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Complex regional pain syndrome (CRPS) is characterized by continuous pain, disproportional to the initial trauma. It usually spreads to the distal parts of the affected limb. Besides continuing pain, a mix of sensory, sudo- and vasomotor disturbances, motor dysfunction, and trophic changes is responsible for physical complaints. Vasomotor disturbance is characterized by changes in skin temperature and color. In CRPS patients with a cold extremity, a decrease in blood flow can cause decreased tissue saturation and tissue acidosis, resulting in ischemic pain. The pathophysiology of vasomotor disturbances is not completely understood. Temperature asymmetry is generally assumed as a result of disturbance in the sympathetic nervous system. Vasodilating drugs and sympathetic blockade have been cornerstones of therapy in cold CRPS for years. However, only a limited part of these patients improve on this kind of therapies. Research has shown a pivotal role for inflammation in the pathophysiology of CRPS. Inflammation can result in endothelial dysfunction. Endothelial function plays an important role in the local regulation of vascular tone. Endothelial dysfunction could be another mechanism responsible for the vasomotor disturbances in cold CRPS. An important goal in the treatment of cold-type CRPS is the restoration of a normal blood flow. Consequently it is important to distinguish the underlying pathophysiological mechanisms of vasomotor disturbances. A disturbance of the sympathetic nervous system may require another type of treatment than inflammation-induced endothelial dysfunction. Diagnostic tools to distinguish these underlying pathophysiological mechanisms of vasomotor disturbances would enable a mechanism-based treatment and improve clinical outcome., (© 2015 World Institute of Pain.)

It was previously shown in a group of 9 patients with complex regional pain syndrome type 1 (CRPS1) that levels of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) are higher in blister fluid from the involved side. We hypothesize that local inflammation is responsible for the characteristics of CRPS1. The aim of this study was to confirm the previous observation in a large group of CRPS1 patients, repeating the measurement of TNF-alpha and IL-6 in blister fluid. Furthermore, we sought to determine whether these cytokines are responsible for the characteristics of CRPS1 and characterize the relationship between cytokine levels and duration of the disease. Sixty-six patients with CRPS1 participated. Skin blisters were artificially induced for measurement of cytokines in both extremities. The following disease characteristics were assessed: pain and differences in temperature, volume, and mobility between the extremities. TNF-alpha and IL-6 levels were significantly higher in blister fluid from the involved side. However, cytokine levels did not correlate with the characteristics or duration of the disease. Our findings confirm the presence of local inflammation in a population of 66 patients in the first 2 years of CRPS1. Proinflammatory cytokines seem to be only partly involved in the pathophysiology of CRPS1, as indicated by the lack of coherence between TNF-alpha and IL-6 levels and the signs and symptoms of inflammation and disease duration. Other inflammatory mediators and mechanisms, such as central sensitization, are probably involved in the early stages of CRPS1.

Objective: In this study, we assessed the validity of skin surface temperature recordings, based on various calculation methods applied to the thermographic data, to diagnose acute complex regional pain syndrome type 1 (CRPS1) fracture patients., Methods: Thermographic recordings of the palmar/plantar side and dorsal side of both hands or feet were made on CRPS1 patients and in control fracture patients with/without and without complaints similar to CRPS1 (total in the three subgroups = 120) just after removal of plaster. Various calculation methods applied to the thermographic data were compared using receiver operating characteristics analysis to obtain indicators of diagnostic value., Results: There were no significant differences in demographic data and characteristics among the three subgroups. The most pronounced differences among the subgroups were vasomotor signs in the CRPS1 patients. The involved side in CRPS1 patients was often warmer compared with the noninvolved extremity. The difference in temperature between the involved site and the noninvolved extremity in CRPS1 patients significantly differed from the difference in temperature between the contralateral extremities of the two control groups. The largest temperature difference between extremities was found in CRPS1 patients. The difference in temperature recordings comparing the palmar/plantar and dorsal recording was not significant in any group. The sensitivity and specificity varied considerably between the various calculation methods used to calculate temperature difference between extremities. The highest level of sensitivity was 71% and the highest specificity was 64%; the highest positive predictive value reached a value of 35% and the highest negative predictive 84%, with a moderate 0.60 > or = area under the curve < or = 0.65., Conclusion: The validity of skin surface temperature recordings under resting conditions to discriminate between acute CRPS1 fracture patients and control fracture patients with/without complaints is limited, and only useful as a supplementary diagnostic tool.

This study aimed at evaluating the sensitivity, specificity, reliability and repeatability of observer assessment of thermographic images taken from Complex Regional Pain Syndrome (CRPS) type 1. A computer program was developed to let observers rate the difference between randomly presented thermographic images of pairs of hands of individuals. The sensitivity and specificity, and potential learning effects were measured. Effects of the colours and rank number of the images were analysed. The sensitivity was 71% and the specificity 85%. The repeatability was 0.5267 and the reliability was 0.4967. No significant relation was found between the rank number and the rating. There was a significant correlation between the colour pallet and the rating (r = 0.76). Although the colour pallet used partly explained the variance in the rating scores, this study shows that observer assessment of thermographic images may distinguish between CRPS1 patients and healthy controls. However, the reliability and repeatability of this assessment was rather low.

Background: Complex Regional Pain Syndrome type 1 (CRPS1) is a clinical diagnosis based on criteria describing symptoms of the disease. The main aim of the present study was to compare the sensitivity and specificity of calculation methods used to assess thermographic images (infrared imaging) obtained during temperature provocation. The secondary objective was to obtain information about the involvement of the sympathetic system in CRPS1., Methods: We studied 12 patients in whom CRPS1 was diagnosed according to the criteria of Bruehl. High and low whole body cooling and warming induced and reduced sympathetic vasoconstrictor activity. The degree of vasoconstrictor activity in both hands was monitored using a videothermograph. The sensitivity and specificity of the calculation methods used to assess the thermographic images were calculated., Results: The temperature difference between the hands in the CRPS patients increases significantly when the sympathetic system is provoked. At both the maximum and minimum vasoconstriction no significant differences were found in fingertip temperatures between both hands., Conclusion: The majority of CRPS1 patients do not show maximal obtainable temperature differences between the involved and contralateral extremity at room temperature (static measurement). During cold and warm temperature challenges this temperature difference increases significantly. As a result a higher sensitivity and specificity could be achieved in the diagnosis of CRPS1. These findings suggest that the sympathetic efferent system is involved in CRPS1.