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Effectiveness of Transcranial Direct Current Stimulation as an Adjuvant to Aphasia Treatment Following Stroke: Evidence From Systematic Reviews and Meta-Analyses

Raymer AM, Johnson RK

American journal of speech-language pathology, 2024

Abstract

PURPOSE: Transcranial direct current stimulation (tDCS) is a neuromodulation tool to amplify neural excitability and enhance outcomes associated with speech-language therapy (SLT). Stimulation currents to the left and right hemispheres vary in applying anodal (excitatory), cathodal (inhibitory), or bihemispheric signals. Several systematic reviews (SRs) and meta-analyses (MAs) have summarized the large literature examining tDCS for aphasia rehabilitation. The purpose of this project was to appraise the quality of SRs and MAs of tDCS for aphasia and examine the weight of the evidence for language outcomes in individuals with aphasia beyond SLT alone.

METHOD: We searched four databases for SRs/MAs examining effects of tDCS for poststroke aphasia. We identified 16 reviews, with nine that incorporated MA to quantify results. Two reviewers reliably coded articles for methodological rigor using the AMSTAR 2 (A MeaSurement Tool to Assess Systematic Reviews, Version 2). We then summarized findings of the 16 reviews.

RESULTS: The AMSTAR 2 appraisal criteria suggest that critical weaknesses were noted among all reviews except those by Elsner et al. (2015, 2019). Reviews summarized three to 48 studies, as some included only randomized crossover trials and others included all trial designs. All SRs and one MA reported improvements following tDCS stimulation for general aphasia abilities and measures of repetition and speech fluency. Five recent MAs reported significant naming…

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