The purpose of this study is to understand how carotid endarterectomy (CEA) or percutaneous carotid angioplasty and stenting (CAS) affect memory and thinking resulting in improving or worsening of thinking or memory. There have been many studies on this subject, some finding that certain patients gain improvement in their brain function and others might get worse. The goal of this study is to discover which patients are more likely to have improved cognitive functioning. Carotid endarterectomy (CEA) and percutaneous carotid angioplasty and stenting (CAS) are not investigational and are an accepted treatment for your condition. In addition, subjects that choose not to undergo surgery will also be included in this study.

At the present time, large multi-center clinical trials support the use of carotid revascularization for symptomatic carotid stenosis and for asymptomatic carotid stenosis (greater than 60%) to prevent stroke. Guidelines supporting the use of carotid endarterectomy for asymptomatic stenosis are based largely on the Asymptomatic Carotid Atherosclerosis Study (ACAS) which reported a 47% relative risk reduction for ipsilateral stroke or death in patients randomized to surgery compared to best medical management over 5 years. These data were further substantiated by the recent publication of the Medical Research Council Asymptomatic Carotid Surgery (ACST) trial results (1); however, both trials estimated that at least 40 operative procedures were required to prevent a single disabling stroke or death in one patient after 5 years (2). These data underscore the importance of understanding the cognitive risks of carotid revascularization and developing strategies to limit factors that contribute to this risk especially in asymptomatic patients.

The purpose of this study is to better understand the effect of carotid revascularization (using either carotid endarterectomy (CEA) or percutaneous carotid angioplasty and stenting (CAS)) on cognitive outcome by prospectively collecting cerebral blood flow data and cognitive testing data prior to and after carotid revascularization procedures.

Inclusion Criteria:

• Patients with asymptomatic (defined as no symptoms in past 6 months) carotid stenosis
• Patients with hemodynamically significant carotid artery stenosis (according to CREST criteria: ≥ 60% by angiography, OR ≥ 70% by ultrasound, OR ≥ 80% by CTA or MRA)

Exclusion Criteria:

• Patients with prior large vessel infarct
• Patients with intracranial stenosis
• Patients with major depression
• Patients with Alzheimer disease (clinically defined or Wechsler IQ <80)
• Patients who have had previous ipsilateral carotid surgery
• Patients with baseline dementia defined as: Mini-Mental Status Examination score < 21 OR Mini-Mental score ≥21 AND Baseline HVLT scores more than 3 standard deviations below normal or FAS scores more than 2 standard deviations below normal OR other clinical symptoms that were not as evident on direct cognitive assessment (e.g. sundowning, getting lost while driving).

Note: A control group would be comprised of about 15 patients who meet eligibility criteria as above, but elect to have their condition followed rather than undergo revascularization.

Patients with unilateral, asymptomatic, significant carotid artery stenosis who are ≥18 years of age who do not present with past or current significant cerebrovascular and neuropsychological disease.