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Audiometric Findings in Children with a Large Vestibular Aqueduct

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Audiometric Findings in Children with a Large Vestibular Aqueduct ORIGINAL ARTICLE Audiometric Findings in Children With a Large Vestibular Aqueduct Ellis M. Arjmand, MD, PhD; Audra Webber, BS Objective: To characterize audiometric findings in chil- profound in 10 ears (38%). Thirteen (50%) of 26 ears had dren with a large vestibular aqueduct (LVA). a downsloping or high-frequency SNHI, and 8 (31%) of 26 ears had a midfrequency-peaked audiogram. Bilat- Design: Retrospective review. eral LVAs were seen in 7 children, 6 of whom had bilat- eral and asymmetrical SNHI. Of 12 patients with a uni- Methods: Audiometric records of children with an iso- lateral LVA, 5 had bilateral SNHI. lated LVA, diagnosed by computed tomography of the tem- poral bone, from 1995 through 1998 were reviewed. Conclusions: In this series, the children with LVAs typi- cally had moderate-severe or worse SNHI. An unusual Results: Nineteen children had an isolated LVA in one midfrequency-peaked audiogram was present in approxi- or both ears. In all, 26 ears with an isolated LVA were mately one third of the study patients. The majority of identified. An LVA was seen in association with another the patients had a unilateral LVA; however, nearly 50% inner ear anomaly in an additional 7 ears. The hearing of the patients with a unilateral LVA had bilateral SNHI. impairment was sensorineural in 22 ears (85%) with an The patients with bilateral LVAs generally had asym- isolated LVA and mixed in 3 (12%). The hearing was nor- metrical SNHI. mal in 1 ear. The sensorineural hearing impairment (SNHI) was moderate-severe in 12 ears (46%) and severe- Arch Otolaryngol Head Neck Surg. 2004;130:1169-1174 HE LARGE VESTIBULAR AQUE- toms have also been reported by some duct (LVA) is reported to be patients.4,5 the most common inner ear The mechanism of hearing impair- anomaly identified on com- ment associated with an LVA is un- puted tomograms (CTs) in known, although many hypotheses have children with sensorineural hearing impair- been presented.3,4,15 Treatment of an LVA T 1 ment (SNHI). As such, hearing impair- remains controversial. The purpose of this ment is frequently attributed to the pres- study is to examine the audiometric find- ence of an LVA.2 The description of LVA ings in children with isolated enlarge- syndrome in 1978, which included associ- ment of the VA as identified on temporal ated inner ear anomalies,3 led to an inter- bone CTs. The characteristics of hearing est in the LVA as an isolated anomaly.4 How- impairment (eg, severity and audiomet- ever, associated cochlear anomalies are ric configuration) are described, as is the thought to be more difficult than LVAs to relationship between VA findings and hear- detect on CTs.5 ing status. Radiographic criteria for the diagno- sis of LVAs have yet to be standardized. METHODS From the Department of The definition of a normal vestibular aq- Pediatric Otolaryngology, ueduct (VA) diameter varies consider- We performed a retrospective review of the Children’s Hospital of ably in published reports, as do the place medical records of children with SNHI who un- Pittsburgh, Pittsburgh, Pa. of measurement and the plane of CT derwent temporal bone CT scans from 1995 Dr Arjmand is now with the scans.2-4,6-11 The clinical presentation of the through 1998. All children in this study were Department of Pediatric seen in the pediatric otolaryngology depart- LVA is variable; both stable and progres- Otolaryngology, Cincinnati 4,9,11-14 ment at Children’s Hospital of Pittsburgh Children’s Hospital Medical sive SNHI have been described, and (CHP), Pittsburgh, Pa, a university-affiliated Center, Cincinnati, Ohio. the characteristics of hearing impair- tertiary care children’s hospital. The study was The authors have no relevant ment (severity, type, and audiometric con- approved by the institutional review board of financial interest in this article. figuration) vary as well. Vestibular symp- CHP. (REPRINTED) ARCH OTOLARYNGOL HEAD NECK SURG/ VOL 130, OCT 2004 WWW.ARCHOTO.COM 1169 ©2004 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/25/2021 fied in 7 ears. The following inner ear anomalies were Profound Normal 8% 12% diagnosed on CTs (n=33): Anomaly No. (%) of Ears Isolated enlarged VA 26 (79) Severe Enlarged VA with cochlear anomalies 1 (3) 15% Enlarged VA with SCC anomalies 2 (6) Enlarged VA with cochleovestibular anomalies 1 (3) Enlarged VA with SCC and vestibular anomalies 3 (9) AUDIOMETRIC FINDINGS Mild Severity 38% Of the 26 ears with isolated LVAs, 22 (85%) had SNHI, Moderate 27% 3 (12%) had mixed hearing impairment, and 1 (3%) had no hearing loss. The severity of hearing impairment as determined by pure-tone averages ranged from none (3 of 26 ears; 12%) to profound (2 of 26 ears; 8%), with 17 Figure 1. Severity of sensorineural hearing impairment in 26 children with ears (65%) demonstrating mild or moderate hearing loss isolated large vestibular aqueducts. The severity of hearing impairment is classified according to the pure-tone average in the affected ear. and 6 ears (23%) with severe or profound hearing loss (Figure 1). As the use of pure-tone averages to de- scribe severity of hearing impairment does not measure Patients were referred for temporal bone imaging at the hearing above 2000 Hz, the degree of hearing impair- request of the evaluating pediatric otolaryngologist. Not all chil- ment can be underestimated in patients who are more dren diagnosed as having SNHI were referred for imaging. For severely affected at higher frequencies. example, some children with a known cause for acquired SNHI were not referred for CT. The study included only children with Audiometric Configuration unilateral or bilateral SNHI; therefore, the incidence of LVAs in normal-hearing subjects cannot be determined. High-resolution coronal or axial and coronal temporal bone In 13 (50%) of 26 ears with an isolated LVA, the audio- CT scans were performed (at 1- or 1.5-mm intervals) in accor- gram was downsloping or showed a high-frequency SNHI. dance with the standard clinical imaging protocol at CHP. The Eight (31% of the total) of the remaining 13 ears had au- VA was classified as enlarged by the evaluating radiologist if diograms with a midfrequency peak at 1000 or 2000 Hz. its width at the proximal intraosseous portion exceeded that The midfrequency-peaked audiogram is defined by the pres- of the adjacent posterior semicircular canal (SCC).16 The CTs ence of thresholds at 1000 or 2000 Hz that are 15 dB or of patients diagnosed as having an LVA were subsequently re- better than the adjacent octaves (Figure 2). Other audio- viewed, and the diameter of the VA at its widest intraosseus metric configurations were seen in 5 ears, including a flat portion was measured. hearing loss in 1 ear. The following tabulation shows the The audiometric records for all patients identified as hav- audiometric configuration in 26 ears with isolated LVAs: ing an LVA were reviewed. Behavioral audiograms or auditory brainstem response test results for all patients were available Configuration No. (%) of Ears from the department of audiology at CHP. The type of hearing Downsloping 11 (42) impairment, the severity of hearing impairment, and the High frequency 2 (8) audiometric configuration were characterized by an individual Midfrequency peak 8 (31) review of the audiograms for each patient found to have an Flat 1 (4) LVA. Other 3 (11) Normal 1 (4) RESULTS Laterality PATIENT POPULATION Seven patients had bilateral isolated LVAs, and 12 pa- We reviewed the records of 221 children. At the time of tients had unilateral isolated LVAs. Of the 7 patients with evaluation, the patients ranged in age from 1 month to bilateral LVAs, 6 had bilateral SNHI and 1 had unilat- 17.2 years (mean age, 5.5 years). The female-male ratio eral SNHI. All 6 patients with bilateral LVAs had asym- was 1.1:1.0. metrical audiometric thresholds. Of the 12 patients with unilateral LVAs, 7 had unilateral SNHI and 5 had bilat- RADIOGRAPHIC FINDINGS eral SNHI. (In 1 patient with a unilateral isolated LVA, the contralateral ear had an LVA with associated anoma- Nineteen children had an LVA diagnosed as an isolated lies, and the patient had bilateral SNHI.) anomaly in one or both ears. An isolated LVA was iden- Overall, 11 patients with LVAs had bilateral SNHI. Au- tified in a total of 26 ears. The incidence of isolated LVAs diometric thresholds were asymmetrical in 7 of these pa- in this group was 8.6% (19 of 221 subjects), with a mean tients, inlcuding 6 children with bilateral isolated LVAs VA diameter of 2.3 mm (range, 1.2-3.9 mm). Also, an (Figure 3). Asymmetry was defined as hearing thresholds LVA with an associated inner ear anomaly was identi- differing 15 dB or more at 2 or more frequencies between (REPRINTED) ARCH OTOLARYNGOL HEAD NECK SURG/ VOL 130, OCT 2004 WWW.ARCHOTO.COM 1170 ©2004 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/25/2021 ears. Therefore, all patients with both bilateral LVAs and Frequency, Hz bilateral SNHI had asymmetrical audiometric thresholds. 125 250 500 1000 2000 4000 8000 – 10 0 COMMENT 10 15 dB DIAGNOSTIC CRITERIA 20 Radiographic 30 50 dB 40 The diagnostic criteria for LVAs are controversial and not 3 standardized. Valvassori and Clemis defined VA en- 50 largement as a diameter exceeding 1.5 mm. Subse- 60 quently, other investigators have defined VA enlarge- Hearing Level, dB ment as a diameter greater than or equal to 1.4,9 1.5,11 2.0,1,2,4,9 or 4.0 mm.8 The place at which the VA is mea- 70 3-5-11 sured varies from midway between the common crus 80 and external aperture to the external pore.
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