Reviewed by
John K. Fink, M.D.,
SPF Medical Advisor
Please see Glossary to help
with medical terms
Index:
What is PLS?
What are the symptoms?
How does PLS cause my
symptoms?
How severe will my symptoms get?
How is PLS diagnosed?
How is PLS different from ALS?
What is the treatment?
What is the life expectancy?
What other conditions cause spasticity and
weakness of muscles?
Other questions
What is PLS?
Primary Lateral Sclerosis (PLS) is a group of rare,
degenerative, neurological disorders. They are sporadic,
meaning there is no clear familial link, although there
are hereditary forms of PLS.
PLS is caused primarily by degeneration of
the upper motor neurons in the brain and spinal cord,
which results in increasing spasticity and weakness
of voluntary muscles. It is often referred to as a benign variant
of Amyotrophic Lateral Sclerosis (ALS, Lou Gehrig's
disease). The primary difference between the two is that
in PLS the spinal motor neurons or lower motor neurons
stay intact. Thus, there is no muscle wasting
(amyotrophy), which is the symptom that ultimately
causes fatal complications in ALS.
The disorder usually begins in the legs but can
begin in the upper body or bulbar (speech and
swallowing) muscles. The age of onset is generally
between 35 and 66 years of age, with a median age of 50.
The incidence rate for PLS is difficult to
determine. One study puts it at 500 individuals in the
United States. However, many researchers feel this is
inaccurate, and that the actual incidence rate is closer
to 2000. The issue is further complicated by the fact
that researchers also believe a good portion of those
initially diagnosed with PLS may actually have ALS or
HSP.
PLS was first identified in France in the 1850s by Dr.
Jean-Martin Charcot. During his landmark analyses of ALS
patients, Dr. Charcot encountered a woman with severe
spasticity and limb contractures but no muscle wasting.
After her death in 1856, the autopsy revealed extensive
scarring in the lateral columns of her spinal columns,
or primary lateral sclerosis.
Here's a quick overview Chart.
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What are the
symptoms?
The hallmark of PLS is progressive weakness and
spasticity of voluntary muscles. The first symptoms are
often tripping or difficulty lifting the legs. Other
people may be the first to notice a change in the
affected person's gait. Occasionally, speaking
(dysarthria) and swallowing (dysphasia) difficulties, or
arm weakness are the first symptoms. Speech problems can
begin with hoarseness, a reduced rate of speaking,
excessive clearing of the throat, or slurred speech when
a person is tired. In some cases, speech becomes so
slurred that others cannot understand it. Drooling can
be a problem as well due to weakened bulbar muscles.
Wherever symptoms originate, the legs, arms, hands, and
speech and swallowing muscles will all eventually be
affected. In time, assistive devices are needed, such as
canes, walkers, or wheelchairs. Speech therapy and
communication aids may become necessary as well. Many
people report painful muscle spasms and other
pain.
Other common symptoms are hyperactive reflexes and
Babinkski's sign. Emotional liability is often reported
as well.
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How
does PLS cause my symptoms?
 As
noted above, PLS
is caused by degeneration of the upper motor neurons in
the brain and spinal cord. Upper motor neurons control
voluntary movement.
The cell bodies of these neurons are located in the
motor cortex area of the brain. They have long,
hair-like processes called axons that travel to the
brainstem and down the spinal cord. Axons relay the messages to
move to lower motor neurons that are located
all along the brainstem and spinal cord. Lower motor
neurons then carry the messages out to the muscles.
Click on the diagram at right to see how upper motor
neurons connect to lower motor neurons that innervate
leg muscles.
When upper motor neurons degenerate, impulses cannot
adequately reach the lower motor neurons and the lower
motor neurons cannot deliver the proper message to the
corresponding muscle. The result is muscle weakness
and spasticity. As the degeneration progresses, symptoms
increase.
In PLS, the degenerative process impacts the length
of the spinal cord, thus affecting the legs, arms and
speech and swallowing muscles. For most patients, the
process begins in the legs and then travels up the
spinal cord. In some people, the process begins in the
brainstem, affecting the speech and swallowing muscles
first, and then descends down the spinal cord.
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How
severe will my symptoms get?
The rate at which symptoms will progress and how
severe they will become is impossible to predict. In
general, the course is a slowly progressive one. Some
individuals report periods of acceleration, while others
have long plateaus where progression appears to stop.
Researchers believe it can take several years for all
parts of the body to become affected. An individual's
genes, environment, nutrition, general health, and other
factors may influence the rate of progression and
severity of the disease.
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How is PLS
diagnosed?
PLS is diagnosed via a careful clinical examination,
by excluding other disorders that cause progressive
spasticity and weakness, and by an extended observation
period. Tests include a complete neurological
examination, blood work, an MRI of the brain and spine,
motor and sensory nerve conduction studies, and
cerebrospinal fluid analysis. Some of these tests are
repeated periodically. Conditions that can be ruled out
with testing are tropical spastic paraparesis (TSP),
vitamin deficiencies (B12 or E), thoracic spine
herniated disks, spinal cord tumors or injury, cerebral
palsy, and multiple sclerosis.
Some that may not be ruled out initially include
forms of Amyotrophic Lateral Sclerosis where there is no
or minimal lower motor neuron involvement, and
Hereditary Spastic Paraplegia where there is just lower
body and no lower motor neuron involvement. Within a few
years, it is evident whether the disorder is actually
ALS. Continued observation of clinical symptoms helps
differentiate PLS from HSP.
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How
is PLS different from ALS?
ALS is a rapidly progressive, fatal, neuromuscular
disease. As noted above, ALS is caused by degeneration
of the lower motor neurons (the nerves that travel from
the brainstem and spinal cord out to the muscles), which
results in muscle wasting, as well as the upper motor
neurons. Fifty-percent of ALS patients die from
respiratory failure or pneumonia within three to five
years of diagnosis.
However, there are some slowly progressing forms of ALS
that are difficult to distinguish from PLS. In fact, up
to 10% of ALS patients survive more than ten years. In
addition, improved medical care is resulting in longer
and more productive lives for all ALS patients. For more
information on ALS, please see the ALS Fact Sheet by the
National Institute of Neurological Disorders and Stroke.
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What is the
treatment?
No
treatments are currently available to prevent, stop, or
reverse PLS. Treatment is focused on symptom relief,
such as medication to reduce spasticity; physical
therapy and exercise to help maintain flexibility,
strength, and range of motion; assistive devices and
communications aids; and supportive therapy and other
modalities. For detailed information about treatment and
therapies,
click here.
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What
is the life expectancy?
Life expectancy is normal. However, complications
from falls or immobility may inadvertently shorten a
person's life.
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What other conditions cause spasticity and
weakness of muscles?
Muscle spasticity and weakness can also be caused
by other conditions including (but not limited to) Hereditary
Spastic Paraplegia, spinal cord injury or
tumors, cerebral palsy, multiple sclerosis, amyotrophic
lateral sclerosis, vitamin absorption, and thoracic
spine herniated disks.
There is a virus-caused disease called
Tropical Spastic Paraparesis
and conditions called
Lathyrism and
Konzo caused by toxins
in the plants lathyrus sativus and cassava that also
cause muscle spasticity and weakness.
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Does stress affect symptoms?
Many people find the tightness in their muscles worsens
when they are angry, stressed, or upset. This may make
it more difficult to walk and speak. It is unknown exactly
how emotions affect muscle tone, but it may involve
adrenalin levels. Most people also report increased
stiffness in cold weather.
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Is depression common?
Periods of feeling down about having PLS are normal
and expected. It is not uncommon for people to also
experience periods of clinical depression.
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Can PLS affect sexual function?
The short answer appears to be "yes", although it is
important to remember that sexual desire and/or function
can be affected by many other factors such as older
age, stress, depression, fatigue, medical disorders
or medications.
Some people report that stiffness, spasms and cramps
that are part of PLS may either inhibit (or intensify)
orgasm, or that orgasm may bring on leg stiffness, spasms
or clonus. Stiffness of the legs or arms may cause difficulty
using certain positions for intercourse.
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Can I donate blood?
PLS cannot be passed to others through donation of
blood. There is no medical reason why a person with
PLS cannot donate blood.
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Is PLS more prevalent in certain ethnic groups?
There is no evidence that PLS is more prevalent in
one ethnic group than another.
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