The Effectiveness of Transcranial Stimulation in Improving Swallowing Outcomes in Adults with Poststroke Dysphagia: A Systematic Review and Meta-analysis

Transcranial stimulation has been proposed as an alternative rehabilitation therapy for adults with post-stroke dysphagia (PSD). This systematic review sought to determine the effectiveness of transcranial stimulation in patients with post-stroke dysphagia to improve swallowing function. From inception to January 3, 2021, an extensive search was conducted in PubMed, EMBASE, Cochrane, CINAHL, and Scopus, Web of Science. The randomized controlled trials (RCTs) included studies in adults aged 18 years and older who suffered from post-stroke dysphagia. Using Hedges' g as effect size, meta-analyses were conducted using random-effects models. To investigate potential sources of heterogeneity, subgroup analyses, and multivariable meta-regression analyses were conducted. Sixteen RCTs were included in this review, and 13 RCTs were used for meta-analysis. The meta-analysis showed that a large effect size in improving swallowing function after repetitive Transcranial Magnetic Stimulation (g = - 0.86, 95% CI - 1.57, - 0.16) and medium effect size in Transcranial Direct Current Stimulation (g = - 0.61, 95% CI - 1.04, - 0.17) at post-intervention, respectively. Subgroup and meta-regression analysis indicated that stimulation of the esophagus cortical area and middle-aged adults had a greater effect on swallowing function. The overall certainty of evidence assessed using the GRADE approach was low. Despite the positive results, transcranial stimulation requires additional research to reach definitive conclusions about the optimal stimulation protocol and to achieve the greatest benefit. Future trials should be more rigorous and include a larger sample size to demonstrate the efficacy of transcranial stimulation. Transcranial stimulation enables a more efficacious approach to dysphagia mitigation in PSD rehabilitation.