1. 2022;25;521-530Parameters of Spinal Cord Stimulation in Complex Regional Pain Syndrome: Systematic Review and Meta-analysis of Randomized Controlled Trials
   Systematic Review
   Elver Ho, BA, Nima Yazdanpanah, DO, Johnson Ho, MD, Benjamin Drukman, BS, Alvin Chang, MD, and Sanjeev Agarwal, MD.

BACKGROUND: Complex Regional Pain Syndrome (CRPS) is a chronic debilitating neuropathic pain condition characterized by autonomic and inflammatory features that typically occurs after a traumatic event. Spinal cord stimulation (SCS) has been shown to be effective in the treatment of chronic CRPS refractory to conventional treatment modalities. The collective evidence of novel parameters of SCS for treating CRPS has not been characterized extensively.

OBJECTIVE: To provide evidence for the use of SCS to treat CRPS and characterize the additional benefits of various SCS waveforms.

STUDY DESIGN: Systematic Review and Meta-analysis.

METHODS: PubMed, Embase and CINHLA were screened for all randomized controlled trials (RCT) comparing SCS parameters for the treatment of CRPS.

RESULTS: Four RCTs were identified that included SCS as a treatment arm for CRPS. Of these, one study compared low frequency tonic SCS (LF-SCS) versus conventional physical therapy, 2 studies compared placebo/sham SCS with LF-SCS and a multitude of waveforms, and one study compared LF-SCS with high-frequency SCS (HF-SCS). Two of the studies were rated as having a low risk of bias, one study was rated as having some concerns for bias, while the final study was rated as having a high risk of bias. A meta-analysis of 4 studies comparing conventional therapy/placebo SCS stimulation against LF-SCS revealed increased benefit of LF-SCS in pain reduction up to a month (mean difference [MD] = -1.17 points; 95% CI = -1.61 to -0.73; P < 0.001, I2 = 42%). Another meta-analysis of 2 studies showed that LF-SCS results in higher global perceived effect scores relative to conventional therapy/placebo SCS stimulation (MD = 1.58; 95% CI = 1.00 to 2.15; P < 0.001, I2 = 0%).

LIMITATIONS: A pooled analysis using different designs for RCTs was conducted. Some studies folded in multiple neuropathic pain pathologies in addition to CRPS. One study was at a high risk for bias in at least one domain.

CONCLUSION: LF-SCS is superior to conventional therapy/placebo SCS stimulation. However, more evidence is required to demonstrate that novel SCS parameters are superior to LF-SCS in improving pain scores and functional outcomes.

KEY WORDS: Complex Regional Pain Syndrome, spinal cord stimulation, meta-analysis, systematic review, tonic, burst, high frequency, waveform