What Is Multiple Sclerosis (MS)?


Multiple sclerosis (MS) is an autoimmune disease that affects the central nervous system. With MS, the immune system attacks the protective shell (myelin) of nerve fibers throughout the body. Scar tissue then accumulates around the nerves, which eventually causes nerve damage. Once the nerves are damaged with scar tissue, they cannot receive signals sent from the brain to properly operate. Since the nervous system controls every movement of the body, MS can cause vision issues, movement and muscle control problems, balance issues, and other health complications. The exact cause of multiple sclerosis is not yet clear.


The severity of multiple sclerosis is highly individualized. It can range from mild to completely disabling. Because MS is an autoimmune disease that affects nerves throughout the body, the symptoms are unpredictable — they can come and go (relapse and remission) and change in intensity. Symptoms include, but are not limited to, the following:

  • Double vision or blurred vision
  • Weakness on one side of the body or the upper or lower half of the body
  • Balance issues, dizziness or difficulty walking
  • Fatigue
  • Musculoskeletal or neurogenic pain
  • Muscle spasms
  • Numbness, weakness or tingling in the limbs
  • Shock sensations, especially when bending the neck forward (Lhermitte’s sign)
  • Cognitive issues
  • Sexual dysfunction
  • Tremors
  • Slurred speech
  • Bladder or bowel control issues
  • Loss of vision (generally in one eye at a time with pain during eye movement)

Incidence and prevalence

Epidemiologists estimate that 1 in every 750 people in the U.S. will be diagnosed with multiple sclerosis in their lifetime. The diagnosis is usually made between the ages of 20 and 50, but diagnosis is certainly not exclusive to that age range.

Risk factors

Although the cause of multiple sclerosis is not known, certain genetic and environmental factors increase the risk of developing the condition.

Genetic factors

Gender is a risk factor for the development of multiple sclerosis. Women are two to three times more likely than men to be diagnosed with the condition. The medical community believes this may be due to changing hormones in females rather than female genetics.

The risk of developing multiple sclerosis does not substantially increase for first-degree relatives of those who have MS. Individuals with an immediate family member with MS, such as siblings or parents, have a 2.5 to 5 percent higher risk than the general population. For identical twins of people with MS, the chance is substantially higher; they are 25 percent more likely than the general population to be diagnosed with multiple sclerosis.

Although it occurs in most ethnic groups — including African-Americans, Latinos, and Asians — multiple sclerosis most often occurs in Caucasian populations of northern European descent. African-American women are also at greater risk.

Environmental factors

Smoking cigarettes and certain viruses, such as Epstein-Barr, have been linked to an increased risk of multiple sclerosis.

The farther a person lives from the equator, the higher the risk of a multiple sclerosis diagnosis. However, certain populations see very low to non-existent diagnosis rates regardless of where they live (even if the region is far from the equator); the risk of an MS diagnosis increases if they move from their native land to a place where MS is more common. This information shows that there is a complicated relationship between genetic and environmental factors in the development of MS.

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