[Sensitivity of the sympathetic skin response and scintigraphy in the diagnosis of complex regional pain syndrome]

Objective: To evaluate the sensitivity of sympathetic skin response (SSR) and compare it with scintigraphy in patients with complex regional pain syndrome diagnosed according to the Budapest criteria.

Material and methods: Twenty-two patients with complex regional pain syndrome who attended the Rehabilitation and Physical Medicine Department between January-2018 and May-2022 have been prospectively evaluated. The scintigraphy was considered positive if in the 1st-2nd phase slight asymmetric and diffuse uptake was observed, or when in the 3rd phase marked periarticular radioisotope uptake was observed. SSR was abnormal if: a) no response after 20 stimuli; b) lack of habituation with permanence of the stimuli greater than 67.2%.

Results: Age 55.4±8.57 years. Complex regional pain syndrome was more frequent in women (90.9%), more common in upper limbs (68.2%) than lower limbs (31.8%). In SSR, we have observed normal response (<67.2%) in 2 patients (11.1%), lack of SSR in 2 patients (11.1%) and lack of habituation (>67.2%) in 14 patients (77.8%). In total, 16 patients presented abnormal or absent responses (88.8%). The diagnostic sensitivity of scintigraphy is similar to that of SSR (89.5% vs 88.8%), with no statistical difference (P=.6721).

Conclusion: Scintigraphy has shown similar sensitivity to SSR, although the simplicity, security, low cost, non-ionizing and non-invasiveness of the latter technique suggest that it could be more cost-effective. The lack of habituation and the absence of response could identify response patterns and localize the involvement in the afferent, central, efferent or post-ganglionic pathways.