VULNERABILITY OF HEARING FUNCTION DURING ACOUSTIC NEUROMA SURGERY

Intraoperative monitoring of auditory evoked potentials reveals possib le correlations between surgical maneuvers and the function of auditor y structures and pathways in cerebellopontine angle surgery. Direct co chlear nerve action potentials (CNAPS) furnish realtime information on the function of the cochlea and cochlear nerve and were utilized in 1 4 patients undergoing removal of small (12-18 mm) unilateral acoustic tumors. The latency of the first negative component (N-1) of the CNAPs proved extremely sensitive in detecting intraoperative auditory damag e and was a good predictive index of postoperative auditory outcome. E valuation of temporal and morphological CNAP patterns allowed identifi cation of coagulation close to the cochlear nerve, drilling of the int ernal auditory canal and removal of the intrameatal portion of the tum or as the most critical steps in hearing preservation.