Cognitive outcomes after carotid revascularization: the role of cerebral emboli and hypoperfusion.

OBJECTIVE: Carotid artery stenting (CAS) and carotid endarterectomy (CEA) are currently being compared in ongoing randomized, controlled trials using postprocedural 30-day stroke rate, myocardial infarction, and mortality as primary endpoints. Recent data suggest that cognitive function may decline after CEA. Understanding the mechanisms that affect cognitive outcomes after carotid revascularization will be important in the design of future comparative studies of CAS and CEA incorporating cognitive outcome as an endpoint. SUMMARY OF REVIEW: The effects of carotid revascularization procedures on cognitive outcome are unclear. Several factors contribute to the difficulty in interpreting cognitive data, including patient heterogeneity, variability of surgical techniques, and the differences in neuropsychological testing methodology. Mechanisms underlying cognitive effects during CEA have emerged, including the potential detrimental effect of procedural emboli and the beneficial effect of improved cerebral hemodynamics. The emergence of CAS as an alternative to CEA for treating carotid stenosis again raises questions about cognitive outcomes. Despite the use of distal protection devices, CAS is associated with a higher burden of microemboli. CAS does not, however, require the extent of temporary vessel occlusion associated with CEA. Quantifying microemboli and changes in cerebral hemodynamics along with standardization of neuropsychological testing may lead to meaningful comparisons of cognitive data for patients undergoing carotid revascularization procedures.
CONCLUSION: As use of CAS increases, it is important for randomized, controlled trials comparing CAS with CEA to include cognitive outcomes assessments. Furthermore, understanding the key mechanisms resulting in cognitive impairment during carotid revascularization procedures might limit injury.