I'm seeing several posts about vitamin B1 and Parkinson's, but nothing about B12. I posted an article below.
I was researching numbness in the arms for my husband who is 2 years into his PD diagnosis, and came across this article. In reading other articles not related to PD, I read numbness in the extremities could be due to b12 deficiency. If PD patients are prone to this type of deficiency, then it makes sense why he might have this tingling/numbness. I am currently trying him on 1000 mg of sublingual b12 once a day, but I'm concerned this may be too much. I have read that you can't overdose on b12, but would be interested in the opinion of others on this topic. It has only been a week, we think there may be a very slight improvement, but nothing significant so far.