Patients with multiple sclerosis (MS) have a higher risk for ischaemic stroke. The current hypothesis states that white matter (WM) fibers alterations causes, through astrocytes, a cerebral vasoreactivity (CVR) disruption resulting in a hypoperfusion. Due to the location of the astrocytes, we expect an altered vasoreactivity mainly around WM tracts. Using a MR vasoreactivity experiment, we could identify altered WM pathways. In MS patients a path from left anterior insula to both precentral gyrus and right middle and superior frontal gyrus highlighted an altered CVR compared to controls. A negative association was found with fNART in the cingulum limbic pathway.