hey there, thought i'd chime in because i was b12 deficient (among other things - poor nutrition - 15yr vegan) before dx, and b12 deficiency is one of the differential diagnoses docs are supposed to consider before they label you an ms patient.
in my case, there was a mix-up with my doctor's computer so they did not plot the 'no data' point on my b12 history - that was the test where no level was detected. therefore i got put in the ms round file. later i found out i had a lot of other nutrient deficiencies in common with ms patients.
you're smart to take the b12 thing seriously - you could think about taking a b50 complex because b12 also needs B6 and B9(folic acid) to absorb properly. magnesium and iron are also needed (but don't supplement iron without knowing that your zinc status is optimal - many ms patients are low in zinc and low zinc results in iron deposition which can cause an inflammatory reaction in the body - you don't want that)! if you want to know about good forms of zinc, magnesium, and iron, i can help you out.
classic b12 deficiency causes thoracic and cervical lesions, it is less common to have brain lesions from b12 deficiency but not unheard of - there was a study out in 2009 where they treated a man who had brain lesions with b12 and he improved.
fyi oligoclonal bands in the CSF indicate chronic inflammation, not ms in particular. you might want to learn about the 'inflammation factor' concept in foods - you can track your score over the course of the day. if you are feeding yourself an inflammatory diet, you can switch it up and aim for an anti-inflammatory score on the order of +100 or higher per day. the web site www.nutritiondata.com
below provides IF rating info on a wide variety of foods.
ms patients are known to be lower than healthy controls in b12, b vitamins in general, vitamin d3, magnesium, selenium, and zinc. uric acid levels are also typically low (secondary to the low zinc). if you are interested in pursuing that line of inquiry i can help you with what tests to ask for, what your results mean, and what to aim for. the links included in my signature below provide additional reading if you want to follow up on this idea.