This study will investigate the effect of teriflunomide in reducing cortical gray matter (CGM) atrophy and leptomeningeal (LM) inflammation over 24 months compared to dimethyl fumarate (Tecfidera®)

Inclusion Criteria:

• Diagnosed with MS according to McDonald criteria
• Age 18-65 years
• Relapsing disease course
• Expanded Disability Status Scale (EDSS) score of ≤ 5.5
• MRI obtained at baseline (medication start date), 12 months, and 24 months
• Treated with 14mg of teriflunomide ≥ 3 months or with 240mg of dimethyl fumarate ≥ 3 months to meet inclusion, reflective of recommended dosing on the package label
• Clinical information available over the 24 month follow-up
• None of the exclusion criteria

Exclusion Criteria:

• Diagnosis of non-relapsing MS
• Use of experimental drug or investigational procedure during the study period
• Pregnancy during study period
• Severe hepatic impairment
• Relapse within 30 days prior to any of the 3 MRIs
• Corticosteroid use within 30 days prior to the MRIs
• Teriflunomide patients who have used leflunomide
• Pre-baseline use of alemtuzumab, cladribine, rituximab, or mitoxantrone
• Any other factor that, in the opinion of the investigator, would make the subject unsuitable for participation

Individuals diagnosed with MS who have used dimethyl fumarate or teriflunomide and had magnetic resonance imaging at baseline (before starting disease modifying therapy (DMT) in question), 12 months after starting DMT, and 24 months after starting DMT.

No data will be shared with other researchers