Introduction We hypothesized that patients with complex regional pain syndrome (CRPS) would describe a more negative pain phenotype including higher pain severity, more neuropathic pain descriptors, more centralized pain symptoms, poorer physical function, and more affective distress when compared with patients with neuropathic pain of the extremities not meeting CRPS criteria.
Materials and methods This was a retrospective cross-sectional study conducted at a tertiary pain center. The sample included 212 patients who met Budapest Criteria for CRPS and 175 patients with neuropathic pain of the extremities who did not meet criteria. All patients completed a packet of questionnaires before their initial visit containing validated outcome measures assessing pain severity, pain interference, physical functioning, depression, anxiety, and catastrophizing.
Results Patients with CRPS reported higher physical disability (p=0.022) and more neuropathic pain symptoms (p=0.002) than patients not meeting CRPS criteria, but the groups did not otherwise differ significantly. There were no significant differences in pain severity or affective distress, despite power analyses suggesting the ability to detect small to medium effect sizes (d=0.29; w=0.14). Subanalyses of differences in neuropathic pain symptoms revealed that patients with CRPS, compared with patients not meeting CRPS criteria, were more likely to report pain with light touch (p=0.003), sudden pain attacks (p=0.003), pain with cold or heat (p=0.002), sensation of numbness (p=0.042), and pain with slight pressure (p=0.018).
Discussion Counter to our hypothesis, the present study suggests that patients with CRPS do not have a worse clinical phenotype compared with patients not meeting CRPS criteria, with the exception of higher physical disability and more neuropathic pain symptoms. This corresponds to recent evidence that patients with CRPS are similar to other patient populations with chronic pain.
- neuropathic pain
- physical function
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Contributors OA and SM had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: CMB, GG. Acquisition, analysis, or interpretation of data: OA, BZ, SM, JP. Drafting of the manuscript: OA, JP. Critical revision of the manuscript for important intellectual content: CMB, PH, GG. Statistical analysis: SM, JP. Administrative, technical, or material support: SM, CMB, GG. Study supervision: SM, CMB.
Funding This study was supported by the Department of Anesthesiology at the University of Michigan. CMB receives research funding from the National Institutes of Health (R01 DA042859-05; R01 HD088712-05; R01 NR017096-05; K23 DA038718-04; R01 DA038261-05; P50 AR070600-05 CORT), the Michigan Department of Health and Human Services, and UM Michigan Genomics Initiative.
Disclaimer Heron Therapeutics and Recro Pharma are not associated with the content or preparation of this manuscript. This study represents the authors’ own work and does not represent the views of the funding entities.
Competing interests CMB serves as a consultant to Heron Therapeutics and Recro Pharma, and has a patent for peripheral perineural dexmedetomidine. The other authors (OA, GG, PH, SM, JP, and BZ) have no disclosures.
Patient consent for publication Not required.
Ethics approval This study was approved by the University of Michigan Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request.