Multiple sclerosis, << sklih ROH sihs, >> often called MS, is a disease of the nervous system. It is characterized by repeated attacks of nervous system damage, followed by recovery. The time and severity of attacks are unpredictable. The illness can cause serious disabilities, including paralysis of the legs and partial loss of vision. MS afflicts more women than men. Most patients begin to have symptoms of MS when they are from 20 to 25 years old. MS is the most common cause of disability for people under the age of 45 in the United States.
MS is characterized by scattered areas of inflammation and by destruction of myelin in the white matter of the brain and spinal cord. Myelin is a fatty substance that surrounds and protects certain nerve fibers. Many small, hard, platelike areas of scar called plaques appear throughout the myelin and interfere with the normal function of nerve pathways. The word sclerosis comes from a Greek term that means hard and refers to the plaques. Some studies suggest that MS may kill nerve cells in addition to damaging myelin.
The symptoms of MS depend on which areas of the brain and spinal cord are affected. Therefore, the symptoms differ with each attack. In time, more and more plaques develop in the victim’s myelin, causing new symptoms. Physicians diagnose MS chiefly from the symptoms. A technique called magnetic resonance imaging (MRI) can aid in diagnosis. MRI produces highly detailed images of the brain that can rule out other diseases or reveal the telltale plaques. See Magnetic resonance imaging (MRI).
The first symptoms may appear suddenly, but they may also start slowly and gradually worsen. Difficulty walking is commonly the first problem. Loss of vision, double vision, loss of balance, and weakness in an arm or leg may also occur. Numbness or tingling may occur in the fingers or elsewhere, and problems of coordination are also common. After several days to several weeks, these symptoms decrease and may disappear entirely. New attacks appear unpredictably after periods of recovery lasting months to years. In a small number of patients, symptoms are progressive, with no apparent recovery between attacks. About a third of MS patients become seriously disabled, but few die from MS.
Physicians do not know the cause of MS. Many experts think that the disease may involve malfunctions in the body’s immune system. Normally, the immune system defends the body against disease by attacking bacteria, viruses, and other invaders. Immune defenses include substances called antibodies and white blood cells. In MS, a defect in the immune system may allow antibodies or white blood cells to attack myelin.
Certain genes that control the body’s immune system are associated with MS. Many scientists think the immune system, under the control of genes, may react with an unidentified environmental factor—possibly a virus—to produce a condition that can lead to MS. Recent research has found that the common Epstein-Barr virus may be a cause of MS. In a study of over 10 million patients, those infected with the Epstein-Barr virus were 32 times more likely to develop MS than those who had never been infected with the virus.
There is no cure for MS. Physicians prescribe drugs called corticosteroids as treatment for attacks. Other drugs, such as interferons and glatiramer acetate are prescribed to slow the progression of the disease and reduce the frequency of attacks in some patients.
See also Myelin; Myelitis; Nervous system; Neurology; Paralysis.
