Multiple Sclerosis
Uploaded by Admin on Jan 22, 2000
The name itself is revealing: multiple, more than one, and sclerosis, which refers to areas of sclerotic (scarred) tissue. Multiple sclerosis is a demyelinating disease of the white matter of the central nervous system.
These areas of sclerosis, also referred to as lesions or plaques, occur in the white matter of the central nervous system. Gray matter consists primarily of nerve cells. Axons (nerve fibers) are the connections between the cell body and the muscles, sensory organs, and primary organs such as the heart. These nerve cells are the communication system both within the central nervous system and between it and the rest of the body. Axons are sheathed in myelin, a white substance (hence the term "white matter") that insulates them and speeds transmission of impulses along the cell fibers. Electrical impulses move along the nerve fiber to the synapse (the connection point between cells) to the next nerve cell.
The lesions or plaques of multiple sclerosis are areas of tissue damage arising from inflammation, which occurs when white blood cells and fluid accumulate around blood vessels. This inflammation causes destruction of myelin. After the fragments are cleared away, a scar is formed--the lesion--in the area of demyelinization. The cause-and-effect process of inflammation and demyelinization is unclear. These lesions impede conduction of signals by blocking or slowing communication, either completely or partially and from time to time. The process can be thought of as similar to an electrical short circuit. The symptoms of multiple sclerosis result from that loss or diminution of signal conduction.
MS is the most common demyelinating disease of the central nervous system. In the United States alone, there are at least 250,000 cases. For reasons that remain unclear, it is more prevalent in northern temperate zones and affects noticeably more women than men. The average age of onset is thirty years.
Research into the underlying causes and processes of MS is ongoing, and in recent years, advances in virology and immunology have rapidly increased knowledge and understanding of the disease. However, its etiology remains unclear. Epidemiological studies indicate that an environmental factor, perhaps exposure to a virus, when combined with a genetic predisposition to the disease, may well control occurrence of the disease. MS is not a genetically transmitted disease. MS may also be or involve a defect of some kind in the body's autoimmune system--some part of the body may, in effect, attack itself.
Diagnosis of MS is difficult....