Welcome to Neuro Talk. You found a good site, and there are lots of compassionate people here as well. I also have PN in my left foot and calf. Maybe RSD I really don't know yet. My doctor put me on the same B12 as you, and told me that is one of the best things I can do. She is a physiosist, and did give me some other suppliments too. I am sorry you suffer with this. There are medications that help. I don't know if I would have a spinal tap for this or not. It would take a lot of convincing for me anyway. I don't go quietly to invasive proceedures very well. Keep posting to the PN forum with any of your concerns. Ginnie