In this prospective study, patients with carotid stenosis will be randomly assigned to one of the two surgical procedures (carotid endarterectomy (CEA) and carotid stenting (CAS)). Pre- and postoperative neuropsychological functions, levels of several biomarkers and intraoperative embolization load will be examined. In a subgroup of patients, MRI-data will also be gathered. The mix of these data will allow us to answer several questions regarding the absence or presence of preoperative impairments, postoperative changes in cognitive performance and possible differences between CEA and CAS regarding postoperative neuropsychological functions. The use of a matched control group and implementation of a long term follow-up will contribute to the uniqueness of this study. It will meet several flaws of previous studies and will complete the ongoing randomized studies comparing CEA and CAS that are lacking neuropsychological data.