Several therapies for multiple sclerosis (MS) exist, although there is no known cure. Multiple sclerosis is a chronic inflammatory demyelinating disease that affects the central nervous system (CNS). The most common initial course of the disease is the relapsing-remitting subtype, which is characterized by unpredictable attacks followed by periods of relative remission with no new signs of disease activity. After some years, many of the people who have this subtype begin to experience neurologic decline without acute relapses. When this happens it is called secondary progressive multiple sclerosis...