Motor neuron disease: Types, symptoms, causes, and treatments

Motor neuron diseases are a group of conditions that cause the nerves in the spine and brain to progressively lose function. They are a rare but serious and incurable form of progressive neurodegeneration.

Motor neurons are nerve cells that send electrical output signals to the muscles, affecting the muscles’ ability to function.

Motor neuron disease (MND) can appear at any age, but most patients are over 40 years old at diagnosis. It affects men more than women.

The most common type, amyotrophic lateral sclerosis (ALS), probably affects around 30,000 Americans at any given time, with over 5,000 diagnoses each year.

The renowned English physicist Stephen Hawking lived with ALS for many decades until his death in March 2018. Guitar virtuoso Jason Becker is another example of someone who has been living with ALS for several years.

Fast facts on motor neuron diseases

Here are some key points about motor neuron diseases. More detail is in the main article.

Motor neuron diseases (MND) are a group of conditions that affect the nerve cells that send messages to the brain.

There is a progressive weakening of all the muscles in the body, which eventually affects ability to breathe.

Genetic, viral, and environmental issues may play a role in causing MND.

There is no cure, but supportive treatment can improve the quality of life.

Life expectancy after diagnosis ranges from 3 years to longer than 10 years.


Stephen hawking <br>Image credit: Doug Wheller, 2008</br>
Stephen Hawking was one of the most well-known people with a motor neuron disease.
Image credit: Doug Wheller, 2008

There are several types of motor neuron disease.

ALS, or Lou Gehrig’s disease, is the most common type, affecting muscles of the arms, legs, mouth, and respiratory system. Mean survival time is 3 to 5 years, but some people live 10 years or more beyond diagnosis with supportive care.

Progressive bulbar palsy (PBP) involves the brain stem. People with ALS often have PBP too. The condition causes frequent choking spells, difficulty speaking, eating, and swallowing.

Progressive muscular atrophy (PMA) slowly but progressively causes muscle wasting, especially in the arms, legs, and mouth. It may be a variation of ALS.

Primary lateral sclerosis (PLS) is a rare form of MND that advances more slowly than ALS. It is not fatal, but it can affect the quality of life. In children, it is known as juvenile primary lateral sclerosis.

Spinal muscular atrophy (SMA) is an inherited MND that affects children. There are three types, all caused by an abnormal gene known as SMA1. It tends to affect the trunk, legs, and arms. Long-term outlook varies according to type.

The different types of MND share similar symptoms, but they progress at different speeds and vary in severity.


MND can be divided into three stages, early, middle, and advanced.

Early stage signs and symptoms

Symptoms develop slowly and can be confused with symptoms of some other unrelated neurological conditions.

Early symptoms depend upon which body system is affected first. Typical symptoms begin in one of three areas: the arms and legs, the mouth (bulbar), or the respiratory system.

They include:

a weakening grip, making it hard to pick up and hold things


muscle pains, cramps, and twitches

slurred and sometimes garbled speech

weakness in the arms and legs

increased clumsiness and stumbling

difficulty swallowing

trouble breathing or shortness of breath

Middle stage signs and symptoms

[Motor neuron mobility]
Motor neuron diseases can leave those with the disease severely restricted in mobility.

As the condition progresses, symptoms become more severe.

Muscle pain and weakness increase, and spasms and twinges worsen.

Limbs become progressively weaker.

Limb muscles start to shrink.

Movement in affected limbs becomes more difficult.

Limb muscles may become abnormally stiff.

Joint pain grows.

Eating, drinking, and swallowing become harder.

Drooling occurs, due to problems controlling saliva.

Yawning occurs, sometimes in uncontrollable bouts.

Jaw pain may result from excessive yawning.

Speech problems worsen, as muscles in the throat and mouth become weaker.

The person may show changes in personality and emotional state, with bouts of uncontrollable crying or laughing.

Previously, it was believed MND did not significantly affect brain function or memory, but studies have now shown that up to 50 percent of people with ALS have some type of brain function involvement.

This includes difficulties with memory, planning, language, behavior, and spatial relationships. Up to 15 percent of people with ALS have a form of dementia known as frontotemporal dementia (FTD).

Breathing problems may occur as the diaphragm, the main breathing muscle, deteriorates. There may be a shortage of breath, even when sleeping or resting. Ultimately, breathing assistance will be necessary.

Secondary symptoms include insomnia, anxiety, and depression.

Advanced stage signs and symptoms

Eventually, the patient will be unable to move, eat, or breathe without assistance. Without supportive care, an individual will pass away. Despite the best of care currently available, complications of the respiratory system are the most common causes of death.

All about amyotrophic lateral sclerosis (ALS)All about amyotrophic lateral sclerosis (ALS)
ALS is the most common type of MND. Find out more
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Risk factors

Here are some of the risk factors associated with MND.

Heredity: In the United States (U.S.), around 1 in every 10 cases of ALS is inherited. SMA is also known to be an inherited condition.

Age: After the age of 40 years, the risk rises significantly, although it is still very small. ALS is most likely to appear between the ages of 55 and 75 years.

Sex: Men are more likely to develop an MND.

Some experts have linked military experience to a higher chance of developing the disease.

Studies have found that professional footballers are more likely to die from ALS, Alzheimer’s disease, and other neurodegenerative diseases, compared with other people. This implies a possible link with recurrent head trauma and neurological disease.


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