内耳道内脂肪腫の1例

Lipoma in the Internal Auditory Meatus:A Case Report

　はじめに

　内耳道に発生する腫瘍の大部分は聴神経腫瘍すなわち前庭神経鞘腫であるが，まれに脂肪腫も発生しうることが知られている。内耳道内脂肪腫は，難聴，耳鳴，めまいなど前庭神経鞘腫と同様の症状をきたすが，その発育・進展様式は異なり，また，MRI画像でも神経鞘腫とは異なった特徴的な所見を呈する。今回，極めてまれな内耳道内脂肪腫の1例を経験し経中頭蓋窩法を用いて摘出した。診断，治療方針などにつき文献的考察を加え報告する。

A 59-year-old female had been suffered from left tinnitus for 10 months and vertigo for 2 months. She did not notice hearing impairment, but pure tone audiograms revealed a sensorineural hearing loss of 45 dB. A small tumor, 5 mm in diameter, in the internal auditory meatus was found by MRI. The tumor showed characteristic findings of lipoma by MRI; a high intensity on T1 without Gd enhance-ment and a low intensity on T2-weight image. The tumor was totally removed by the middle fossa approach preserving hearing and facial nerve func-tion. Histologically lipoma was confirmed.