Subarachnoid hemorrhage in a patient with a meningioma and an unruptured aneurysm

Subarachnoid hemorrhage (SAH) is usually elicited by cerebrovascular disease and infrequently by brain tumors. A 64-year-old woman presented with SAH with a left petrous meningioma and an unruptured left internal carotid-posterior communicating artery (IC-PcomA) aneurysm. She suffered sudden onset of headache and nausea followed by consciousness disturbance 7 days after onset. Computed tomography (CT) revealed diffuse SAH and a tumor at the petrous portion. Angiography demonstrated a left IC-PcomA aneurysm. Under a diagnosis of a ruptured aneurysm and a coincidental meningioma, we performed neck clipping of the aneurysm. However, intraoperatively we found that the aneurysm was unruptured and we subsequently performed tumor resection. Intraoperatively we could not find the cause of SAH during resection of the meningioma. The histological diagnosis was transitional meningioma with deposition of fibrin on the surface of the tumor. The findings of initial CT and magnetic resonance imaging, and pathological results could not conclude the definitive etiology of SAH in this case.