TDCS effects on cortical excitability in multiple sclerosis fatigue

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Objectives Fatigue could affect up to 90% of patients with multiple sclerosis (MS) [1] . Facing the modest benefits and numerous side effects of pharmacological therapies, transcranial direct current stimulation (tDCS) has recently emerged as an appealing tool to treat several neuropsychiatric complaints, including MS fatigue [3] . Previous tDCS protocols did not assess long-term effects of tDCS on MS fatigue, neither did they investigate its potential mechanism of action in this context. Methods We hereby present the case of a 37-year-old MS patient who sought medical attention for debilitating fatigue. The patient has previously participated in a sham-controlled tDCS trial and was found to be among responders to real but not sham stimulation [3] . At presentation, he did not have secondary causes of fatigue. The protocol lasted for 9 weeks (5 consecutive daily sessions in week 1; 4 sessions per week in week 2 and 3; 3 sessions in week 4; 2 sessions in week 5; 1 session in week 6 and a follow-up in week 9). We tested tDCS effects over fatigue as well as other neuropsychological symptoms. Cortical excitability measures were obtained at baseline [2] and then at the end of week 1, week 3 and week 6. Results tDCS resulted in a significant improvement of fatigue which was obtained after the first week, but the most important anti-fatigue effects were documented after week 5. This effect was paralleled by amelioration of cognition and mood scores as well as changes in cortical excitability parameters (increase in short-interval intracortical inhibition and decrease in short-interval intracortical facilitation). Conclusion This is the first report that presents long-term assessment of tDCS effects in the context of fatigue and other MS-related symptoms. Left prefrontal tDCS appears to improve MS fatigue and seems to have a modulatory effect on inhibitory and facilitatory intracortical circuits.