Multiple sclerosis is a chronic disease of the central nervous system characterized by demyelination of nerve fibers. It is an autoimmune disorder where the body's immune system attacks the protective myelin sheath surrounding nerve fibers. Symptoms vary depending on the location of demyelination and include weakness, numbness, vision problems, and difficulties with coordination and balance. There are several types of MS including relapsing-remitting, secondary progressive, primary progressive, and clinically isolated syndrome. The exact cause is unknown but genetic and environmental factors such as infections are thought to play a role in its development.