Treat it as aggressively as you can as quickly as you can.

My RSD spread last year and treatment got delayed because of doctors bouncing me around from one to the next while it just continued to spread until it was in my whole upper body. Don't let them delay on this.

I don't know what sorts of treatment you have done or are doing but you definitely should be doing something. Definitely make sure you keep moving it and don't immobilize or fall into any of those bad traps that many of us do when we are trying to get a diagnosis the first time around with RSD.

Have you considered tDCS? There's a thread on here about it and several have had wonderful success in treating the areas of spread with this treatment. I am only a couple months into treatment but I have already seen some excellent improvement in the last areas that my RSD spread to and hopefully with time I will see it in the other areas as well.

I hope you find something that helps and that it does not spread any further. Definitely fight to get treatment and don't let the doctors delay if at all possible.