両側内耳道拡大を伴う特発性感音難聴の症例

Bilateral Sensorineural Hearing Impairment Associated with Bilateral Internal Auditory Canal Enlargement

I．はじめに

　特発性の感音難聴は原因不明であり徐々に進行することが多い。先天性障害を除くと，特発性感音難聴の症例で骨迷路・側頭骨の形態異常を伴うものは少ない。しかし最近の神経放射線診断学の発展に伴って，内耳道の狭小化あるいは拡大を伴う感音難聴の症例が報告^1,2）されている。これらの症例は原因不明の特発性感音難聴の症例のなかでは，特異なグループに属すると考えられるが，明らかな骨迷路の形態異常を示す症例の検索は，特発性感音難聴の原因究明の糸口となる可能性がある。筆者らは両側の著明な内耳道拡大を呈した特発性感音難聴の症例を経験したので，これらの症例について放射線学的特徴を中心に検討し，感音難聴の原因について考察した。

　The purpose of this study was to demonstrate the neuroradiological findings of two cases with a long-standing history of bilateral sensorineural hearing impairment. Both cases had an extremely dilated bilateral internal auditory canals. The lateral and third ventricles were dilated on a CT scan in a 69-year-old man (case 1). The sella turcica was also enlarged. However, no tumor was demonstrated in the ventricles, sella or cerebellopontine angles. An air CT scan demonstrated no filling defect in the bilateral internal auditory canals of a 39-year-old matt (case 2). The etiology of hearing impairment and the enlarged internal auditory canals has not yet been determined.