Electrical Stimulation of the Motor Cortex or Paretic Muscles Improves Strength Production in Stroke Patients: A Systematic Review andMeta-Analysis

Objective Transcranial direct current stimulation (tDCS) and functional electrical stimulation (FES) are two widely applied methods of electrical stimulation for motor recovery among stroke patients. This systematic review and meta-analysis investigated the efficacy of tDCS and FES for strength production in stroke patients. Type Systematic review. Literature Survey Studies that explored the effects of tDCS or FES on the strength production of paralyzed muscles in stroke patients were retrieved on a comprehensive set of three databases: (1) Google Scholar, (2) PubMed, and (3) the Cochrane Database of Systematic Reviews until July 2019. Methodology Systematic study retrieval led to the inclusion of 15 studies that reported on strength production effects after tDCS and FES interventions among stoke patients. A sham control group and randomization were used in each study. The 15 studies included 20 comparisons with sham controls, 7 of which involved tDCS and 13 of which involved FES. Synthesis Random-effects models showed that strength production was improved after tDCS (effect size [ES] = 0.52, 95% confidence interval [CI] = 0.35-0.69,P < .001, Z = 6.05) and FES (ES = 0.47, 95% CI = 0.16-0.78,P < .003, Z = 2.99). Additionally, tDCS was shown to improve strength production in the acute (ES = 0.52, 95% CI = 0.24-0.80,P < .001, Z = 3.65), subacute (ES = 0.85, 95% CI = 0.37-1.32,P < .001, Z = 3.51), but not chronic (ES = 0.06, 95% CI = -0.47-0.60,P = .82, Z = 0.23) phases of stroke recovery. Out of the 13 studies involving FES, 12 investigated strength production in the chronic phase and one investigated in the acute phase, showing a positive effect in these two stages. Conclusions The results of the meta-analysis showed that tDCS and FES successfully improved strength production in stroke patients.