Cochlear Microphonic Potentials in Patients with Vestibular Schwannomas

Abstract

We evaluated the cochlear function of 44 patients with unilateral vestibular schwannomas by measuring cochlear microphonic potentials (CM) in electrocochleography. We used short tone bursts with 0.5-, 1-, 2-, and 4-kHz frequencies as acoustic stimuli to evoke CMs, and determined CM detection thresholds. The CM detection thresholds in vestibular schwannomas ranged from normal to no response. Cochlear dysfunction was seen in 35 (79.5%) of the 44 cases; these patients had higher CM detection thresholds than normal subjects. Although a significant correlation was found between mean hearing level (0.5–4 kHz) and mean CM detection threshold (0.5–4 kHz), 20 patients had lower CM detection thresholds than were found using audiometry. This suggests that there is an additional retrocochlear component responsible for this hearing loss.

Cochlear Microphonics for Hearing Preservation in Vestibular Schwannoma Surgery

“…Although most electrocochleography procedures are used to record cochlear nerve action potentials (AP) and summating potentials (SP), 6 measurement of cochlear microphonics yields detailed findings on various aspects of inner ear diseases 7,8 . Even in patients with vestibular schwannomas, cochlear microphonics aids determination of the existence and degree of cochlear dysfunction 9 . Our goal was to determine whether electrophysiological findings for cochlear function obtained from cochlear microphonic recording are useful for decision‐making concerning hearing preservation surgery for vestibular schwannomas.…”