純音聴力が正常であった小脳橋角部腫瘍症例の術前後の聴覚障害の推移

Hearing, Disturbances before and after Resection of Cerebello-pontine Angle Tumor with Normal Pure Tone Hearing Level: Report of a Case

　はじめに

　聴性脳幹反応，CTやMRIなどの検査法の進歩により聴神経腫瘍をはじめとする小脳橋角部腫瘍が早期に発見される機会が多くなった。その結果，最近では純音聴力が正常な症例も見出されるようになった^1〜4）。われわれは，耳閉感，難聴，耳鳴を主訴として来院し，純音聴力が正常であった小脳橋角部腫瘍を経験した。この症例では，術後も純音聴力が正常であったが，語音聴力検査やABRなどの聴覚検査には異常が認められ，術後の改善に検査間で差が認められた。症例の詳細を若干の考察を加えて報告する。

A 29-year-old male underwent total resection of a left cerebello-pontine angle tumor by the poster-ior cranial fossa approach. Before and after the operation he had normal pure tone hearing level.Speech discrimination decreased and temporary threshold shift was demonstrated preoperatively. II, III and IV waves of ABR were not demonstrated and I -V latency was prolonged. Interaural time differ-rence discrimination was defect within 2 msec. These examinations suggested that hearing distur-bance of this patient might be due to the compres-sion of the tumor to the cochlear nerve.

Six months after the operation speech discrimina-tion returned to normal. Although ABR and inter-aural time difference discrimination were improved, incompletely. This implies that ABR and interaural time difference discrimination may he useful for early diagnosis of disturbance of the cochlear nerve.