高音漸傾型の伝音難聴について

CONDUCTIVE HIGH-TONE HEARING LOSS

　I．はじめに

　伝音難聴であるが多くの感音難聴にみられるように気導聴力損失が高い周波数ほど大きくなる症例がある。このなかには伝音連鎖中に索状物が介在していて，これが高音振動の減衰をおこすために，この様な高音漸傾型の聴力像を示す例がある。これらの症例のなかには感音難聴と誤診されていたものもあつたが，術前に病変が推定でき，かつ手術的に聴力改善が可能である点で重要である。われわれは最近4例の症例を経験したのでここに報告する。

　Conductive high-tone hearing loss is discovered in 4 cases in which their pathology was revealed by tympanoplasty. In two congenital cases, the incudostapedial joint was replaced by connectivetissues ; in the other two traumatic cases, the connective tissue was found between the ear-drum and the head of the stapes and between the handle of the malleus and the head of the stapes.

　Connective tissues interspersed between the ossicular chains would naturally dampen sound transmission for higher frequencies. The hearing was improved by transposing the incus between the eardrum and the head of the stapes.