Multiple sclerosis (MS) is a nervous system condition that affects the brain and spinal cord. It damages the myelin sheath, the material that surrounds and protects your nerve cells. This damage slows down or blocks messages between the brain and the body. While MS can sometimes cause disabilities for those diagnosed with it, advances in treatment and patient care have made it possible for most people with MS to enjoy a normal life expectancy. There are four general classes of MS including: Relapsing-Remitting MS, Secondary- Progressive MS, Primary-Progressive MS, and Progressive-Relapsing MS.