あぶみ骨手術における高音障害の成因について

Hearing Loss Caused by Stapes Surgery

I．はじめに

　現在耳硬化症に対し多くのあぶみ骨手術が行われているがそのほとんどはstapcdectomyかstapedotomyである。両者とも気導骨導差は解消できるが8,000Hzの気導聴力は（とくにstapedectomyで）改善しない例が多い。この8,000Hzの障害の成因についてはいくつかの意見はあるがまだはっきりしていない。筆者はこの障害はあぶみ骨底板を除去するさいの内耳液の圧縮，膨張により生ずるという仮説をもっていたが，今回にれを裏づける症例を経験したので報告したい。

　Seven patients with otosclerosis were operated with two different methods of stapes surgery. Inone group, a large fenestra (0.8mm diameter) was created before breaking the superstructure of the stapes, while in the other group, a small fenestra was created.

　Hearing threshold change in 8,000Hz was compaired between these two groups. The hearing improvement with the large fenestra was significantly better than those with the small fenestra (p<_O.05), and no significant difference was found between the patients with stapedectomy and those with stapedotomy.

　It seems obvious that any perilymphatic pressure change during the removal of the footplate impairs the function of the basal end of the cochlea.