Multiple Sclerosis (MS) is an unpredictable, often disabling disease of the central nervous system that disrupts the flow of information within the brain, and between the brain and body. It occurs if the myelin sheaths surrounding nerve fibers are damaged. In temperate regions of the world, multiple sclerosis affects one in a thousand people, and more women than men. There may be just a single attack, or repeated attacks that lead to increasing disability. Only in a minority of cases, however, is the condition crippling.