Ruptured blister-like aneurysm arising from the proximal posterior cerebral artery: a case report

Abstract Background Blister-like aneurysms (BLAs) arise mostly at the supraclinoid internal carotid artery. We report a rare case of ruptured BLA arising at the P1 segment of the posterior cerebral artery (PCA). Case Description A 34-year-old woman presented with disturbance of consciousness. Computed tomography (CT) of the head showed diffuse subarachnoid hemorrhage (SAH). A tiny bulge on the right PCA P1 segment was observed on initial CT angiography. The lesion enlarged little-by-little, with re-rupture occurring 10 days after initial hemorrhage. We diagnosed BLA arising at the P1 segment, and performed emergent endovascular parent artery occlusion (PAO) of the P1 segment. No infarction was observed in the territory of the PCA postoperatively. Conclusions Proximal PCA is a rare but possible location for BLA. When the cause of bleeding SAH cannot be identified, repeated radiological assessments including posterior circulation should be performed. If perforators of the unaffected site supply the thalamus and midbrain bilaterally and an ipsilateral posterior communicating artery exists, PAO of P1 seems feasible as a treatment. Elective intervention is not recommended because of the characteristics of ruptured BLAs.