伝音性難聴を呈した中・内耳奇形の1例

A Case of the Middle and Inner Ear Malformation presenting Conductive Hearing Loss

　はじめに

　先天性高度難聴には原因不明のものが多いが，その中には内耳奇形によるものの存在が知られている。現在，内耳奇形は高分解能CTやMRIなどの画像診断により詳細な検討が可能になり，MondiniやScheibeなど古典的な分類に当てはまらない様々なタイプが確認され，その中に純音聴力検査で気導骨導差を示す例も少数ながら存在する。今回われわれは伝音性難聴，温度眼振反応が無反応を呈した中・内耳奇形の1症例を経験し，神経耳科学的に検討したので報告する。

A 5-year-old girl presented with hearing loss and balance disorder. The pure tone audiometry revealed a conductive hearing loss with 50 dB air-bone gap. High resolution computed tomography showed hypoplastic semicircular canals and normal vestibule and cochlea in both ears. Caloric test showed no response to ice water irrigation. No nystagmus was elicited by the damped earth verti-cal axis rotation, but nystagmus was presented by the damped off vertical axis rotation. In explora-tory operation of the left ear, agenesis of stapes and the bony atresia of the oval and round windows were found.