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In this report, the following criteria were used for the diagnosis of causalgia: (a) the presence of continuous, burning pain distal to a site of injury; (b) hyperalgesia and allodynia in the painful area; and (c) a traumatic event occurring proximal in the painful area and within weeks prior to the onset of pain. The McGill pain questionnaire was used to test the selected pain population for homogeneity. The scores were similar among the patients and different from the scores in other pain syndromes. It is concluded that the above criteria are sufficient to make the diagnosis of causalgia. In addition, it appears that a central nervous system abnormality best accounts for the clinical features of causalgia.

To test the hypothesis that causalgia is a reflex sympathetic dystrophy with focal sympathetic hyperactivity in the painful area, we studied skin conductance, temperature, and a radiometric index of blood flow in 10 patients and 10 controls. Skin conductance was significantly higher, and both skin temperature and blood flow index were significantly lower in the patient extremities. When the affected and homologous, non-affected extremity values were compared, asymmetries were more common and of larger magnitude in the patient group. There was no consistent pattern of asymmetry. These results do not support the hypothesis that causalgia is a reflex sympathetic dystrophy.