The effects of noninvasive brain stimulation on cognitive function in patients with stroke : a systematic review

Abstract

Introduction: Cognitive impairments occur frequently in stoke survivors, yet current conventional post-stroke care focuses mainly on motor function. Transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) are noninvasive brain stimulation techniques (NIBS) that are used in neurological rehabilitation. Its efficacy is well-established in motor recovery post-stroke, but research on its effects on the associated cognitive decline after stroke is fairly new. The aim of this review is to evaluate recent studies and provide a summary on the effects of NIBS on post-stroke cognitive decline.

Methods: PubMed and CINAHL were searched using the keywords: “cerebrovascular accident”, “stroke”, “NIBS” or “noninvasive brain stimulation”, “tDCS” or “transcranial direct current stimulation”, and “TMS” or “transcranial magnetic stimulation”. PEDro system was used to assess the quality of the studies that passed the inclusion and exclusion criteria.

Results: The initial search returned 1081 citations, among which 12 were included in this review. The mean PEDro score of the studies was 7.5 out of 10. The trials had a total of 176 participants with stroke. Lesion site was heterogeneous. Six trials investigated tDCS, and the other 6 investigated rTMS. The main outcome measures were grouped into 3 domains: memory, visuospatial, and attention. Both tDCS and rTMS resulted in significant changes in the visuospatial domain in terms of improving spatial neglect. The results on memory and attention are mixed, but tDCS shows more consistent results.

Conclusion: NIBS is a safe and low-cost treatment that can improve cognitive decline post-stroke. However, the evidence is still lacking due to the small number of trials and sample sizes. More studies need to be conducted in order to establish a proper guideline for usage. Long term effects also need to be investigated.