自然血栓化し再開通を来した後下小脳動脈遠位部の小型破裂瘤の稀な1症例

A Rare Case of Spontaneous Thrombosis and Recanalization of a Ruptured Small Aneurysm in the Distal Posterior Inferior Cerebellar Artery

Ⅰ．はじめに

　破裂脳動脈瘤における自然血栓化はよく知られた現象であるが，その多くは巨大あるいは大型の動脈瘤の報告であり^4,18)，小型脳動脈瘤における自然血栓化の報告は少なく，その自然歴も不明な点が多い^{2,3,6-9,11-17)}．

　今回われわれは，後下小脳動脈（posterior inferior cerebellar artery：PICA）遠位部に発生した小型破裂脳動脈瘤が自然血栓化し，早期に再開通を来した稀な1症例を経験したので，文献的考察を加え報告する．

　The incidence of spontaneous thrombosis of intracranial aneurysm ranges from 1% to 2% of ruptured aneurysms. Most of them are giant or large aneurysms, and various factors have been discussed in previous literatures. Recanalization of thrombosed aneurysms may be rare, but its mechanism is poorly understood. Reports on recanalization of small aneurysms after spontaneous thrombosis are rare, and the natural history is still unknown. We describe a rare case of spontaneous thrombosis and recanalization of a ruptured small aneurysm of the distal posterior inferior cerebellar artery.

　Spontaneous aneurysmal thrombosis should not always be considered as a good or safe sign, as it may recanalize in a short time, resulting in re-rupture. In the acute stage, periodic follow-up of patients with a spontaneously thrombosed aneurysm is important.