Multiple sclerosis is a disorder in which patches of myelin and underlying nerve fibres in the eyes, brain,
and spinal cord are damaged or destroyed.
The term "multiple sclerosis" refers to the many areas of scarring (sclerosis)
that result from demyelination of nerves. In the United States, about 400,000 people, mostly young adults,
have multiple sclerosis. Most commonly, it begins between the ages of 20 and 40. It 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, the disorder often worsens slowly over time.
Causes
The cause of multiple sclerosis is unknown, but a likely explanation is that
a virus (possibly a herpesvirus or retrovirus) or some unknown antigen somehow triggers a reaction directed against the body's
own tissues (autoimmune reaction), usually early in life. The autoimmune reaction results in inflammation, destruction of
myelin, and damage to the myelin sheath and the underlying nerve fibre.
Heredity seems to have a role in multiple sclerosis. About 5% of people with
the disorder have a brother or sister who is affected, and about 15% have a close relative who is affected. In my case,
I was adopted as a baby, so we dont know my 'blood' line as Ive never been interested in doing the 'search'. Also,
multiple sclerosis is more likely to develop in people with certain genetic markers for proteins (human leukocyte antigens)
that help the body to distinguish self from oneself.
Environment also has a role in multiple sclerosis. Where people spend the first
15 years of life affects their chance of developing multiple sclerosis. Multiple sclerosis occurs in 1 of 2,000 people who
grow up in a temperate climate but in only 1 of 10,000 people who grow up in a tropical climate. Multiple sclerosis almost
never occurs in people who grow up near the equator. The climate in which later years are spent does not change the chances
of developing the disorder.
Symptoms
The symptoms of multiple sclerosis vary greatly, from person to person and from
time to time in one person, depending on which nerve fibers are demyelinated. If nerve fibers that carry sensory information
are demyelinated, abnormal sensations (sensory symptoms) result. If nerve fibers that carry signals to muscles are demyelinated,
problems with movement (motor symptoms) result. Symptoms often come and go, affecting one or several parts of the body. The
fluctuating symptoms result from damage to myelin sheaths, followed by repair, followed by more damage.
Multiple sclerosis may progress and regress unpredictably. However, there are
several patterns of symptoms. In the relapsing-remitting pattern, flare-ups (relapses) alternate with remissions, in which
symptoms are stable. Remissions may last months or years. Relapses can occur spontaneously or can be triggered by an infection
such as influenza. High temperatures, such as very warm weather, a hot bath or shower, or a fever, can also trigger relapses
or intensify symptoms. In the primary progressive pattern, the disease progresses gradually with no remissions, although there
may be temporary plateaus during which the disease does not progress. The secondary progressive pattern begins with relapses
alternating with remissions, followed by gradual progression of the disease. In the progressive relapsing pattern, the disease
progresses gradually, but progression is interrupted by sudden relapses. This pattern is rare. About 20% of people with multiple
sclerosis have one episode, after which the disease progresses little if at all. Very rarely, multiple sclerosis progresses
quickly, resulting in severe disability or death soon after the symptoms develop.
Common early symptoms include tingling, numbness, pain, burning, and itching
in the arms, legs, trunk, or face and loss of strength or dexterity in a leg or hand. A person may feel unusually tired. Mild
psychologic or neurologic symptoms (such as mood swings, inappropriate giddiness, euphoria, depression, and apathy) may occur.
Cognitive problems include memory disturbances, decreased judgment, and inattention. These vague symptoms of demyelination
in the brain sometimes begin long before the disorder is diagnosed.
Some people develop only eye symptoms, such as partial blindness and pain in
one eye, dim or blurred vision, or loss of central vision; peripheral vision is not affected. Such symptoms are due to inflammation
of the optic nerve (optic neuritis). Eye movements may be uncoordinated, sometimes resulting in double vision (a condition
called internuclear ophthalmoplegia).
When the back part of the spinal cord in the neck is affected, bending the neck
forward causes an electrical shock or a tingling sensation that shoots down the back, down both legs, down one arm, or down
one side of the body (a response called Lhermitte's sign). Usually, the sensation lasts only a moment and disappears when
the neck is straightened. Often, it is felt as long as the neck remains bent.
As
the disorder progresses, movements may become shaky, irregular, and ineffective. Muscle weakness and spasticity may interfere
with walking, sometimes eventually making it impossible. Multiple sclerosis can cause partial or complete paralysis. Speech
may become slow, slurred, and hesitant. Late in the disorder, dementia and mania (excessive elation) may develop. The nerves
that control urination or bowel movements can also be affected, leading to frequent and strong urges to urinate, retention
of urine, constipation, and, occasionally, urinary and fecal incontinence.
If relapses become more frequent, people become increasingly disabled, sometimes
permanently. Nonetheless, about 75% of people who have multiple sclerosis never need a wheelchair, and for about 40%, normal
activities are not disrupted. Most people with multiple sclerosis have a normal life span.
Source and more infomation:
http://www.merck.com/mmhe/sec06/ch092/ch092a.html
