I am seeing two neurogist who have different opinions.... One suspects B12 deficiency caused demyelination problem shown in MRI another wants to rule out MS. I was given cognitive examines by my the neurologist who thinks it most likely is B12 and he determined I am NOT cognitive impaired! I was having brain fog when tested the first time SO another MRI with contrast and a spinal tab is being scheduled to figure out the problem. In the mean time I am getting weekly shots and my B12 is rocket high nearly 4000 and MMA in normal range. I am wondering if B12 could of done the demylination of white matter so quickly????? .... First symthoms of deficiency were pricks 14 months ago... Injections in started in late January 2016... Stopped until symthoms came back lates summer. I have had 13 weeks of injections.... Had 11 weeks when I had MRI.