Characterized by chronic inflammation and selective destruction of CNS myelin; peripheral nervous system is spared. Pathologically, the multifocal scarred lesions of multiple sclerosis (MS) are termed plaques. Etiology is autoimmune, with susceptibility determined by genetic and environmental factors. MS affects >350,000 in the United States and 2.5 million worldwide; onset is often in early to middle adulthood, and women are affected three times as often as men.