John K. Fink, M.D.,
SPF Medical Advisor
What is PLS?
What are the 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?
How does PLS cause my symptoms?
What other conditions cause spasticity and
weakness of muscles?
Where can I get more information?
What is PLS?
PLS is a term used to represent a small group of very
rare, neurodegenerative disorders along the motor neuron
disease continuum. They are thought to be sporadic (not
obviously familial), although there are rare, hereditary
forms of PLS.
The disorders are caused primarily by degeneration of
the upper motor neurons in the brain and spinal cord.
This condition causes increasing spasticity and weakness
of various voluntary muscles. It is disabling, but not
fatal. It may be referred to as a benign variant
of Amyotrophic Lateral Sclerosis (ALS, Lou Gehrig's
disease). In PLS, however, there is no evidence of the
degeneration of spinal motor neurons or muscle wasting (amyotrophy)
that occurs in ALS.
The condition usually begins in the legs but can
begin in the upper body or bulbar (speech and
swallowing) muscles. Symptoms progress to include the
arms, hands and bulbar muscles. This usually takes a few
years, but can take up to ten years, and in some very
rare cases, even longer.
It is difficult to estimate an incidence rate for
PLS. One study suggests there are some 500 individuals
with PLS in the United States. Many researchers feel
this is an underestimate.
Here's a very quick overview Chart.
What are the
The hallmark of PLS is progressive weakness and
spasticity of various voluntary muscles. Age of onset is
typically between 35 and 66 years of age with a median
of 50 years.
Symptoms usually begin with tripping (toe-drop) or
difficulty lifting the legs. Onset is gradual. Often,
other people who notice a change in a person's gait, first.
Occasionally, difficulty with speaking (dysarthria),
swallowing (dysphagia) or with the arms are the first
Symptoms eventually include the legs, arms, hands
and speech and swallowing muscles. This usually takes
a few years. In time, assistive devices generally become
needed, such as canes, walkers, or wheelchairs. Speech
therapy and communication aids may become necessary. A
good portion of people report painful spasms and other
pain. (Editor's Note: One of our community
members, who is a primary care physician with HSP, has
submitted an article about pain management. Please see
Articles - Pain.)
Speech problems can begin with hoarseness, reduced
rate of speaking, excessive clearing of the throat,
or slurring of words when tired. As these symptoms progress,
words become progressively more slurred. In some cases,
speech becomes so slurred that others can not understand
it. In other cases, speech disturbance is only mild.
There can be a problem with drooling.
Other symptoms that commonly occur include hyperactive
reflexes, muscle spasms, presence of Babinkski's signs,
muscles spasms and pain. Some individuals report having
severe will my symptoms get?
There is no way to predict the rate at which symptoms
will progress or how severe they will become. In general,
the course is a slowly progressive one. Some individuals
have reported periods of acceleration, or, that progression
seems to stop worsening and plateau for a
period of time.
Researchers feel it can take several years for all
parts of the body to become involved. An individual's
other genes, environment, nutrition, general health, and other factors may have influence on any one individual's
rate of progression and severity.
How is PLS
Diagnosis of PLS is a made through a careful clinical
examination, a process of exclusion of other disorders
causing progressive spasticity and weakness and an observation
period. Tests include a complete neurological examination,
blood tests, MRI of the brain and spine, motor and sensory
nerve conduction studies, EMG, and often cerebrospinal
fluid analysis. Most conditions with symptoms similar
to PLS can be ruled out through testing.
Conditions similar to PLS that may not be ruled out
Amyotrophic Lateral Sclerosis when there is no
lower motor neuron involvement and Hereditary
Spastic Paraplegia when there is just lower body
involvement and no lower motor neuron involvement. It
should be evident within a few years if the disorder is
actually ALS (see next section). Continued observation
of clinical symptoms help differentiate PLS from HSP.
is PLS different from ALS?
Amyotrophic Lateral Sclerosis is a rapidly
progressive, fatal, neuromuscular disease. Fifty-percent
of ALS patients die from respiratory failure or
pneumonia within three to five years of diagnosis.
ALS is caused by degeneration of the lower motor
neurons (the nerves that travel from the brainstem and
spinal cord out to the muscles) as well as the upper
motor neurons. The involvement of both the upper and
lower motor neuron differentiates ALS from PLS. PLS is caused by
primary upper motor neuron degeneration.
There is no, or very minimal, lower motor neuron involvement.
Upper motor neuron degeneration causes muscle
spasticity and weakness in the voluntary muscles. It is disabling, but
not terminal. Lower motor neuron degeneration causes
muscle wasting, which eventually affects the respiratory
system and leads to death.
are some slow progressing forms of ALS. Up to 10%
of ALS patients survive more than ten years.
Sometimes, it is difficult to differentiate slow
progressing forms of ALS from PLS.
medical care is resulting in longer and more productive
lives. For more information on ALS, please see the
ALS Fact Sheet by the National
Institute of Neurological Disorders and Stroke.
What is the
There is currently no treatment to prevent, stop, or
reverse PLS. Treatment is focused on symptom relief,
such as medication to reduce spasticity and other symptoms;
physical therapy and exercise to help maintain flexibility,
strength, and range of motion; assistive devices and
communications aids; supportive therapy and other modalities.
For detailed information about treatment and therapies,
is the life expectancy?
Life expectancy is considered normal. However,
complications arising from falls or immobility caused by
the symptoms of PLS may inadvertently shorten a person's
does PLS cause my symptoms?
is caused by degeneration of the upper motor neurons in
the brain and spinal cord. Upper motor neurons control
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
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
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.
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
Konzo caused by toxins
in the plants lathyrus sativus and cassava that also
cause muscle spasticity and weakness.
Does stress affect symptoms?
Individuals often report that their symptoms worsen
when they become upset, angry or emotionally stressed.
Becoming tired can also have this effect, especially
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.
Does emotional 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
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
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.
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.
Is PLS more prevalent in certain ethnic groups?
There is no evidence that PLS is more prevalent in
one ethnic group than another.
Information to get a listing of articles you
can download from the Internet or order from the SPF
or other organizations.