De Novo Aneurysm Associated with Superficial Temporal Artery to Middle Cerebral Artery Bypass: Report of Two Cases and Review of Literature

BACKGROUND: De novo aneurysm formation has been reported as a rare complication of superficial temporal artery (STA) to middle cerebral artery (MCA) bypass surgery. CASE DESCRIPTION: The first patient with intracerebral hemorrhage had a ruptured de novo aneurysm arising from the recipient MCA at 6 years after undergoing STA-MCA bypass for hemispheric hemodynamic insufficiency. In the second case, an enlarging unruptured STA aneurysm was detected by follow-up magnetic resonance angiography at 8 years after the patient underwent STAMCA bypass for moyamoya disease. Both patients were successfully treated by surgical clipping. CONCLUSIONS: Persistent hemodynamic stress with hypertension in an artificial T-shaped vasculature and traumatic injury during surgical manipulation are the most important causes for de novo aneurysms after STA-MCA bypass. Follow-up magnetic resonance and computed tomography angiography examinations, along with appropriate blood pressure control, are recommended for patients who have undergone STA-MCA bypass surgery.