Rapidly growing distal choroidal artery aneurysm re-rupture following revascularization for hemorrhagic Moyamoya disease: A case report.

Intracranial hemorrhage is the leading cause of neurological deficits and poor prognosis in adult patients with Moyamoya disease (MMD). Intracranial hemorrhage is occasionally accompanied by MMD-associated aneurysm and requires additional treatment. To date, direct or indirect bypass surgery or endovascular treatment, such as coil embolization, has been adopted and has achieved successful outcomes. The rapid growth of MMD-associated aneurysms and rebleeding after direct bypass surgery via superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis has rarely been reported. We report a case of a rapidly growing fragile arterial pseudoaneurysm in a patient with MMD. A 45-year-old female was admitted with a headache and decreased mental status. Radiological evaluation, including distal subtraction angiography, revealed intraventricular hemorrhage with a left posterior choroidal artery pseudoaneurysm. Within 4 days after revascularization surgery via STA-MCA direct bypass, the size of the pseudoaneurysm rapidly increased and rebleeding occurred, requiring coil embolization. After endovascular therapy and a second STA-MCA bypass surgery, the patient recovered well and was discharged 8 days later. Follow-up radiological imaging revealed an obliterated pseudoaneurysm without rebleeding or complications. In this case, the rapid growth of an MMD-associated pseudoaneurysm was observed after revascularization surgery because of temporary hemodynamic instability. This report raises questions regarding the causes and management of unstable postbypass hemodynamics.