Multiple sclerosis, or MS, is a disease that affects the central nervous system –the brain and spinal cord.
Our nerve cells have a protective covering called myelin and without myelin, the brain and spinal cord can’t communicate with the nerves in the rest of the body. MS gradually destroys myelin in patches throughout the brain and spinal cord, causing muscle weakness and other symptoms. These patches are called lesions.
There’s no known cause of MS but most experts believe it is an autoimmune disease, in which the immune system attacks the central nervous system. MS is not a heritable disease, but genes may increase a person’s risk of developing the condition.
Generally, MS follows one of four courses:
- Relapsing-remitting, in which symptoms fade and then return off and on for many years.
- Secondary progressive, which at first follows a relapsing-remitting course and then becomes progressive. "Progressive" means it steadily gets worse.
- Primary progressive, in which the disease is progressive from the start.
- Progressive relapsing, in which the symptoms are progressive at first and are relapsing later.