Non-Invasive Brain Stimulation for Amyotrophic Lateral Sclerosis: Current Evidence and Future Perspectives

Background and Objectives: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting the upper and lower motor neurons, with a bleak prognosis and few treatment options. Non-invasive brain stimulation (NIBS) techniques, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), represent emerging approaches aimed at modulating cortical hyperexcitability, a relevant pathogenetic mechanism in ALS. Materials and Methods: A systematic review of the literature was conducted following the PRISMA guidelines, exploring the Scopus and PubMed databases from April to June 2025 with terms related to ALS and NIBS. A total of 18 relevant studies were selected from the initial 708 articles, analysing stimulation protocols, clinical and neurophysiological outcomes, and associated biomarkers; their validity was assessed using the revised Cochrane risk-of-bias (RoB2) tool. Results: The selected studies were extremely heterogeneous, with NIBS techniques, including magnetic (rTMS, cTBS, tSMS) and electrical (tDCS) stimulation, showing variable effects. Low-frequency protocols (1 Hz rTMS) and cTBS showed a slight slowing of clinical progression, while prolonged home stimulation with tDCS and tSMS showed more significant improvements in terms of efficacy, tolerability, and adherence. The main limitations concern the heterogeneity of patients and protocols and the lack of standardised biomarkers, which is why the analysis remained at a descriptive level. The use of telemonitoring and caregiver training are essential to ensure safety and accessibility. Conclusions: NIBS represents a promising therapeutic approach for ALS, but further multicentre, standardised studies with prolonged follow-up are needed. Future strategies should include customisation of stimulation, combination with other therapies, and extension of application to pre-symptomatic phases.