Complex regional pain syndrome I (CRPS I): prospective study and laboratory evaluation

To relate clinical features to autonomic laboratory indices used in the diagnosis of Complex Regional Pain Syndrome type I (CRPS I) (reflex sympathetic dystrophy) to generate improved diagnostic criteria.

CRPS I is a chronic pain syndrome, characterized by diffuse limb pain with allodynia and prominent vasomotor and sudomotor dysfunction.

We conducted a prospective study on 102 patients referred for possible CRPS I. These patients completed a structured questionnaire and underwent neurologic examination, with special attention to the evaluation of clinical features of vasomotor, sudomotor, motor, and sensory, including pain, dysfunction. All patients were tested using a standard autonomic protocol that compared side-to-side skin temperature, resting sweat output, and quantitative sudomotor axon reflex test (QSART) measurements. Composite autonomic clinical (CRPS-Sx) and laboratory (CRPS-LAB) scores were defined. The clinical (subjective and objective) and the laboratory data were analyzed using Pearson's correlation analysis and Bonferroni's probability value to assess concordance and their value in correctly diagnosing CRPS I.

All cases occurred after limb injury. One-third of cases did not fulfill our criteria of CRPS I. Highly significant correlations (p<.001) were found among certain clusters of symptoms and signs that shared unifying pathophysiologies. CRPS-Sx correlated with CRPS-LAB (p = .035). The indices that correlated most reliably with clinical data and with each other were RSO, QSART, and skin temperature reductions.

Clinical and autonomic laboratory probability scores correlate in an internally consistent manner. Both CRPS-Sx and CRPS-LAB are sensitive and reliable tools to formulate a correct diagnosis of CRPS I and can be combined to provide an improved set of diagnostic criteria for CRPS I.