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Multiple Sclerosis is a disease caused by inflammation and scarring of tissues in the brain and spinal cord. More specifically, the inflammation breaks down myelin, the white, fatty material that provides a thick sheath or covering for nerve fibers in the central nervous system. A healthy myelin sheath enables a nerve cell to send electrical impulses along its fiber at high velocity, a function critical for accomplishing such basic activities as walking, eating or breathing.

As multiple sclerosis causes more and more of the sheath to be stripped away, a process called demyelination, electrical impulses proceed more and more slowly down the fiber. Depending on which nerves are affected, severe or mild disabilities can occur. If myelin in sensory nerves is lost, for example, a person may have an impaired sense of touch.

Multiple Sclerosis gets its name because the demyelination is often followed by sclerosis, or hardening of nervous system tissue, usually at multiple sites. The sclerosis is the result of scar tissue forming in the central nervous system (a process called gliosis). In part because we can not determine in advance which nerve fibers will be affected in a particular patient – the disease can impair any part of the central nervous system – the severity of multiple sclerosis is often unpredictable. Some people may have mild problems, with no significant permanent disability. For others, multiple sclerosis means severe paralysis and confinement to a wheelchair. We do know that the disease often strikes people in the prime of life, most commonly between the ages of 20 and 40, although some people do not develop multiple sclerosis until their forties or fifties. The disease strikes about twice as many women as men.

Although severe forms of multiple sclerosis can be devastating, the illness shortens a person’s average life expectancy by only about five years. Common symptoms of the disease include fatigue and loss of strength. Patients often have increased muscle stiffness due to a condition known as spasticity, or muscle stiffness. There may be a loss of sensation, like feeling pins and needles. People also may have facial pain. If multiple sclerosis has affected the cerebellum, a portion may have poor coordination, loss of balance, or tremors.

If the optic nerve is involved, the patient may have blurred or reduced vision. Patients with demyelination of the brain stem, a region that controls eye movement, commonly have double vision, since each eye may no longer focus on the same object. If the illness has impaired the spinal cord, in addition to losing leg strength, the patient may lose bladder control, become constipated, or become impotent.

One common feature of multiple sclerosis is that many symptoms worsen when patients are exposed to heat. This is because elevated temperatures – whether from a hot bath, exercise, or exposure to the sun – further slow the conduction of electrical impulses in nerve fibers. Conversely, a cold bath can sometimes temporarily relieve symptoms or reduce some of the fatigue multiple sclerosis patients often feel.

Neurologists divide multiple sclerosis into two types. The first, known as exacerbating-remitting disease, is characterized by fluctuations in nerve function. Periods of deteriorating ability are followed by periods of recovery, although, as time passes, recovery often becomes less and less complete. The second form of the illness, chronic progressive disease, has more of a steady downhill course, typically without periods of temporary recovery. Frequently, people who initially have the fluctuating form of multiple sclerosis go on to develop the chronic form.

There is no knowledge of the cause of this disease. Although there is considerable evidence that a virus may trigger the disease, researchers are still uncertain. Genetic factors and an imbalance in the immune system also may help predispose an individual to the illness. People generally do not think multiple sclerosis as an inherited disease, but its prevalence in families of patients with the disease runs somewhat higher than in the general population. For example, the prevalence of multiple sclerosis in the general population is about five to 10 cases per 10,000 people, but in a family with one member who has the illness, the chance of a brother or sister developing the disease is about 20 times higher.

There are two basic strategies for treating multiple sclerosis. One regimen attempts to reduce the underlying inflammation and the presumed impaired immune attack against the nervous system. The other strategy emphasizes relief of symptoms.