Disappearance of a moyamoya-related distal anterior cerebral artery aneurysm after target bypass revascularization: illustrative case

BACKGROUND: Aneurysm formation is a complication of moyamoya disease (MMD). Distal anterior cerebral artery (ACA) aneurysms account for approximately 1% of MMD-related aneurysms. We report a case of target bypass for adult patients with MMD who presented with intracranial hemorrhage due to rupture of a distal ACA aneurysm, whose disappearance was confirmed postoperatively. OBSERVATIONS: A 45-year-old woman presented with sudden-onset headache and loss of consciousness. Head computed tomography showed hemorrhage in the genu of the corpus callosum with intraventricular extension. Digital subtraction angiography (DSA) revealed Suzuki stage III MMD and a left A3 segment aneurysm. Superficial temporal artery (STA)–middle cerebral artery (MCA) bypass and STA-ACA target bypass were performed to reduce hemodynamic stress on the left ACA. DSA 6 months after surgery showed patency of both bypasses and disappearance of the aneurysm. At the 20-month follow-up, the patient was asymptomatic and neurologically intact. LESSONS: Bypass revascularization may be an effective treatment to reduce hemodynamic stress and eliminate MMD-related aneurysms.