Air-bone gap and resonant frequency in large vestibular aqueduct syndrome

Background: Conductive hearing loss is occasionally recognized in large ves tibular aqueduct (LVA) syndrome: however, the incidence rate and the cause are not known. Objective: To compare air and bone conduction levels between patients with LVA syndrome and those with idiopathic sudden sensorineural hearing loss, a nd to investigate the cause of the air-bone gup. Study Design: Retrospective study. Setting: The patients were treated at a tertiary referral center. Patients: Twenty-eight ears of 15 patients with LVA syndrome and 28 ears of patients with idiopathic sudden sensorineural hearing loss were examined. The latter patients were selected from a computerized database to match the former patients in air conduction levels. Main Outcome Measures: Pure-tone audiometry, multiple frequency tympanometr y, acoustic reflex, otoacoustic emission, vestibular evoked myogenic respon se. Results: The air-bone gap in patients with LVA syndrome was always larger t han that in patients with idiopathic sudden sensorineural hearing loss with the same air conduction level, The resonant frequency in patients with LVA syndrome was rather low compared with that in normal control subjects, in contrast to the finding that resonant frequency was significantly high in p atients with otosclerosis. Conclusions: An air-bone gap exists: to some degree in almost all patients with LVA syndrome. The air-bone gap may not be associated with the movement restriction of the stapes as it is with otosclerosis.