A good rehab program by a PT experienced in CRPS can work wonders, especially early after the CRPS begins. Lots of work with desensitization and gently moving it more and more, very slowly. It has to be done only to the point of feeling it will touch something off, not to tolerance like you would normally do when working out. It is a whole different way of doing things. There's a word for it that is escaping me right now!

A sympathetic block CAN stop the spread and reduce symptoms, but it isn't magic and it works for some and not others.