内頸動脈閉塞に合併した後大脳動脈末梢部動脈瘤の1例

A Case of Distal Posterior Cerebral Artery Aneurysm Associated with Occlusion of the Internal Carotid Artery

I．はじめに

　脳動脈瘤の成因は中膜の欠損，結合織の脆弱化などの先天的要因に加え，後天的因子としてhemodynamic stressがその発生に重要な役割を果たしていると考えられている．

　今回内頸動脈の閉塞に伴い，中大脳動脈領域への側副血行路として後大脳動脈が発達し，その末梢部（P4 portion）に増大したhemodynamic stressの影響により発生したと考えられた脳動脈瘤の症例を経験したので報告する．

Hemodynamic stress is considered one of the most important factors in the growth of cerebral aneu-rysms. The authors report a rare case of cerebral aneurysm located at the distal posterior cerebral artery (PCA) in which collateral circulation developed due to occlusion of the internal carotid artery (ICA).

A 73-year-old male was admitted to our hospital with a sudden headache and nausea. Computerized tomography (CT) revealed an intracerebral hematoma in the right parieto-occipital lobe and the acute sub-dural hematoma in both the cerebral interhemispheric fissure and the convexity. Moreover, angiography revealed a saccular aneurysm at the P4 portion of the PCA. The right ICA was occluded at the cervical portion and collateral circulation which had developed in the PCA was extended to the region of the right middle cerebral artery.

The aneurysm was clipped 15 days after admission without new neurological complications. This case demonstrates that increased hemodynamic stress plays a role in the growth and rupture of cerebral aneu-rysm.