良性発作性頭位めまい症と鑑別が困難であった聴神経腫瘍症例

A case of acoustic tumor with nystagmus and vertigo similar to BPPV

はじめに

　聴神経腫瘍（vestibular schwannoma：VS）の経過中での前庭，蝸牛症状などの臨床症状の発症は30％程度とされている^1）。また聴力が正常あるいは左右差がない場合に腫瘍の診断に至る症状としての重要な症状はめまいとされており，めまいを訴える症例では常にVSの可能性を念頭に置く必要がある^2,3）。今回，頭位変換時の回転性めまいと吐き気にて発症し，良性発作性頭位めまい症（benign paroxysmal positional vertigo：BPPV）に類似した眼振所見を認めた比較的稀なVSの1症例を経験したので報告する。

　In this case, there was no difference of pure-tone audiometry between the right and left ears. A auditory brainstem response and caloric test showed no abnormal findings. On the other hand, an eye-tracking test and the optokinetic nystagmus test revealed abnormal findings. From the nystagmus findings, right posterior canal type BPPV was the most likely, so the Epley maneuver was performed three times daily. However, there was no improvement. It was believed that the cases that are most likely to be BPPV from the symptoms and nystagmus findings, the neuro-otological testing should be performed, and if any abnormalities were observed or if it was refractory with the canalith repositioning procedure, MRI imaging should be performed.