The other big difference is that SMP is associated with a lot of cytokines and neuroinflamation, and so responds to all sorts of things, like regional blocks with Remicade. See, Successful Intravenous Regional Block with Low-Dose Tumor Necrosis Factor-[Alpha] Antibody Infliximab for Treatment of Complex Regional Pain Syndrome 1, Int Anesth Res Soc. 2007;105(4):1148-1151 FREE FULL TEXT @
http://www.rsds.org/2/library/articl...teck_Rolke.pdf

Whereas, by the time the pain is SIP, it's literally in your head and is apparently maintained by the abnormal thalamocortical occillations it set up in the first place! See, generally, Abnormal thalamocortical activity in patients with Complex Regional Pain Syndrome (CRPS) Type I, Walton KD, Dubois M, Llinas RR, Pain 2010 FREE FULL TEXT @ http://www.rsds.org/2/library/articl..._Pain_2010.pdf Hence, at that stage, the only chance lies in "resetting" the brain itself.

Forgive the lack of complete citations, but the list would go on for pages. Suffice to say that it's well established that there is far less evidence of activity - beyond the involvement of a single neuropeptide calcitonin gene-related peptide (CGRP) - in the immunological arena at the chronic stage, whereas that's the name of the game at the start. (Okay, citations available upon request.)

Mike

PS [REVISED] The whole distiction between SMP/SIP may be an historical anacronism. The bug got called RSD when people saw the clear involvment of the sympathetic nervous system, most notabily in the dysregulation of the "tone" of blood vessels, wheich are known to be filled with nerve ("innervated") and controlled by the sympathetic nervous system: typically, we experience vasocontriction in most of the small blood vessels, with compensatory vasodilation (resulting in edema) in others. Then, once they were focussed on the sympathetic nervous system, some bright lights had the idea of doing surgical sympathectomies and ablations, which gave at most a year or two, after shredding, cutting or burning away all control of the SNS over the affected area of the body . . . and lo and behold, they worked! Only to see the pain return as it became "sympathetically independant."

Later, the same rational was used to explain why things like lumbar sympathetic blocks stopped working over time. The only thing they missed was one minor detail: the blocks worked during the presence of neuroinflammation (as confirmed by cytokine panels) and stopped working once the inflammatory processes were largely at an end. That said, I've got to go back and re-read the old studies on sugical sypathectomies and the like, where a haunting voice is telling me they may have lasted a little longer than the point at which people stopped becoming responsive to the blocks, in which case it remains possible that they did more than simply interrupt a neuroinflammatory resonse: or perhaps simply did so more authoritartively than the blocks.

In any event - and possibly because of the ambiguious timing on the failure point of blocks and more radical procedures - instead of SMP/SIP, the favored distinction has now shifted to between acute/intermediate stages of CRPS on the one hand, and chronic CRPS on the other hand. Apologies for initially omitting part of the history.