Systematic review of efficacy of TENS for management of central pain in people with multiple sclerosis.

BACKGROUND: Transcutaneous electrical nerve stimulation (TENS) is a non-pharmacological therapy that can be used for central pain (CP) management without the side effects of pharmacological interventions. Currently, the efficacy of TENS for management of CP in people living with multiple sclerosis (MS) is considered questionable. METHODS: Relevant electronic databases were searched from their inception to November 2014 using appropriate terms for case-control (CC) studies or randomized controlled trials (RCTs) utilizing TENS for management of CP in MS. Included studies were combined in a meta-analysis. A standardized mean difference (SMD) expressed as Hedges׳ g and 95% confidence interval (CI) of efficacy of TENS intervention were computed using a random effects model. The resulting evidence was graded in accordance to the GRADE system. RESULTS: A total of 11 effect sizes were extracted from four studies. High and low frequency TENS was utilized in separate subgroup of participants in three studies and conventional TENS in one study. These seven effect sizes were combined for the final analysis (one effect size for each subgroup of participants). Two studies measured pain using visual analog scale and McGill Pain Questionnaire. The findings of this study demonstrate a medium sized statistically significant effect of TENS for management of CP in people with MS [Hedges׳ g=0.35; p=0.009]. The frequency of TENS or outcome used to measure pain had no effect on our study results. These findings are consistent with GRADE 2 level of evidence. CONCLUSION: TENS is a safe and effective non-pharmacological alternative in the management of central pain in people living with MS. TENS intervention to address CP is desirable.