Functional Mri Evaluation of the Cognitive Outcome in the Patients Receiving Carotid Artery Stenting

Stenosis of the extracranial internal carotid artery has been identified as a major risk factor for stroke. Carotid artery stenting (CAS) is effective in reducing stroke in patients with carotid stenosis. However, the role of CAS in asymptomatic patients is still controversial. Besides stroke, patients with carotid stenosis are also at risk for cognitive impairment. Recently, cognitive function is being increasingly recognized as an important outcome measure for CAS. Conventional vascular risk factors (hypertension, diabetes, dyslipidemia and smoking) are common risk conditions for stroke, carotid stenosis and dementia. Whereas stroke is a well-known cause of dementia, carotid stenosis itself is a less well-established independent risk factor for a cognitive impairment. Furthermore, the exact mechanism of cognitive impairment in patients with asymptomatic carotid stenosis is still poorly understood. We hypothesize that impaired neurovascular response may be a potential cause of impaired cognitive function in asymptomatic patients with carotid stenosis. The impairment, possibly affected by decreased cerebrovascular reactivity (CVR), could not only be a decrease in amplitude of response, but also a delay in response, which is less directly investigated before. In this study, we would use task functional MRI to exam the patients with asymptomatic carotid stenosis before and 3 month after receiving CAS. A working memory (WM) task would be used to evaluate patient’s attention and memory function, visuomotor task to processing speed and breath-hold CVR task to impairment of vascular response. The results may help us better understand the pathophysiology of cognitive impairment in asymptomatic carotid stenosis as well as the treatment effect of CAS, which may better rationalize CAS in asymptomatic carotid stenosis.