A ruptured middle cerebral artery aneurysm originating from the site of anastomosis 20 years after extracranial-intracranial bypass for moyamoya disease: case report

Abstract

Background: Direct revascularization through a superficial temporal artery-middle cerebral artery (STA-MCA) bypass is often performed to prevent ischemic or hemorrhagic attack in patients with moyamoya disease. This is the first reported case of aneurysm formation and rupture due to an STA-MCA bypass in a patient with moyamoya disease.

Case description: A 52-year-old man who had undergone bilateral STA-MCA bypass for caudate hemorrhage due to moyamoya disease 20 years previously suffered from sudden-onset unconsciousness. Computed tomography revealed a massive intracerebral hematoma (ICH) in the left frontoparietal region. Angiography showed good patency of the anastomoses and stage IV moyamoya disease. However, no other abnormality was found. Emergency evacuation of the hematoma was performed. The patient's postoperative course was uneventful, but consciousness disturbance of sudden onset occurred 1 month later. Computed tomography showed a hematoma in the lateral ventricle and acute hydrocephalus. Repeat angiography revealed an aneurysm on the left side of the anastomosis. Bilateral ventricle drainage tubes were inserted, and the aneurysm was clipped. A ventriculoperitoneal shunt was later performed.

Conclusion: In patients with moyamoya disease who have undergone extracranial-intracranial bypass surgery, progressive hemodynamic stress may cause the formation of de novo aneurysms after a postoperative period of several decades. Imaging examinations should therefore be performed periodically for follow-up, and a de novo aneurysm should be suspected in a patient who has an unusual ICH.