MULTIPLE SCLEROSIS

(MS) also called disseminated sclerosis a progressive disease of the central nervous system characterized by the destruction of the myelin sheath surrounding the nerve fibres of the brain, spinal chord, and optic nerves. As a result, the transmission of nerve impulses becomes impaired, particularly in pathways involved with vision, sensation, and the use of limbs. MS has a worldwide distribution but is more common in the temperate zones than in the tropics. The disease primarily arises in individuals between the ages of 20 and 40, and women are affected by the disease more often than men. MS usually begins slowly, with alternating intervals of exacerbation and remission of symptoms. The onset of MS is marked by a number of neurological signs and symptoms, including numbness or tingling in the extremities or on the side of the face, muscle weakness, dizziness, unsteady gait, and visual disturbances such as blurred or double vision and partial blindness. These early symptoms abate in most individuals for months or even years, but, as the disease progresses, such remissions usually become briefer. In subsequent recurrences, old symptoms become more severe, and new signs and symptoms appear. Other manifestations may include abnormal reflexes, difficulty in coordinating and controlling movement, bladder dysfunction, and neuropsychological problems such as depression, cognitive impairment, and emotional instability. Eventually the impairment of motor control can develop into complete paralysis. The course of MS is not rapid, and the average interval from onset of the disease to death is 35 years. In about 30 percent of cases, the disease progresses without remission. The cause of MS remains uncertain, although evidence suggests that the disease results from an autoimmune reaction in which a malfunctioning immune system produces white blood cells called T lymphocytes that react and damage the body's own cells, specifically the myelin sheath of nerve fibres. The trigger for this autoimmune reaction is not known, but it may be caused by exposure to a virus. There is no cure for MS, but a number of medications, such as corticosteroids, are used to alleviate symptoms. Immunotherapy with different forms of beta interferon, a protein the body normally produces to modulate the immune response, is used to reduce the frequency and severity of the disease.