Definition of Multiple sclerosis
Multiple sclerosis: Abbreviated MS. A disease of the central nervous system (CNS) marked by numbness, weakness, loss of muscle coordination, and problems with vision, speech, and bladder control. MS is an autoimmune disease in which the body's immune system attacks myelin, a key substance that serves as a nerve insulator and helps in the transmission of nerve signals. The progress, severity and specific symptoms in MS are unpredictable. One never knows when attacks will occur, how long they will last, or how severe they will be. Most people with MS are between the ages of 20 and 40 at the time of diagnosis. The term "multiple" refers to the multiple places in the CNS that are affected and to the multiple relapses and remissions characteristic of MS.
MS causes demyelinization of the white matter of the brain, with this process sometimes extending into the gray matter. Demyelinization is loss of myelin, which is composed of lipids
(fats) and protein. The white matter is the part of the brain which contains myelinated nerve fibers and appears white, whereas the gray matter is the cortex of the brain which contains nerve cell bodies and appears gray. When myelin is damaged in MS, nerve fiber conduction is faulty or absent. Impaired bodily functions or altered sensations associated with those demyelinated nerve fibers give rise to the symptoms of MS.
The understanding of the basic causes of the disease is notably incomplete. It is known that nerve cell death is part of the nervous system injury in MS. It is known, too, that in MS some types of blood cells, namely lymphocytes and monocytes, gain access to the central nervous system by breaking through the blood-brain barrier at sites of inflammation. The migration of these cells across the endothelium (lining of the blood vessels) and the activation of these immune cells depends on the cell surface molecule called integrin.
Many such important facts are coming clear. However, current knowledge of MS can be likened to what a number of blind men learned by feeling different parts of an elephant. No one has yet seen MS in its entirety.
Last Editorial Review: 12/20/2003Common Misspellings: multiple sklerosis, multiple sclorosis, multiple schlerosis, multiple scleroses
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