後下小脳動脈末梢部の解離性動脈瘤の一例—症例報告と文献的考察

Dissecting Aneurysm of Distal Posterior Inferior Cerebellar Artery : Case Report and Review of the Literature

　くも膜下出血にて発症した後下小脳動脈末梢部解離性脳動脈瘤の稀な一例を報告する。症例は51歳，女性。突然の激しい頭痛と嘔吐にて発症し，CTで後頭蓋窩に強いくも膜下出血，脳血管写で左後下小脳動脈末梢部のtelovelotonsillar segmentに動脈瘤を認めた。左後頭蓋窩開頭による動脈瘤の摘出術を施行した。動脈瘤は血管分岐部を含むfusiform型であり，摘出動脈瘤の組織所見では内膜の著明な肥厚と内弾性板の低形成と断裂，中膜筋層の低形成を認め，内弾性板と中膜間で解離が起こっていた。文献的に渉猟すると，頭蓋内解離性動脈瘤の発生部位は，内頸動脈，中大脳動脈近位部，椎骨脳底動脈が大部分であり，非主幹動脈末梢部，特に後下小脳動脈皮質枝の解離性動脈瘤は極めて稀であった。

A rare case of dissecting aneurysm of distalposterior inferior cerebellar artery (PICA) is repor-ted. A 51-year-old woman was admitted to our hospital complaining of severe headache and nau-sea. CT scan revealed subarachnoid hemorrhage which was thicker in the posterior fossa. The vertebral angiography demonstrated an aneurysm on the telovelotonsillar segment (Lister's classification) of the left PICA. On the third day, the left suboccipital craniotomy was performed and the fusiform aneurysm was resected. The postoper-ative course was uneventful. Histological examina-tion of the resected aneurysm showed a dissection between the ruptured elastic lamina and the tumica media.

Dissecting aneurysm of distal PICA is still belong to a rare entity. In all three cases found in the literature, the dissecting aneurysms are sited in the anterior medullary segment of PICA. Probably, this is the first report described a dissecting aneurysm on the more distal part-telovelotonsillar segment of PICA. The clinical features, pathogenesis and treat-ment of intracranial dissecting aneurysms are briefly discussed with reviewing the literature.