Clinical use of vestibular evoked myogenic potentials in the evaluation of patients with air-bone gaps.

OBJECTIVE: To determine the value of vestibular evoked myogenic potential (VEMP) test in clinical evaluation of air-bone gaps. STUDY
DESIGN: Retrospective case review.
SETTING: Tertiary referral center. PATIENTS: A total of 120 patients underwent VEMP testing during clinical investigation of significant air-bone gaps in their audiograms. INTERVENTION(S): Otologic examination and surgeries, high-resolution computerized tomography (CT), air and bone audiometry, tympanometry, acoustic reflex, and VEMP test. MAIN OUTCOME MEASURE(S): Imaging studies demonstrating structural anomalies in the temporal bone. Audiologic outcomes of air-bone gaps and VEMP thresholds. Surgical findings confirming imaging results.
RESULTS: Middle ear pathologies, such as otosclerosis and chronic otitis media, were identified in 50 patients, and all of them had absent VEMP responses elicited by air-conduction stimuli. Moreover, 13 of them had successful middle ear surgeries with closures of the air-bone gaps. Abnormally low VEMP thresholds were found in 71 of 73 ears with inner ear anomalies, such as semicircular canal dehiscence and enlarged vestibular aqueduct. Seven patients with superior semicircular canal dehiscence underwent plugging procedure via middle fossa approach, and VEMP thresholds became normalized after the surgery in 3 of them. VEMP test failed to provide accurate diagnosis in only 3 cases.
CONCLUSION: Air-bone gaps may be a result of various otologic pathologies, and the VEMP test is useful during clinical evaluation, better than tympanometry and acoustic reflexes. To avoid unnecessary middle ear surgery for air-bone gaps with unknown or unsure cause, VEMP test should be used in the differential diagnosis before an expensive imaging study.