Influence of Transcranial Direct Current Stimulation Dosage and Associated Therapy on Motor Recovery Post-stroke: A Systematic Review and Meta-Analysis

Abstract

Purpose(1) To determine the impact of transcranial direct current stimulation (tDCS) applied alone or combined with other therapies on the recovery of motor function after stroke and (2) To determine tDCS dosage effect.MethodsRandomized controlled trials comparing the effects of tDCS with sham, using the Barthel Index (BI), the upper and lower extremity Fugl–Meyer Assessment (FMA), and the Modified Ashworth Scale (MAS), were retrieved from PubMed, Medline (EBSCO), and Cumulative Index to Nursing and Allied Health Literature (CINAHL) from their inception to June 2021. Calculations for each assessment were done for the overall effect and associated therapy accounting for the influence of stroke severity or stimulation parameters.ResultsA total of 31 studies involving metrics of the BI, the upper extremity FMA, the lower extremity FMA, and the MAS were included. tDCS combined with other therapies was beneficial when assessed by the BI (mean difference: 6.8; P < 0.01) and these studies typically had participants in the acute stage. tDCS effects on the upper and lower extremity FMA are unclear and differences between the sham and tDCS groups as well as differences in the associated therapy type combined with tDCS potentially influenced the FMA results. tDCS was not effective compared to sham for the MAS. Stimulation types (e.g., anodal vs. cathodal) did not influence these results and dosage parameters were not associated with the obtained effect sizes. Conventional therapy associated with tDCS typically produced greater effect size than assisted therapy. The influence of stroke severity is unclear.ConclusionPotential benefits of tDCS can vary depending on assessment tool used, duration of stroke, and associated therapy. Mechanistic studies are needed to understand the potential role of stimulation type and dosage effect after stroke. Future studies should carefully conduct group randomization, control for duration of stroke, and report different motor recovery assessments types.Systematic Review Registration[https://www.crd.york.ac.uk/PROSPERO/], identifier [CRD42021290670].

Transcranial-Direct-Current-Stimulation Accelerates Motor Recovery After Cortical Infarction in Mice: The Interplay of Structural Cellular Responses and Functional Recovery

“…Consistently, the recent literature shows that in humans, tDCS improved long-term motor recovery when applied in addition to established rehabilitation regimes but not alone. [56][57][58] In this context, it would be interesting to investigate tDCS combined with physical exercise or an enriched environment, which was not addressed in this study. However, both enhanced recovery of function and modulation of inflammation after stroke have repeatedly been demonstrated.…”

Transcranial direct current stimulation for upper extremity motor dysfunction in poststroke patients: A systematic review and meta-analysis

“…The findings indicated that transcranial direct current stimulation was more effective in patients with subacute stroke than in those with acute and chronic stroke experiencing upper limb dysfunction. However, three studies reached different conclusions, among which two 8,9 showed a more effective effect of transcranial direct current stimulation in patients with chronic stroke, while one 11 showed a more effective effect in those with acute stroke. Notably, transcranial direct current stimulation can interfere with or even disrupt spontaneous recovery in the acute phase, emphasizing the need for caution when interpreting these results.…”

“…10 Previous systematic reviews and meta-analyses investigating the effects of transcranial direct current stimulation in combination with other treatments and at different doses have not yielded conclusive results. [11][12][13] Additionally, guidelines for selecting transcranial direct current stimulation types or stimulus parameters are currently unavailable.…”

Combination of different noninvasive brain stimulation treatments for upper limb recovery in stroke patients: A systematic review

“…tDCS can also be applied with various set‐ups including anodal stimulation (a‐tDCS), cathodal stimulation (c‐tDCS), and dual stimulation (d‐tDCS; the most common) (List et al., 2015 ; Vines et al., 2008 ). Recent studies have shown inconclusive results when applying tDCS for motor skill improvement using scales such as the FMA (Chow et al., 2022 ); however, considering the ICF division, that same study and other systematic reviews with meta‐analyses have shown that all types of tDCS stimulation are effective, but it appears that ctDCS may have greater effectiveness in improving activities of daily living and independence (Chow et al., 2022 ; Elsner et al., 2020 , 2017 ). The atDCS approach appears to show more significant improvements in motor ability (Xue et al., 2022 ).…”