Objectives: The precise causes of Complex Regional Pain Syndrome (CRPS) are as yet not well known. Some consider CRPS type 1 without apparent nerve injury to arise due to a prolonged inflammatory state after initial trauma and its underlying pathophysiology indicates Nociceptive/Inflammatory Pain (NocP) components. Yet others have shown clear direct evidence of nerve injury in CRPS type 1-affected limbs, and they consider CRPS type 1to be Neuropathic Pain (NeP). The McGill Pain Questionnaire (MPQ) has the potential to diagnose pain disorders as well as suggest the underlying pathophysiology. Methods: We investigated pain characteristics of 165 NeP and 66 NocP patients, by using the 78 words of the MPQ, and thereby developed a discriminant function which efficiently discriminates NocP from NeP. We then applied this function to 36 CRPS type 1 patients' complaints and classified their pain into either NocP or NeP. Results: The discriminant probability of the function was 81.0% (chi-square, p=0.24) and this function revealed 47.2% of CRPS type 1 patients' complaints were classified as NocP and 52.8% as NeP. These subgroups showed almost comparable demographic data. Considerations: Our results indicate that CRPS type 1 cannot be classified as NeP or NocP dichotomously according to pain descriptions. This raises the possibility that CRPS type 1 represents a "mixed" pain mechanism comprised of both NeP and NocP.
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