This document discusses multiple sclerosis (MS), including its diagnostic criteria, classification, clinical courses, and current and emerging treatments. It describes the typical demyelinating diseases associated with MS, including radiologically isolated syndrome, clinically isolated syndrome, relapsing-remitting MS, secondary progressive MS, and primary progressive MS. It also covers the McDonald criteria for diagnosing MS and examines radiological and clinical evidence for dissemination in space and time. The document discusses approaches for determining treatment goals and assessing whether those goals are being met, and considerations for switching or changing MS disease-modifying therapies.