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What is Multiple Sclerosis?
Multiple sclerosis (abbreviated MS, also known
as disseminated sclerosis or encephalomyelitis
disseminata) is an
autoimmune condition in which the immune system attacks
the
central nervous system (CNS), leading to
demyelination. It may cause numerous physical and mental
symptoms, and often progresses to physical and cognitive
disability. Disease onset usually occurs in young adults, is
more common in women, and has a
prevalence that ranges between 2 and 150 per 100,000
depending on the country or specific population.[1]
MS was first described in 1835 by
Jean-Martin Charcot.
MS affects the areas of the
brain and
spinal cord known as the
white matter. White matter cells carry signals between the
grey matter areas, where the processing is done, and the
rest of the body. (see a picture of
the white and grey (gray) matter in the brain) More specifically, MS destroys
oligodendrocytes which are the cells responsible for
creating and maintaining a fatty layer, known as the
myelin sheath, which helps the neurons carry
electrical
signals. MS results in a thinning or complete loss of
myelin and, less frequently, the cutting (transection) of the
neuron's extensions or
axons. When the myelin is lost, the neurons can no longer
effectively conduct their electrical signals. The name
multiple sclerosis refers to the scars (scleroses - better
known as plaques or lesions) in the white matter. Loss of
myelin in these lesions causes some of the symptoms, which
vary widely depending upon which signals are interrupted.
However, more advanced forms of imaging are now showing that
much of the damage happens outside these regions. Almost any
neurological
symptom can accompany the
disease.
MS takes several forms, with new symptoms occurring either
in discrete attacks (relapsing forms) or slowly accumulating
over time (progressive forms). Most people are first diagnosed
with relapsing-remitting MS but develop secondary-progressive
MS (SPMS) after a number of years. Between attacks, symptoms
may go away completely, but permanent neurological problems
often persist, especially as the disease advances.
Although much is known about the mechanisms involved in the
disease process, the cause remains elusive: the most
widely-held being that the condition results from attacks to
the
nervous system
by the body's own
immune system. Some believe it is a metabolically
dependent disease while others think that it might be caused
by a virus such as
Epstein-Barr. Still others believe that its virtual
absence from tropical areas points to a deficiency of
vitamin D during childhood.
This disease does not have a cure, but several therapies
have proven helpful. Treatments attempt to return function
after an attack, prevent new attacks, and prevent disability.
MS medications can have adverse effects or be poorly
tolerated, and many patients pursue alternative treatments,
despite the paucity of supporting scientific study. Many
candidate therapies are still under investigation.
The
prognosis, or expected course of the disease, depends on
the subtype of the disease, the individual patient's disease
characteristics, the initial symptoms, and the degree of
disability the person experiences as time advances.
Life expectancy of patients, however, is nearly the same
as that of the unaffected population, and in some cases a
near-normal life is possible. |
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