To test whether anodal transcranial direct current stimulation (tDCS) over primary motor cortex (M1) reduces fatigue and improves sleep quality in multiple sclerosis (MS).

Transcranial direct current stimulation (tDCS) is an emerging non-invasive brain stimulation technique that can reduce MS-related fatigue and may positively affect neural pathways involved in arousal and sleep.

MS participants were randomly assigned to complete 10 sessions of either active (2.5 mA) or sham tDCS targeting M1 (anode over C3/cathode over FP2) paired with unloaded cycling for 20 minutes. Fatigue was measured with the 21-item Modified form of the Fatigue Impact Scale (MFIS) at baseline, treatment end, and at a 3-week follow-up. An actigraphy device was worn on nondominant wrist throughout the study in order to measure sleep efficiency (SE), total sleep time (TST) and wake after sleep onset (WASO). Daily sleep quality scores were aggregated to represent baseline, end of tDCS treatment, and 3-week follow-up. Two-way repeated measures-ANOVA (Time, Treatment) was performed to investigate differences between active and sham conditions.

Twelve MS participants were enrolled: n=6 active (age 48.8±13.2 years, EDSS 3.5 to 6.5) and n=6 sham (53.5±8.9 years, EDSS 3.5 to 6.5). Post-hoc analysis revealed a significant reduction of fatigue score (MFIS) after active treatment (Baseline vs. End Treatment, 42.7 vs. 31.4, p<0.001). The active group reported an improvement in sleep quality, including  an increase in SE (Baseline vs. End Treatment, 89.5 vs 93.77 %, p<0.05) and TST (Baseline vs. End Treatment, 347.2 vs. 415.5 min, p<0.05), and a reduction trend for WASO (Baseline vs. End Treatment, 39.5 vs. 22.5 min), with no significant differences detected in the sham group.

Repeated application of anodal tDCS over M1 can reduce fatigue in MS. This effect may be consequent to the efficacy of tDCS in modulating sleep patterns.