Do take the B12 deficiency possibility seriously. It is usually due to malabsorption, and although it usually attacks the spinal cord before the brain, it can cause brain problems first. Serious problems can occur with spinal cord before lesions show. One of the latest in my many problems, which came on subtly and multipled slowly for a long time before snowballing, was heart racing.

B12 deficiency is very underdiagnosed and can cause an endless list of problems. Please see the website I am putting together. Entirely non-commercial and stemming from my learning the hard way.

rose