A nationwide study on enlargement of the vestibular aqueduct in Japan.

Objective: To document the clinical features and associated pure-tone audiometry data in patients with enlargement of the vestibular aqueduct (EVA), and to identify risk factors for fluctuating hearing loss (HL) and vertigo/dizziness in EVA patients.

Methods: In this nationwide survey in Japan, a first survey sheet was mailed to 662 board-certified otolaryngology departments to identify the ones treating EVA patients. A second survey sheet, which contained solicited clinical information and the results of the hearing tests, was mailed to all facilities that reported treating EVA cases. We analyzed clinical information, including age at the time of the most recent evaluation, gender, EVA side, age at onset, initial symptoms, precipitating factors, and etiology from survey responses, and assessed 4-frequency (500, 1000, 2000, and 4000Hz) pure-tone average (PTA) from accompanying pure-tone audiometry data. A multivariate logistic regression analysis was utilized to identify the possible risk factors for fluctuating HL and vertigo/dizziness.

Results: In total, 513 hospitals (response rate, 77.5%) responded to the first survey, and 113 reported treating patients with EVA. Seventy-nine out of the 113 hospitals (response rate 69.9%) responded to the second survey, and the data of 380 EVA patients were registered and analyzed. Of the 380 patients, 221 (58.2%) were female, suggesting female preponderance. The patient age ranged from 0 to 73 years (mean, 16.7 years; median, 13 years; interquartile range, 6-24 years). EVA was bilateral in 91.1% of the patients (346/380). The most prevalent initial symptom was HL (341/380), followed by vertigo/dizziness/imbalance (34/380). Sudden HL occurred secondary to head trauma in 5.3% of the patients and upper respiratory infection in 5.0%. Pure-tone audiometry showed profound HL (PTA >91dB) in 316 (52.0%) of the 608 ears in the 304 patients tested, and asymmetric HL, defined as >10dB, in 147 (48.4%) of the 304 patients. The mean PTA was 83.7dB (median, 91.3dB; interquartile range, 71.3-103.8dB), and the severity in PTA did not correlate with age. Multivariate logistic regression identified age ≥10 years (compared to age of 0-9 years), bilateral HL (compared to unilateral HL/normal hearing), a history of head trauma, and Pendred syndrome (compared to the other EVA-associated disorders) as significant risk factors for fluctuating HL and/or vertigo/dizziness.

Conclusion: The present nationwide survey of 380 EVA patients provided a more precise description of the clinical features, including risk factors for fluctuating HL and vertigo/dizziness.