内耳道奇形2症例の検討

Vestibular Evoked Myogenic Potentials（VEMP） in Patients with Hypoplasia of the Cochlear Nerve and Stenosis of the Internal Auditory Canal

I．はじめに

　近年画像技術の向上は，内耳道，蝸牛，前庭などの微細な側頭骨形態の異常所見を提供し，日常診療において感音難聴の原因を推定することが可能となった。その結果，側頭骨形態異常に伴う感音難聴に関する報告も増え，内耳奇形を伴わない内耳道狭窄症例の報告も散見されるようになった^1～5）。しかし，内耳道単独形態異常例は極めて稀であり，このため実際にはその臨床像を詳しく検討されているとはいい難い。

　今回われわれは内耳道狭窄，蝸牛神経形成不全症例について，前庭誘発筋電位検査（vestibular evoked myogenic potential：VEMP）を施行し若干の知見を得たので，文献的考察を加えて報告する。

　We report two cases with profound sensorineual hearing loss.

　Case 1：a 6-year-old girl was assessed by CT and MRI which revealed that the left cochear nerve was hypoplastic and other nerves（the superior and inferior vestibular nerves,facial nerve） were normal.

　Case 2：a 7-year-old girl revealed stenosis of the right internal auditory canal on CT and hypoplasia of the right cochlear nerve on MRI.

　DPOAE showed normal response on the left side in case 1 but abnormal response on the right side in case 2. The caloric test was normal in both cases. VEMP was applied to both cases to evaluate the function of the inferior vestibular nerve,showing normal response in them.

　VEMP was found to be very useful tool in functional evaluation of the 8th nerve in the stenosis of the internal auditory canal.