Audiological findings after stereotactic radiosurgery in acoustic neurinomas

Stereotactic radiosurgery was used in the treatment of 126 patients with acoustic neurinomas up to 30 mm in diameter from 1969 to 1984. Adequate follow-up data (mean follow-up period 4.7 years) were available for 111 (116 ears) of these 126 patients; of these 111 patients, 64 (65 ears) had a pure-tone threshold of less than 90 dB before the treatment and were followed up audiologically. Preserved hearing was found in 26% of the ears one year postoperatively. Shrinkage of the tumour was obtained in 44% and arrest of its growth in 42%. There was no mortality related to the radiosurgical treatment. Transitory facial weakness was noted in 15% of the patients (3% in 1983-84). Eighteen per cent of the patients had some, usually transitory, trigeminal dysfunction. The stapedius reflex threshold was improved in 13 ears (20%). In one patient the audiological tests became pathological in the contralateral ear during growth of a new tumour. Initially the stapedius reflex threshold was elevated, and 11 months later the BRA pattern also became abnormal.