Transcranial direct current stimulation for post-stroke dysphagia: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND Transcranial direct current stimulation (tDCS) has been investigated as a tool for dysphagia recovery after stroke in several single-center randomized controlled trials (RCT). OBJECTIVE The aim of this investigation was to quantitatively evaluate the effect of tDCS on dysphagia recovery after a stroke utilizing a systematic review and meta-analysis. METHODS Major databases were searched through October 2019 using a pre-defined set of criteria. Any RCT investigating the efficacy of tDCS in post-stroke dysphagia using a standardized dysphagia scale as outcome measure was included. Studies were assessed for risk of bias and quality using the Physiotherapy Evidence Database (PEDro) scale. Effect sizes were calculated from extracted data and entered into a random effects analysis to obtain pooled estimates of the effect. RESULTS Seven RCTs with a total sample size of 217 patients fulfilled the criteria and were included in the analysis. The overall results revealed a small but statistically significant pooled effect size (0.31; CI 0.03, 0.59; p = 0.03). The subgroup which explored the stimulation intensity yielded a moderately significant effect size for the low-intensity stimulation group (g = 0.44; CI = 0.08, 0.81 vs. g = 0.15, CI - 0.30, 0.61). For the other subgroup analyses, neither comparisons of affected vs. unaffected hemisphere or acute vs. chronic stroke phase revealed a significant result. CONCLUSION This meta-analysis demonstrates a modest but significant beneficial effect of tDCS on improving post-stroke dysphagia. Whether benefits from this intervention are more pronounced in certain patient subgroups and with specific stimulation protocols requires further investigation.