Pendred syndrome, branchiooto-renal syndrome) or a variant of MondiniAlexandre dysplasia (Arcand et al, 1991;
Temple et al, 1999). An occasional finding of
vestibular complications can be found with
LVAS (Madden et al, 2003).
LVAS
is
the
most
common
radiographically detectable malformation
found in children. It typically coexists with
other anatomical structural abnormalities
in patients with early onset of hearing loss
(Okumura et al, 1995). Histopathology
sections of enlarged human vestibular
aqueducts demonstrate thin-walls lined with
flattened epithelium without the normal
architecture of papillary folds (Harnsberger
et al, 1995). It appears that LVAS results
from an arrest in development during the
fifth week of gestation, prior to a narrowing
of the vestibular aqueduct (Jackler and De La
Cruz, 1989).
In this paper, the audiological
management of a toddler referred for a
hearing aid evaluation and subsequently
diagnosed with LVAS is described. LVAS has
been well documented in the medical and
radiological literature, but little has been
published in audiological journals.
CASE REPORT
A
23-month-old toddler was referred to
the UT Dallas/Callier Center for
Communication Disorders from a nearby
medical facility for a hearing aid evaluation.
This youngster had several previous
diagnostic ABRs and pediatric behavioral
audiometric evaluations. Birth and medical
history were unremarkable, with no known
family history of hearing loss. Diagnostic
ABR evaluation, six and a half months
following a failed newborn hearing screening,
showed 70 and 80 dB nHL thresholds using
clicks and tone bursts (500 and 4000 Hz) for
the right and left ears, respectively. A 40 dB
nHL unmasked bone-conduction threshold
was obtained using click stimuli. Subsequent
diagnostic ABR evaluations indicated
fluctuations between 50 and 80 dB nHL for
clicks and tone bursts and consistent 40–45
dB nHL unmasked bone-conduction click
thresholds (see Figure 1a and 1b). Behavioral
audiometric minimum response levels (MRL)
in sound field using visual reinforcement
audiometry, completed when the patient was
23 months old, revealed warble tone and
speech awareness thresholds at 50–70 dB
HL. Unmasked pure-tone bone-conduction
and speech-awareness thresholds were
present at 30 dB HL. Tympanograms varied
significantly over time from Type “B” with
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Journal of the American Academy of Audiology/Volume 16, Number 10, 2005
Figure 1. Audiometric data obtained at five months showing a severe bilateral hearing loss: (a) click-evoked
ABR thresholds for each ear; (b) click-evoked latency-intensity functions for each ear and a bone-conduction
response at 45 dB nHL; (c) 500 Hz tone-evoked ABR responses for each ear.
both high and low C1 values, “A,” “As,” “C,” and
borderline “A”/“As,” with absent ipsilateral
reflexes. The child’s otolaryngologist suspected
a middle ear pathology, and tympanostomy
tubes were placed bilaterally, but she was
cleared for binaural hearing aid fitting.
Simultaneously, an MRI was ordered to
investigate the abnormal middle ear findings,
as well as the suspected fluctuating hearing
loss.
Due to the fluctuating status of hearing
loss and the aggressive medical and
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audiological monitoring, wide dynamic range
compression (WDRC) digital behind-the-ear
hearing aids were programmed using the
SP3 portable programmer (DSL i/o) and
dispensed binaurally. Both simulated probe
microphone (Figure 2a, 2b) and
electroacoustic measures validated
programming parameters and level of
amplification. Verification of fit was
established (AudioScan RM500) while each
hearing aid was placed in the test box, and
using three simulated input parameters with
Large Vestibular Aqueduct Syndrome/Clark and Roeser
a.
Right Ear
Estimated SPL in dB at TM
140
120
100
Gain
MPO
Target Gain
80
Dynamic
a
Range
R g of
o Soft
S t Sounds
o
Threshold
60
40
20
250
500
1000
2000
4000
8000
Frequency in Hz
Left Ear
b.
Estimated SPL in dB at TM
140
120
100
Gain
MPO
80
Target Gain
Threshold
Dynamic
a
Range
R g of
o Soft
S t Sounds
o
60
40
20
250
500
1000
2000
4000
8000
Frequency in Hz
Soundfield Audiometry
c.
Hearing Level in dB
0
-20
-40
-60
-80
-100
Aided
-120
0 0 k k k k k k k
25 50 1 1.5 2 3 4 6 8
Frequency in Hz
SAT = 35 dB HL
Figure 2. Verification of fit using real-ear and behavioral
soundfield aided thresholds at two years of age. Real-ear
performance was verified (AudioScan RM500) while each
hearing aid was placed in the test box and using three simulated input parameters (soft, normal, and loud) with
age predicted real-ear-to-coupler differences. Verification
of fit using the test box and simulated mode became necessary since the patient was unable to tolerate in situ probe
microphone measurements. Probe microphone measures
were essentially the same for each ear: (a) right ear, (b)
left ear. Aided soundfield thresholds at 500 Hz and 2000
Hz (c) confirmed significant improvement in threshold sensitivity.
Figure 3. Pre-implant audiometric data showing (a)
severe/profound bilateral mixed hearing loss; (b) binaural
aided thresholds showed significant benefit through 2000
Hz
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Journal of the American Academy of Audiology/Volume 16, Number 10, 2005
Figure 4. Soundfield thresholds obtained following
cochlear implantation.
age predicted real ear to coupler differences.
Verification of fit using the test box and
simulated mode became necessary since the
patient was unable to tolerate in situ probe
microphone measurements. Simulated probe
microphone measures confirmed that the
Maximum Power Output did not exceed the
toddler’s predicted Uncomfortable Loudness
Levels for each ear (Figure 2a, 2b). Minimal
response levels for binaurally aided
behavioral sound field using warble tones
and speech stimuli demonstrated a significant
improvement in hearing status (Figure 2c).
The toddler’s mother was counseled on the
care and use of the instruments and advised
to return in 30 days for a follow-up hearing
aid check.
Upon returning for the scheduled 30-day
follow-up hearing aid check, the medical
diagnosis of bilateral LVAS and mild cochlear
dysplasia was made. At the time of the
hearing aid check, parental subjective
observation of the toddler’s auditory behavior
indicated an apparent significant
improvement in audibility when hearing aids
were worn, and no complications with the
instruments were noted. Electroacoustic
analysis of both instruments verified
appropriate function.
Six months following the hearing aid
fitting, ear specific behavioral play
audiometry showed progression of the hearing
loss to severe to profound with a 35–55 dB
conductive component, as well as decreased
high-frequency aided benefit (Figure 3). Based
on the progression of hearing loss that is
expected to accompany LVAS, this toddler
was considered an appropriate cochlear
implant candidate.
A multichannel cochlear implant (Med El
Combi 30+) was implanted in the right ear
ten months post–initial evaluation without
complications, and stimulation was
successfully initiated one month later. Ear
choice for cochlear implantation was made by
criteria determined by the otolaryngologist at
the medical facility where implantation was
conducted. A two month post–cochlear
implant follow-up audiological evaluation
revealed significant improvement in
soundfield awareness with the implant
(Figure 4). The toddler was enrolled in the UT
Dallas/Callier Center Preschool oral program.
Table 1 shows pre-implant and twomonth postimplant speech-language test
results. As shown, significant gains were seen
in all four tests administered. Parental and
school reports were consistent with test
scores. The prognosis for functional auditory
and speech/language skills for this youngster
appears to be very positive.
DISCUSSION AND CONCLUSIONS
T
his paper describes findings for a young
child with a severe bilateral fluctuating
Table 1. Speech-Language Evaluation Results, Pre- and Postimplant
Pre-Implant 11/03
Postimplant 4/04
Early Speech Perception Test (ESP)
2/12
8/12
Category 2
Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS)
9/40
27/40
Spontaneously respond to environmental sounds?
Rarely
Always
Glendonald Auditory Screening Procedure (GASP) Words
CNT
Approximates
phonemes
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Large Vestibular Aqueduct Syndrome/Clark and Roeser
mixed hearing loss diagnosed with LVAS.
Hearing aid fitting provided adequate benefit
initially, but the progressive nature of the
hearing loss indicated that traditional
amplification would not allow for long-term
benefit for this child. Based on the probability
of decreased hearing sensitivity, a cochlear
implant was placed on the child’s right ear,
and significant improvement in sound
awareness and speech and language
performance was observed within a twomonth period.
Despite sensorineural hearing loss being
most prevalent in LVAS, a conductive
component may occur in some individuals,
such as the case reported here.
Tympanometric findings may or may not be
normal in the presence of a mixed hearing
loss. It is believed that the conductive finding
can be the result of decreased mobility of the
stapes resulting from increased perilymphatic
pressure, stapes fixation, or an incomplete
transmission of the ossicles/ossicular
discontinuity because of incomplete bone
formation around the inner ear (Valvasorri,
1983; Shirazi et al, 1994; Nakashima et al,
2000). Due to the apparent conductive
component in some of the LVAS children
(both with an air-bone gap in the absence or
presence of Type “B” tympanograms), a
medical misdiagnosis of otitis media with
effusion can easily delay the eventual finding
of LVAS. Without the cooperative interaction
between the otolaryngologist, audiologist,
and radiologist, the finding of LVAS becomes
very difficult to make in such a timely manner
as in this particular case.
A variety of theories have been postulated
to explain the progressive sensorineural
hearing loss component found with LVAS.
Some believe that architectural changes
result in a dysfunctional regulating
mechanism or utriculoendolymphatic valve
for endolymph electrolytes causing an
accumulation of toxic by-products or fluid
reflux within the inner ear (Jackler and de
La Cruz, 1989; Levenson et al, 1989; Pyle,
2000). Others suggest an abnormally patent
endolymphatic system is more vulnerable to
sudden fluctuations in cerebral spinal fluid
(Arenberg, 1980) or that there is a weakness
at the level of the membranous cochlear
partitions leading to rupture following sudden
pressure changes (Jackler et al, 1987).
The finding that the child in this report
received significant benefit from a cochlear
implant was not necessarily unexpected. Au
and Gibson (1999) reported results from ten
children with LVAS who received
multichannel cochlear implants. Electrode
insertion for these children was uneventful,
with the exception of an initial gush of
perilymph when the otic capsule was opened
in seven ears, and no postoperative
complications were observed. Within six
months, the average Bamford-Kowal-Bench
(BKB) sentence recognition scores improved
from 31–79%. Positive outcomes were also
reported by Temple et al (1999) for seven
patients (five adults and two children)
diagnosed with LVAS who received cochlear
implants. It appears that the outcome
observed with this patient and also by Temple
et al (1999) suggest that patients with LVAS
should be considered as candidates for
cochlear implants even if their hearing
sensitivity is not in the severe-to-profound
range, based on the prognosis of the
progressive hearing loss.
Since LVAS is associated with sudden
or progressive hearing loss, typically with
onset within the first few years of life, it is
possible for an infant to “pass” a universal
newborn infant hearing screening yet acquire
hearing loss shortly thereafter. This
observation reinforces the need for followup audiological testing when infants are felt
to be delayed in sound awareness and/or
speech and language skills.
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