Multiple sclerosis is an autoimmune disease that affects the central nervous system
(the brain and spinal cord).
Causes, incidence, and risk factors:
Multiple sclerosis (MS) usually affects woman more than men. The disorder most commonly
begins between ages 20 and 40, but can be seen at any age.
The exact cause is not known, but MS is believed to result from damage to the myelin
sheath, the protective material which surrounds nerve cells. It is a progressive
disease, meaning the nerve damage (neurodegeneration) gets worse over time.
In addition to nerve damage, another part of MS is inflammation. Inflammation occurs
when the body's own immune cells attack the nervous system. The inflammation destroys
the myelin, leaving multiple areas of scar tissue (sclerosis). It also causes nerve
impulses to slow down or become blocked, leading to the symptoms of MS. Repeated
episodes, or flare ups, of inflammation can occur along any area of the brain and
Symptoms vary because the location and extent of each attack varies. Usually episodes
that last days, weeks, or months alternate with times of reduced or no symptoms
Recurrence (relapse) is common although non-stop progression without periods of
remission may also occur.
Researchers are not sure what triggers an attack. Patients with MS typically have
a higher number of immune cells than a healthy person, which suggests that an
immune response might play a role. The most common theories point to a virus
or genetic defect, or a combination of both. There also appears to be a genetic
link to the disease.
MS is more likely to occur in northern Europe, the northern United States, southern
Australia, and New Zealand than in other areas. Geographic studies indicate there
may be an environmental factor involved.
People with a family history of MS and those who live in a geographical area with
a higher incidence rate for MS have a higher risk of the disease.