Multiple sclerosis, often called MS, is a disease that affects
the central nervous system—the brain and spinal cord. It can
cause problems with muscle control and strength, vision,
balance, feeling, and thinking. Your nerve cells have a
protective covering called myelin. 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 of damage are called lesions. MS is
different for each person. You may go through life with only
minor problems. Or you may become seriously disabled. Most
people are somewhere in between. Generally, MS follows one of
four courses: The exact cause is unknown, but most experts
believe that MS is an autoimmune disease. In this kind of
disease, the body's defenses, called the immune system,
mistakenly attack normal tissues. In MS, the immune system
attacks the central nervous system—the brain and spinal cord.
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