DefinitionMultiple sclerosis is an autoimmune disease that affects the brain and spinal cord (central nervous system).Alternative NamesMS; Demyelinating diseaseCauses, incidence, and risk factorsMultiple sclerosis (MS) affects woman more than men. The disorder most commonly begins between ages 20 and 40, but can be seen at any age.MS is caused by damage to the myelin sheath, the protective covering that surrounds nerve cells. When this nerve covering is damaged, nerve impulses are slowed down or stopped.MS is a progressive disease, meaning the nerve damage (neurodegeneration) gets worse over time. How quickly MS gets worse varies from person to person.The nerve damage is caused by inflammation. Inflammation occurs when the body's own immune cells attack the nervous system. Repeated episode