multiple sclerosis

n. (MS) A chronic and usually progressive disease in which there is inflammation of many small patches of the myelin sheathing of nerves in the brain and spinal cord which leads to destruction of the patch of sheathing and the nerve beneath it, disrupting the neural pathway in which the nerve lies. The symptoms of MS depend on which nerves are attacked by the disease. Often, the first symptom is disruption of vision, which can be followed by fatigue and weakness, particularly in the hands and feet, and numbness, stiffness, muscular spasms, bodily pain, incoordination, and difficulty in maintaining balance. Eventually the person loses control of the bladder and bowels, and most persons with the disease become depressed. Some victims also suffer cognitive impairment of various sorts. MS usually appears in early adulthood and has periods of remission followed by periods of further deterioration. It is difficult to predict the course of the disease in individuals, although the more different symptoms that appear early in the course of the disease the worse the prognosis. More than 10% of individuals die within the first 25 years of diagnosis. The causes of the disease are unknown, but some experts believe it to be an autoimmune disorder. It is more common in people of northern European ancestry and those who spend their childhood in colder climates.