骨性鼓膜を伴った先天性外耳道狭窄症の1例

Congenital Malformation of the Middle Ear with Stenosis of the External Auditory Meatus: Report of a Case

I．はじめに

　外耳と中耳の発達は緊密な関係をもっているため，外耳奇形をもつ大多数の症例には鼓膜，鼓室，耳小骨の形成異常を伴うものが多い。同じ理由で先天性に伝音性難聴を示す疾患には外耳，中耳いずれかに奇形が発見される^1）。鎖耳，耳介奇形は生下時に発見されうるが，外耳道狭窄では発見が遅れやすい。とくに一側性難聴の場合は普通ことばの発達が正常であるので発見が遅れることが多い。われわれは一側性外耳道狭窄と中耳奇形を伴いながら，ことばの発達が正常なために11歳で発見された症例で鼓膜部分が骨性を示した1例を経験したので，文献的考察を加えて報告する。

　A bony tympanic membrane on the right ear was found in a 12-year-old female, but otoscopic examination did not reveal the tympanic membrane. She had a conductive hearing loss of approximately 55dB, and she underwent a tympanoplasty type II with canalplasty. Postoperative hearing was improved up to 35dB. In the ossicular findings, the malleus and incus were fixed together and the malleus handle was short. The lenticular process of incus and crus of stapes were slightly malformed. The clinically characteristic point was that bony plate was found on the position of the tympanic membrane and it was considered that the bone was differentiated from some of the mesenchymal tissue at the embryonal stage.