The etiology of Complex Regional Pain Syndrome (CRPS) is unknown but a patient typically presents with a triad of clinical findings: sensory abnormalities, perfusion abnormalities and alterations in motor function. Since some of these findings are seen in the other disease states, the diagnosis is often not clear. A response to a sympathetic ganglion block (stellate or lumbar) is also suggestive of the disorder. However, there is no definitive diagnostic test for CRPS. Experience has shown that early aggressive treatment improves the prognosis. Therefore, tests that facilitate the early diagnosis would have important clinical implications.