Inclusion Criteria:  Written informed consent is obtained Patients with age between 4-60 years Cerebral digital subtraction contrast angiography (DSA) reveal severe stenosis or occlusion of the distal internal carotid or proximal middle and anterior cerebral arteries with prominent lenticulostriate 'moyamoya collaterals'  Exclusion Criteria:  There are other vascular diseases, including systemic vasculitis, neurofibroma, meningitis, sickle cell disease, down's syndrome, and previous basilar radiotherapy Patients with cardiogenic embolism, including a history of atrial fibrillation, valvular disease or cardiac valve replacement Physical or subjective failure to cooperate with the examination or serious comorbid diseases