Significance of infundibular dilatation in unexplained subarachnoid hemorrhage.

Angiographically equivocal aneurysmal dilatation at the junction of the internal carotid and the posterior communicating arteries was noted in a patient with documented subarachnoid hemorrhage. This was initially thought to be infundibular dilatation. A craniotomy revealed an actual aneurysm, which was obliterated successfully. Whether infundibular dilatation is a preaneurysmal state or a benign dilatation is controversial. The management of angiographically noted infundibular dilatation in cases of "essential" subarachnoid hemorrhage is discussed.