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Multiple Sclerosis: A Disorder of the Nervous SystemDocument Transcript
Multiple Sclerosis, 1
Multiple Sclerosis: A
Disorder of the Nervous
Lisa Skiver and Haily Vora
Topics in Medicine and Biology
Mr. Wilson Kwok
Summer Ventures July, 2006
Multiple Sclerosis, 2
Multiple Sclerosis (MS) is a disorder of the nervous system. It is characterized by the
gradual decay of the myelin sheath and axons of the nerves. There are two main types of MS:
Relapsing-remitting MS and Chronic-progressive MS. What factors actually cause multiple
sclerosis are still unknown, but there are many theories derived from extended research by
scientists and doctors. Two of the most supported beliefs among experts for the cause of MS are
genetic factors and infectious agents. People who are susceptible to MS usually start developing
symptoms after the age of 20 and women are twice as likely to acquire the disorder. Even
though the causes are unknown, the accepted theory is that the body’s damaged immune system
is unable to differentiate between a virus and its own myelin, causing autoimmunity, or a self-
attack. To diagnose MS, a brain MRI scan is usually used. The symptoms of multiple sclerosis
differ from person to person and day to day. Weakness, fatigue, pain and bladder difficulties are
just a few symptoms among many. Though there is no cure for multiple sclerosis, most cases
can be treated and cared for with a number of drugs currently on the market. Research is
continuously being done to try and solve the mystery of multiple sclerosis.
Multiple Sclerosis, 3
Multiple Sclerosis is the most common cause of neurological debilitation in young people
around the world. It affects approximately 500,000 people in the United States and occurs in
about 0.1% of all people worldwide. Affecting every 3 in 10,000 people, Northern Europe and
the Northern US have the highest diagnosis rate. No two people have the exact same form of
MS and the course of each patient’s disorder is as unique as the number of hairs on their head.
The advance of the disease, within an individual and a whole population, largely differ in their
timing, severity and location. So, where does this decaying, degenerative disorder emerge from?
The Nervous System
Multiple Sclerosis originates in the central nervous system, and to fully understand this
disorder, one must be familiar with the system. The body’s nerves do not form one single
system, but several which are interrelated. Some of these are physically separate; others are
different in function only. The brain and spinal cord make up the Central Nervous System
(CNS) and the Peripheral Nervous System (PNS) is responsible for the body functions which are
not under conscious control such as the heartbeat or the digestive system. The CNS represents
the largest part of the nervous system. Working with the PNS has the essential role in the control
of behavior and information processing. The CNS stems from the neural plate which forms the
neural tube during embryonic development. This tube will eventually branch off into two major
subdivisions, the spinal cord and the brain. These two vital parts of the body form what is
known as the CNS. Its overall function is to collect information about the external conditions in
relation to the body's internal state, to analyze this data, and to trigger the appropriate response to
satisfy certain needs.
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Within the CNS, the brain and spinal cord play a vital role in body communication. The
spinal cord is the crucial link between the whole body and the brain. It emerges from the base of
the skull and continues down the back for 42-45 cm through the vertebral column. There are 31
pairs of spinal nerves, part of the PNS, which stem from the spinal cord. Each one of these
nerves contains a dorsal root and a ventral root. The dorsal roots contain the neurons that carry
messages to the CNS from numerous sensory neurons. The ventral roots contain the axons of
motor neurons. There are also interneurons within the spinal cord. Besides carrying signals to
and from the brain, the spinal cord also regulates reflexes, the simplest response to a stimulus.
Most reflexes never reach the brain due to the immediate response of the sensory and motor
neurons in the spinal cord. Even though the spinal cord does all the work, there would be no
nervous system without the brain. The brain is divided into three main sections: the forebrain,
the midbrain, and the hindbrain. The forebrain is the largest and most complex part of the brain
and contains the cerebrum. The cerebrum contains the information that makes a person;
intelligence, memory, personality, emotion and speech. The outer layer of the cerebrum is called
the cortex. It collects information coming in from the spinal cord from the five senses. The
brain then directs this data to other parts of the nervous system for more processing. The
midbrain is located underneath the middle of the forebrain. It acts as an efficient organizer for
all the messages going in and out of the brain through the spinal cord. The hindbrain sits
underneath the back of the cerebrum and contains the cerebellum, pons and medulla. The
cerebellum is responsible for balance, movement and coordination. Together with the midbrain,
the pons and medulla are often called the brainstream. They take in, send out and coordinate all
of the brain’s messages.
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The messages the spinal cord carries from the body to the brain are analyzed and
interpreted and response messages are sent throughout the rest of the body. The cells that carry
these messages are called neurons. The messages they send take the form of electrical signals,
also known as impulses, which only travel in one direction. Neurons can be further classified
into three different types: sensory receptor neurons, motor neurons, and interneurons.
Sensory receptor neurons carry impulses from the sensory organs to the brain and spinal
cord. Receptors sense changes, both internal and external, and send the information to the CNS
through electric signals. They are responsible for converting external stimuli to internal motor
mechanisms and some forms of involuntary behavior. Sensory neurons are commonly located in
the spinal cord and carry sensations such as feelings, impressions and awareness throughout the
Figure 1. Sensory Neuron - Picture adapted from http://www.biotopics.co.uk/humans/recodr.html
Motor neurons, also known as efferent neurons, carry messages to muscles and glands.
They originate in the spinal cord or brain stem and promote muscle contraction. With enough
stimulation, the motor neuron will release a flood of neurotransmitters that will bind to receptors
on muscle fiber and initiate a response. The response of a muscle fiber to a neurotransmitter is
contractile and inhibition of muscle contraction can only occur when the motor neuron itself is
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Figure 2. Motor Neuron – picture adapted from
Interneurons connect sensory neurons to motor neurons and carry impulses between the
two. They are found only in the CNS and the brain, alone, contains over 100 billion
interneurons. They only communicate to other neurons and are sometimes called relay neurons.
Interneurons can be used as inhibitors which theoretically help block out boring or irrelevant
input and help focus attention on relevant sensory input.
Figure 3. Interneuron – picture adapted from http://webanatomy.net/anatomy/neuro_notes.htm
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All neurons have a cell body, dendrites, and one axon. The cell body is the largest part,
containing the nucleus, most of the cytoplasm and metabolic cell activity. It generates ATP and
synthesizes proteins. The dendrites are short branch extensions that spread out from the cell
body. They receive stimulus and carry impulses from the environment toward the cell body.
The axon of a neuron is a long fiber that carries impulses away from the cell body. The axon
ends with an array of swellings called axon terminals. Neurons can have hundreds of dendrites,
but usually only one axon. These axons are covered with a lipid layer known as a myelin sheath.
Myelin can greatly increase the speed at which an impulse travels along an axon. It is made of
Schwann cells that form an insulated wrap around the axon. Along the axon, there are gaps
between the myelin sheaths called the Nodes of Ranvier. As an impulse moves down an axon, it
jumps between the sheaths instead of traveling straight down the membrane. This jumping from
node to node decreases the time it takes for an impulse to travel. However, sometimes these
crucial myelin sheaths can be destroyed and nerve function becomes impaired, thus, causing
What is it?
So what exactly is MS? The principal characteristic of the disorder is the destruction of
the myelin. The end result of this process is multiple patches of hard, scarred tissue called
plaques. This is called demyelination. Another important feature in the disease is the
destruction of axons, which is now considered to be a major factor in the permanent disability
associated with MS.
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Figure 4. Neuron and Myelin – picture adapted from
Types of MS
Relapsing-remitting multiple sclerosis is the most common type of MS and usually
occurs in young people. The most common characteristic of relapsing-remitting MS is the attack
or relapse. It is an attack of MS symptoms such as facial pain or bladder instability that lasts at
least 24 hours and usually for a few days. Most of these attacks are fairly mild and are followed
by a period of remission. The symptoms improve or disappear for about six to eight weeks. To
be considered a remission, there must be 30 days between relapse sessions. Remissions are
almost always followed by a flare-up. Some relapsing-remitting MS patients can go years
without experiencing any progression, although by 25 years, most patients have converted to a
Chronic-progressive multiple sclerosis is a type of MS where the patient has no periods
of remission and their symptoms continue to worsen slowly. Most patients who develop MS
after the age of 45 are afflicted with the chronic-progressive type of MS without first developing
relapsing-remitting MS. Chronic-progressive MS has a wide spectrum of severity and is
categorized into three groups: Primary-Progressive MS (PPMS), Secondary-Progressive MS
(SPMS), Progressive-Relapsing MS (PRMS). PPMS progresses gradually with no remission but
can occasionally level off and even have minor improvement. SPMS occurs after the relapsing-
remitting phase in about half of MS patients within 10 years and almost all after 25 years. It’s an
evolving course of nerve and muscle decay with intermittent flare-ups, remissions and plateaus.
PRMS is progressive from the beginning with intense symptoms and continued disintegration
between relapses. It is the least common type of MS, occurring in only 5% of patients.
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Despite the great progress that has been made in trying to find a cute for MS, the cause for this
degenerative disorder is still unknown. Genetics most probably play a role in MS, but no single
gene is responsible for the disorder. Currently, the most popular theory is that the disease occurs
in people with a genetic susceptibility who were exposed to some environmental attack (a virus
or a toxin) that disrupts the blood-brain barrier. Immune factors gather in the nerve cells and
cause inflammation and an autoimmune attack on myelin and axons. Still, some experts believe
that MS may prove not just be a single disorder, but may represent several diseases with several
Genetic factors may make a person more vulnerable to MS, but the risk for someone
inheriting the disorder is less than 5%. Close relatives of a patient with MS are more likely to
develop it themselves. Some researchers believe that there is more than one gene that increases
susceptibility. Other scientists believe that MS develops because a person is born with a
genetically lower tolerance to some environmental agents, and instead of a normal response, the
exposure triggers an autoimmune response. However, as technology improves, techniques are
being developed to identify genes that are most likely responsible for MS.
Infectious agents, viruses in particular, are most likely the cause of an autoimmune
response in people genetically susceptible to MS. Much research and experimentation has been
done to support this belief:
• Geographical Distribution – MS is a disease of temperate climates. The number
of MS cases increases the further one gets from the equator in either direction.
Multiple Sclerosis is very rare in traditional culture, but it increases in
industrialized Western nations.
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• MS Clusters – Four separate clusters of MS outbreaks occurred between 1943 and
1989 in the Faroe Islands (located between Iceland and Scandinavia). During
WWII, the area was occupied by British troops and the number of patients with
MS increased each year for 20 years, following the war. Some researchers think
that the troops could have brought the disease causing agent with them.
• Sexually Transmitted Infection – The disease clusters in the Faroe Islands could
be related to high sexual activity between the troops and the native women. High
diagnosis rates are found in countries with a high degree of sexual
• Viral Similarity – Some viruses are extremely similar to myelin protein and could
therefore confuse the immune system, causing the T-cells to attack their own
protein instead of the virus.
• HIV-6 – Herpesvirus 6 is known to cause encephalitis, or brain inflammation in
patients with damaged immune systems. Many studies have shown that some MS
patients have higher rates of HHV-6 infection than normal. Some scientists and
doctors believe this may be important to discovering the cause of MS, while
others argue that nearly everyone harbors this virus and there is not a strong
enough relationship between MS and HHV-6.
• Chlamydia Pneumoniae – This bacterium has been associated with persistent
inflamed small vessels. A few studies have shown that patients with MS have a
significantly higher rate of previous Chlamydia infection. Many experts disagree,
but it is possible that the infection, which widely spreads inflammation, could
play an early role in the course of MS.
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• Epstein-Barr virus (EBV) – Almost all people with MS have evidence of EBV
infection, the cause of mononucleosis. However, EBV is very common in people
who will never develop mono.
• Other viruses have been explored such as the measles virus, adenovirus,
polyomavirus, and the retroviruses (HIV, HTLV-I, HTLV-II).
Figure 5. Environmental Theory – picture adapted from http://mscenter.ucsf.edu/faq.htm
Who is most likely to get MS?
Women are twice as likely to get MS as men. Most people start developing symptoms
between the ages of 20 and 40. People from Northern Europe, the United States and Canada are
more likely to develop MS than Asian people, Eskimos and American Indians. It is an inherited
disease in the sense that a child or sibling of someone with MS is about 10 times more likely to
get MS than someone in the population at large.
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Although the causes are unknown, research has led scientists to better understand what
exactly happens within an MS patient’s body. The common and accepted theory for the
development of MS is that a damaged immune system is unable to differentiate a virus protein
and the body’s own myelin. It generates antibodies to attack and basically becomes allergic to
itself, causing autoimmunity. In the case of MS, the body attacks the myelin tissues.
In MS, an unknown trigger activates helper T-cells whose antigen specific receptors
recognize central nervous system myelin as an antigen. Once triggered, the activated T-cells
reproduce clones that have the same myelin-specific activation. All of the activated T-cells then
release cytokines and adhesion molecules that enable the T-cells to adhere to and cross over the
blood-brain barrier, which normally prohibits the flow of substances into the brain. The greatly
weakened barrier becomes easily permeable, allowing additional immune system cells, such as
B-cells and cytotoxic T-cells to cross over. Once through the barrier, B-cells produce antibodies
which bind to the oligodendracytes (the cells of the CNS which create myelin) and the myelin
itself. Associated macrophages proceed to destroy the myelin and may also damage the
As the body starts to attack itself, the myelin sheath is destroyed, marking the climax of
multiple sclerosis. The nodes in the sheath house channels for sodium ions that boost the
electrical charge required to pass nerve signals. As the myelin insulation is being destroyed,
signals transmitted from nerve to nerve throughout the CNS are disrupted. The destruction of
axons is now well established as a major feature of MS. Research shows that axons are severed
early on in the process and as the disease progresses, the exposed axons decay even further. This
is most likely the major reason for MS irreversibility.
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The body does seem to have some sort of defense against MS though. Studies show that
the body increases the density of sodium ions that carry electric charges. By increasing these
ions, the nerves can continue to communicate despite the lack of myelin. It has also been shown
that the body can retain some remyelinate, used to restore the insulating myelin. These processes
are most likely responsible for the remission that some MS patients experience. However, the
disease is too powerful and eventually outpaces the body’s attempt to correct itself.
The diagnosis of MS is based on the presence of central nervous system (CNS) lesions
that occur in different parts of the CNS at least three months apart, with no better explanation for
the disease process. No single test is totally reliable in identifying MS and other conditions of the
CNS can occur that are very similar to the disease. CNS infections such as Lyme disease,
syphilis, human immunodeficiency virus infection and human T-lymphotrophic virus type I
mimic MS. Also, CNS inflammatory conditions such as sarcoidosis and systemic lupus
erythematosus and genetic disorders such as leukodystrophy, hereditary myelopathy and
mitochondrial disease can be very similar in nature to MS.
The International Panel on MS Diagnosis has made several changes to the older
diagnostic criteria in 2001 referring to the newer criteria as the McDonald criteria. They have
incorporated specific MRI (magnetic resonance imaging) findings into the diagnostic scheme.
The major advantage of the proposed criteria is that an early diagnosis of MS can be made if an
MRI scan performed three months after a clinically isolated attack demonstrates formation of a
new lesion. The proposed diagnostic criteria also define MRI lesion characteristics that increase
the likelihood of MS. This includes
• number of lesions: nine or more
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• location of lesions position abutting the ventricles: juxtacortical, infratentorial, or spinal
• lesion enhancement with the use of contrast medium.
The MRI lesion characteristics that suggest multiple sclerosis consist of brain lesions and spinal
cord lesions. These characteristics are shown in Table 1. Table adapted by
MRI Lesion Characteristics Suggestive of Multiple Sclerosis
High signal on T -weighted and FLAIR MRI sequences (more than nine lesions)
When actively inflamed, often enhanced with gadolinium contrast
Position abutting ventricles (often perpendicular)
Juxtacortical position (gray-white junction)
Involvement of brainstem, cerebellum, or corpus callosum
Spinal cord lesions
One or two vertebral segments in length
Incomplete cross-sectional involvement (dorsolateral common)
Less likely to enhance with gadolinium contrast
No cord swelling
Better seen with STIR MRI sequences
MRI = magnetic resonance imaging; FLAIR = fluid attenuation inversion recovery; STIR = short tau inversion
Table 1. MRI Lesion Characteristics Suggestive of MS – table adapted from
Types of testing
A brain MRI scan is the most useful test for confirming the diagnosis of MS. MRI is a
test that produces very clear pictures of the human body without the use of X-rays. It uses a large
magnet, radio waves and a computer to produce these images. Disease-related changes in the
brain or spinal cord are detected by MRI in more than 90% of people suspected of having MS.
MRI scanning is useful for detecting structural pathology in regions that can be difficult to see
through computer images, such as the posterior fossa, craniocervical junction, and cervical cord.
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Figures 6 and 7. MS Brains – pictures adapted from http://www.aafp.org/afp/20041115/1935.html
In the image above to the right, the arrows show the multiple high-signal white lesions,
showing suggestive characteristics of MS. In the image to the left, a fluid attenuation inversion
recovery (FLAIR) image of a slice of the brain is shown.
A lumbar puncture, or a spinal tap, where a sample of cerebrospinal fluid is taken by
inserting a needle between two vertebrae of the spine can be performed to diagnose MS. A spinal
tap that reveals a large number of immunoglobulins as well as oligoclonal bands or certain
proteins that are the breakdown products of myelin is suggestive of MS. These findings indicate
an abnormal autoimmune response within the brain and spinal cord, meaning that the body is
attacking itself. Over 90% of people with MS have oligoclonal bands in their CSF. While
increased immunoglobulin in the CSF and oligoclonal bands are seen in many other brain and
spinal cord conditions, their presence is often useful in helping to establish a diagnosis of MS.
Sensory evoked potential testing may also be used in finding MS in the human body.
Evoked potential tests measure electrical activity in certain areas of the brain in response to
stimulation of certain groups of nerves. These tests are often used to assist in the diagnosis of MS
because they can indicate problems along the pathways of certain nerves that are too small to be
noticed or found on a physician’s exam. Direst results of the disease are problems along the
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nerve pathways. The demyelination causes the nerve impulses to be slowed or stopped
altogether. The three main types of evoked potential tests are visual, brainstem auditory, and
sensory. In visual evoked potentials, or VEP, the patient looks at a screen on which an
alternating checkerboard pattern is displayed. In brainstem auditory evoked potentials, or BAEP,
the patient hears a series of clicks in each ear. And, in sensory evoked potentials, or SEP, short
electrical impulses are sent to a patient’s arm or leg.
The symptoms of MS obviously vary from person to person and even from day to day.
There are many common symptoms, though, to indicate a potential case of MS. These are the
common possible symptoms of MS:
• Weakness • Pain
• Bladder and Bowel Dysfunction • Fatigue
• Cognitive dysfunction • Difficulty in walking (gait)
• Dizziness and Vertigo • Numbness
• Sexual Dysfunction • Spasticity
• Depression and other emotional changes • Vision Problems
Table 2. MS Symptoms – table adapted from http://www.nationalmssociety.org/Symptoms.asp
When caused by MS, weakness is a result of damaged nerve impulse flow, preventing
instructions from reaching the extremities. This type of weakness does not result from any type
of loss in muscle strength.
About 75% of MS patients experience bladder difficulties at some time. The most
common symptoms are frequency (the urge to urinate often) and urgency (the urge to urinate
immediately and the inability to hold the urine once the urge is felt).
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For a patient with MS, having bowel dysfunctions means having constipation.
Constipation is more apparent in those with MS than the general population and can be regulated
when Timing, fluid intake, diet and physical activity are taken into consideration.
Approximately 50% of people with MS will develop some degree of cognitive
dysfunction, affecting the ability to think, reason, concentrate or remember. The memory is the
cognitive function most likely to be affected. Other cognitive functions frequently affected in MS
include speed of information processing, executive functions (planning and prioritizing),
visuospatial functions (impairment in visual perception and constructional abilities), abstract
reasoning and problem-solving, and attention and concentration. One of the reasons MS may
affect cognitive function for several reasons is because MS damages both myelin and the nerve
cells within the brain, thereby compromising a variety of functions handled by the brain.
Dizziness is a common symptom of MS. Those with MS may feel off balance or
lightheaded. Much less often, they have the sensation that they or their surroundings are spinning
—a condition known as vertigo. These symptoms are due to lesions, or damaged areas, in the
complex pathways that coordinate visual, spatial, and other input to the brain needed to produce
and maintain equilibrium.
Sexual problems are often experienced by people with MS. Sexual arousal begins in the
central nervous system, as the brain sends messages to the sexual organs along nerves running
through the spinal cord. If MS damages these nerve pathways, sexual response—including
arousal and orgasm—can be directly affected. Sexual problems also stem from MS symptoms
such as fatigue or spasticity, as well as from psychological factors relating to self-esteem and
mood changes. In both men and women, symptoms of sexual dysfunction include difficulty
achieving orgasm and loss of libido.
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Depression may be the result of difficult life situations or stresses. It is easy to understand
how a diagnosis of multiple sclerosis, a chronic condition with the potential for progressing to
permanent disability, can bring on depression. It may also be a result of the MS disease process
itself, since MS damages the myelin and nerve fibers deep within the brain. If MS damages areas
of the brain that are involved in emotional expression and control, a variety of behavioral
changes can result, including depression. Also, some of the emotional changes observed in MS
include major depressive episodes as well as less severe depressive symptoms, grieving for
losses related to the disease, stress and reactions to stressful situations, generalized distress and
anxiety and emotional lability or mood swings.
Another symptom a person with MS might experience is pain. When experiencing acute
pain, one has cases of trigeminal neuralgia, Lhermitte's sign and burning or aching around the
body. In trigeminal neuralgia is a stabbing pain in the face which is neuropathic, or caused by
damage to the trigeminal nerve. It can occur as an initial symptom of MS. Lhermitte's sign is a
brief, stabbing, electric-shock-like sensation that runs from the back of the head down the spine,
brought on by bending the neck forward. Burning and aching around the body are all
neurological symptoms. The technical name for them is dysesthesias. Acute symptoms of pain
are milder than chronic symptoms. Chronic pain includes burning, aching or prickling, pain of
spasticity and back and other musculoskeletal pain. Burning, aching or prickling can be a chronic
form of the acute symptoms. Pain of spasticity has two categories. Muscle spasms or cramps,
called flexor spasms, may occur. Tightness and aching in joints is another type of spasticity.
Fatigue is one of the most common symptoms of MS, occurring in about 80% of people. It is
a debilitating kind of overall weariness, which is not predictable and unrelated to your
activity level. Increase in body temperature will temporarily worsen fatigue. It can
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significantly interfere with a person's ability to function at home and at work, and may be the
most prominent symptom in a person who otherwise has minimal activity limitations. MS
fatigue is unique in that it:
• Generally occurs on a daily basis
• May occur early in the morning, even after a restful night's sleep
• Tends to worsen as the day progresses
• Tends to be aggravated by heat and humidity
• Comes on more easily and suddenly
• Is generally more severe than normal fatigue
• Is more likely to interfere with daily responsibilities
Table 2. MS fatigue characteristics - Table adapted by http://www.nationalmssociety.org/Sourcebook-
Problems with gait (difficulty in walking) are among the most common mobility
limitations in MS. Gait problems are usually related to several factors including weakness,
spasticity, loss of balance, sensory deficit and fatigue.
Numbness of the face, body, or extremities (arms and legs) is another one of the most
common symptoms of MS, and is many times the first symptom experienced by those eventually
diagnosed with MS. The numbness may be mild or so severe that it interferes with the ability to
use the affected body part. Numb hands may prevent writing, dressing, or holding objects safely.
Many people with MS have problems with spasticity, a condition that primarily affects
the lower limbs. Spasticity refers to feelings of stiffness and a wide range of involuntary muscle
spasms. It may be as mild as the feeling of tightness of muscles or may be so severe as to
produce painful, uncontrollable spasms of extreme levels, usually of the legs. Spasticity may also
produce feelings of pain or tightness in and around joints, and can cause low back pain. Two
types of severe MS-related spasticity are flexor spasticity and extensor spasticity. Flexor
spasticity, involving the hamstrings and hip flexors, refers to bent hips and knees that are
difficult to straighten. Extensor spasticity, on the other hang, involves the quadriceps and
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adductors. Here, the hips and knees remain straight with the legs very close together or crossed
over at the ankles.
Vision problems can also be a symptom of MS but very rarely does it result in vision
loss. The problems with vision include optic neuritis, uncontrolled eye movement and double
vision. Optic neuritis is an inflammation of the optic nerve, the nerve that transmits light and
visual images from the retina to the brain. The condition is also known as retrobulbar neuritis
because the nerve is located behind the globe of the eye. Optic neuritis is generally experienced
as an acute blurring, graying, or loss of vision, almost always in one eye. Nystagmus, or
uncontrolled horizontal or vertical eye movements, is another common symptom. It may be mild,
only occurring when the person looks to the side or it may be severe enough to impair vision.
Diplopia, or double vision, happens when muscles controlling eye movement are not perfectly
coordinated due to weakness in one or both pairs of muscles. When the images are not properly
synched, a false double image occurs. Double vision may increase with fatigue or overuse of the
eyes. Patching one eye can be done until regular eyesight returns.
A cure has not been found for multiple sclerosis. Diagnosed early, most cases of MS can
be cared for. Studies indicate that early treatment delays disability, presumably by decreasing the
injury to the nervous system caused by the disease. Generally, treatment of the disease falls into
two categories: treatments that address symptom management, and treatments that change the
course of the disease by modifying the number and severity of attacks and the progression of
disability. Five different products have been approved by the FDA as disease modifying
treatments for MS since 1993. These included three interferon-beta products (Betaseron®,
Avonex®, and Rebif®) and two unrelated products (Copaxone®, Novantrone®).
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Betaseron® was the first beta interferon to be approved by the FDA and marketed in the
United States. The product shuts down the inflammation of MS lesions through various
mechanisms including repairing the blood brain barrier and reducing the inflammatory process in
the lesions. Betaseron® decreases relapse rate, increases time between attacks, decreases the
severity of attacks, while decreasing the amount of accumulated lesions seen on MRI.
Betaseron® is to be taken every other day through an injection under the skin. This product
provides the highest dose of interferon-beta available for treatment of MS. Marketed by Berlex
Avonex® is known to slow the rate of progression of disability in relapsing-remitting
MS. It has been demonstrated to decrease the relapse rate and the amount of accumulated
damage seen on MRI, but to a lesser extent than other available agents. Avonex® is given every
week through an intramuscular injection. Avonex® treats the relapsing-remitting type of MS.
Marketed by Biogen, Inc.
Rebif® is identical in chemical structure to Avonex®. The difference is that Rebif® is
given just under the skin rather than in the muscle in higher and more frequent doses. Rebif is
effective in reducing the number and severity of relapses, delaying the progression of disability,
and reducing the number of new and accumulated lesions seen on MRI. It is approved for use in
relapsing-remitting MS. Marketed by Serono, Inc.
Copaxone® is different from beta interferon in chemical structure and mechanisms of
action. It consists of a group of amino acids that looks something like myelin itself. It acts by
suppressing the immune system's attack on myelin and possibly other mechanisms. It decreases
the frequency and severity of attacks to the same extent as Betaseron and Rebif, but with slightly
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less effect on MRI lesions. Copaxone® is taken daily through an injection just underneath the
skin and is used for relapsing-remitting MS.
Novantrone® another chemotherapy agent that slows disease progression in MS and
lessens the number of relapses through its ability to suppress the activity of T cells and B cells.
These white blood cells attack the myelin that protects nerve cells, and by doing so causes the
scarring associated with MS. It is approved for MS that is getting worse and worse including
secondary progressive and relapsing-remitting forms of the disease. Novantrone is typically
administered through an injection into the vein once every three months for two years. Marketed
by Immunex Corporation.
For acute exacerbations, steroids have been reported to shorten the duration of acute
attacks by lessening the swelling and inflammation in MS lesions. However they do not alter the
frequency of exacerbations or the progression of the MS, and long term use should be avoided
except in selected patients.
Though multiple sclerosis is not a fatal disease, it has been known to shorten the lifespan
of those who have been diagnosed with MS by about six years. Understanding MS and its origins
are often difficult to understand because of the complexity of the part of our body we call the
nervous system. Scientists and medical doctors everywhere are trying to understand the nervous
system and therefore understand the diseases that come from it. Doing this takes them one step
closer to finding a cure. Those with MS can lead their daily lives with little complication, but
they know that they will be living with the disease forever. To find a cure would be a dream
come true. With the technology of today, this dream is just around the corner.
Multiple Sclerosis, 23
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