There is with RSD sympatheticly mediated pain (SMP) and that is what the blocks are most efective against, thing is there is also independently mediated pain (IMP) and the blocks don't help that type of pain at all.

IMP can come in the later stages of RSD, and that is why they say that blocks can put a person into remission if given early enouph, but as we know we are all diffrent and react diffrently to diffrent treatments, some of us have both SMP and IMP very on and blocks just don't help IMP.. BOTH are CRPS even though both don't test like RSD when blocks are used to test for RSD, same symptoms etc, just that the central nervous system takes on alot of the pain channels as well as the sympathetic system.
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Temporary relief:
The idea is to give the sympathetic system a break I supose, you get a nice warm limb and some pain relief and the effect IS compounding over time.. infact too many blocks can have the opposite effect and actualy give a virtual hot sympathecomy to that limb, I have seen pictures in a thermography scan.. not good, caused more problems aparently.

Good luck, stop when you stop getting benifit from them because they are invasive. I think they helped me to a certain extent, but I also feel that one specific block caused my spread.

Sandra