Dilatation of the bridging cerebral veins in multiple sclerosis correlates with fatigue and suggests an increase in pressure

A perspective on the evidence for glymphatic obstruction in spaceflight associated neuro-ocular syndrome and fatigue

“…There is evidence of glymphatic outflow disruption in MS 43,44 and also evidence of cortical venous outflow dilatation. In multiple sclerosis, the superficial cortical veins were 29% larger and the vein of Galen 25% larger in cross-sectional area than in the controls 45 . Despite the cortical vein dilatation, no evidence of obstruction at the outflow to the sagittal sinus or straight sinus was seen 45 .…”

“…In multiple sclerosis, the superficial cortical veins were 29% larger and the vein of Galen 25% larger in cross-sectional area than in the controls 45 . Despite the cortical vein dilatation, no evidence of obstruction at the outflow to the sagittal sinus or straight sinus was seen 45 . Modelling of the cortical vein dilatation found could only be due to an increase in transmural pressure (a reduction in wall thickness or stiffness were not feasible).…”

“…In multiple sclerosis, fatigue severity correlates with the number, site and size of the enlarged cerebral perivascular spaces 63 . Fatigue in MS also correlates with the size of the dilated cortical veins 45 . This raises a possible glymphatic cause for the fatigue in MS and perhaps also the asthenia in astronauts.…”

“…The normal internal pressure within the cortical veins is higher than the ICP (the opposite of the sinus wall transmural pressure direction), indicating the cortical vein pressure in MS and SANS must be much higher than the elevated ICP for them to dilate. An impedance pump model was suggested to account for the finding of increased pressure localised to the cortical vein segments, which cannot be accounted for by the ICP or sinus pressure 45 . Thus, in SANS there is likely to be structural changes in the sinus walls, altering their impedance.…”

Syringomyelia Is Associated with a Reduction in Spinal Canal Compliance, Venous Outflow Dilatation and Glymphatic Fluid Obstruction

“…The findings from patients with multiple sclerosis (MS) appear to be similar to those found for patients with hydrocephalus. The cortical veins in MS are 29% larger in crosssection than those in matched controls, suggesting an increase in venous transmural pressure of approximately 6.5 mmHg [15]. In syringomyelia secondary to Chiari 1 malformation, Capel et al measured the arterial inflow and pulsation stroke volume at the skull base and compared it to the venous outflow from the sagittal and straight sinuses in patients with Chiari 1 malformation with and without syrinx formation [16].…”