Amyotrophic lateral sclerosis (ALS) refers to a group of progressive, neurological diseases that cause dysfunction in the nerve cells in the brain and spinal cord that control muscle movement.

Many experts refer to ALS as a single disease, though it is an umbrella term for a group of diseases.

Collectively, ALS is the most common type of motor neuron disease. It is sometimes called Lou Gehrig’s disease, after a famous baseball player who had the condition.

The exact cause is unclear, but environmental and genetic factors may be involved. While there is no cure, treatments can help alleviate the symptoms and improve the quality of life.

ALS attacks the nerve cells used in voluntary muscle actions, actions that a healthy body can control, in the arms, legs, and face, for example. The targeted cells are called motor neurons.

As ALS progresses, these cells degenerate and die. They stop sending messages to muscles, and the brain can no longer control voluntary movement. Over time, the muscles weaken and degenerate.

Progressive muscle weakness occurs in all cases of ALS, but this may not be the first indication of the condition.

In the early stages, signs and symptoms may be barely noticeable. They become more noticeable over time, but the progression varies from person to person.

Common symptoms include:

  • difficulty with daily activities, including walking
  • increased “clumsiness”
  • weakness in the feet, hands, legs, and ankles
  • cramping and twitching in the arms, shoulders, or tongue
  • difficulty maintaining good posture and holding the head up
  • uncontrolled outbursts of laughing or crying, a condition called “emotional lability”
  • changes in thinking or memory
  • slurred speech and difficulty with voice projection
  • pain
  • fatigue
  • problems with saliva and mucus
  • difficulty breathing and swallowing, in the later stages

Early symptoms often include clumsiness, unusual limb fatigue, muscle cramps and twitches, and slurred speech. A person experiences symptoms throughout their body as the disease progresses.

Some people with ALS have problems with decision-making and memory, eventually leading to a form of dementia called frontotemporal dementia.

Emotional lability can cause fluctuations in mood and emotional responses.

The Centers for Disease Control and Prevention (CDC) estimate that more than 16,000 people in the United States have ALS, with around 5,000 receiving the diagnosis annually. Worldwide, it may affect 2–5 people in every 100,000.

Risk factors for ALS include:

  • Gender: ALS is slightly more common in men than women before age 65. This difference disappears after age 70.
  • Age: ALS symptoms most commonly appear in a person’s late 50s or early 60s, but it can develop at other ages.
  • Race: Caucasian, non-Hispanic people are more likely to develop ALS. But anyone may develop the disease.

There are two types of ALS: sporadic and familial. Sporadic ALS develops at random, and it accounts for 90–95% of cases. There is no clear risk factor or cause.

Familial ALS is inherited. Around 5–10% of cases are familial. The child of a person with ALS has a 50% chance of developing the condition. Rarely, it can affect a person in their teens.

ALS eventually affects all the voluntary muscles, which removes a person’s ability to control movements. In the later stages, ALS affects the nerves that control breathing, which can lead to respiratory failure.

Half of all people with ALS live for 3 years or longer after receiving the diagnosis. Around 20% of people live for 5 years or more, 10% live for 10 years or more, 5% of people with the condition live for 20 years or longer after the diagnosis.

Steven Hawking, a leading physicist, received an ALS diagnosis at the age of 21 and died in 2018 at the age of 76.

A small minority of people inherit ALS, but for the majority, the cause is unclear. Research has focused on genetics and environmental factors as possible causes of ALS.

Genetics

About 20–40% of familial ALS cases, and a small number of sporadic cases, stem from a difference in the C9ORF72 gene. This gene makes a protein in nerve cells in the brain and spinal cord.

And 12–20% of familial cases result from mutations in the SOD1 gene, which is key to the functioning of motor neurons and other cells.

A 2021 study, meanwhile, linked mutations in the SPTLC1 gene with a rare form of genetic ALS that affects children as young as 4 years.

People with ALS might consider genetic testing. If the test identifies a disease-causing variant, family members might also get tested.

Other possible causes of ALS include:

  • Disorganized immune response: The immune system may attack some of the body’s cells, possibly killing nerve cells.
  • Chemical imbalance: People with ALS often have higher levels of glutamate, a chemical messenger in the brain, near the motor neurons. Glutamate in high quantities can be toxic to nerve cells.
  • Mishandling of proteins: If nerve cells do not process proteins correctly, the resulting atypical proteins might accumulate and cause the nerve cells to die.

Possible environmental factors

One study reports that military personnel deployed in the Gulf region during the 1991 war were more likely to develop ALS than those deployed elsewhere.

Also, research indicates some possible links between ALS and:

  • mechanical or electrical trauma
  • military service
  • high levels of exercise
  • exposure to high quantities of agricultural chemicals
  • exposure to high levels of a variety of heavy metals

However, there is no conclusive evidence that any lifestyle changes reduce the risk of developing ALS.

No single test can diagnose ALS. Doctors consider the symptoms and the results of various tests to rule out other conditions with similar signs and symptoms.

Tests that may help diagnose ALS are:

  • electromyography, which detects electrical energy in muscles
  • nerve conduction study, which tests how well the nerves send signals

These can help rule out peripheral neuropathy and myopathy, which is muscle disease.

An MRI scan can detect other problems that could be causing the symptoms, such as a spinal cord tumor or a herniated disk in the neck.

Blood and urine tests and a muscle biopsy can help rule out other conditions.

Some health issues that can cause similar symptoms to ALS include HIV, Lyme disease, multiple sclerosis, polio, and West Nile virus.

If there are symptoms in both the upper and lower motor neurons, ALS may be present.

Upper motor neuron symptoms include stiffness and resistance to movement in the muscles, as well as brisk reflexes. Lower motor neuron symptoms include weakness, muscle atrophy, and twitching.

There is no cure for ALS, so treatment aims to alleviate symptoms, prevent complications, and slow the progression.

ALS can cause a range of physical, mental, and social changes. As a result, managing the symptoms, improving the quality of life, and prolonging life may involve a team of specialists.

The Food and Drug Administration (FDA) approved riluzole (Rilutek) for ALS treatment in 1995, and it appears to slow the progression of the disease. It may work by reducing the body’s levels of glutamate, an excitotoxin that has been linked to neuronal damage.

In May 2017, the FDA approved radicava (Edaravone) to treat ALS. It may slow the decline in physical function by one-third.

Several research projects are looking at ways to use new and existing drugs to treat individual aspects of ALS.

Doctors can also prescribe medications to treat the different symptoms.

Therapy

Physical therapy can help people with ALS manage pain and improve mobility.

A physical therapist may recommend:

  • low-impact exercises to enhance cardiovascular fitness and overall well-being
  • mobility aids, such as walkers and wheelchairs
  • devices to make life easier, such as ramps

Occupational therapy can help people maintain their independence for longer. An occupational therapist may:

  • help choose adaptive equipment and assistive technologies that enable a person to keep up their daily routine
  • provide training about how to compensate for hand and arm weaknesses

Speech therapy can be useful when ALS makes speaking difficult. A speech therapist can teach a person adaptive techniques and other methods of communication, including writing and computer-based communication equipment.

Nutritional support is also important, as difficulty with swallowing can make it hard to get enough nutrients. A registered dietitian can advise about making meals that are easy to swallow. Suction devices and feeding tubes can also help.

As the respiratory muscles get weaker, a person may benefit from breathing therapy. This might involve using a breathing device at night.

Some people need mechanical ventilation. This involves having a respirator that is connected to a tube. The other end of the tube is inserted into the windpipe through a surgically created hole in the neck, or tracheostomy.

Several strategies can help people with ALS and their loved ones adjust to a changing situation.

  • Keep in touch: Social contact is important. Stay in touch with friends and keep up with as many activities as possible.
  • Reach out: In-person or online support groups can help answer questions and provide insight through shared experiences.
  • Get equipped: Have a bag ready with tissues, hand wipes, and easy-to-hold cutlery for going out. Register to get a disability sign for the car. Make any necessary adjustments at home, such as purchasing a device that raises the toilet seat.
  • Plan ahead: It can be hard for a person to find that they can no longer do something. Foreseeing possible limitations and preparing can help make this easier when the time comes.
  • Research financial help: As the disease progresses, treatment can become expensive. A person in the U.S. may be eligible for financial assistance through the Social Security Administration, Medicare, or Medicaid. There may also be specific benefits for veterans.
  • Arrange time off for caregivers: Caregivers should make sure to look after their own health, as well as that of their loved one. Arrange for a friend, relative, or another caregiver to stay for a weekend or take the person with ALS out for the day.

What you can do will depend to some extent on your finances. Support groups can help people cope with many of the challenges of ALS by providing advice, empathy, or practical help.