Multiple sclerosis, or MS, is a disease in which the protective outer coverings of nerves are attacked by the body's immune system, explains Mayo Clinic. When these outer coverings, or myelin sheaths, become damaged, nerves may begin to deteriorate, and the brain and nerves fail to communicate properly.
The most common form of MS exhibits remission and relapse periods, with remission periods of months or years followed by active periods lasting from several days to several weeks, notes Mayo Clinic. Patients with relapsing-remitting MS develop secondary-progressive MS in 60 to 70 percent of cases, typified by a steadier progression of symptoms, with or without periods of relapse. Primary-progressive MS patients suffer from a gradual onset but steady progression of symptoms with no relapse periods.
People with MS may experience numbness or weakness in their limbs, partial or complete loss of vision, tremors, slurred speech and fatigue, depending on which nerves in the body are affected, according to MedlinePlus. Doctors diagnose MS through the use of magnetic resonance imaging, spinal taps to examine fluids and blood tests that rule out other diseases that cause symptoms similar to those associated with MS. There is no cure for MS, though patients with MS who were young when they contracted the disease and those who have infrequent attacks in relapsing-remitting courses have a normal or near-normal life expectancy.