Multiple sclerosis (MS)

Multiple sclerosis (MS) affects women more than men. The disorder is most commonly diagnosed between ages 20 and 40, but can be seen at any age.
MS is caused by damage to the myelin sheath, the protective covering that surrounds nerve cells. When this nerve covering is damaged, nerve impulses are slowed down or stopped.
The nerve damage is caused by inflammation. Inflammation occurs when the body's own immune cells attack the nervous system. Repeated episodes of inflammation can occur along any area of the brain, optic nerve, and spinal cord.
Researchers are not sure what triggers the inflammation. The most common theories point to a virus or genetic defect, or a combination of both. 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 where MS is more common have a slightly higher risk of the disease.
Symptoms vary widely, depending on the amount of damage and which nerves are affected. People with severe cases of multiple sclerosis may lose the ability to walk or speak. Multiple sclerosis can be difficult to diagnose early in the course of the disease because symptoms often come and go — sometimes disappearing for months.