Introduction

Complex Regional Pain Syndrome (CRPS) is a debilitating pain condition often preceded by trauma to an extremity. The acute phase is characterized by inflammation and peripheral sensitization, whereas the chronic phase is mainly due to central mechanisms.^1-3 Standard treatment modalities are often inadequate. Where this is the case, spinal cord stimulation (SCS) may be an option.⁴ We aim to assess the effect of SCS for CRPS and to elucidate whether symptom duration preceding implantation is a predictor of treatment efficacy.

Methods/Materials

The study includes 50 CRPS patients implanted with an SCS system at the University Hospital in Aarhus or Odense, Denmark. Data for the analysis are recorded in the Neurizon Neuromodulation Database. Pain intensity determined by 7-day average pain and 7-day worst pain on a numeric rating scale (NRS 0-10) and The Patient Global Impression of Change (PGIC) is considered the primary outcomes of treatment. Change in pain intensity was assessed by means of a paired t-test. A simple linear regression was conducted to investigate whether preoperative symptom duration predicts the change in pain intensity.

Results

Data analysis is currently ongoing. Preliminary results indicate a significant effect of SCS treatment in patients with CRPS, with a mean reduction in 7-day average pain of 28.1% (n=39, [95% CI: 38.1-18.2], P < 0.001) and 21.2% (n=41, [95% CI: 30.2-12.2], P < 0.001) in 7-day worst pain. At the latest registered follow-up, 58.1% of the patients reported a clinically important effect of treatment, determined as at least much improved or better on the PGIC scale, in accordance with the IMMPACT recommendations.⁵ A linear regression established that symptom duration prior to implantation does not statistically significantly predict the effect of treatment in terms of change in 7-day average pain [F(1, 37) = 0.22, P = 0.64, R² = 0.006] and 7-day worst pain [F(1, 39) = 0.01, P = 0.91, R² = 0.0003]. The final results will be ready for presentation at the e-INS 2020.

Discussion

SCS may be an effective treatment modality for CRPS patients. Our results are in accordance with previous published studies.^4,6

Conclusions

From the preliminary results, we conclude that SCS significantly reduced both 7-day average pain and 7-day worst pain in CRPS patients. This effect does not appear to be predicted by preoperative symptom duration. Based on the latest registered PGIC ratings, 58.1% of the patients reported their overall change since implantation as much improved or better.

References

1. Marinus J, Moseley GL, Birklein F, et al. Clinical features and pathophysiology of complex regional pain syndrome. Lancet Neurol. 2011;10(7):637-648.

2. Reimer M, Rempe T, Diedrichs C, Baron R, Gierthmuhlen J. Sensitization of the Nociceptive System in Complex Regional Pain Syndrome. PLoS One. 2016;11(5):e0154553.

3. Ji RR, Woolf CJ. Neuronal plasticity and signal transduction in nociceptive neurons: implications for the initiation and maintenance of pathological pain. Neurobiol Dis. 2001;8(1):1-10.

4. Kemler MA, Barendse GA, van Kleef M, et al. Spinal cord stimulation in patients with chronic reflex sympathetic dystrophy. N Engl J Med. 2000;343(9):618-624.

5. Dworkin RH, Turk DC, McDermott MP, et al. Interpreting the clinical importance of group differences in chronic pain clinical trials: IMMPACT recommendations. Pain. 2009;146(3):238-244.

6. Geurts JW, Smits H, Kemler MA, Brunner F, Kessels AG, van Kleef M. Spinal cord stimulation for complex regional pain syndrome type I: a prospective cohort study with long-term follow-up. Neuromodulation. 2013;16(6):523-529; discussion 529.