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

Inclusion Criteria:

1. Age of 18-65 years;

2. Confirmed as chronic occlusion of unilateral middle cerebral artery (MCA) by digitalsubtraction angiography (DSA) or computed tomography angiography (CTA). Othercerebral artery stenosis should be less than 50%.

3. CT perfusion demonstrates severe hemodynamic insufficiency in the territory of thequalifying MCA with MTT (symptomatic side) ≥ 6s or rCBF (symptomaticside/contralateral side) ≤ 0.8;

4. mRS score is 0-2 points;

5. A history of ischemic events (including<1/2 cerebral infarction in the middlecerebral artery supply area, or transient ischemic attack [TIA]) related to thequalifying artery within 12 months ;

6. The onset of acute stroke should be more than 1 month;

7. CT or MRI excludes large cerebral infarction (infarction>1/2 of the territory of thequalifying middle cerebral artery);

8. Patients or their guardians voluntarily participate of the study and sign theconsent form.

Exclusion Criteria:

1. History of intracranial hemorrhage, subarachnoid hemorrhage, subdural hemorrhage, orextradural hemorrhage within 6 weeks;

2. Unstable angina pectoris or myocardial infarction, congestive heart failure within 6months;

3. Women who are pregnant or lactating;

4. Coagulation dysfunction or hemorrhagic tendency (e.g. INR > 1.5 and/or plateletcount < 100,000 mcL);

5. Other diseases with a life expectancy of less than 2 years

6. Previous treatment with EC-IC bypass surgery

7. Known allergy or contraindication to aspirin or clopidogrel or other antiplateletdrugs.

8. Known cardiac conditions that may lead to cardiogenic embolism: including prostheticvalves, infective endocarditis, left atrial or left ventricular thrombosis, atrialfibrillation, sick sinus node syndrome, atrial mucinous tumor or cardiomyopathy,ejection fraction <25%;

9. Allergy to iodine or x-ray contrast, blood creatinine > 3.0 mg/dl or othercontraindications to arteriography

10. Uncontrolled diabetes mellitus with fasting blood sugar (FBS) >16.7 mmol/L

11. Uncontrolled hypertension with a sitting systolic blood pressure >180 mmHg or asitting diastolic blood pressure >110 mmHg;

12. Persistent worsening of neurological symptoms within 72 hours;

13. Severe liver dysfunction, defined as serum alanine transaminase (ALT) and/orglutamic oxalacetic transaminase (AST) > 3 times the upper limit of normal range;

14. Active peptic ulcer disease;

15. Having received a clinical trial drug or device within 30 days prior to screening,or being enrolled in another clinical trial;

16. Other diseases or medical history that, in the judgment of the investigator, mayaffect the efficacy or safety evaluation of this study.