There is a lot of pain, and anxiety on this "thread." There is also evidence of people determinedly searching for answers. I do not claim to know the answer to the question of the relationship between B12 and Neuropathy but I honestly think that some people are putting too much reliance upon B12 as a clue as to why they experience their neuropathy like symptoms. B12 defficiency is rare, being on the low end of the normal range for B12 levels is NOT the same as a B12 defficiency. Some of the dose levels cited on this "thread" are horrendously high. Luckily B12 is water soluble so well over 90% of your B12 supplements are excreted in your urine and harms your wallet not your body. Statistically you are more likely to need to drink more water than to need mega doses of B12. Having said that IF you actually do need B12 supplements you should take it in a form that is free of impurities and readily bioavailable. There are some excellent articles on B12 on HEALTHLINE.COM among other sites but it might be that instead of focussing on B12 some of us would be better served by reducing our anxiety levels and increasing our overall wellbeing? This is more likely to be achieved by exercise, diet control, meditation and mindfulness than by any "magic bullet" be it a megadose of B12 or a so called "nerve tonic."
On a lighter note some 70 years ago in the East End of London, my Aunt who,suffered from "bad nerves" was told by her Doctor to drink brown ale (for nutritional purposes.) She did….and she lived to be 95 ….because of the ale or despite it!