A syndrome characterized by severe burning pain in an extremity accompanied by sudomotor, vasomotor, and trophic changes in bone without an associated specific nerve injury. This condition is most often precipitated by trauma to soft tissue or nerve complexes. The skin over the affected region is usually erythematous and demonstrates hypersensitivity to tactile stimuli and erythema. (Adams et al., Principles of Neurology, 6th ed, p1360; Pain 1995 Oct;63(1):127-33) Complex regional pain syndrome type 1 (CRPS1) is a form of complex regional pain syndrome in which the pain is disproportionate to any known inciting event and is characterized by continuous pain, allodynia, or hyperalgesia as well as edema, coloration (changes in skin blood flow), or abnormal sudomotor activity in the region of pain. Onset of CRPS1 symptoms may occur within a few days to a month after an injury or trauma to the affected limb.