Enlargement to a saccular aneurysm and subsequent rupture of infundibular widening of posterior communicating artery.

A small dilatation known as infundibular widening (IFw) is frequently seen (7%-25%) on the posterior communicating artery (PComA) at its origin from the internal carotid artery. Development and subsequent rupture of an aneurysm on a previously radiographically demonstrated IFw has rarely been documented. We present two patients who suffered from subarachnoid hemorrhage (SAH). Initial cerebral angiography demonstrated IFw on PComA. They were readmitted to the hospital 9 and 11 years later, after a new SAH. Repeated cerebral angiography revealed an aneurysm arising from the site where the IFw had been seen previously in both cases. The aneurysms were clipped with favorable outcome. This report adds two new cases documenting enlargement of PComAIFw into an aneurysm. Patients with PComAIFw, especially those who have experienced SAH, should be considered for periodic follow-up to rule out the development of an aneurysm over time.