[Intraoperative monitoring auditory function during surgery of internal auditory canal and C-P angle]

Intraoperative measurement of electrocochleography, auditory brainstem responses and eighth nerve action potentials are utilized to assess the functional integrity of the cochlea and cochlear nerve. All such assessments have only one purpose: for warning the surgeon the possibility of damage the auditory system or its surrounding structure. Eighteen patients with various otoneurological diseases undergoing surgery had intraoperative monitoring of such evoked electrophysiological responses. Hearing was preserved in sixteen patients. However, the CM/N1 in ECochG still keep for a few minutes even after transection of the cochlear nerve and there is another disadvantage of need for signal averaging in BAER. Recording of the response of the the auditory nerve directly from the eighth nerve provides the surgeon with immediate information when an insult has been made to the cochlear and eighth nerve. Therefore, combination of these three measurements are recommended depending on the situation.