Surgical Intervention for Angiographically Unexplained Subarachnoid Hemorrhage —Report of Three Cases—

We report three patients with subarachnoid hemorrhage in which no causative lesion was detected angiographically. Surgical intervention revealed a ruptured aneurysm in all three cases, which were clipped successfully. Although the prognosis for a patient with subarachnoid hemorrhage of unknown cause is good, there still remain long-lasting unpleasant complaints probably arising from psychogenic factors. We especially recommend exploratory craniotomy when subarachnoid hemorrhage is located anterior to the circle of Willis, accompanied by thick and obviously lateralizing subarachnoid clots on computed tomography and/or rebleeding in the same anatomical location, even if no causative lesions can be found angiographically.