LAUSR

BACKGROUND Aplastic or twig-like MCA, a congenital anomaly related to the abnormal development of the MCA, is rare. It is usually unilateral; bilateral lesions are extremely rare. An aplastic or twig-like MCA may lead to cerebral ischemic stroke, intracranial hemorrhage, and SAH. In patients with ischemic stroke due to hemodynamic stress, EC-IC bypass surgery is indicated. As hemodynamic stress may also elicit SAH, it is important to select the appropriate treatment. EC-IC bypass surgery was successful in a patient with bilateral aplastic or twig-like MCA who suffered SAH due to hemodynamic stress. CASE DESCRIPTION A 64-year-old female with a history of surgery for tetralogy of Fallot experienced SAH in the left Sylvian fissure. As angiography showed a bilateral aplastic or twig-like MCA and single photon emission computed tomography revealed a decrease in the cerebral blood flow in the left MCA territory, we attributed her SAH to hemodynamic stress due to the decreased blood flow in the MCA territory and to the vulnerability of abnormal vessels as are seen in Moyamoya disease. We performed EC-IC bypass surgery to reduce hemodynamic stress. A cerebral angiogram obtained 2 weeks postoperatively revealed sufficient blood flow in the MCA territory from the STA used for bypass. In the course of 2-year follow she remained stroke-free. CONCLUSION The presence of aplastic or twig-like MCA may lead to stroke due to hemodynamic stress. EC-IC bypass surgery may help to prevent stroke recurrence and SAH.