RESUMEN
OBJECTIVE AND IMPORTANCE: A rare case of an aneurysm arising at the fenestration of the P2 segment of the posterior cerebral artery is reported. CLINICAL PRESENTATION: A 37-year-old man presented with severe headache and disturbance of consciousness. Computed tomographic scanning showed diffuse subarachnoid hemorrhage. Cerebral angiography revealed an aneurysm at the fenestration of the P2 segment of the right posterior cerebral artery. The aneurysm was located at the middle portion of the lower trunk of the fenestration. An unruptured arteriovenous malformation was incidentally found in the right thalamus. INTERVENTION: A right frontotemporal craniotomy with orbitozygomatic osteotomy was made, and the aneurysm was successfully clipped. One year after the operation, gamma knife surgery was performed for the right thalamic arteriovenous malformation. CONCLUSION: This is the first reported case of an aneurysm originating from the middle portion of a fenestrated posterior cerebral artery.