The effect of tDCS on the fatigue in patients with multiple sclerosis: A systematic review of randomized controlled clinical trials

Introduction: Fatigue is one of the most common disabling symptoms in patients with multiple sclerosis (MS) which is present in 75% of these patients and is usually associated with functional disabilities. According to the literature, there is no general agreement on the effectiveness of the existing treatments for fatigue in patients with MS. As transcranial direct current stimulation (tDCS) is a relatively new method in the treatment of fatigue symptoms in patients with MS, the purpose of this study was to systematically review published evidence conducted to assess the effects of tDCS on fatigue in patients with MS. Material & methods: A thorough literature search of published articles was conducted from 1996 to 2019 in different databases including PubMed, Science Direct, OVID, Google Scholar, Cochrane Library, Scopus, Embase, ProQuest and web of science with keywords of tDCS, multiple Sclerosis and Fatigue. Results yielded 1017 studies, which after excluding articles based on duplication and title and abstract, 8 of them were selected for review in this study. Results: The results from the literature revealed that six studies indicated positive effects of tDCS stimulation on fatigue reduction. In four studies stimulation was over the right dorsolateral prefrontal cortex (DLPFC); in three studies stimulation placed over the whole body's primary somatosensory cortex (S1); and in one study stimulation applied over the posterior parietal cortex. In most studies, no serious side effects were reported. Conclusion: Most studies revealed that tDCS can reduce the adverse effects of MS-related fatigue in particular cognitive type. As follow-ups were either absent or short period, as well as the application of treatment protocols and measurement instruments were different, it was very difficult to draw strong conclusion on the effects of tDCS in patients with MS. However, further large scale studies with long term follow-up are still recommended. (C) 2020 Elsevier Ltd. All rights reserved.