Impact of transcranial direct current stimulation on fatigue in multiple sclerosis

Purpose: Fatigue is a frequent and difficult to treat symptom affecting patients with multiple sclerosis (MS) with a profound negative impact on quality of life. Fatigue has been associated with functional and structural abnormalities of the frontal cortex, including frontal hypo-activation. The aim of this exploratory study was to assess whether fatigue symptoms can be reduced by excitability-enhancing anodal transcranial direct current stimulation (tDCS). Methods: In this sham-controlled, double-blind intervention study, tDCS was applied over the left prefrontal cortex of MS patients with fatigue for five consecutive days. Symptoms were tracked for 1 month via questionnaires. Lesion load at baseline was calculated for each patient and correlated with fatigue levels and responsiveness to stimulation. Results: In the whole group analysis the scores of the fatigue scales were not altered by tDCS. However, in an exploratory analysis we found a correlation between response to the stimulation regarding subjectively perceived fatigue and lesion load in the left frontal cortex: patients responding positively to anodal tDCS had higher lesion load, compared to non-responding patients. Conclusion: We conclude that in patient subgroups discernible by specific morphological alterations, tDCS may be a tool for MS fatigue management.