Abstract
Two cases with cerebral aneurysms and bilateral carotid occlusion are described. They had no cerebral ischemic attack prior to aneurysmal subarachnoid hemorrhage because of sufficient collateral blood flow from the posterior circulation. The cerebral aneurysms were both located in the posterior circulation where the hemodynamic stress might have occurred.
Case 1. A 54-year-old hypertensive man was admitted with headache. Computerized tomography scan and cerebral angiography revealed subarachnoid hemorrhage, bilateral internal carotid occlusion, and two saccular aneurysms of the right posterior cerebral artery at the junction of the posterior communicating artery. The blood flow for both cerebral hemispheres was mainly supplied through the posterior circulation via the right posterior communicating artery. Physical examination on admission was unremarkable except for moderate nuchal rigidity and headache. He was discharged after clipping of the aneurysms.
Case 2. A 81-year-old woman was admitted because of sudden loss of consciousness. She had an unremarkable an history except for a short term loss of consciousness three months prior. On admission she was in a semicomatose state, and showed no lateralizing signs. Computerized tomography scan revealed subarachnoid hemorrhage. On aortography, the innominate artery and the left common carotid artery were not opacified from their origin. The left vertebral artery, which was enlarged and elongated, supplied most of the cerebral hemispheres through both posterior communicating arteries. The saccular aneurysm was located at the lower part of the basilar artery where the hemodynamic stress might have occurred. She died without recovery.
The present report indicates that the hemodynamic stress caused by bilateral carotid occlusion in combination with hypertension or aging may play an important role in aneurysmal formation in the posterior circulation.
