Infundibular widening of the posterior communicating artery progressing to true aneurysm

Infundibular widening has been defined as a triangular or rounded dilatation of diameter not greater than 3 mm occurring at the origin of the posterior communicating artery, with the posterior communicating artery in continuation with the apex of the dilatation (Saltzman, 1959). In February 1970 a woman aged 35 presented with severe pain in the first branch of the left 5th nerve accompanied by diplopia and left ptosis. Her past medical history was unremarkable and she was normotensive. Bilateral carotid angiography demonstrated an aneurysm arising from the origin of the left posterior communicating artery (Fig. 1) while on the right side there was infundibular widening of the origin of the posterior communicating artery (Fig. 2). The left common carotid artery was ligated and the facial pain resolved completely leaving slight residual 3rd nerve palsy. In January 1979 she suddenly lost consciousness and was found to have neck stiffness and a right 3rd nerve palsy. Lumbar puncture revealed uniformly bloodstained CSF. A right carotid angiogram on this occasion demonstrated a multilocular aneurysm arising from the site of the previous infundibular widening. There was associated spasm of the internal carotid artery and the anterior and middle cerebral arteries (Fig. 3). This aneurysm was successfully clipped (Fig. 4) and when last seen in 1980 she remained well.