Multiple sclerosis (MS) is a disorder that affects the central nervous system. In this condition, the immune system mistakenly attacks myelin, the protective covering around nerve fibers. Damage to myelin disrupts communication between the brain and the rest of the body. Common symptoms include muscle weakness—often in the arms and legs—tingling or burning feelings, numbness, long-term pain, problems with balance and coordination, fatigue, vision disturbances, and bladder control difficulties.