Impaired Cerebral Hemodynamics in Asymptomatic Carotid Artery Stenosis Assessed by Resting-State Functional MRI

Background/Objectives: Cerebrovascular reactivity (CVR) and time shift (TS) are vascular-related parameters that reflect cerebral perfusion and may be associated with the risk of developing stroke in patients with asymptomatic carotid artery stenosis (ACAS). We investigated CVR and TS in patients with ACAS using resting-state magnetic resonance imaging based on blood-oxygen-level-dependent contrast (BOLD-MRI). Methods: We included twenty patients with severe unilateral ACAS and twenty age-matched controls. Individual CVR maps were obtained through a voxel-wise regression of the MRI signal, using the global signal filtered in a specific frequency range (0.02–0.04 Hz) as the regressor. A recursive cross-correlation method provided individual TS maps through the BOLD low-frequency fluctuation. CVR and TS values were obtained for the territories irrigated by the main cerebral arteries (anterior, middle, and posterior) separated into proximal, intermediary, and distal regions. Results: Compared to controls, ACAS patients presented reduced CVR and increased TS in the distal parts of the brain vascular territories. Individual CVR and TS values varied more within the patient group than controls. Such individual variability may help identify patients eligible for intervention better than the stenosis grade. Conclusions: CVR and TS may indicate subtle hemodynamic changes and assist in identifying regions at higher risk of neuronal damage or ischemic stroke on an individual basis, aiding in the stratification of patients with ACAS based on their risk of progressing to stroke.