The Swiss MS Cohort Study (SMSC) is a multicentre cohort study that involves 8 Swiss Multiple Sclerosis centres. The key aims of the SMSC are 1. To maintain a long-term cohort for an undefined duration of patients with Multiple Sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD) and Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) in Switzerland. This requires effective measures to limit drop-outs and the continuous recruitment of MS patients and 2. To conduct a systematic follow-up with standardized, high quality collection of clinical and magnetic resonance imaging (MRI) data, as well as body fluids. The significant heterogeneity within the diagnostic entity and phenotype of MS is incompletely understood. A central and necessary prerequisite of further advance is a sufficient amount of high quality clinical and paraclinical (imaging, body fluids) patient data. Nested projects will address specific research topics, and facilitate collaboration of the most qualified investigators within the group of SMSC investigators. The nested projects will focus on the: 1. Development and validation of diagnostic and prognostic markers of spontaneous disease evolution and therapeutic response. 2. Exploration of the safety and impact on long-term disability of existing and next generation MS treatments 3. Individualized therapy: A number of highly active but potentially also harmful therapies have lately been established for the treatment of MS. To date, due to the lack of individual prognostic markers patients may not receive aggressive therapy due to safety concerns, or patients with benign disease may receive expensive and potentially harmful treatments without the need for it. 4. Evaluation of intervention effects by conducting embedded pragmatic trials using the SMSC as data-infrastructure.