Multiple sclerosis occurs when the protective sheath covering the brain's nerves is destroyed. The destruction leads to loss of muscle coordination and a breakdown of motor functions.
Women are twice as susceptible as men and whites are more more at risk than blacks. Additionally, northern latitudes may be a factor; there are twice as many cases in Canada as the U.S.
Appearance of the disease ranges from relatively minor physical annoyances to debilitating side effects. In patients for whom the disease is crippling, loss of muscle coordination, impaired vision, and severe nervous attacks occur.
Symptoms include muscle weakness, tremors, loss of vision, fatigue and bladder problems.
Researchers theorize the disease may arise from a deficiency in the immune system. The exact cause is unknown, but a virus is thought to perhaps cause an autoimmune repsonse in which the body's own tissue is treated like an outside invader.
There is no cure for the disease and treatment is limited. Medications can only treat symptoms -- such as vision, muscle stiffness, and fatigue.
The disease usually shows itself between the ages of 20 and 40. Around a quarter of those who suffer MS deteriorate to the point where a wheelchair is required. For most, however, it is less severe.