Non-invasive brain stimulation in the treatment of post-stroke aphasia: a scoping review

PurposeAphasia is an acquired language impairment that commonly results from stroke. Non-invasive brain stimulation (NIBS) might accelerate aphasia recovery trajectories and has seen mounting popularity in recent aphasia rehabilitation research. The present review aimed to: (1) summarise all existing literature on NIBS as a post-stroke aphasia treatment; and (2) provide recommendations for future NIBS-aphasia research.Materials and methodsDatabases for published and grey literature were searched using scoping review methodology. 278 journal articles, conference abstracts/posters, and books, and 38 items of grey literature, were included for analysis.ResultsQuantitative analysis revealed that ipsilesional anodal transcranial direct current stimulation and contralesional 1-Hz repetitive transcranial magnetic stimulation were the most widely used forms of NIBS, while qualitative analysis identified four key themes including: the roles of the hemispheres in aphasia recovery and their relationship with NIBS; heterogeneity of individuals but homogeneity of subpopulations; individualisation of stimulation parameters; and much remains under-explored in the NIBS-aphasia literature.ConclusionsTaken together, these results highlighted systemic challenges across the field such as small sample sizes, inter-individual variability, lack of protocol optimisation/standardisation, and inadequate focus on aphasiology. Four key recommendations are outlined herein to guide future research and refine NIBS methods for post-stroke aphasia treatment. A comprehensive review of non-invasive brain stimulation (NIBS) post-stroke aphasia literature, including all study designs, was required.Review of this literature revealed that anodal transcranial direct current stimulation is the mostly commonly used type of NIBS in aphasia treatment research.Systemic challenges across the field hinder prospective translation of NIBS into aphasia practice.Aphasia rehabilitation professionals should note that further research is required before NIBS is suitable for translation into clinical practice.