Effects of transcranial direct current stimulation (tDCS) on motor function among people with stroke: evidence mapping.

Objective: To present, organize, and assess the methodological quality of the current research related to tDCS on motor function after a stroke and to identify gaps and clinical implications using an evidence mapping approach.

Methods: Six electronic databases (PubMed, Embase, Cochrane Library, Web of Science, CINAHL, PEDro), gray literature, and reference lists of articles were searched from inception until October 2023. The Assessment of Multiple Systematic Reviews 2 (AMSTAR-2) checklist and PEDro scale were used to assess the methodology quality of systematic reviews (SRs) and randomized controlled trials (RCTs).

Results: A total of 172 articles met the inclusion criteria from 5759 records, including 46 SRs and 126 RCTs. Related studies came from 29 countries around the world, and China has performed the most, with 12 SRs and 21 RCTs. More than half of SRs (65.22%) were evaluated with low or critically low quality, while 78.58% of RCTs have shown excellent or good quality. A total of 26 SRs and 93 RCTs have reported outcomes on upper limb motor function with kinds of tDCS, and 15 SRs and 44 RCTs have focused on lower extremity function. Studies with safety concerns have reported no or mild adverse events.

Conclusions: This study systematically identified gaps and indicated that tDCS is a kind of potential and safe intervention. Given potential concerns on the clinical application, more high-quality research with large sample size and kinds of objectives is needed in the future.