Dear Sandra -

Thanks for that. And I've read the article, Regulation of peripheral blood flow in Complex Regional Pain Syndrome: clinical implication for symptomatic relief and pain management, George Groeneweg, Frank JPM Huygen, Terence J Coderre and Freek J Zijlstra, BMC Musculoskeletal Disorders 2009, 10:116, to which you link at http://www.biomedcentral.com/1471-2474/10/116

Unfortunately, this review article appears to have focused almost exclusively on studies comparing the blood flow in the "affected" limb with that of the "contralateral" [why not just say opposite(?)] limb, using that as a control, without taking into account the possibility that CRPS may - and almost certainly does - trigger systemic vascular changes. A limitation that was explicitly acknowledged in at least one of the articles cited in "Regulation of peripheral blood flow in Complex Regional Pain Syndrome, etc." See, Exaggerated vasoconstriction in complex regional pain syndrome-1 is associated with impaired resistance artery endothelial function and local vascular reflexes, Dayan L, Salman S, Norman D, Vatine JJ, Calif E, Jacob G, J Rheumatology 2008 Jul;35(7):1339-45 at 1344:

We compared one limb with its counterpart rather than with a normal subject’s limb. Although one cannot assume normalcy of the contralateral limb, the fact that CRPS tends to affect only one limb might indicate that local rather than systemic effectors dominate its pathogenesis.

I'll be happy to send a copy of the article to anyone interested.

It's my own view that documenting and understanding systemic vascular changes in CRPS is an essential prerequisite for developing effective therapies beyond the acute stage of the illness. And so far, there appears to be less written on the subject than I would have imagined going into this.

However, and in all fairness, some of this stuff is harder than Chinese algebra - to steal an out of context phrase from Tom Waits - where the mechnisms of action run all the way from the simple constriction of the blood vessels due to sympathetic overactivation or something as complicated as "arterial abnormalities characterized by an overall loss of PGP-positive innervation coupled with hypertrophic, multi-laminated vascular walls." Albrecht PH, Hines S, Eisenberg E, et al, Pathologic alterations of cutaneous innervation and vasculature in affected limbs from patients with complex regional pain syndrome, Pain 2006;120:244-266, 259-263, full text with numerous and occasionally gruesome colored slides at http://www.rsds.org/2/library/articl..._PAIN%2006.pdf

I would be curious as to your thoughts on this.

Mike