Multiple Sclerosis Multiple Sclerosis

Multiple sclerosis (MS) is a disorder of the central nervous system whereby the outer covering of nerve cells, called myelin, is destroyed. Myelin is a type of fat (lipoprotein) that wraps around most nerve fibers inside and outside the brain. These layers form the myelin sheath. Much like the insulation around an electrical wire, the myelin sheath enables electrical impulses to be conducted along the nerve fiber with speed and accuracy. When the myelin sheath is damaged, nerves do not conduct impulses normally.

Multiple sclerosis involves repeated episodes (flares) of inflammation along the nerves in the brain and spinal cord. These episodes develop as an immune response, whereby the body's own immune cells attack the nervous system. The progressive nerve damage of MS develops after episodes of inflammation along the nerves of the central nervous system. The nerve damage following an MS flare results in decreased nerve function, leading to a variety of symptoms depending on which nerves are affected. The location of inflammation varies from person to person and from episode to episode. However, multiple sclerosis most commonly affects nerve fibers in the eyes, brain, and spinal cord. The term 'multiple sclerosis' refers to the many areas of scarring (sclerosis) that result from myelin damage (demyelination) of nerves.

Symptoms vary according to the nerves that are involved. The most common symptoms include weakness of one or more extremities, muscle spasticity, double vision, urinary incontinence, and loss of coordination.

The exact cause of MS is unknown. In the United States, about 400,000 people, mostly young adults, have multiple sclerosis. Most commonly, MS develops in people between the ages of 20 and 40. Multiple sclerosis is more common among women than among men. Most people with multiple sclerosis have periods of relatively good health (remissions) alternating with debilitating flare-ups (relapses). However, multiple sclerosis often worsens slowly over time.

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