Effect of non-invasive brain stimulation on motor function after spinal cord injury: a systematic review and meta-analysis

Abstract

Background: In recent years, non-invasive brain stimulation (NIBS) has often been used for therapeutic effects on motor functions. However, there is no clear evidence for the efficacy of NIBS in populations with spinal cord injury (SCI). This study aims to conduct a meta-analysis to summarize the existing evidence on the effectiveness and safety of NIBS for motor dysfunction after a spinal cord injury to obtain new insights. Methods: Two investigators systematically screened English articles from PubMed, MEDLINE, Embase, and Cochrane Library for eligible Randomized and prospective controlled trials regarding the effects of NIBS in motor function recovery after SCI. Studies with at least three sessions of NIBS were included. We assessed the methodological quality of selected studies as described in the evidence-based Cochrane Collaboration’ tool. A meta-analysis of the motor function was performed by pooling thestandardized mean difference (SMD)with 95% confidence intervals (CI). Results: A total of 14 studies involving 225 patients were included. Nine studies used repetitive transcranial magnetic stimulation (rTMS) and 5 studies used transcranial direct current stimulation (tDCS). The meta-analysis showed that NIBS could improve the lower extremity strength (SMD = 0.58, 95% CI= 0.02 to 1.14, P = 0.004), balance (SMD = 0.64, 95% CI= 0.05 to 1.24, P= 0.03) and decrees the spasticity (SMD = -0.64, 95% CI=-1.20 to-0.03, P =0.04); while functional mobility of the NIBS group was not statistically significant than that of the control group (upper extremity strength: P=0.07; spasticity: P=0.12). The motor function of upper extremity strength in the NIBS group did not reach statistical significance when compared with the sham group. Only one patient reported seizures occurred during stimulation; no other serious adverse events were reported. Conclusion: NIBS appears to have a positive effect on motor function of the lower extremity in SCI patients. However, the marginal p-value and a high heterogeneity suggest that these results should be interpreted with caution. Further high-quality clinical trials are needed to support or refute the use and optimize the stimulation parameters of NIBS in clinical practice.