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Other articles:
What is Epilepsy
Epilepsy in
the Workplace
By
Leena Chitnis
Myelin, the white, fatty covering for nerve fibers in the central
nervous system, enables nerve cells to send electrical impulses at
high velocity, a function critical for accomplishing such basic
activities as walking, eating, or breathing.
Multiple Sclerosis (MS) is a condition in which destruction
of this insulation disrupts normal transmission of nerve impulses.
As MS causes more and more of the sheath to be stripped away,
a process called demyelination,
electrical impulses are degraded.
Depending on which nerves are affected, mild to severe
disability may occur. If
myelin in certain sensory nerves is lost, for example, a person may
have difficulty with sight, hearing or even touch.
Demyelination
can be followed by sclerosis, or hardening of nervous system tissue.
This usually occurs at multiple sites.
The sclerosis is the result of scar tissue forming in the
central nervous system (gliosis).
Scientists have not been able to determine in advance exactly
which nerve fibers will be affected in a particular patient—the
condition can occur in any part of the central nervous system.
MS
has a special predilection for fibers in the optic system, brain
stem and spinal cord. A
degenerative disorder, its hallmarks include progressive development
of neurological symptoms and behavioral affectation.
MS is most notable for the erratic appearance and duration of
symptoms that flare up acutely, punctuating relatively stable
periods of unpredictable lengths. Great individual variation is common, with some persons
having almost no symptoms, and others having many.
Each flare-up may involve a different part of the brain’s
white matter than the last, thus producing very different symptoms.
These often resolve, but may leave the patient a little worse
off each time. Common
symptoms may include fatigue, loss of strength, and decreased muscle
control. It should be
remembered, however, that MS is a highly individualized condition,
and symptoms may vary greatly in individuals.
If MS has affected the cerebellum, the patient may have poor
coordination, loss of balance, or tremors.
If it has affected the optic nerve, the patient may have
blurred or reduced vision. And,
if MS has traveled down the spinal cord, the patient may have
concerns with spinal nerve function.
Scientists have
learned much about MS in recent years; still, its cause remains
elusive. Many
investigators believe MS to be an autoimmune condition—one in
which the body launches a defensive attack against its own tissues.
In the case of MS, it is the nerve-insulating myelin that
comes under assault. Such
assaults may be linked to an unknown environmental trigger; perhaps
even a certain childhood virus may be the origin.
Like epilepsy,
MS affects a relatively large population. Most commonly affected are persons of northern European
ancestry. MS 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 condition also strikes about twice as many women as men,
with patients largely experiencing either one of two major
categories of MS.
The
relapse-remitting form of MS affects 90% of all MS patients.
Early symptoms can be mild and sensory—many times visual.
Over the years, flare-ups (which may average less than once a
year), can build up symptom residuals.
Thus, symptoms may worsen.
Many individuals experience some cognitive concerns, such as
memory difficulties or reduced processing speed.
The longer the delay in appearance of new symptoms after
onset, the more likely will the course be milder.
With frequent relapses, however, a chronic-progressive course
may evolve.
The chronic-progressive
(CPMS) presentation of MS occurs in 10-15% of most patient groups.
Generally, it occurs in those who tend to have a later age of
onset. CPMS typically
first appears in motor disturbances involving gait or limb weakness,
with new symptoms appearing at an average rate twice that of the
exacerbating-remitting form. Therefore,
deterioration proceeds more rapidly.
More cognitive functions are likely to be affected in
chronic-progressive MS than in a relapse-remitting course and the
severity of cognitive dysfunction may be greater.
Effective treatment has been developed for
relapse-remitting MS. Interferon
beta-1b appears to slow MS progression, at least in the early
stages. Anti-inflammatory
drugs are also often used to reduce the severity and duration of
acute episodes of the MS exacerbations, but their benefits tend to
be short term. Research
with interferon b-1, meanwhile, is continuing.
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