External RSD is able to be treated with the correct type of PT treatment which involves finding a physical therapist that has had previous experience in treating RSD/CRPS so they all ready have an idea of the push/determination needed even through the pain and not be easy and give into you. Problem is a lot of times the PT's that have dealt with treating RSD patients usually have only dealt with cases that are a level one which usually is either just a foot/leg or hand/arm and quite often still not able to fully help the patient as they do not continue to help push the patient through the pain as most therapists are used to not causing/doing things that cause pain and are usually to nice/lenient in whatever program there doing. So please where ever you are look to see if any physical therapy groups near you have had any experience and if so that will be a great first step.
Now as you mentioned your RSD has been let go for 20 years which is quite some time and while you are probably full body now with some limbs bending/twisting inward you first must understand this process is not going to fix you in a second as you have been let go for so long its going to take a good while to start to see improvement. You must also understand that with RSD no matter what level your at and no matter what treatment you've done, even for those patients that reach a form of remission(which can differ for each case), there is no treatment that is an exact perfect cure. As RSD even when your in remission can come back at anytime and anywhere it likes and is usually aided by times of lots of stress, an injury, or illness. Which the good part though these possible relapses or re-occurrences (if you even ever get one as some people never do or only get one) are able to be dealt with at home and should not be any issue unless you yourself give into it and allow it to take over again which relapses/re-occurrences can be talked about at another time as your not there yet.
With that understood, the reason I suggest PT as a treatment to be tried first for cases with External RSD is because even I myself which have went through just about every treatment to help combat my RSD which has went internal now and spread like wildfire to the point of organ involvement can tell tell you that the only treatment which has a lasting form of remission for external in terms of regaining functionality and for a lot of solely external RSD patients can reduce the pain to the point of it either being easily manageable then or completely gone. Its success rate is greater then most other treatments when done correctly and is not dangerous like ketamine or SCS. Which as you'll find those patients that use Ketamine or SCS as well as other types of treatment are not in remission and basically only getting a somewhat form of help that does not last long, which for external RSD there is no reason whatsoever to begin with ketamine or the SCS as those options should be saved for internal involvement and can cause your RSD to become worse permanently for some.
If you are unable to find a therapist with past experience that is ok as long as you can find one that's willing to work with you and help you push through the pain that's the key part. Now while your an adult your body cannot be pushed like the youth (that go through a very intense physical therapy program at Children's Hospital of Philly with Dr. Sherry and can usually be to remission in 3-4 weeks of treatment or less for some) so yours is going to be more drawn out and because of you being left go for so long. RSD patients usually become trapped in a vicious cycle in which guarding and activity restrictions perpetuate the pain. Therapy should be directed toward breaking the pain cycle by creating a program with your therapist to involve the effected parts and begin using them as well as desensitizing them. Desensitization is a huge I cannot stress this enough. Each full body is different in terms of symptoms and how your RSD has progressed as each case is different. Now before I go into more detail.....
This website (http://emedicine.medscape.com/article/328054-treatment) as well as the LAST page on this one (http://www.lni.wa.gov/ClaimsIns/Files/OMD/MedTreat/Complexregionalpain.pdf) will be of some help to your physical therapist to get a basic idea. The second website does in its writing mention about the use of nerve blocks while doing therapy. Some adults have been able to find benefit from the use of nerve blocks to help with the pain while undergoing therapy. With full body nerve blocks are hard to use as full body is wide spread all over and nerve blocks are aimed at only sections such as a leg or arm. You can pursue the use of these along with therapy that is your decision but it is not a guaranteed helper.
Therapy for RSD is difficult because literally it is power through pain. External RSD is basically a vicious cycle that uses humans normal response to pain against them. Usually when an area becomes painful people usually try to not use it and baby it because in most causes by using it your hurting yourself even worse but with RSD this is not the case. Instead by babying it you are allowing your pain to become worse and allowing the RSD to over time spread and take over more. The use of pain meds are worthless when trying to deal with the pain caused from external RSD and the only way to get to a point of remission from this never ending painful monster is to do exactly what is currently painful. Your pain will increase initially but in time it will break that pain cycle and you will begin to get better.
So for example if your foot is severely sensitive not only to touch but temperature as well as water you begin to force it to do the things it does not like. Basically begin working with the foot in sense of massaging it usually the use of a lotion while doing this is beneficial as your skin is no doubt dry from the poor circulation in the foot. You do not have to begin heavy or roughly you can start out lighter but over time increase the amount of pressure/force in the massaging of the foot. The use of a therapeutic brush is very helpful in desensitization as well. Warm and cold water is also helpful. Which each of these things can be used on the different areas. Remember even though it is painful to do therapy the key part is to break the cycle of that pain and reset the nerves, a lot of people can't deal with the increased pain from the use of the effected parts and therapy itself and give up but you need to remember to keep telling yourself do you want to live in pain forever that can keep getting worse and move to internal as well or do you want to take control of your body's functionality again!
The use of weight bearing is also important as well especially for the feet/legs by use of your own body weight which you can increase ever couple of days, as well as light weights that can be attached to the arms or even legs as well as you lift your leg or arm to help also build up muscle as over time your body has most definitely atrophied. See you have not described what shape you are in whether you are bed ridden or wheelchair bound, whether you can still walk some or with crutches/cane. Are you still able to wear clothing like socks and pants and shirts. I do not know where your starting at but basically initially begin with forms of desensitization like I mentioned as well as the therapists protocol for desensitization he/she might have as well and include the use of light weight bearing and basically using the effected areas lightly to start out.
This is not something you can go to therapy and then expect that by going every week will be enough and not do anything at home. It doesn't work that way, depending on how often you can get into therapy you will also have to incorporate a home based program as well. Which at home the desensitization stuff I mentioned earlier you can do. In therapy there are the use of colored bands that are excellent for RSD therapy as you can use them with the arms and legs which hopefully where ever you go for therapy they will have access to these which are great for home use.
Your therapist and yourself can tailor make a therapy program which includes desensitization, weight bearing, stretching, other physical exercises, if needed relearning to walk as well as use of stairwells, even further along in treatment the use of some yoga can help. It is very difficult to write a lot of the therapy exercises I know because I cannot describe them on here right. But you should be able to find a therapist that once they evaluate you can help work with you to regain function and reduce your pain over time.
If you want to give me your email I can email you exercises that I have from my therapy program that I went too that are illustrated and I could scan and send to you in an email as well as other info. I apologize this reply is so massive there was just a lot to say initially and it is hard trying to tell you which stuff would be perfect for you when I don't know much about your case. I hope you can get some use out of what I mentioned. As well as the idea that the major factor of how well you do relies in how much you push yourself to do and to not give in. This would be so much easier to explain in person as I could show you what would best suit to help you but sadly that's not possible. But you should at least between yourself and your therapist be able to come up with a program to help you its basically just the idea of working on desensitizing yourself, starting to apply weight and using the effected parts and then as your able to do more increasing the stuff you do and starting to do more physical exercises as well stretches. I wish you the best of luck and if you want that info just let me know or have any other questions feel free to ask whenever.
I currently take: Cimzia 2-200mg injections, Adderall 5mg 1x daily, Vyvanse 70mg 1x daily, Dilaudid 8mg 4x daily
Health Issues: RSD, Crohns, Gastroparesis, Arthritis, Osteoporosis, Dysautonomia, & Remicade Induced Psoriasis.