A partially thrombosed, fenestrated basilar artery mimicking an aneurysm of the vertebrobasilar junction: case report.

We report a patient with a subarachnoid hemorrhage in whom a partially thrombosed, fenestrated basilar artery mimicked an aneurysm of the vertebrobasilar junction on preoperative angiography. Intraoperatively, no aneurysm was detected; instead, the patient was found to have partial thrombosis of one limb of the fenestrated basilar artery. The nodular appearance of the residual lumen of the vessel corresponded exactly to the angiographic findings. To our knowledge, no similar case has been reported.