title: Complex regional pain syndrome: are there distinct subtypes and sequential stages of the syndrome?
abstract: This study tested for evidence supporting the clinical lore of three sequential stages of complex regional pain syndrome (CRPS) and examined the characteristics of possible CRPS subtypes. A series of 113 patients meeting IASP criteria for CRPS underwent standardized history and physical examinations to assess CRPS signs and symptoms in four domains identified in previous research: pain/sensory abnormalities, vasomotor dysfunction, edema/sudomotor dysfunction, and motor/trophic changes. K-Means cluster analysis was used to derive three relatively homogeneous CRPS patient subgroups based on similarity of sign/symptom patterns in these domains. The resulting CRPS subgroups did not differ significantly regarding pain duration as might be expected in a sequential staging model. However, the derived subgroups were statistically-distinct, and suggested three possible CRPS subtypes: (1) a relatively limited syndrome with vasomotor signs predominating, (2) a relatively limited syndrome with neuropathic pain/sensory abnormalities predominating, and (3) a florid CRPS syndrome similar to "classic RSD" descriptions. Subtype 3 showed the highest levels of motor/trophic signs and possible disuse-related changes (osteopenia) on bone scan, despite having directionally the briefest pain duration of the three groups. EMG/NCV testing suggests that Subtype 2 may reflect CRPS-Type 2 (causalgia). Overall, these results are consistent with limited previous work that argues against three sequential stages of CRPS. However, several distinct CRPS subtypes are suggested, and these could ultimately have utility in targeting treatment more effectively.
authors.affiliation: Department of Anesthesiology, Vanderbilt University School of Medicine, Suite 403-G MAB, 1211 Twenty-First Avenue South, Nashville, TN 37232-1557, USA. stephen.bruehl@mcmail.vanderbilt.edu
authors.forename: Stephen
authors.initials: S
authors.lastname: Bruehl
authors.forename: R Norman
authors.initials: RN
authors.lastname: Harden
authors.forename: Bradley S
authors.initials: BS
authors.lastname: Galer
authors.forename: Samuel
authors.initials: S
authors.lastname: Saltz
authors.forename: Miroslav
authors.initials: M
authors.lastname: Backonja
authors.forename: Michael
authors.initials: M
authors.lastname: Stanton-Hicks
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016000:Cluster Analysis; D020918:Complex Regional Pain Syndromes / Q000145:classification* / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged