Fighting Fatigue in Multiple Sclerosis: TMS vs. tDCS Efficacy.

Multiple Sclerosis (MS) is a chronic neurological disease impacting 2.8 million individuals globally, with fatigue being its most debilitating symptom, reported by 75% of patients. Despite its prevalence, the pathophysiology of MS-related fatigue remains poorly understood, and current pharmacological treatments have limited effectiveness. This research addresses this critical gap by investigating two non-invasive brain stimulation (NIBS) techniquestranscranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS)as innovative, effective and scalable therapeutic approaches for MS fatigue. The study employs a parallel, randomized, triple-blind, multicentric, sham-controlled design to assess and compare the short- and long-term efficacy of TMS and tDCS in addressing MS-related fatigue. 80 participants will be recruited from multiple centers in Spain and randomly assigned to one of four experimental groups: TMS, tDCS, Sham-TMS, Sham-tDCS. Each intervention will consist of 20 sessions, conducted daily from Monday to Friday, over 4 weeks. The left dorsolateral prefrontal cortex (DLPFC, F3 following the 10/20 system for EEG) was selected as the stimulation site based on its involvement in MS-related self-reported fatigue and in cognitive fatigability. For TMS experimental groups, intermittent theta-burst protocol (iTBS) will be used to increase the cortical excitability of the stimulated area. iTBS delivers a total of 600 pulses, organised into 50 Hz triplets repeated at 5 Hz, with 2second blocks of pulses, interleaved with 8 seconds of rest, repeated 20 times (total duration: 190s). The intensity of stimulation will be individually tailored based on the active motor threshold (aMT), setting it at 80% of the aMT. The sham stimulation will follow the same protocol, but using a sham coil (placebo). For tDCS experimental groups anodal tDCS will be applied (increasing cortical excitability) with the anode over the left DLPFC (F3), and the cathode over