A Systematic Review of effect of Non-Invasive Brain Stimulation on Cognition Impairment after a Stroke and Traumatic Brain Injury

BackgroundIn recent years, the potential of non-invasive brain stimulation (NIBS) for therapeutic effects on cognitive functions has been explored for stroke and traumatic brain injury (TBI) populations. MethodsAll English articles from the following sources were searched from inception up to December 31, 2018: PubMed, Scopus, CINAHL, Embase, PsycINFO and CENTRAL. Randomized and prospective controlled trials, including cross-over studies, were included for analysis. Studies with at least five individuals post stroke or TBI, whereby at least five sessions of NIBS were provided and used standardized neuropsychological measurement of cognition, were included. ResultsA total of 17 studies met eligibility criteria which included 546 patients receiving either repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS). Sample sizes ranged 5-25 subjects per group. Seven studies used rTMS and ten studies used tDCS. Target symptoms included global cognition (n=8), memory (n=1), attention (n=1), and unilateral spatial neglect (USN) (n=7). Nine studies combined rehabilitation or additional therapy with NIBS. Six of ten studies showed significant improvement in attention, memory, working memory, and executive function. In the USN study, five of the seven studies had a significant improvement in the intervention group. ConclusionsThe effect of NIBS on executive functions including attention and memory post stroke or TBI yielded mixed results with variable stimulation parameters. A significant, consistent improvement was observed for USN post stroke or TBI. Future studies using advanced neurophysiological and neuroimaging tools to allow network-based approach to NIBS for cognitive symptoms post stroke or TBI are warranted.