Multiple sclerosis (MS) is a chronic, inflammatory and disabling disease of the Cnetral Nervous System characterized by relapsing and / or progressive somatosensory, motor and vestibular clinical manifestations. Moreover, fatigue, depression, anxiety, and cognitive impairment are also present in most MS patients. These symptoms substantially impact quality of life and often show limited response to conventional pharmacological treatment.

Transcranial direct current stimulation (tDCS) is a non-invasive technique that applies a weak direct current to the scalp via surface electrodes, modulating cortical excitability in a polarity-dependent manner.

The objective of this study is to evaluate the efficacy and safety of tDCS for fatigue, depression, anxiety, and cognitive performance in patients with relapsing or progressive MS.

Inclusion Criteria:

• Age 18-55 years at the time of enrollment
• Clinical diagnosis of Relapsing Multiple Sclerosis (RMS) or Progressive Multiple Sclerosis (PMS), with or without active progression, established per the 2014 McDonald diagnostic criteria
• Expanded Disability Status Scale (EDSS) score of 0-3 at the time of screening
• Time since initial MS diagnosis of at least 6 months
• Active fatigue symptoms reported by the participant for at least the 6 months prior to enrollment

Exclusion Criteria:

• History of neuropsychiatric illness (including major depression, bipolar disorder, schizophrenia, or any anxiety disorder) prior to the onset of multiple sclerosis
• Diagnosis of neuromyelitis optica spectrum disorder (Devic's disease)
• Presence of any other central nervous system disease
• Disease duration greater than 10 years combined with an EDSS score of ≤ 2
• Visual impairment secondary to optic neuritis, internuclear ophthalmoplegia (oculomotor disorder), or any other uncorrected visual impairment that would affect task performance on cognitive assessments
• Current pharmacological treatment for fatigue or depression
• Current neuropsychiatric pharmacological treatment, including any antidepressant, anxiolytic, neuroleptic, or anticonvulsant medication
• Clinical relapse requiring corticosteroid treatment in the 3 months prior to enrollment
• Severe upper-limb motor deficit that would prevent task performance on neuropsychological assessments

De-identified individual participant data (IPD) underlying the results reported in the published article will be made available to qualified researchers upon reasonable request. Shared data will include the de-identified clinical dataset (outcome scores at baseline, post-sham, and post-treatment time points for all 33 completers), the statistical analysis plan, and the data dictionary. Requests should be directed to the corresponding author (asdrubalhuerta@gmail.com) and will be reviewed on a case-by-case basis. Data will be shared after deposition of the dataset in an institutional or public repository upon publication of the primary manuscript.

Starting 3 months following publication of the primary manuscript; available for at least 5 years thereafter.

Researchers with a methodologically sound research proposal and a signed data access agreement with the corresponding institution. Requests submitted to the corresponding author.