This is one of the most baffling of all diseases because we understand so little of its causes and the factors that influence its course and outcome. The immediate problem is localized inflammatory damage to the sheaths surrounding nerve fibers, resulting in interference with the conduction of nerve impulses and disturbance of body functions.
Typical symptoms are loss of vision, motor strength, coordination, and bowel and bladder control.
Although the immune system is certainly the agent of the nerve damage, multiple sclerosis does not look like a simple matter of autoimmunity. Researchers have long suspected viral involvement, suggesting, for example, that the measles virus may somehow trigger the immune reaction. That does not explain why multiple sclerosis is most common in northern latitudes and rare near the equator. Medical science also cannot explain why the disease takes so many different forms. Some people have transient symptoms at the onset and are never bothered again for the rest of their lives.