Aneurysm on the cortical branch (P4 segment) of the posterior cerebral artery. Case report.

A 75-year-old woman presented with a rare aneurysm on the distal portion (P(4)) of the posterior cerebral artery (PCA) causing subarachnoid hemorrhage (SAH) and manifesting as sudden onset of headache, nuchal rigidity, and nausea. Computed tomography on admission revealed thin SAH in the left parietooccipital sulcus. Cerebral angiography demonstrated a small saccular aneurysm on the cortical branch of the left PCA. The aneurysm was successfully clipped via the occipital interhemispheric approach. Distal PCA aneurysms frequently affect middle-aged persons and tend to be small, with good clinical course but may cause visual field defects. Direct aneurysm clipping is recommended for patients without visual defect from the onset. Parent artery occlusion by the endovascular technique should be considered for patients with visual loss caused by the initial hemorrhage.