Multiple sclerosis (MS) is a chronic, disabling disease of the central nervous system. The disease causes inflammation, destruction, and scarring of the sheath (called myelin) that covers nerve fibers in the brain and spinal cord. As a result, electrical signals from the brain are slowed or blocked from reaching the eyes, muscles, and other parts of the body.
There are several types of MS:
Benign MS –
symptoms are mild to moderate and don't get worse or cause permanent disability.
Relapsing-remitting MS –
symptoms suddenly reappear every few years, last for a few weeks or months, and then go back into remission. Symptoms sometimes worsen with each occurrence.
Primary progressive MS –
symptoms gradually worsen after symptoms first appear. Relapses and remissions usually do not occur.
Secondary progressive MS –
after years of relapses and remissions, symptoms suddenly begin to progressively worsen.
Progressive relapsing MS –
symptoms gradually worsen after symptoms first appear. One or more relapses may also occur.
A malfunction of the body's immune system seems to be the cause of MS, but exactly why that occurs is not known. Researchers are still working to understand autoimmune diseases, in which the immune system, which normally protects the body from infection and other disease, starts attacking the body. The following conditions may contribute to MS:
- Viral or other infection
- Genetic factors (heredity)
- Environmental factors
According to the National Institute of Neurological Disorders and Stroke, about 250,000 to 350,000 people in the United States have multiple sclerosis, .
