Efficacy of scrambler therapy in chronic neuropathic pain: pairwise and dose-response meta-analysis

Chronic neuropathic pain (CNP) affects 7% of the world's population and is challenging to control since existing medications are inadequate and have negative effects. Electro-cutaneous devices, such as Scrambler Therapy (ST), have emerged as a possible option and have shown promising results in multiple randomized controlled trials (RCTs). However, the long-term efficacy of ST remains unknown. We aimed to evaluate the efficacy of ST in CNP reduction over time. We used the data sources including PubMed, Embase, Scopus, and Cochrane Central Register of Controlled Trials from inception to September 2023. Five placebo and three routine-care controlled RCTs were selected among the screened abstracts. Two authors independently extracted the data. Data was pooled using a model under the common parameters assumption. The studies were evaluated for methodological quality using the MethodologicAl STandard for Epidemiological Research (MASTER) scale. The primary outcome measure was pain reduction; pain was converted to a common 0 to 10 scale, and a weighted mean difference of more than 2 points on a 10-point pain scale was considered clinically important. Eight RCTs that evaluated the effect of ST on CNP were included, with a total sample size of 350 participants. None of the participants withdrew in all these trials owing to adverse events or lack of efficacy. There was high-quality evidence that ST reduced pain in the short term, with a mean difference of -3 points. The dose-response meta-analysis demonstrated a significant reduction in pain scores post-treatment, with a peak reduction at day 40. The effect of ST remained below the baseline values for 90 days, although with limited certainty. This study is the first dose-response meta-analysis to assess the duration of efficacy of ST in the treatment of CNP. The results demonstrated a clinically significant and more sustained reduction in pain created by ST compared to conventional treatments. Our findings indicate that ST could be used as a safe and effective alternative for managing CNP.