Efficacy and Safety of Stent Implantation in Symptomatic Extra- and Intracranial Artery Stenosis

Inclusion Criteria: 1. Aged between above 40 year-old and 75 year-old. 2. Ischemic stroke related to extra- and intracranial atherosclerosis stenosis, transient ischemic attack (TIA ), onset time within 90 days 3. Implantation of stent should be at least 1 week after stroke onset, and patient's medical condition stable, no time limit for TIA, 4. Stenosed ICA or MCA or BA or VA is the candidate arteries for stent implantation. 5. Degree of stenosis of target artery ranges between 51%-99% 6. Modified Rankin score≤3 or NIHSS Score ≤4 7. Informed consent is obtained. Exclusion Criteria: Patients will be excluded from entry if any of the criteria listed below are met: 1. Target stenosis artery is not suitable for stent implantation after evaluation. 2. Previous carotid endarterectomy or carotid artery stent ,or intracranial artery stent implantation. 3. Ischemic stroke is caused by conditions other than atherosclerosis . 4. Documented non-atherosclerosis angiopathy. 5. Clinically unstable at the time of enrollment, 6. Conditions which may lead to cardiogenic embolism : arterial fibrillation，left ventricular thrombi,Myocardiac infarction within 6 weeks,etc. 7. Severe hypertension (systolic blood pressure \>180 mmHg or diastolic blood pressure \>110 mmHg) 8. Severe co-morbid or unstable medical condition, ie，severe heart failure, pulmonary failure or renal failure, liver dysfunction (serum liver enzyme twice or more than normal level),malignancy with likelihood of death within the next 2 years 9. Significant memory or behavioral disorder, ie, Alzheimer disease, etc.daily care needed. 10. Concurrent participation in another clinical trial 11. Unable to return follow up 12. History of hemorrhagic disease(ie, intracranial hemorrhage, Idiopathic Thrombocytopenic Purpura,etc ) or bleeding tendency conditions. 13. Intracranial arteriovenous malformation or aneurysm.