Transcranial direct current stimulation in post-stroke aphasia rehabilitation: A systematic review.

BACKGROUND: Transcranial direct current stimulation (tDCS) is a non-invasive tool that induces neuromodulation in the brain. Several studies have shown the effectiveness of tDCS in improving language recovery in post-stroke aphasia. However, this innovative technique is not currently used in routine speech and language therapy (SLT) practice.

OBJECTIVE: This systematic review aimed to summarise the role of tDCS in aphasia rehabilitation.

METHODS: We searched MEDLINE via PubMed and Scopus on October 5, 2018 for English articles published from 1996 to 2018. Eligible studies involved post-stroke aphasia rehabilitation with tDCS combined or not with SLT.

RESULTS: We retained 5 meta-analyses and 48 studies. Among the 48 studies, 39 were randomised controlled trials (558 patients), 2 prospective studies (56 patients), and 5 case studies (5 patients). Two articles were sub-analyses of a randomised clinical trial. Methods used in these studies were heterogeneous. Only 6 studies did not find a significant effect of tDCS on language performance. As compared with earlier meta-analyses, the 2 latest found significant effects.

CONCLUSION: Evidence from published peer reviewed literature is effective for post-stroke aphasia rehabilitation at the chronic stages. tDCS devices are easy to use, safe and inexpensive. They can be used in routine clinical practice by speech therapists for aphasia rehabilitation. However, further studies should investigate the effectiveness in the subacute post-stroke phase and determine the effect of the lesion for precisely identifying the targeted brain areas. We discuss crucial challenges for future studies.