Extracranial-intracranial Bypass Surgery for Symptomatic Chronic Middle Cerebral Artery Occlusion: the CMOSS-2 Trial

Inclusion Criteria: Age of 18-65 years; Confirmed as chronic occlusion of unilateral middle cerebral artery (MCA) by angiography. Other cerebral artery stenosis should be less than 50%. CT perfusion demonstrates severe hemodynamic insufficiency in the territory of the qualifying MCA with MTT (symptomatic side) ≥ 6s or rCBF (symptomatic side/contralateral side) ≤ 0.8; mRS score is 0-2 points; A history of ischemic events (including<1/2 cerebral infarction in the middle cerebral artery supply area, or transient ischemic attack [TIA]) related to the qualifying artery within 12 months ; The onset of acute stroke should be more than 1 month; CT or MRI excludes large cerebral infarction (infarction>1/2 of the territory of the qualifying middle cerebral artery); Patients or their guardians voluntarily participate of the study and sign the consent form. Exclusion Criteria: History of intracranial hemorrhage, subarachnoid hemorrhage, subdural hemorrhage, or extradural hemorrhage within 6 weeks; Unstable angina pectoris or myocardial infarction, congestive heart failure within 6 months; Women who are pregnant or lactating; Coagulation dysfunction or hemorrhagic tendency (e.g. INR > 1.5 and/or platelet count < 100,000 mcL); Other diseases with a life expectancy of less than 2 years Previous treatment with EC-IC bypass surgery Known allergy or contraindication to aspirin or clopidogrel or other antiplatelet drugs. Known cardiac conditions that may lead to cardiogenic embolism: including prosthetic valves, infective endocarditis, left atrial or left ventricular thrombosis, atrial fibrillation, sick sinus node syndrome, atrial mucinous tumor or cardiomyopathy, ejection fraction <25%; Allergy to iodine or x-ray contrast, blood creatinine > 3.0 mg/dl or other contraindications to arteriography Uncontrolled diabetes mellitus with fasting blood sugar (FBS) >16.7 mmol/L Uncontrolled hypertension with a sitting systolic blood pressure >180 mmHg or a sitting diastolic blood pressure >110 mmHg; Persistent worsening of neurological symptoms within 72 hours; Severe liver dysfunction, defined as serum alanine transaminase (ALT) and/or glutamic oxalacetic transaminase (AST) > 3 times the upper limit of normal range; Active peptic ulcer disease; Having received a clinical trial drug or device within 30 days prior to screening, or being enrolled in another clinical trial; Other diseases or medical history that, in the judgment of the investigator, may affect the efficacy or safety evaluation of this study.