Can Transcranial Electrical Stimulation Facilitate Post-stroke Cognitive Rehabilitation? A Systematic Review and Meta-Analysis

Abstract

BackgroundNon-invasive brain stimulation methods have been widely utilized in research settings to manipulate and understand the functioning of the human brain. In the last two decades, transcranial electrical stimulation (tES) has opened new doors for treating impairments caused by various neurological disorders. However, tES studies have shown inconsistent results in post-stroke cognitive rehabilitation, and there is no consensus on the effectiveness of tES devices in improving cognitive skills after the onset of stroke.ObjectivesWe aim to systematically investigate the efficacy of tES in improving post-stroke global cognition, attention, working memory, executive functions, visual neglect, and verbal fluency. Furthermore, we aim to provide a pathway to an effective use of stimulation paradigms in future studies.MethodsPreferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines were followed. Randomized controlled trials (RCTs) were systematically searched in four different databases, including Medline, Embase, Pubmed, and PsychInfo. Studies utilizing any tES methods published in English were considered for inclusion. Standardized mean difference (SMD) for each cognitive domain was used as the primary outcome measure.ResultsThe meta-analysis includes 19 studies assessing at least one of the six cognitive domains. Five RCTs studying global cognition, three assessing visual neglect, five evaluating working memory, three assessing attention, and nine studies focusing on aphasia were included for meta-analysis. As informed by the quantitative analysis of the included studies, the results favor the efficacy of tES in acute improvement in aphasic deficits (SMD = 0.34, CI = 0.02–0.67, p = 0.04) and attention deficits (SMD = 0.59, CI = −0.05–1.22, p = 0.07), however, no improvement was observed in any other cognitive domains.ConclusionThe results favor the efficacy of tES in an improvement in aphasia and attentive deficits in stroke patients in acute, subacute, and chronic stages. However, the outcome of tES cannot be generalized across cognitive domains. The difference in the stimulation montages and parameters, diverse cognitive batteries, and variable number of training sessions may have contributed to the inconsistency in the outcome. We suggest that in future studies, experimental designs should be further refined, and standardized stimulation protocols should be utilized to better understand the therapeutic effect of stimulation.

Comparative efficacy of different noninvasive brain stimulation therapies for recovery of global cognitive function, attention, memory, and executive function after stroke: a network meta-analysis of randomized controlled trials

“…27,31–33 For the main outcomes, rTMS improved GCF and memory in stroke patients, 31–33 whereas tDCS does not. 27,31 In the assessment of attention performance, all the meta-analyses of NIBS showed positive results, 27,31–33 except the tDCS part in the review of Hara et al 31 Due to the methodological restrictions of conventional meta-analysis, the authors of these reviews could only conduct pairwise comparisons. Furthermore, the authors analyzed a single group consisting of several rTMS or tDCS stimulation options.…”

“…Our NMA results are partially compatible with a previous evaluation of the impact of NIBS on cognitive performance, especially on attention and memory deficits following stroke. 27,31–33 For the main outcomes, rTMS improved GCF and memory in stroke patients, 31–33 whereas tDCS does not. 27,31 In the assessment of attention performance, all the meta-analyses of NIBS showed positive results, 27,31–33 except the tDCS part in the review of Hara et al 31 Due to the methodological restrictions of conventional meta-analysis, the authors of these reviews could only conduct pairwise comparisons.…”

“…In the present review, we will concentrate primarily on the aspect of cognition impairment from the perspective of the therapeutic efficacy of NIBS with various post-stroke dysfunctions. Some findings have been drawn from meta-analyses about the cognitive function of language 25–28 and unilateral neglect, 27–30 despite the lack of and conflicting evidence on attention, memory, and EF. The current meta-analysis for NIBS showed that most studies concluded that TMS had significant effects on attention, memory, working memory, global cognition, 23,31 and activities of daily living 32 (ADL) in post-stroke patients, while the effect of different frequencies of treatment options did not differ significantly, 33 and HF-rTMS had significant improvements in global cognition on left dorsolateral prefrontal cortex (DLPFC).…”

“…23 Some suggest an acute facilitative effect on repairing attentional impairment, but no improvement in general cognition or working memory. 27 Another report claims that tDCS improves attention and general cognition after stroke, but not memory. 34 But the effect of NIBS stimulation treatment on EF after stroke is limited.…”

Exploring the Frontiers of Neuroimaging: A Review of Recent Advances in Understanding Brain Functioning and Disorders

“…In addition, TES can modulate the activity of pain pathways in the brain, reducing pain perception. Motor functions: TES has been studied as a potential treatment for motor impairments, including stroke and Parkinson's disease [60,61]. Cognitive functions: TES has also been studied as a potential treatment for cognitive impairments, including memory and attention deficits [62,63].…”