Functional Infrared Imaging in the Evaluation of Complex Regional Pain Syndrome, Type I: Current Pathophysiological Concepts, Methodology, Case Studies, Clinical Implications
Complex regional pain syndrome, Type I (CRPS I) is a potentially disabling condition characterized by regional pain that is often disproportionate to or occurs in the absence of an identifiable inciting event. The condition is associated with hyperalgesia, allodynia, spontaneous pain, abnormal skin color, changes in skin temperature, abnormal sudomotor activity, edema, active and passive movement disorders, and trophic changes of nails and hair. CRPS I usually begins after minor or major trauma to soft tissue such as a strain, sprain, or surgery. Although rare, it can also occur following fracture, visceral trauma, or central nervous system insult (e.g., CVA). Although similar-if not identical-in presentation, a related syndrome, Type II (CRPS II), occurs following direct insult or injury to peripheral nerve. A complete address of CRPS-II is beyond the scope of this chapter [1, for review]. Epidemiologically, Sandroni et al.  report that CRPS I occurs more frequently than CRPS II (i.e., CRPS I incidence of 5.5/100,000 person years at risk vs. CRPS II incidence of 0.8/100,000 person years at risk) is more prevalent (21/100,000 vs. 4 /100,000) and occurs more in females than males with reported ratios of 2:1 or greater .