1.Causing a decrease in cerebral blood flow and a decrease in the compensatory capacity of cerebral blood flow. 2.Dislodgement of atherosclerotic plaque at the stenosis site leads to cerebral embolism. 3.Severe stenosis causes a significant reduction of cerebral blood flow directly causing cerebral infarction. According to domestic and foreign data, for severe cerebral artery stenosis, although treated by regular medical treatment, about 1/3 of patients still have a serious stroke within 3 years.