聴神経鞘腫聴力温存企図手術における聴力消失例について—MRI導入以後の経験から

Failure to Preserve Hearing in Acoustic Neuroma Surgery: Experiences after Introduction of MRI

I．はじめに

　最近は，聴神経鞘腫の摘出に際して，有効残存聴力を温存しようとする努力がなされるようになってきたが，現状では小腫瘍であっても有効聴力温存率は極めて低い^1,3,4,7,9）．一方，MRIの出現によって，内耳道内における腫瘍の状態も把握できるようになり聴神経鞘腫診断は新しい局面を迎えた^2）．ここでは，MRI導入後，聴力温存を企図して手術をしながら，術後，聴力消失をみた5耳の経験を述べ，聴力温存手術の現況と問題点について論及する．

This report elucidates our experiences on acoustic neuroma surgery, in which auditory function was lost postoperatively, although conservation of hearing had been intended preoperatively.

Five ears from four patients (two ears: unilateral, three ears from bilateral acoustic neuromas) were oper-ated on via standard retromastoid route, with monitor-ing of auditory evoked potentials.

Abolition of ABR occurred when surgical manipula-tions were performed within the internal auditory canal. Pulling tumor tissue away from the cochlea toward the brain stem has proved to be a hazardous procedure.