Abstract
Objective
Transcranial direct-current stimulation (tDCS) is a noninvasive approach that can alter brain excitability. Several studies have shown the effectiveness of tDCS in improving language and movement function in stroke patients. However, the effect of tDCS on cognitive function after stroke remains uncertain.
Methods
We searched Medline, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL), the China National Knowledge Infrastructure, the China Science and Technology Journal Database, and the Wanfang Data Knowledge Service Platform from inception to April 2, 2019. Two reviewers independently screened the studies, extracted the data, and evaluated the quality of the included studies using the Cochrane Collaboration Risk of Bias Tool. All statistical analyses were performed in RevMan 5.3, and the mean difference (MD) or standard mean difference (SMD) were used as the pooled statistics.
Results
Fifteen studies involving 820 participants were included. When compared with passive tDCS, anodal tDCS was associated with improved general cognitive performance as examined by the Minimum Mental State Examination or Montreal Cognitive Assessment (SMD = 1.31, 95% CI 0.91–1.71, P < 0.00001), attention performance (SMD = 0.66, 95% CI 0.11–1.20, P = 0.02). There was no significant difference in memory performance (SMD = 0.41, 95% CI -0.67–1.50, P = 0.46).
Conclusions
tDCS is likely to be effective for patients with cognitive impairment after stroke. The evidence for different effects based on population characteristics and stimulation methods was limited, but a real effect cannot be ruled out. More high-quality research in this field is required to determine the potential benefits of tDCS in the treatment of cognitive deficits after stroke and to establish the optimal treatment program.
Introduction
Although stroke has fallen from the second leading cause of death to the fourth in the United States, it remains the leading cause of severe adult disability, which produces a major burden to society [1]. In 2010, there were an estimated 11.6 million events of incident ischemic stroke and 5.3 million events of incident hemorrhagic stroke, most of which were in low- and middle-income countries [2]. In addition to the high morbidity and mortality, the burden of stroke-related disability is another major problem in survivors; the incidence of poststroke cognitive impairment (PSCI) ranges from 22% to 47% in different studies [3–5], and it has had a serious impact on both the economy and quality of life.
Transcranial direct-current stimulation (tDCS) was first developed for clinical purposes in 2000[6]; currently, it constitutes a promising method for neurological condition regulation [7, 8]. As a neuromodulatory approach, tDCS works by depolarizing or hyperpolarizing neuronal membrane potentials through the activation of sodium- and calcium-dependent channels and NMDA receptor activity, thereby modulating neural activity and cortical excitability [7, 9].
Several systematic reviews have evaluated the efficacy of tDCS on motor function and aphasia after stroke [10–12]; some preliminary studies have shown beneficial effects of tDCS on cognitive function in healthy subjects as well as in stroke patients [13–16]. However, it remains largely uncertain whether tDCS promotes the recovery of cognitive function after stroke. Therefore, we conducted this systematic review and meta-analysis to evaluate the effectiveness of tDCS on cognition after stroke.[…]