To determine the relationship between the systemic arterial blood flow (SABF) and cerebral perfusion in a heterogeneous group of multiple sclerosis (MS) patients.

Cerebral hypoperfusion has been reported in MS patients. The factors associated with these vascular changes are currently unknown. 

Cerebral and SABF were assessed in 118 patients (75 clinically isolated syndrome (CIS)/relapsing-remitting MS and 43 progressive MS) through MRI examination with dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI) and Doppler ultrasound, respectively. PWI-derived measures of mean transit time (MTT) and time-to-peak (TTP), measured in seconds, of the normal-appearing whole brain (NAWB) and gray matter (GM) were calculated. Ultrasound-measured blood flow through the bilateral common carotid and vertebral arteries, measured as milliliters per minute (mL/min), represent the SABF. Whole brain volume (WBV) and body mass index (BMI) were used as additional covariates in the analysis. Spearman’s correlations, adjusted regression models, and analysis of covariance (ANCOVA) for quartile-based comparisons were performed.

Higher systolic blood pressure was associated with lower SABF (-0.256, p=0.006). In the total MS sample, higher SABF was associated with shorter MTT and TTP times of the NAWB (r=-0.256, p=0.007 and r=-0.307, p=0.001) and GM (r=-0.239, p=0.012 and r=-0.3, p=0.001). The SABF and TTP associations were driven by the PMS patients (r=-0.451, p=0.004 and r=-0.451, p=0.011). Only in PMS patients, SABF remained a significant predictor of NAWB (standardized β=-0.394, p=0.022) and GM TTP (standardized β=-0.351, p=0.037). MTT and TTP were significantly lower in patients within the lower quartiles of SABF when compared to PMS patients within the higher quartiles (age, sex, BMI and WBV-adjusted ANCOVA p<0.025).

The direct relationship between systemic and cerebral blood flow seen in PMS patients suggests failure in the cerebrovascular reactivity mechanisms and insufficient perfusion control. The cerebral blood flow in progressive patients may be increasingly dependent on the SABF.