Multiple sclerosis (MS) is the leading cause of non-traumatic neurological disability in young adults. Between 1990 and 2016, the UK prevalence increased by 28%, due to earlier diagnosis and increased survival. The female to male ratio is 2:1, and patients have a minimally reduced life expectancy. Diagnostic criteria require that clinical, radiological and laboratory signs of MS are disseminated in both time and space. Diagnosis is based on a combination of features (relapses and clinical progression), MRI findings, and CSF analysis.