[A case of ruptured true posterior communicating artery aneurysm thirteen years after surgical occlusion of the ipsilateral cervical internal carotid artery].

A case is presented of ruptured "true" posterior communicating artery aneurysm thirteen years after surgical occlusion of the ipsilateral cervical internal carotid artery. A 58-year-old female developed the sudden onset of blepharoptosis on the right side. She had had a right superficial temporal artery-middle cerebral artery anastomosis and a surgical occlusion of the right cervical internal carotid artery 13 years earlier for a subarachnoid hemorrhage that occurred as the result of a ruptured aneurysm of the right internal carotid artery. Neurological examination on admission revealed an occulomotor palsy on the right. Cerebral angiograms demonstrated an aneurysm arising from the right posterior communicating artery itself near the right posterior cerebral artery. Also, the right intracranial internal carotid artery was supplied through the right posterior communicating artery. Five days later she experienced the sudden onset of severe headache. CT scan showed subarachnoid hemorrhage in the ambient cistern. Neck clipping of the aneurysm was successfully performed by the contralateral zygomatic approach. The postoperative course was uneventful. It has been well known that internal carotid artery occlusion may be associated with cerebral aneurysm in some cases. However, it seems to be very rare that a "true" posterior communicating artery aneurysm should occur following the ipsilateral carotid artery occlusion. Hemodynamic factors were strongly suggested as the reason for aneurysmal formation in this case.