With regard to factors in MS that remain unexplained like areas of cold climate having a greater than average number of incidents, I also think this may have to do with vitamins and sunlight or a lack thereof.
One factor I wonder about is the genetic predisposition which apparently exists, as well. I have two friends in a small Utah town with MS, they're brother and sister. Her daughter has MS, and she related to me that she and her brother had a number of aunts with the disease, as I recall as many as four, and the aunts also had kids who got MS. Makes you wonder about the disease as represented by neurologists. But now the picture may be changing if in fact the disease has its origin in the blood vessels, veins. There you may have a genetic weekness which may show up early, early. We may know soon? Daisyduck