Multiple sclerosis (MS) is an autoimmune disease that affects the brain and spinal cord. In MS, the body's white blood cells attack tissue called myelin sheath. Myelin sheaths are the protective covering for nerve fibers in the brain. Much like an electric wire is insulated with rubber or plastic, the myelin sheaths cover nerve fibers as they transmit nerve impulses within the brain.

MS is a progressive disease, meaning the nerve damage (neurodegeneration) gets worse over time. How quickly MS gets worse varies from person to person. Researchers are not sure what triggers the inflammation. The most common theories point to a virus or genetic defect, or a combination of both.

MS is often difficult to diagnose because symptoms are different for everyone. People who are diagnosed with MS usually have had a history of symptoms that come and go. Some tests that doctors may use to help them diagnose MS are: Magnetic resonance imaging (MRI), Spinal fluid testing, Evoked potentials (measuring how long it takes nerves to react to stimulation)