Ruptured aneurysm of the accessory middle cerebral artery associated with moyamoya disease: a case report.

The accessory middle cerebral artery can provide collateral blood supply in moyamoya disease. We report a case of unilateral moyamoya disease which demonstrates the anatomy of the right accessory middle cerebral artery and a ruptured peripheral aneurysm on the artery. Our patient was a 56-year-old woman who initially suffered from headache and lethargy. Right caudate nucleus hemorrhage with intraventricular extension and spontaneous subarachnoid hemorrhage were found on brain computed tomography. A ruptured peripheral accessory middle cerebral artery aneurysm associated with unilateral moyamoya disease was diagnosed on cerebral angiography. Surgical intervention to excise the peripheral accessory middle cerebral artery aneurysm assisted by frameless navigation guidance to reduce the risk of damage to collateral vessels was done successfully. Histopathology of excised tissue showed this anomaly was a pseudoaneurysm. The management of an aneurysm in moyamoya disease should be modified based on its location and collateral vessels. Prevention of aneurysm bleeding and preservation of collateral vessels during craniotomy are the critical when managing hemorrhagic moyamoya disease. This case suggests that surgical intervention for ruptured intracranial aneurysms is safe with the use of frameless navigation guidance to minimize collateral vessel injuries.