Download D. What Causes Multiple Sclerosis?

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Multiple Sclerosis
A. Introduction
MS is thought to be an auto-immune disease that affects the central nervous
system (CNS). The CNS consists of the brain, spinal cord, and the optic nerves.
Surrounding and protecting the nerve fibers of the CNS is a fatty tissue called
myelin, which helps nerve fibers conduct electrical impulses.
Multiple sclerosis was first recognized as a disorder in the late nineteenth
century, but it wasn’t until the nineteen sixties that researchers began to
understand some of the disease processes that cause symptoms and long-term
disability in multiple sclerosis. These processes seemed to involve inflammation
and the loss of myelin, a protective covering around nerve fibers.
The first standard guidelines for the diagnosis of multiple sclerosis and a
disability rating scale were also established in the nineteen sixties, setting the
stage for controlled research to test new therapies. In the late sixties, the first
controlled clinical trials for multiple sclerosis therapy showed that treatment
with adrenocorticotropic hormone speeded recovery from an attack. While this
therapy helped to reduce inflammation during the acute symptoms of an attack,
it did not slow the progression of multiple sclerosis.
Multiple Sclerosis (MS) is an autoimmune disease, whereby the body destroys
its own myelin (protective coating surrounding the nerves in the central nervous
system). Because the myelin is damaged, messages moving along the nerve are
transmitted more slowly or not at all. Areas of damaged myelin can be viewed
through Magnetic Resonance Imaging (MRI) scanning and are known as
plaques. These plaques, or sites of damage, can cause MS symptoms.
At this time, it is not known what causes MS. It is known that MS affects
approximately one in one thousand people, usually in early adulthood. There are
two main classifications of the disease: progressive and relapsing remitting.
Within the first classification there are two more differentiations, primary
progressive and secondary progressive.
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B. Prevalence of Multiple sclerosis
MS is predominately a disease of temperate latitudes and of the western
hemisphere. Principally, it is a disease prevalent in Europe, North America,
Australia and New Zealand. Although MS is found in Japan, China and some
other temperate, eastern countries, it is very much rarer than it is in the West.
Regions north of 40 degrees latitude have a markedly higher incidence than
those souths of this divide. Within Europe, Scandinavia, The British Isles, the
Low Countries and Germany have very high rates. Canada, northern USA and
New Zealand have an equivalently high prevalence. Within these areas, certain
localities such as the border areas of Scotland (203 per 100,000), Crowsnest
Pass in Alberta, Canada (217 per 100,000), the northern-most province of
Sweden (253 per 100,000) and others have been found to have extremely high
incidences of the disease.
Unequal distribution of multiple sclerosis around the world.
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Worldwide prevalence of MS
Primary Progressive MS (PPMS) is characterized by a slow and continuous
deterioration from the beginning, while Secondary Progressive MS (SPMS)
becomes progressive following a course of attacks and recoveries. Within the
second classification there are also two differentiations, benign and relapsing
remitting. People with benign MS suffer the least amount of disability and seem
to recover fully from their attacks, while people with relapsing remitting MS
(RRMS) do not recover as well from attacks but do enjoy remissions. The
percentage of people suffering from these types of MS at any one time breaks
down to 10 per cent benign MS, 40 per cent RRMS, 10 per cent PPMS, and 40
per cent SPMS (M.S. Freedman, personal communication, November 21, 2002).
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C. The Nerve Function
The CNS nerves are made up of single neurons that are responsible for carrying messages
from the brain. Each neuron is made up of a nucleus, dendrites, axon, cell body and a
covering called the myelin sheath.
The nervous system contains millions of nerve cells, called neurons. Neurons
are highly specialised to transmit messages from one part of the body to another.
All neurons have a cell body and one or more fibres. These fibres vary in length
from microscopic to over 1 metre. There are two different kinds of nerve fibres:
fibres that carry information towards the cell body, called dendrites, and fibres
that carry information away from it, called axons. Nerves are tight bundles of
nerve fibres.
The neurons can be divided into three types:
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Sensory neurons, which pass information about stimuli such as light,
heat or chemicals from both inside and outside the body to the central
nervous system
Motor neurons, which pass instructions from the central nervous system
to other parts of the body, such as muscles or glands
Association neurons, which connect the sensory and motor neurons
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The neurons carry messages in the form of electrical signals called nerve
impulses. To create a nerve impulse, the neurons have to be excited. Stimuli
such as light, sound or pressure all excite your neurons, but in most cases,
chemicals released by other neurons will trigger a nerve impulse.
Although, millions of neurons that are densely packed within the nervous
system, they never actually touch. So when a nerve impulse reaches the end of
one neuron, a neurotransmitter* chemical is released. It diffuses from this
neuron across a junction and excites the next neuron.
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(Neurotransmitter = Chemicals released by one neuron to excite a neighbouring one
e.g. Acetylcholine, Noradrenalin, Dopamine, Endorphin, Serotonin, GABA,
GLUTAMATE… )
Cranial Nerves
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The Nerve System
 The CNS (the brain, spinal cord and optic nerves) is made up of several
different components:
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The gray matter contains the cell bodies of the nerves.
The white matter contains nerve fibers coated with myelin.
The supporting cells form a supporting network.
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 THE PERIPHERAL NERVOUS SYSTEM (PNS) nerve cells perform
two major functions:
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Sensory neurons collect information about the body's internal and
external environment and convey it to the CNS.
Motor neurons carry instructions from the CNS to the glands and
muscles.
The Spinal chord
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- Myelin
The myelin sheath protects the nerve (axon) from damage. In MS, the bodies own
defences (t-cells) attack the myelin, the substance that protects the nerve fibers of the
brain, optic nerves, and spinal cord.
Myelin not only protects nerve fibers, but makes their job possible. When
myelin or the nerve fiber is destroyed or damaged, the ability of the nerves to
conduct electrical impulses to and from the brain is disrupted, and this produces
the various symptoms of MS. Myelin is also a substance rich in protein and
lipids (fatty substances) that forms layers around the nerve fibers and acts as
insulation. The nerve can be likened to an electrical cable; the axon, or nerve
fiber that transmits the nerve impulse is like the wire, and the myelin sheath is
like the insulation around the wire. Myelin is present in both the central nervous
system (CNS) and the peripheral nervous system (PNS), but it is only the
destruction of CNS myelin that produces the symptoms of MS.
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In MS, myelin is lost in multiple areas, leaving scar tissue called sclerosis. These damaged areas
are also known as plaques or lesions. Sometimes the nerve fiber itself is damaged or broken.
D. What Causes Multiple Sclerosis?
Many different causes have been proposed and investigated but as yet the cause
of multiple sclerosis remains elusive. There are however, some leading
contenders by way of theories although none can fully explain how multiple
sclerosis develops and some theories actually seem to fly in the face of others! A
pathogen as the cause of multiple sclerosis has been the leading theory since
multiple sclerosis was first documented. Considering the number of diseases
which are caused by pathogens, it is easy to see why this theory has been
foremost. Although there is some research, such as that on Epstein Barr and the
Herpes virus, which shows some statistical correlation, no virus or other
pathogen has ever been isolated as the cause of multiple sclerosis.
The role of genetics as the cause of multiple sclerosis has not been established,
however, there is strong evidence that there is a genetic component to the
disease. What this means is that the genes the patient have inherited may play a
role in making him/her more susceptible to developing multiple sclerosis. They
do not, however, mean that it will definitely develop the disease.
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Some people with MS develop few symptoms, but for others the disease and
society’s interactions with them lead to problems affecting all aspects of their
lives. The disease often has an impact upon the family. Many people with MS
need to make extensive use of primary and secondary health care, and social
services.
Because MS is twice as common in women as men, its been suggested that
hormonal factors predispose women to develop MS. This theory hasn't been
confirmed. Women however do not have more severe MS than men. No one has
been able to prove conclusively that there significantly more women than men
with MS. Although most researchers conclude there are more women than men
suffering from autoimmune diseases. The researchers found that symptoms of
MS in pregnant women were reduced during the second and third
trimesters — a time when a woman's body contains high levels of estrogens.
A research study on scleroderma an autoimmune disease that affects three times
more woman than men suggests one hypothesis to explain this discrepancy.
Stray cells from foetuses are transferred into a woman's body during pregnancy
and can remain for decades. The transfers go both ways, cells from the mother's
body enter the developing foetus. Most women have cells from their mother and
their children. It is speculated that when these cell relate in precisely the wrong
way it increases the risk of autoimmune disease.
A study of Barrhead Alberta (Switzerland) and surrounding area with an MS
rate of 196/100,000 population has an equal number of women to men with MS
(In Switzerland 73% of MS cases are women).
Women are almost twice as likely to develop MS as men; it is difficult to prove
that more women than men have MS. Women go to doctors more than men.
Men tend to ignore the symptoms whereas women do not. Most researchers
believe that women face a much higher risk of developing autoimmune diseases
such as MS and Lupus. They speculate it may be linked to hormones that may
modulate susceptibility.
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E. Diagnoses of MS:
A multiple sclerosis diagnosis usually begins with a complete neurological
examination and a discussion of the full medical history with the healthcare
provider. He or she will need an overall view of the health, including the
symptoms and when they started. However, it may still be difficult, if not
impossible, to confirm the presence of multiple sclerosis without using certain
procedures.
Many healthcare providers use magnetic resonance imaging (MRI) to help
diagnose MS at an early stage by providing a detailed picture of the brain. Early
diagnosis means that treatment can begin right away, rather than waiting for
continued relapses to confirm diagnosis.
Other tests for multiple sclerosis may include:
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Evoked potential tests, which measure how a person’s nervous system
responds to certain stimulation
Spinal tap, which checks spinal fluid for signs of multiple sclerosis
F. Symptoms of MS:
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Numbness or tingling in the legs, arms, face, or extremities
Impaired vision in one or both eyes, including:
o Blurred vision
o Double vision
o Loss of vision
o Changes in colour perception
o Pain around the affected eye
Fatigue
Dizziness
Muscle stiffness and spasms
Muscle weakness
Poor coordination or falling
Trouble walking or maintaining balance
Paralysis in one or more limbs
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Bladder problems including:
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Urgency
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Hesitancy
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Incomplete emptying
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Incontinence
Bowel problems, including constipation or, less commonly, incontinence
Sexual dysfunction
Slurred speech
Difficulty swallowing
Forgetfulness, memory loss, or confusion
Trouble concentrating or solving problems
Depression
Other psychiatric disorders
Euphoria or inappropriate emotional responses
 Factors that may trigger or worsen symptoms include:
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Internal or external heat, including:
o Hot weather
o Hot baths or showers
o Fever
Overexertion
Infection
G. Treatment of MS
Currently, there is no cure for MS, but there are treatments for the conditions
associated with MS. Early multiple sclerosis diagnosis is very important
because the healthcare provider may want to begin MS treatment at that time,
rather than wait until the disease may have progressed. There are two ways to
treat MS. One is to treat MS symptoms. The other is to treat the underlying
disease to reduce the number of flare-ups and slow the progression of physical
disability. Choosing the right multiple sclerosis treatment is an important step
toward taking control of the multiple sclerosis.
Modern medicine has failed to find an effective treatment for the overall
condition although various drugs give short-term relief of different symptoms.
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Valium or similar tranquilizers are used to treat muscle spasms but can have the
associated side effect of addiction, and doses often have to be increased sharply
over time. MS patients who use Cannabis report a soothing of the painful
muscle spasms and improved muscle coordination.
Some are able to walk unaided when they were previously unable to do so. It
also helps blurred vision, tremors, loss of bladder control, insomnia and
depression.
During symptomatic attacks, patients may be hospitalized and are typically
given high doses of intravenous corticosteroids, such as methylprednisolone, to
end the attack sooner and leave fewer lasting deficits.
For relapsing-remitting MS, there are 5 FDA approved drugs available for
treatment. There are interferons: Interferon beta-1a (Avonex) or beta-1b
(Betaferon). A fourth medication is glatiramer acetate (Copaxone), a mixture of
polypeptides which may protect important myelin proteins by substituting itself
as the target of immune system attack. The final medication, mitoxantrone is
effective but is limited by cardiac toxicity.
Most people with multiple sclerosis eventually become involved with the
rehabilitation process, the goals of which are to restore functions that are
essential to Activities of Daily Living (ADL). While different rehabilitation
therapies may focus on only one specific function, most comprehensive
rehabilitation programs provide assistance, instruction, or advice for nearly all of
a patient's needs. Rehabilitation programs may be managed in an inpatient or
an outpatient setting, or in the individual's home.
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Conclusion
Multiple sclerosis as an autoimmune disease (which means that the body's
immune system mistakenly attacks itself, targeting the cells, tissues, and organs)
is probably the most widely accepted theory among the scientific community at
the present time. MS is a chronic, long-term condition that affects the central
nervous system, which includes the brain and spinal cord.
Making the diagnosis of MS as quickly and accurately as possible is important
because:
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People who are living with frightening and uncomfortable symptoms want
and need to know the reason that they feel this way. This can help them
begin to adjust to their diagnosis and relieves them of worries about other
diseases such as cancer.
Since we now know that permanent damage can occur even in the earliest
stages of multiple sclerosis, it is important to confirm the diagnosis so that
MS treatment can begin as early as possible.
MS is an autoimmune disease; it is thought that the immune system either
mistakenly attacks the myelin believing it to be 'foreign substance', or, that the
immune system attacks some other, unknown tissue or organism and the myelin
gets damaged in the process.
MS is an inflammatory demyelinating condition of the central nervous system
(CNS) that is generally considered to be autoimmune in nature. White matter
tracts are affected, including those of the cerebral hemispheres, infratentorium,
and spinal cord. MS lesions, known as plaques, may form in CNS white matter
in any location; thus, clinical presentations may be diverse. Continuing lesion
formation in MS often leads to physical disability and, sometimes, to cognitive
decline. Scientists now believe that multiple sclerosis results from an abnormal
response to an infection or an environmental factor. Numerous studies show that
genetics may play a role in the development of multiple sclerosis, but are not the
sole cause of the disease.The course of illness is different for each person. Even
when there are no symptoms, there is progression of damage to the central
nervous system over time.
Multiple sclerosis may affect 2.4 million people worldwide…
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