[Stenosis of the posterior cerebral artery (P1) discovered at the time of a meningeal hemorrhage and simulating an arterial aneurysm].

A case is reported, in which a patient 54 years old, was admitted after a SAH. The CT Scan (D1) demonstrated blood in the peri-peduncular cisterns. A first angiogram through femoral route was performed at D1. There was no vascular malformation on both carotid territories. An arterial ectasia was demonstrated on the basilar artery, arising at the origin of the left superior cerebellar artery. The left posterior cerebral artery was supplied only by the left carotid artery through a dilated posterior communicating artery. A second left vertebral angiogram was performed at D8, to make sure whether this ectasia was an aneurysm or a non aneurysmal dysplasia, but failed to provide certainty. The patient was operated upon at D17, with the diagnosis of possible aneurysm at the origin of the left superior cerebellar artery. Through a pterional route the posterior communicating artery was approached, no blood was found in the area of the upper basilar artery; there was an abnormal posterior circle of Willis, the superior cerebellar artery arising with a common trunk from the upper basilar artery; distal to this common trunk, the P1 segment was normal on the first three fourths of its course; the last fourth of the P1 segment was highly narrowed, the outer diameter of the narrowed P1 segment was approximately one third of the normal P1 segment, and was located at the junction with the complex posterior communicating artery-P2 segment. This narrowed part of the P1 segment showed evidence of an atheromatous plaque on its wall. No aneurysm was found in this area.(ABSTRACT TRUNCATED AT 250 WORDS)