[Management of acoustic neurinoma with preserved hearing]

Six cases of acoustic neurinoma (AT) with preoperatively preserved hearing are presented. Their clinical features and surgical management for hearing preservation are discussed. Presenting symptoms were hearing decrease in 3 cases (#1, #2, #6), trigeminal neuralgia in 3 cases (#4, #5, #6), and hemifacial spasm in case #2. Case #3 was an incidentally diagnosed case by CT scan. Preoperative decrease of hearing in the affected ears ranged from 10 dB to 60 dB. In all cases except for case #1, CT scans revealed CP angle tumors sized 1 - 4 cm in diameter. A small intracanalicular tumor was detected in case #1 by metrizamide CT scan. Enlargement of the internal auditory meatus was detected in two cases (#4, #6). Through a lateral suboccipital transmeatal approach, all cases underwent radical total resection of tumor with anatomical preservation of both facial and cochlear nerves. Postoperatively, in spite of good morphological preservation of cochlear nerve, useful hearing function was noted in only one case (#3) who had excellent preoperative hearing (10 dB) and whose tumor was very small (1 cm). Facial nerve function was satisfactory in all patients. According to the previous reports, the level of hearing decrease in AT is related to the origin of tumor, direction of its growth, invasions or involvement to cochlear nerve and extension toward the labyrinth. Major factors to achieve preservation of useful hearing in AT surgery are 1) size of the tumor and 2) preoperative hearing acuity. Early detection of small tumor is extremely important and surgery must be precise to preserve cochlear nerve, internal auditory artery and labyrinth.(ABSTRACT TRUNCATED AT 250 WORDS)