Good question. If the CRPS returns after a new injury of some sort, then I'm pretty sure it's a fresh or "acute" case of CRPS in its own right. As would be the "spread" of CRPS in such circumstances, where a good argument can be made that each case of "spread" secondary to a new injury, is in fact a fresh immune-modulated case of CRPS, on account of which treatments that may have long since lost their effectiveness, such as nerve blocks delivered under fluoroscopy - may have a new lease on life with respect to combating injury-induced spread.

For the complete treatment of whatever it is I happen to know on the subject, including links and citations to some articles of interest, please check out my post from February of this year - "a few quick points on spread" - in the t.D.C.S. Update Could remission be within my reach and your's too? thread, which appears as Post No. 145.

But as to a re-occurrence independent of any injury, I don't know. One way to find out (and treat it should the response be positive) would be if it responded to a nerve block within three months of the re-occurrence. If so, it would be a fresh case, not unlike those reports of CRPS independent of any known injury. Alternatively, a rheumatologist's blood test for TNF-[alpha] and its soluble Receptors I/II should be close to dispositive if performed within six months of symptom re-occurrence. See, Systemic inflammatory mediators in post-traumatic complex regional pain syndrome (CRPS I) - longitudinal investigations and differences to control groups, Schinkel C, Scherens A, Köller M, Roellecke G, Muhr G, Maier C, Eur J Med Res. 2009 Mar 17;14(3):130-5 [ABSTRACT]. This study is important because it found a significant difference in these serum levels (among others) (p = 0.01) in the same patients, from the time their cases were "acute" (defined as being within 6 months of symptom onset) as opposed to when they had become "chronic" (remarkably in the relatively narrow band of only 6 - 12 months from onset).

(And while I'm sorry there isn't a link to the full text of the Schinkel article - which a friend pulled for me - I will be happy to send on a copy of the PDF to anyone who drops me a PM with an email address.)

I hope this is useful.

Mike