Long-term skin temperature measurements - A practical diagnostic tool in complex regional pain syndrome

Despite the development of the IASP criteria, diagnosing complex regional pain syndrome (CRPS) remains a challenge because all symptoms vary interindividually, including the vascular abnormalities. Previous studies showed that skin temperature asymmetries between the affected and contralateral extremity around 2 °C are useful for diagnosing CRPS. However, they were either assessed only at one single point in time or during specific investigations including controlled thermoregulatory modulation of sympathetic activity which limits their practicability. The present study evaluated long-term skin temperature changes under everyday circumstances in 22 patients with CRPS, 18 patients with limb pain of other origin and 23 healthy controls. The asymmetries in skin temperature and oscillation number (QOscill), the percentage of assessed time with a-synchron temperature changes on both body sides and the determination coefficient of the individual regression (r2id) were compared between the groups. Patients with CRPS differed significantly from healthy controls in nearly all parameters. Minor differences between both patient groups were found regarding the percentage of assessed time with side difference >2 °C (ΔT2). However, both patient groups differed significantly in parameters characterizing the skin temperature dynamics. A sum score (2∗QOscill + r2id + ΔT2) allowed diagnosing CRPS with a specificity of 67% vs. patients with other painful diseases and 79% vs. healthy controls (sensitivity: 73%, respectively, 94%) and reflected the severity of the dysfunction in CRPS better than the mean skin temperature side differences alone. The applied skin temperature analysis can be easily applied in the clinical settings and serves as a further facet in the difficult diagnosis of CRPS.