Complex Regional Pain Syndrome (CRPS) usually develops after a noxious event, but spontaneous onsets of RSD/CRPS have been described in 3-11% of the cases acording to this study.
I could only get the abstract to this paper but it would apear that there are some differences in prognosis amongs other things.. I was suprised by this study.
http://www.ncbi.nlm.nih.gov/pubmed/1...,f1000m,isrctn
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