Prediction of Hyperperfusion After Carotid Stenting by Multi-parameter Characteristics Based on Cerebral Autoregulation

1. To analysis the incidence of postoperative complications such as CH and CHS within 1 months and to find the risk factors of CH. A. To enroll 400 cases of patients suffering from carotid artery stenosis. the investigators perform TCD on patients by Sonographer for identifying CH. B. Postoperative CH will be defined in patients whose MCA mean velocity increased by more than 100% within 48 hour after carotid artery stent. C. CH and CHS mostly occurs within one week after CAS. Although there are a few reports of CHS occurring from three weeks to four weeks after CAS. D. All tests are non-invasive. 2. The diagnosis of CHS will be based on the following criteria: A. The appearance of symptoms within 1 month after surgery. B. First-time unilateral headache, convulsions, hemiparesis/hemiplegia, visual disturbances, ataxia, aphasia, signs of cerebral edema or intracerebral hemorrhage. C. Increase in cerebral blood flow in the middle cerebral artery \> 100% compared to the preoperative value measured by transcranial dopplerography. D. Hypertensive encephalopathy, reversible posterior leukoencephalopathy syndrome and reversible cerebral vasoconstriction syndrome are excluded. 3. The parameter of ultrasonic measurement A. The CDU before CAS about plaque imaging and other parameters will be stored in Statistical Package for the Social Sciences （PACS）and analyzed later. B.The TCD peri-CAS will be used to detect main intracranial arteries, the peak systolic velocity（PSV）, end-diastolic velocity（EDV）and PI of bilateral MCA will be recorded. C.The post-CAS imaging and parameters included the characteristics of stent and hemodynamic parameters by CDU and TCD.