Transcranial Direct Current Stimulation for Improving Aphasia after Stroke: What's the Current Evidence?

Background
Transcranial direct current stimulation (tDCS) may be used to improve aphasia after stroke.
Objectives
To assess the effects of tDCS on aphasia in people with stroke.
Methods
We searched the Cochrane Stroke Group Trials Register (June 2018), the CENTRAL (Cochrane Central Register of Controlled Trials; in the Cochrane Library, June 2018), MEDLINE (1948 to June 2018), EMBASE (1980 to June 2018), CINAHL (1982 to June 2018), AMED (1985 to June 2018), Science Citation Index (1899 to June 2018), and 7 additional databases.1 Two review authors independently assessed risk of bias of included trials and extracted data. We included only randomized controlled trials that compared tDCS versus control in adults with stroke. The primary outcome was functional communication at study end and at follow-up; secondary outcomes were accuracy in naming, cognition, and safety.
Main Results
We included 21 studies involving a total of 421 participants. TDCS did not improve functional communication at the end of intervention (standardized mean difference =0.17; 95% CI, −0.20 to 0.55; P=0.37; 112 participants; 3 studies; low quality of evidence), or at follow-up (standardized mean difference) =0.14; 95% CI, −0.31 to 0.58; P=0.55; 80 participants; 2 studies; very low quality of evidence). TDCS improved accuracy in naming nouns at the end of intervention period (standardized mean difference =0.42; 95% CI, 0.19 to 0.66; P=0.0005; 298 participants; 11 studies; moderate quality of evidence; Figure). There were no studies which reported effects on cognition. Dropouts and adverse events were rare and comparable between groups.
Implications for Clinical Practice and Future Research
Our review of 21 trials involving 421 participants found low quality evidence that tDCS does not improve functional communication and moderate quality evidence that tDCS improves accuracy in naming nouns in people with aphasia after stroke. Future research should routinely investigate the effects on functional communication.
This article is based on a Cochrane Review published in The Cochrane Library 2019, Issue 5 (see www.thecochranelibrary.com for information). Cochrane Reviews are regularly updated as new evidence emerges and in response to feedback, and The Cochrane Library should be consulted for the most recent version of the review.