右前頭円蓋部epithelial cystの1例—名称の混乱と統一への考察

An Epithelial Cyst at the Frontal Convexity

I．はじめに

　テント上脳内あるいは円蓋部の上皮性嚢胞，いわゆるepithelial cystは稀で1977年にFriedeら^5）がreviewした17例の後には若干の報告^1,9-12）しかない．そのほとんどは四丘体部^13-15），後頭蓋窩^{4,6,7,10,15-18）}もしくは脊髄腔内^10,11）に発生したものである．

　今回われわれは右前頭円蓋部に生じたepithe-lialcystの稀な1例を経験したので若干の文献的考察を加えて報告する．

We report a rare case of an epithelial cyst at the right frontal convexity. A 60-year-old woman came to our hospital suffering from dysarthria and gait disturbance. Computed tomography (CT) of the brain on admission showed a round low-density area, 6 cm in diameter, at the right frontal convexity. Midline shift and displacement of the lateral ventricle are seen. There is no contrast enhancement effect. Excision of the cyst wall and fenestration into the subarachnoid space was carried out and the patient was discharged with no neurological deficits. After 5 years, regrowth of the cyst was seen. Cyst-peritoneal shunt was performed and she was discharged uneventfully. Light microscopy showed the cyst wall consisted of a monolayer of flat epithelium and loose connective tissue.

An electronmicrograph of the cyst wall showed a non-ciliated epithelial layer with microvilli and base-ment membrane. The epithelial cells connecting with each other through desmosome have numerous endo-plasmic reticulum and mitochondria . Interdigitation of the cytoplasmic membrane was not seen. The term “epithelial cyst” seems ambiguous. We discuss the pathogenesis and the nomenclature for intracranial be-nign cystic lesions based on the previous literature.