Transcranial direct current stimulation for upper extremity spasticity rehabilitation in stroke survivors: A systematic review of randomized controlled trials

Objectives To examine the effects of transcranial direct current stimulation (tDCS) on upper extremity spasticity after stroke and to define the most effective tDCS parameters. Literature Survey Systematic review in the following databases: PubMed, SCOPUS, PEDro, CINAHL, MEDLINE, REHABDATA, AMED, and Web of Science databases. Studies up to June 2020 were included. Methodology Studies were included if the sample was composed of individuals with stroke, the intervention followed a tDCS intervention (alone or combined with another intervention), and the study was a randomized controlled trial including at least one measurement assessing upper extremity spasticity. Two authors independently screened the included studies. Conflicting decisions between authors were resolved by discussion with the third author. The methodological quality was assessed using the Cochrane Collaboration's tool. The authors determined that the meta-analysis was not feasible due to the heterogeneity in the protocols among the included studies. Synthesis After the screening of 1204 records, a total of seven studies met the specified inclusion criteria and involved 320 participants (mean age = 60.3), 31.1% of whom were females. Patients with ischemic stroke comprised 77.2% of the total patients, and 42.2% were with right hemispheric stroke. Six studies exhibited "high" quality and one exhibited "moderate" quality. Five of the selected studies that combined the tDCS intervention and other traditional interventions showed a significant reduction in upper extremity spasticity after stroke following tDCS intervention. The other two studies that delivered tDCs alone did not show a significant difference. Conclusions The evidence for the effect of tDCS on upper extremity spasticity after stroke was limited. The optimal tDCS treatment dosage remains unclear. Additional studies with large sample sizes and long-term follow-up are strongly warranted.