HEARING PRESERVATION AND IMPROVEMENT OF AUDITORY BRAIN-STEM RESPONSE FINDINGS AFTER ACOUSTIC NEUROMA SURGERY

Among 9 patients with acoustic neuroma who underwent tumor removal by the middle cranial fossa approach during the past 5 years, 6 were sele cted for hearing preservation surgery which was successful in 5 cases (83.3%). For the prediction of success in hearing-preservation, factor s related to bearing preservation, including preoperative findings of neurotological examination, were analyzed. Postoperative hearing thres hold correlated significantly with wave V latency and I-V interpeak la tency of preoperative auditory brainstem response (ABR) and the SP/AP ratio of preoperative electrocochleogram and postoperative facial pals y. The size of tumors and preoperative results of speech audiometry di d not correlate with hearing results. Postoperative ABR findings were normalized within the observation period from 5 days to 10 months in 3 hearing-preserved patients. Possible mechanisms for improvement of AB R findings after the removal of acoustic neuroma are discussed.