Brush-evoked allodynia as a predictor of SCS success in CRPS

European Journal of Pain, Volume 14, Issue 2, Pages 164-169 (February 2010)

Brush-evoked allodynia predicts outcome of spinal cord stimulation in Complex Regional Pain Syndrome type 1

Frank van Eijs, Helwin Smits, José W. Geurts, Alfons G.H. Kessels, Marius A. Kemler, Maarten van Kleef, Elbert A.J. Joosten, Catharina G. Faber

ABSTRACT

Background
Spinal cord stimulation (SCS) has proven to be an effective however an invasive and relatively expensive treatment of chronic Complex Regional Pain Syndrome type 1(CRPS-1). Furthermore, in one third of CRPS-1 patients, SCS treatment fails to give significant pain relief and 32–38% of treated patients experience complications. The aim of the current study was to develop effective prognostic factors for prediction of successful outcome of SCS.

Methods and results
The study population consisted of 36 chronic CRPS patients enrolled in a randomized controlled trial of SCS efficacy. We analyzed various prognostic factors in the group of patients treated with SCS and compared baseline values of possible predictors of outcome in the successfully treated and the not successfully treated group. Success was defined as Patient Global Perceived Impression of Change score of at least “much improved” and pain reduction of at least 2.5 on a visual-analogue scale (VAS score 0–10). Univariate analyses showed that patient age, duration of the disease, localization of the disease, intensity of the pain, and the presence of mechanical hypoesthesia did not predict SCS success. The mean and maximum value of brush-evoked allodynia proved to be statistically significant predictors of outcome. Using Receiver-Operating Characteristic (ROC) curve analyses of maximum allodynia values, the diagnostic sensitivity for successful SCS was 0.75 and the specificity 0.81.

Conclusion
Brush-evoked allodynia may be a significant negative prognostic factor of SCS treatment outcome after 1 year in chronic CRPS-1.

Keywords: Spinal cord stimulation (SCS), Complex Regional Pain Syndrome type 1 (CRPS-1), Brush-evoked allodynia, Mechanical hypoesthesia, Prognostic factors

Corresponding author -- Address: Department of Anesthesiology and Pain Management, Maastricht University Medical Centre, Mail Box 5800, 6202 AZ Maastricht, The Netherlands. Tel.: +31 043 3877673.

STUPID QUESTION TIME: Why the insistence on CRPS Type *One* in this study, and most others, too? Is there a possibility that there exist different results for CRPS Type 2?