Multiple Sclerosis Overview

Multiple sclerosis (MS) is a chronic (lifelong) disease that affects a person's central nervous system (brain and spinal cord). MS is believed to be an autoimmune disease. Instead of fighting off viruses and bacteria, the immune system attacks a person's nervous system.

The resulting inflammation damages the myelin sheath, which is an insulating envelope that surrounds nerve fibers. The myelin sheath enables nerves to conduct electrical impulses between the brain and the rest of the body. Areas of scarring (sclerosis) develop on the myelin sheath, which slow or block nerve signals and cause the symptoms common to MS. Eventually the nerves themselves become damaged, which can lead to permanent disability.

Approximately 350,000 Americans and more than 1 million people worldwide develop multiple sclerosis. The first symptoms typically develop between the ages 20 and 40 but may occur at any age.