Hi. I found this info on the "Health Pages" section (upper right hand corner of this page - yellow icon) Take a peek at the other topics too. They are packed with great info.
http://www.medhelp.org/health_pages/Multiple%20Sclerosis/MS-Mimics---Part-I/show/375?cid=36
"Vitamin B12 deficiency may cause demyelination, numbness and tingling of the hands and feet, fatigue, weakness, and in extreme cases, change in mental status. "There is a theory that vitamin B12 can actually produce more myelin, so people with MS may assume that they need more of it," Burks says. "But B12 is only beneficial if you have a deficit to begin with."
It's short, but gets to the point. According to this doctor a deficiency in Vitamin b12 can cause demyelination and symptoms of MS. There are other factors that have to be considered in ruling out MS even if you are low on Vit b12. Being deficient in Vitamin b2 doesn't instantly exclude MS as a possibility. Look at the McDonald Criteria (in the Health Pages) that is used by neurologists for more information on how a diagnosis is made.
Take care.