Ruptured infectious aneurysm of the distal middle cerebral artery manifesting as intracerebral hemorrhage and acute subdural hematoma--case report.

A 21-year-old woman with severe mitral valve regurgitation due to infectious endocarditis was transferred to our institute in a deep coma with intracerebral hemorrhage and acute subdural hematoma. She had no history of head injury. Brain computed tomography revealed left frontoparietal intracerebral hematoma and adjacent acute subdural hematoma that were evacuated on the day of admission, but the distal middle cerebral artery (MCA) aneurysm remained undetected. Follow-up cerebral angiography demonstrated the distal MCA aneurysm, which had enlarged by 25% at 2 weeks following the first operation. The aneurysm originated from a branch of the angular artery and was successfully resected on Day 22. Histological examination of the aneurysm section showed no infectious nature, but the final diagnosis was infectious intracranial aneurysm based on the presence of infectious endocarditis.