Multiple sclerosis

Multiple sclerosis (MS) is caused by inflammatory demyelination and axonal loss in the central nervous system (CNS) (brain and spinal cord). The key characteristics of the scarring (“sclerosis”) and its clinical sequelae are “dissemination in space”, affecting different anatomical sites, and “dissemination in time”, appearing episodically over time. ### Prevalence and incidence In the UK, the prevalence is about 120/100 000 population and the annual incidence is 7/100 000 population. This means the average general practitioner may never be involved in the diagnosis of MS in their career but will have 2–4 MS patients on their list, of which 1–3 will be significantly disabled. Depending on how care is organised, up to 20% of a neurologist’s general follow-up clinic may be made up of people with MS. ### Gender, age and race The natural history of three types of MS is shown in fig 1. Figure 1 The natural history of the three types of multiple sclerosis. Horizontal axis is time passing, vertical axis is “disability”. Relapse is a clinically evident “attack” of demyelination, characterised by gradual onset of symptoms over days, stabilising over days or weeks, and then gradually resolving, completely or partially. Different symptoms of a relapse may appear at different times: by convention, any appearing within …