Transcranial direct current stimulation to improve cognitive function in patients with vascular cognitive impairment: a literature review.

Vascular pathology represents the second most common cause of cognitive impairment after Alzheimer's disease and contributes substantially to mixed dementia involving both vascular and neurodegenerative mechanisms. Vascular cognitive impairment (VCI) emerges as a term encompassing cognitive impairments resulting from stroke, cerebral small vessel disease (CSVD), or other forms of vascular pathology. While numerous studies have demonstrated the beneficial effects of transcranial direct current stimulation (tDCS) on mild cognitive impairment and dementia, evidence specifically addressing its efficacy in VCI remains limited. We conducted a structured narrative review to summarize the effects of tDCS on cognitive rehabilitation in individuals with VCI. Studies were included if participants had cognitive impairment related to vascular pathology and if cognitive severity ranged from mild cognitive impairment to dementia. Eighteen studies met the inclusion criteria. Among the included studies, 15 were conducted in post-stroke cognitive impairment (PSCI) populations, whereas only three studies focused on non-stroke VCI. Across the included studies, tDCS has demonstrated promising effects on global cognition and executive function in PSCI populations. Combining tDCS with cognitive or motor rehabilitation appeared to further facilitate cognitive recovery in PSCI populations. Neuroimaging and EEG findings suggest that tDCS may be associated with cognitive improvement through potential modulation of cortical excitability, neural oscillatory activity, and functional connectivity. In addition, preliminary evidence suggests tDCS may have the potential to modulate cerebral blood flow, indicating a potential modulatory effect on neurovascular coupling. However, most available studies were conducted in patients with PSCI, with insufficient evidence in non-stroke VCI populations related to CSVD. Furthermore, the neurophysiological mechanisms by which tDCS modulates vascular and cognitive function remain poorly understood, warranting further investigation in future studies.