TRANSCRANIAL DIRECT CURRENT STIMULATION FOR COGNITIVE IMPAIRMENT IN MULTIPLE SCLEROSIS: A NARRATIVE REVIEW

Background: Cognitive impairment is a common and disabling consequence of multiple sclerosis (MS), affecting information processing speed, memory, attention, and executive functioning. Despite its substantial impact on daily functioning and quality of life, effective therapeutic options remain limited. Transcranial direct current stimulation (tDCS), a portable, non-invasive neuromodulation technique that modulates cortical excitability and promotes neuroplasticity, has emerged as a potential adjunctive intervention for cognitive dysfunction in MS. Objective: To summarize current evidence on the use of tDCS for cognitive impairment in MS and to explore factors contributing to variability in treatment response. Methods: A literature search was conducted in PubMed to identify clinical studies evaluating the cognitive effects of tDCS in individuals with MS. Randomized controlled trials and observational studies were reviewed, and findings were synthesized narratively to provide a broad overview of the topic. Results: Evidence suggests that tDCS may improve cognitive performance in MS, particularly in information processing speed, attention, working memory, and executive function. More consistent benefits have been reported when stimulation is combined with cognitive training. Treatment response may depend on baseline cognitive status, neurological disability, stimulation parameters, and targeted cortical regions. Considerable heterogeneity across studies limits direct comparison of findings. Conclusions: tDCS appears to be a promising and well-tolerated approach for cognitive impairment in MS. However, methodological variability and small sample sizes preclude definitive conclusions. Larger, standardized trials are needed to clarify optimal stimulation protocols and identify reliable predictors of response.