小脳橋角部腫瘍症例のEvoked Response Audiometry

EVOKED RESPONSE AUDIOMETRY IN A CASE OF CELEBELLOPONTINE ANGLE TUMOR

　I．緒言

　Evoked Response Audiometry（ERA）は，現在，聴力の推定，難聴の部位診断，難聴の病態の把握，神経学への応用などに利用されている。後迷路性難聴症例のERAの面からの検討はされてはいるが，まだ報告は少ない。今回，著者らは，小脳橋角部腫瘍の症例において，emectrocochleo‐gram（ECochG），brain stem response（BSR）を記録し，難聴の部位診断に有用であつたので報告する。

　Electrocochleogram (ECochG) and brain stem response (BSR) were taken on a female patient suffering from cerebellopontine angle hemangioblastoma. Click sounds were used for acoustic stimulation. ECochG recording was made by extratympanic method. BSR was recorded with forehead-ear lobe electrodes. N₁ was found to be composed of L and H parts. N₂ was observed by stimulating at high intensities. The BSR was recorded only with waves I and II. Operation revealed the eighth nerve to be compressed between the tumor and the feeding artery of the tumor.

　From the operative findings, the hearing loss of this patient was apparently due to conduction disturbance of the cochlear nerve.