Is transcranial direct current stimulation (tDCS) effective for chronic low back pain? A systematic review and meta-analysis

Transcranial direct current stimulation (tDCS) has been used to reduce pain in range of chronic pain states. The aim of this review is to evaluate the effectiveness of tDCS on pain reduction and related disability in patients with non-specific chronic low back pain (CLBP). A computer-based systematic literature search was performed in five databases according to PRISMA guidelines. Randomized controlled trials (RCTs) that assessed the effects of tDCS on pain and related disability in patients with non-specific CLBP were included. Modified Jadad scale and Cochrane's risk of bias assessment were used to determine the studies' quality and risk of bias. Meta-analyses were performed by calculating the standardized mean difference (SMD) at 95% confidence interval (CI). Nine RCTs (411 participants) were included in the systematic review according to inclusion criteria, while only five studies could be included in the meta-analysis. The primary motor cortex (M1) was the main stimulated target. The meta-analysis showed non-significant effect of multiple sessions of tDCS over M1 on pain reduction and disability post-treatment respectively, (SMD = 0.378; 95% CI = - 0.264-1.020;P = 0.249), (SMD = 0.143; 95% CI = - 0.214-0.499;P = 0.434). No significant adverse events were reported. The current results do not support the clinical use of tDCS for the reduction of pain and related disability in non-specific CLBP. However, the limited number of available evidence limits our conclusions on the effectiveness of these approaches.