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General information

Reviewed by John K. Fink, M.D., SPF Medical Advisor

Index:

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?
Other questions
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.

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What are the symptoms?

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, it is 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.

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 emotional lability.

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How 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.

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How is PLS diagnosed?

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 initially include 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.

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How 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.

There 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.

Improved 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.

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What is the treatment?

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, click here.

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What 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 life.

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How does PLS cause my symptoms?

Motor SystsemPLS 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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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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Other Questions

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 on speech.

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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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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 adrenalin levels.

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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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Where can I get more information?

Please visit Information to get a listing of articles you can download from the Internet or order from the SPF or other organizations.

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