The results of 248 cases of acoustic neuroma surgery carried out mainly by the extended middle cranial fossa approach during a 16-year period from 1976 to 1991 are analyzed. Hearing preservation was attempted in 69 cases and successfully achieved in 35 (51%) cases. Hearing was preserved in 24 (57%) of 42 cases in which a tumor was 20 mm or smaller in diameter, pure-tone hearing level was 50 dB or lower, and speech discrimination score was 50% or higher. The hearing preservation rate (76%) in the cases with a tumor extending 3 mm or less from the internal auditory canal was much higher than in cases with a larger tumor. Hearing was preserved in three of seven cases with a tumor of 21 mm or larger and in two of four cases of neurofibromatosis type 2. The evaluation of postoperative hearing is also discussed.
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