[A case of distal posterior cerebral artery aneurysm associated with occlusion of the internal carotid artery].

Hemodynamic stress is considered one of the most important factors in the growth of cerebral aneurysms. 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 subdural 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 aneurysm.