What is the definition or description of: multiple sclerosis?

Autoimmune disorder: Which attacks brain and spinal cord nerve coverings in young people who have both genetic susceptibilities and environmental triggers. About 3.5 women to men, peak age about 30, more frequent in northern climates. More frequent in whites, more intense in people of color. Incidence of 400, 000 or more in usa.

Clinical definition: A disorder causing usually episodic loss of myelin (demyelination) which disrupts function of central nervous system. Can lead to nerve damage because nerve requires myelin to function best. Classically relapsing and remitting or chronic and progressive. The former is characterized by transient neurological episodes of dysfunction separate in time and in space (different symptoms over time).