Multicenter study on the asymmetry of skin temperature in complex regional pain syndrome: An examination of temperature distribution and symptom duration

According to the International Association for the Study of Pain (IASP) and American Medical Association (AMA), the diagnostic criteria for complex regional pain syndrome (CRPS) require the presence of skin temperature asymmetry. In CRPS, it is generally accepted that the temperature of skin of affected limbs changes from warm to cold; however, in our clinical practice, we have experienced many cases with different thermographic characteristics. Therefore, we conducted a retrospective multicenter study that examined the distribution of skin temperature in patients with CRPS and skin temperature asymmetry versus symptom duration. Patients diagnosed with type 1 or 2 CRPS were recruited. After confirming CRPS according to the IASP diagnostic criteria, infrared thermographic images were evaluated for skin temperature differences (ΔT) between the affected and unaffected limbs. A total of 296 patients with CRPS were included in this study. The median duration of symptoms was 6 months and the mean ± standard deviation of ΔT was –0.72 ± 1.65°C. A skin temperature difference between bilateral limbs (|ΔT|) of 1°C or less was seen in 131 patients (44.3%); thus, these 131 patients did not meet the IASP criteria for CRPS. Further, cool skin temperature was not observed in 88 patients (29.7%), meaning that these patients did not meet the AMA criteria for CRPS. There was no correlation between the symptom duration and ΔT (Spearman's rho = –0.075, P = 0.196) and there was no significant difference in the average ΔT among the 4 symptom duration groups (0–3 months, 4–6 months, 7–12 months, >12 months, P = 0.08). In conclusion, a considerable proportion of the patients that participated in this study did not meet the thermal criteria set forth by the IASP and AMA. Further, there was no correlation between symptom duration and skin temperature difference.