Bone-anchored hearing aid in unilateral inner ear deafness: electrophysiological results in patients following vestibular schwannoma removal.

CONCLUSIONS: The results show that the healthy cochlea perceives one auditory stimulus from two auditory signals: the first through normal air conduction and the second provided by the bone-anchored hearing aid (BAHA). This artificial acoustic difference could partly explain 'pseudo' binaural hearing. Functional cerebral imaging using the same experimental procedure is now necessary.

OBJECTIVES: The aim of this study was to evaluate electrophysiological phenomena induced by BAHA on brainstem and long-latency auditory evoked potentials (AEPs) to understand how patients recover a 'pseudo' binaural sensation with only one functional cochlea.

PATIENTS AND METHODS: This prospective study included 10 patients operated via the translabyrinthine approach and who received implants on the deaf side. Electrophysiological recordings were performed at least 2 months after BAHA use. Brainstem and long-latency (N1, P2, N2, P300) AEPs were studied in free field according to four conditions: 1, without BAHA; 2, with BAHA; 3, with BAHA and normal ear occluded; 4, without BAHA and normal ear occluded.

RESULTS: For brainstem AEPs, we found significantly longer latencies of waves III and V in condition 3 compared with condition 1. For long-latency AEPs, comparison between conditions showed no significant differences.