One is the positive ANA titer, even if the sub-types show up negative--this could be an indication, as I'm sure you know, of a vasculitic/connective tissue autoimmune condition, and neural symptoms often result from these, from both vasculitic and compressive effects.

The second is that B12 level--it's nowhere near high enough, and could explain a lot of those symptoms. In the US we seem to have the "normal" ranges for B12 set around 200; in Japan and many parts of Europe it is 550. There are many reports of neural symptoms of B12 deficiency with serum values in the 200's--500's, and even higher; even moderate serum levels are not an indication of sufficient B12 at the cellular level. At the levels you report, it's almost certain you don't have a lot at the cellular level. (Rose/Mrs. D/others can explain better than I the other testing--MMA/homocysteine-- that can help identify true B12 deficiency.)

Kidney problems can result in neuropathy due to build-up of toxins, but this usually doesn't occur until there is a considerable degree of failure.

I suspect that you may find you have some sort of autoimmunity going on. You should be titred up for a number of antibodies--to thyroid, to intrinsic factor (anti-parietal--the B12 connection), and you may want to have some of the panels for nerve-cell specific antibodies.

Take a look at:

http://www.neuro.wustl.edu/neuromusc...oantibody.html

http://www.neuro.wustl.edu/neuromusc...nd.htm#thyroid

http://www.neuro.wustl.edu/neuromusc...itamin.htm#B12