Health Conditions

What causes it?

MS is an autoimmune disorder in which the body's natural defenses (the immune system) suddenly attack the central nervous system. Several types of white blood cells are involved in the process in which the myelin sheath is mistaken for a harmful substance. Although the exact cause of MS remains unknown, a combination of factors is probably involved in its development.

Genetic susceptibility has been established and is a result of an unlikely combination of several genes (US citizens have a 1 in 750 chance of developing MS whereas children of a parent with MS have a 1 in 40 chance of getting the disease). It is recognized, however, that the development of MS is not solely determined genetically, since identical twin studies reveal only a 1 in 3 chance of getting MS.

Several theories have been proposed to explain how MS begins. One is that unidentified environmental factors trigger a genetically expressed immune response. A second theory is that a virus or bacteria, possibly acquired during childhood, either attacks the cells that make myelin, attacks the myelin itself, or changes cells in the immune system.

MS is usually diagnosed with a magnetic resonance imaging scan (an MRI). An MRI is a type of x-ray that looks for problems in the body that cannot be found by other means. In MS, an MRI is useful in locating plaques.