Acute subdural hematoma from ruptured posterior communicating artery aneurysm.

Acute spontaneous subdural hematoma is infrequent in association with rupture of intracranial saccular aneurysm. In the majority of cases, aneurysms of the middle cerebral artery along the convexity or of the anterior cerebral artery along the interhemispheric fissure are found to be the culprits. We present two recent cases of internal carotid-posterior communicating artery aneurysms causing acute subdural hematoma with little or no subarachnoid hemorrhage and discuss the possible mechanisms for this occurrence.