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Primary Lateral Sclerosis

Table of Contents

Primary Lateral Sclerosis

PLS; Adult-onset PLS; Adult-onset primary lateral sclerosis

Primary lateral sclerosis (PLS) is a rare neuromuscular disease that affects the upper motor neurons of the arms, legs, and face. PLS is more common in men than in women, with a very gradual onset that generally occurs between ages 40 and 60.

Spinal Neuron

Image by Scientific Animations, Inc.

Overview

Difference in the physical exam findings seen between UMN vs LMN lesions.

Image by Rcchang16

Difference in the physical exam findings seen between UMN vs LMN lesions.

Difference in the physical exam findings seen between UMN vs LMN lesions.

Image by Rcchang16

What Is Primary Lateral Sclerosis?

Primary lateral sclerosis (PLS) is a rare neuromuscular disease that affects the nerve cells that control the voluntary muscles. Problems in the legs (such as weakness, stiffness, spasticity, and balance problems) are often observed first, but hand clumsiness and changes in speech can be early symptoms, as well. The condition is progressive (gradually becomes worse over time); however, affected people have a normal life expectancy. The underlying cause of adult PLS is currently unknown. In most cases, it occurs sporadically in people with no family history of the condition. A subtype of PLS, called juvenile PLS, is caused by changes (mutations) in the ALS2 gene and is inherited in an autosomal recessive manner. Treatment is based on the signs and symptoms present in each person.

Source: Genetic and Rare Diseases (GARD) Information Center

Additional Materials (1)

Illustration showing the most common types of ALS and how the upper and lower motor neurons may be affected in each area.

Illustration showing the most common types of ALS and how the upper and lower motor neurons may be affected in each area. On the top row, most classical ALS is either "spinal onset" in which case the arms or legs are affected first, or "bulbar onset" in which case the mouth and throat region is affected first. Degeneration of the upper motor neuron, lower motor neuron, or both, cause a different set of symptoms in each region, such as weakness, atrophy, spasticity, and/or cramps. On the bottom row, three rarer subtypes of ALS are shown which start in isolated regions (such as the feet or lower leg in the "flail leg" variant) and tend to stay isolated to that region either for the duration of the illness or for a long time. Primary lateral sclerosis (PLS) resembles ALS except that only the upper motor neurons are affected, causing symptoms like spasticity and/or cramps but not weakness, atrophy, or fasciculations. One challenge for diagnosis is that while ALS may initially present in one way, over the course of years it can change, so some clinicians prefer not to state categorically that an individual patient has ALS as opposed to a rarer variant. The rarer variants of flail leg, flail leg, PLS, and PMA are generally associated with a longer survival period than classical ALS.

Image by PaulWicks

Illustration showing the most common types of ALS and how the upper and lower motor neurons may be affected in each area.

PaulWicks

How Does It Affect Motor Neurons?

Spinal Neuron

Image by Scientific Animations, Inc.

Spinal Neuron

Image by Scientific Animations, Inc.

How Does Primary Lateral Sclerosis Affect Motor Neurons?

Primary lateral sclerosis (PLS) affects only the upper motor neurons, causing the movements in the arms, legs, and face to be slow and difficult. The disorder often affects the legs first, followed by the torso, arms and hands, and, finally, the muscles used for swallowing, speaking, and chewing.

The legs and arms become stiff, clumsy, slow, and weak, making it difficult to walk or carry out tasks requiring fine hand coordination. Speech may become slowed and slurred. Individuals may have difficultly balancing, increasing the risk of falls. Affected individuals may also experience emotional changes and become easily startled.

Like ALS, PLS most often occurs in midlife. It is more common in men than in women. The cause of PLS is unknown.

PLS is sometimes considered a variant of ALS, but it progresses much more slowly than ALS and is not fatal. A significant proportion of those with PLS will develop lower motor neuron disease, changing the diagnosis to ALS. Because of this, most neurologists monitor an individual for at least 4 years before making a diagnosis of PLS.

Source: National Institute of Neurological Disorders and Stroke (NINDS)

What You Need To Know

Motor Neuron

Image by OpenStax College

Motor Neuron

At the NMJ, the axon terminal releases ACh. The motor end-plate is the location of the ACh-receptors in the muscle fiber sarcolemma. When ACh molecules are released, they diffuse across a minute space called the synaptic cleft and bind to the receptors.

Image by OpenStax College

Primary Lateral Sclerosis Information

What is primary lateral sclerosis?

Primary lateral sclerosis (PLS) is a rare neuromuscular disease with slowly progressive weakness in voluntary muscle movement. PLS belongs to a group of disorders known as motor neuron diseases. PLS affects the upper motor neurons (also called corticospinal neurons) in the arms, legs, and face. It occurs when nerve cells in the motor regions of the cerebral cortex (the thin layer of cells covering the brain which is responsible for most higher level mental functions) gradually degenerate, causing movements to be slow and effortful. The disorder often affects the legs first, followed by the body, trunk, arms and hands, and, finally the bulbar muscles (muscles that control speech, swallowing, and chewing). Symptoms include weakness, muscle stiffness and spasticity, clumsiness, slowing of movement, and problems with balance and speech. PLS is more common in men than in women, with a varied gradual onset that generally occurs between ages 40 and 60. PLS progresses gradually over a number of years, or even decades. Scientists do not believe PLS has a simple hereditary cause. The diagnosis of PLS requires extensive testing to exclude other diseases. When symptoms begin, PLS may be mistaken for amyotrophic lateral sclerosis (ALS) or spastic paraplegia. Most neurologists follow an affected individual's clinical course for at least 3 to 4 years before making a diagnosis of PLS..

Is there any treatment?

Treatment for individuals with PLS is symptomatic. Muscle relaxants such as baclofen, tizanidine, and the benzodiazepines may reduce spasticity. Other drugs may relieve pain and antidepressants can help treat depression. Physical therapy, occupational therapy, and rehabilitation may prevent joint immobility and slow muscle weakness and atrophy. Assistive devices such as supports or braces, speech synthesizers, and wheelchairs ma help some people retain independence.. Speech therapy may be useful for those with involvement of the facial muscles.

What is the prognosis?

PLS is not fatal. There is no cure and the progression of symptoms varies. Some people may retain the ability to walk without assistance, but others eventually require wheelchairs, canes, or other assistive devices.

Source: National Institute of Neurological Disorders and Stroke (NINDS)

Symptoms

Speech

Image by Manouk Abkarian/Wikimedia

Speech

One can see saliva filaments stretching and breaking into tiny droplets when a speaker says the first syllable of 'Pa' in the french word 'PaPa'. For more details see https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.5.102301

Image by Manouk Abkarian/Wikimedia

What Are the Signs and Symptoms of Primary Lateral Sclerosis?

Muscle weakness
Muscle stiffness and spasticity
Difficulty with balance and clumsiness
Slowed movement
Problems with speech

Source: Genetic and Rare Diseases (GARD) Information Center

Diagnosis

4 vials of human cerebrospinal fluid

Image by James Heilman, MD

4 vials of human cerebrospinal fluid

4 vials of human cerebral spinal fluid of normal appearance, collected via lumbar puncture from the L3/L4 disk space.

Image by James Heilman, MD

How Is Primary Lateral Sclerosis Diagnosed?

Blood work
Magnetic resonance imaging (MRI) of the brain and spine
Motor and sensory nerve conduction studies
Electromyogram (EMG)
Cerebrospinal fluid (CSF) analysis

Although a preliminary diagnosis of PLS can be made after other conditions are ruled out, it may take repeated testing over three to four years to confirm the diagnosis.

Source: Genetic and Rare Diseases (GARD) Information Center

Treatment

physical therapy

Image by Noun Project - https://thenounproject.com/icon/616 : Author undefined

physical therapy

Physical Therapy - The Noun Project icon from the Noun Project

Image by Noun Project - https://thenounproject.com/icon/616 : Author undefined

How Might Primary Lateral Sclerosis Be Treated?

The treatment of primary lateral sclerosis (PLS) is based on the signs and symptoms present in each person. For example, certain medications may be prescribed to treat the muscle stiffness and/or pain that can be associated with the condition. Physical therapy and occupational therapy can help maintain muscle strength, flexibility and range of motion, and may prevent joint immobility. Assistive devices such as braces, canes, walkers or wheelchairs may be needed for continued mobility. Speech therapy may be recommended when facial muscles are involved.

Source: Genetic and Rare Diseases (GARD) Information Center

Related HealthJournals

Motor Neuron Diseases

Motor neuron diseases (MNDs) are a group of progressive neurological disorders that destroy cells that control essential muscle activity such as speaking, walking, breathing, and swallowing. Learn how MNDs are diagnosed and treated.

Degenerative Nerve Diseases

Degenerative nerve diseases are disorders that destroy motor neurons. They may affect many of your body's activities, such as balance, movement, talking, breathing, and heart function. Parkinson's disease is one example. Explore common degenerative nerve diseases.

Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive nervous system disease that affects motor neurons, the nerve cells responsible for controlling muscles under voluntary control, such as those in the arms, legs, and face. ALS is also known as Lou Gehrig’s disease, named after the New York Yankees player who had the condition. Learn more about ALS.

Juvenile Primary Lateral Sclerosis

Juvenile primary lateral sclerosis is a rare disorder characterized by progressive weakness and tightness (spasticity) of muscles in the arms, legs, and face. Symptoms begin in early childhood and progress over a period of 15 to 20 years.

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Primary Lateral Sclerosis

Primary lateral sclerosis (PLS) is a rare neuromuscular disease that affects the upper motor neurons of the arms, legs, and face. PLS is more common in men than in women, with a very gradual onset that generally occurs between ages 40 and 60.

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