Multiple sclerosis: it's not the disease you thought it was.

Multiple sclerosis (MS), the most common disabling neurologic disease of young people, afflicts approximately a quarter of a million Americans. The symptoms of MS result from recurrent attacks of inflammation in the central nervous system, which probably occur through an autoimmune mechanism. The target of the immune attack is myelin, the lipoprotein sheath that surrounds the axons and insulates them, and enhances nerve conduction. The white matter of the brain takes its name from the glistening white appearance of this lipid wrapping, which contains most of the pathways, tracts and axonal projections of the central nervous system. (The gray matter contains primarily the cell bodies of the neurons themselves.) Myelin is made by cells called oligodendrocytes and when it is inflamed and damaged, nerve conduction is disrupted and nerves thus lose function, thereby producing the neurologic symptoms of MS.