Drug Eluting Stents Versus Bare Metal Stents for Treatment of Symptomatic Extracranial Vertebral Artery Stenosis

Inclusion Criteria: * Symptomatic posterior circulation ischemia（Vertebral basilar artery system TIA or non-disabling ischemic stroke）result from the stenosis in the extracranial proximal vertebral artery stenosis. * Atherosclerotic extracranial proximal vertebral artery stenosis demonstrated by angiography(any of the following): 1) bilateral vertebral artery stenosis ≥70%, or vertebral artery stenosis ≥70% concomitant occlusion of contralateral vertebral artery; 2) superior lateral vertebral artery stenosis ≥70%; 3) non-superior lateral vertebral artery stenosis ≥50%, but the vertebral artery was directly extended to the posterior inferior cerebellar artery on this side and symptoms were related to insufficiency of the ipsilateral posterior inferior cerebellar artery. Exclusion Criteria: * 1\) lesions characteristics (such as diffuse lesions) which was not suitable for interventional treatment, or unstable condition that cannot tolerate the interventional therapy; * 2\) vertebral artery stenosis caused by non atherosclerosis disease: Takayasu arteritis or other diseases; * 3\) severe stroke within 3 months; * 4\) contraindicated using contrast agents: such as chronic renal insufficiency or had serious contrast agents allergy history; * 5\) malignant tumor; * 6\) with Alzheimer's disease or mental illness previously or currently ; * 7\) patients or family members refuse the operation.