Efficacy of transcranial direct current stimulation in patients with dysphagia after stroke: a systematic review.

BACKGROUND: Swallowing is a complex function that can be disrupted after stroke. Transcranial Direct Current Stimulation (tDCS) is a non-invasive brain stimulation therapy that recently has been tested to treat stroke-related dysphagia. METHODS: The authors performed a search in the literature to review the described evidence of the use of tDCS in dysphagia after stroke. Three electronic databases were searched. The risk of bias evaluation was carried out through the RoB-2 tool. The Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) framework was also implemented. RESULTS: Of 265 articles, only nine studies were included in this review. The most common location of the tDCS stimulation was the unaffected hemisphere (44%). Regarding the outcome measure, the Dysphagia Outcome and Severity Scale (DOSS) was the most commonly used (55%). However, due to the high heterogeneity of the protocols, and considering the differences between the types of stroke, the authors opted not to perform a metanalysis. Instead, a systematic review with a thorough analysis of each individual study and the impact of the differences to the outcomes was preferred. CONCLUSIONS: The final considerations are that even though the majority of studies described benefits from tDCS in post-stroke dysphagia, as they present too many methodological differences, it is not possible to compare them. In addition, many articles included patients with less than 6 months after stroke, which is an important bias as the swallowing function can be recovered spontaneously within this period, turning the certainty of the evidence really low.