Extracranial Carotid Artery Stenosis: The Effects on Brain and Cognition with a Focus on Resting‐State Functional Connectivity

Extracranial carotid artery stenosis (ECAS) due to the presence of atherosclerotic plaque is a well-known risk factor for stroke.Several structural imaging studies have investigated the effect of ECAS on the brain, focusing on structural damage (in particularcerebral small vessel disease) and on the rearrangement of the cerebral circulation. For example, it is known from the literaturean association between carotid stenosis and cerebral small vessel disease, and it is also noted that a series of compensatorymechanisms are activated by the cerebrovascular system in order to overcome the cerebral hypoperfusion that is induced by theECAS. Several neurocognitive studies have also investigated the association of ECAS with cognitive deficits. While the evidencetends to favor a direct association between ECAS and cognition, the actual relationship remains controversial. In the last decade,various resting-state functional connectivity (rs-fc) magnetic resonance (MR) studies have tried to elucidate the “in vivo”mechanisms underlying the cognitive impairment observed in these patients. Although these studies have been performed onsmall cohorts of patients without standardized protocols, it is plausible that in the future, such studies will help find earlystage markers of cognitive impairment. This could permit an extension of indications for revascularization for the treatment ofcognitive impairment in selected patients. The aim of this narrative review is to discuss the current knowledge on the effects ofECAS on brain and cognition by analyzing the main evidence from animal and clinical studies, with a special focus on rs-fc MRstudies