Degenerative Diseases - Multiple Sclerosis
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Multiple sclerosis (MS) is a chronic, degenerative, and often intermittent disease of the central nervous system. It eventually destroys the myelin protein sheaths that surround and insulate nerve fibers in the brain and spinal cord. Myelin is a fatty substance that aids the flow of electrical impulses from the brain through the spinal cord. These nerve impulses control all conscious and unconscious movements. In MS the myelin sheath disintegrates and is replaced by hard sclerotic plaques (scar tissue) that distort or prevent the flow of electrical impulses along the nerves to various parts of the body.
MS usually appears in young adulthood and is common enough to have earned the title "the great crippler of young adults." Many problems and symptoms are associated with the disease, but the major problem is lost mobility. Symptoms can range from mild problems, such as numbness and muscle weakness, to uncontrollable tremors, slurred speech, loss of bowel and bladder control, memory lapses, and paralysis. Although almost all parts of the nervous system may become involved, the spinal cord is the most vulnerable. Wild mood swings, from euphoria to depression, are another manifestation of the disease. The disease is not fatal in itself, but it weakens its victims and makes them far more susceptible to infection. Life expectancies for those with MS are six years shorter than for people without the disease.
The disease is called "multiple" because it usually affects numerous parts of the nervous system and often is characterized by relapses followed by periods of partial and sometimes complete recovery. It is, therefore, multiple both in how it affects the body and in how often it strikes.
At the beginning of 2006 the National Multiple Sclerosis Society estimated that four hundred thousand people in the United States had been diagnosed with MS, and every week approximately two hundred people are newly diagnosed with the disease (http://www.nationalmssociety.org/Who%20gets%20MS.asp). Symptoms appear most often between ages twenty and thirty-five. A possible clue to the cause of MS is that it is most common in cold, damp climates. In Europe it is found most often in the Scandinavian countries, the Baltic region, northern Germany, and Great Britain. It is rare in the Mediterranean countries, China, and Japan, and among Native Americans. It is also rare among African-Americans. White females are affected twice as often as males. In the United States most cases are found in the northern areas, and it is more common in Canada than in the southern United States. The disease cannot be cured, however, by moving to a warmer climate.
Diagnosing Multiple Sclerosis
The diagnosis of MS generally is made after a thorough history and physical examination and the results of diagnostic tests—such as magnetic resonance imaging (MRI, which provides a detailed view of the brain), spinal tap (to examine spinal fluid for signs of the disease), and evoked potentials (which measure how quickly and accurately a person's nervous system responds to certain stimulation)—have been evaluated. No single test can detect MS; several must be done and compared.
The neurologic examination for MS focuses on detecting hyperactive (as opposed to normal) reflexes and balance and gait disturbances. An eye examination evaluates damage to the optic nerve. Although some cases of MS are readily diagnosed by the physician based on the history and physical examination, most physicians confirm the diagnosis using an imaging study to document evidence of plaques in at least two locations of the central nervous system.
Cause of Multiple Sclerosis
The exact cause of MS is unknown. Many theories about its cause have been proposed—genetics, gender, or exposure to environmental triggers such as viruses, trauma, or heavy metals—but none have been proven. The most widely accepted theory is that damage to myelin results from an abnormal response by the body's immune system. Normally, the immune system defends the body against foreign invaders such as viruses or bacteria; however, in an autoimmune disease the body attacks its own tissue. Some believe that MS is an autoimmune disease in which myelin is attacked.
Like other diseases, genetic factors very likely play a significant role in determining who develops MS. Close relatives of persons with MS—such as children, siblings, or a nonidentical twin—have a higher chance of developing the disease than do persons without relatives with MS, and an identical twin of someone with MS has a one in four chance of developing the disease. If genes were the sole determinant, an identical twin of someone with MS would have a 100% chance of developing the disease. The fact that the risk is only one in four reveals that other factors, such as geography, ethnicity, and viral infection, are probably necessary to trigger development of the disease. Because MS is two to three times more common in women than in men, it also is possible that hormones play a role in determining susceptibility to MS (Multiple Sclerosis Information Sourcebook, Information Resource Center and Library of the National Multiple Sclerosis Society, 2003).
Treatment of Multiple Sclerosis
No known specific treatment halts the disease process. Once nerve fibers have been destroyed, they cannot recover their function. Current methods of treatment include powerful immune-suppressant drugs that often leave patients vulnerable to secondary infections. The best treatment seems to be to build general resistance and avoid fatigue and exposure to extremes in temperature. Physical therapy and psychotherapy are useful in helping patients and their families cope with the limitations caused by MS.
The National Multiple Sclerosis Society recommends that persons diagnosed with the disease should start drug treatment immediately, before symptoms worsen. The society recommends prompt treatment with medication, because it appears that patients who receive early treatment probably will have fewer disabling symptoms than those who do not. There are five disease-modifying drugs on the market that slow the progression of the disease.
Three drugs to treat MS—Avonex, Betaseron, and Rebif—are beta-interferon products that act by reducing the inflammation of MS lesions and reducing the accumulation of the lesions. All have demonstrated effectiveness in reducing the number and severity of relapses. Two other medications, Copaxone and Novatrone, also are used to treat MS. Copaxone is believed to work by suppressing the immune system's attacks on myelin. Novatrone reduces the activity of white blood cells that attack myelin and is generally prescribed for patients with worsening MS.