It has been suspected for decades that obstruction to venous outflow can effect CSF flow and cause normal pressure hydrocephalus. I found that pearl of wisdom in a textbook "Neurology" by Adams and Victor. I mention it in my book. It goes back to the early part of my investigation. The problem according to Adams is that blockages were never found. But researchers only looked for blockages inside the cranial vault and stopped at the dural sinuses. The most likely place for obstructions to occur, however, is outside the vault in the craniocervical junction.
Autoimmune and inflammatory responses in MS are most likely consequences of chronic ischemia, edema and hydrocephalus not the cause of it. In many cases the supratentorial (above the posterior fossa), periventricular and perivenular lesion locations seen in MS are unrelated to the signs and symptoms seen, which are often related to nerves in the posterior fossa (infratentorial).
The link below is to a study showing excess sodium and calcium in axons of the lower brain in MS patients. In my opinion, these are most likely signs of chronic ischemia and the glutamate cascade.http://brain.oxfordjournals.org/content/early/2010/01/27/brain.awp334.full