D'haeseleer et al. Vascular aspects of multiple sclerosis. Lancet Neurol. 2011 Jul;10(7):657-66.
This review claims that there are potentially three types of blood vessel or vascular abnormalities in MS:
(1) The study of diseases in the general population suggest that people with MS have a higher risk for stroke than people who do not have MS. The underlying mechanism of this unknown, but might involve damage to blood vessels secondary to brain inflammation that occurs in MS. Another proposed explanation is that MS'ers have a global reduction in blood flow to the brain.
"This is probably secondary phenomenon due to previous tissue damage as a result of MS. Whether this reduced blood flow predisposes MS'ers to stroke is not known."
(2) Data suggest that a subtype of focal MS lesions might originate from reduced blood flow.
"This is very controversial and there is no consensus among card-carrying MS neuropathologists on this proposal."
(3) CCSVI: the pathology of MS might be the consequence of a chronic state of impaired venous drainage from the CNS, for which the term chronic cerebrospinal venous insufficiency (CCSVI) has been coined. A number of recent studies do not support the CCSVI theory, but some elements of CCSVI might be explained by slower cerebral venous blood flow secondary to the reduced cerebral perfusion in people with MS compared with healthy individuals.
"I agree with the latter and would add the possible con-founder of dehydration, please see my previous post (click here)."
"On balance I don't think the evidence is very strong that vascular abnormalities play a large role in MS. It is hard to explain a lot of what we know about MS with these vascular hypotheses or theories."