Background and Objectives We hypothesized that patients with complex regional pain syndrome (CRPS) with a longer time since their inciting event would demonstrate more symptoms of centralized pain.
Methods We conducted a cross-sectional analysis of 160 patients with CRPS using validated measures of pain, negative mood, and functioning at the time of their new patient evaluation. The 2011 Fibromyalgia Survey Criteria is a validated self-report measure of widespread body pain and comorbid symptoms (eg, trouble thinking, headaches). The measure was used as a surrogate for centralized pain symptoms. Univariate analyses and multivariate linear regression models were used to assess the associations between patient characteristics and the duration of CRPS.
Results The cohort was divided into tertiles based on the time since the inciting event (<12 months; 1–3 years; >3 years) for univariate comparisons. Unlike the other measures of pain, mood, and function, the fibromyalgia survey score was significantly associated with a longer duration of symptoms. In a multivariate model adjusting for age and sex, each year since the inciting event was associated with an increase of 0.28 in fibromyalgia survey score (Est 0.28; 95% confidence interval, 0.11–0.46; P = 0.002). The finding was distinct from self-reported spread of CRPS symptoms, which was not different based on time since the inciting event.
Conclusions Our findings suggest that the longer the patients have CRPS the more likely they are to report symptoms suggestive of centralized pain. These data may explain why some patients with a longer duration of CRPS do not respond to peripherally directed therapies.
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The University of Michigan holds a patent for the use of peripheral perineural dexmedetomidine alone and in combination with local anesthetics. Application number 12-791,506; Issue Date 4-2-13; Patent Number 8410140. Dr Brummett is also a consultant for Tonix Pharmaceuticals (New York, NY).
Dr Brummett receives research funding from the National Institutes of Health, NIAMS R01 AR060392, and NIDA 1R01DA038261-01A1, as well as the University of Michigan Medical School Dean's Office (Michigan Genomics Initiative). Dr Brummett also receives research funding from Neuros Medical Inc (Willoughby Hills, Ohio). None of the funding is relevant to the subject matter of this review.The other authors declare no conflict of interest.