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Definition of Multiple Sclerosis

The cause of MS is still unknown. Scientists believe that a combination of environmental and genetic factors contribute to the risk of developing MS.

Diagnosed in 2012


Multiple sclerosis is an immune-mediated disease. This means that an abnormal response of the body’s immune system causes the disease. In this case, the immune system attacks the central nervous system (CNS) by mistake. The CNS is made up of the brain, spinal cord and optic nerves.

Results of the immune system attack

The immune system attack damages the myelin — the fatty substance that surrounds and insulates the nerve fibers — and the cells that make it. This damage to the myelin and the failure to replace it is called demyelination. Without myelin to protect the nerve fibers, they are also damaged.

Two images, one of a healthy nerve cell and one with a myelin sheath damaged by MS.

Two images, one of a healthy nerve cell and one with a myelin sheath damaged by MS.

Results of nerve damage

The nerve damage caused by MS has different results:

  • When myelin or nerve fibers are damaged or destroyed in MS, messages within the CNS are altered or stopped completely. 
  • Damage to areas of the CNS may produce a variety of neurological symptoms that will vary among people with MS in type and severity.
  • The damaged areas develop scar tissue. This gives the disease its name — multiple areas of scarring or multiple sclerosis.

The cause of MS is not known, but it is believed that genetic susceptibility, infectious disease, and environmental factors combine to trigger the disease. People with MS typically experience one of 4 disease courses (types of MS). There are over a dozen treatments to help modify the MS disease process. Learn about ongoing MS research to stop disease progression, restore what has been lost and end MS forever.


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