ALS overview
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Amyotrophic lateral sclerosis (ALS) is a progressive neurological disorder that damages nerve cells and causes disability. The condition also is known as Lou Gehrig’s disease, after the famed New York Yankees baseball player who was diagnosed with the disorder in the late 1930s.
ALS specifically damages motor neurons, the nerve cells that control voluntary movements, causing them to shrink and die. With the loss of these nerve cells, the brain is no longer able to control muscle movement and patients progressively lose the ability to perform everyday tasks, such as walking up steps, reaching for items, or dressing themselves. In later stages, paralysis typically occurs, and the disorder affects a person’s ability to breathe.
Causes of ALS
ALS is caused by the progressive dysfunction and death of motor neurons. The disease affects both upper motor neurons, which send messages from the brain to the spinal cord, and lower motor neurons, or those that run through the spinal cord and connect to the muscles.
The exact mechanisms leading to ALS remain largely unknown, but a number of risk factors, including genetics, lifestyle choices, and environmental exposures have been identified.
Genetic and biological risk factors
Mutations in more than 40 genes have been linked with the development of ALS. In about 10% of cases, ALS runs in families because disease-associated mutations are passed from parents to their biological children.
In most other cases, ALS is not inherited but genetics are still thought to play a significant role in determining disease risk. A minority of patients — about 10% — with no family history of ALS have been found to harbor disease-associated mutations.
Beyond genetics, other biological factors like sex and age also play a role in determining disease risk: ALS most commonly develops between the ages of 55 and 75, and the disease is 20% more common in men than women. Biological changes, like inflammation, variations in nerve signaling, and abnormalities in how cells handle proteins and other molecules, also have been linked to ALS.
Environmental and lifestyle risk factors
Some lifestyle habits have been linked with ALS, and certain environmental exposures are thought to increase the risk of developing the disorder. These include:
- smoking
- excessive exercise
- certain careers, particularly military service
- exposure to toxins like pesticides and heavy metals
- increased exposure to electric shocks or electromagnetic fields
- head injury and trauma
- certain viral infections.
ALS symptoms
The hallmark symptom of ALS is muscle weakness. This weakness generally starts off as fairly subtle, and usually affects one part of the body at first. However, as the disease progresses, it tends to become more severe and spread to other regions of the body.
Early symptoms
Most patients first notice weakness in their hands, manifesting as difficulty writing or grasping objects, or in their feet, leading to issues walking or running. In about one-third of patients, however, muscle weakness first affects muscles around the throat and mouth, manifesting as swallowing problems and trouble with speech.
As time goes on, muscle weakness in ALS becomes progressively more severe and spreads to affect other parts of the body. Muscle weakness is often accompanied by muscle atrophy (shrinking), spasticity or stiffness, cramps, and twitches or shaking as muscles become exhausted. Constipation and other digestive issues also may occur.
Later symptoms
Muscle weakness over time evolves into paralysis, where voluntary movements are no longer possible. Eventually, most people with ALS will have little to no ability to move around on their own, and swallowing and speaking become difficult or impossible.
ALS also affects the muscles in the chest that are needed to control breathing, and in later stages of the disease, most patients have difficulty breathing on their own. Respiratory failure, where the lungs are not able to adequately supply the body with oxygen, is the most common cause of death in ALS.
Cognitive issues and mental health
In addition to muscle problems, many people with ALS struggle with mental health issues, such as anxiety and depression. These are particularly more common after the disease is diagnosed, as most patients retain their mental reasoning and are therefore aware of their increasing limitations.
While many people with ALS will never experience any cognitive symptoms, up to 50% of patients with the disease will experience changes in thoughts or behavior as a result. These changes most commonly manifest as difficulty regulating behavior — for example, patients may have difficulty concentrating or controlling strong emotional reactions.
Up to 20% of people with ALS will develop dementia, where cognitive and behavioral symptoms reflect a dramatic change in the person and are severe enough that they impair day-to-day life. A specific form of dementia called frontotemporal dementia, or FTD, is particularly common in ALS.
Some ALS patients also experience pseudobulbar affect, a condition marked by sudden bursts of laughing or crying that are exaggerated or may be unrelated to the person’s emotional state.
ALS diagnosis
No single test can diagnose ALS. The diagnostic workup for the disease broadly involves assessments that check for ALS-like damage to motor neurons and confirmation of ALS disease progression, combined with tests to rule out other potential causes for the symptoms. It usually takes about a year from the time symptoms first appear until the diagnosis of ALS is confirmed.
Some of the diagnostic tests commonly used to evaluate potential ALS and exclude other conditions include:
- nerve conduction studies, measuring the speed at which nerve cells send electrical signals to muscles
- electromyography, which measures the electrical activity in muscle cells at rest and during contractions
- MRI scans, to image the brain, spinal cord, and/or muscles
- muscle or nerve biopsy, in which a small piece of tissue is collected for analysis in a laboratory
- spinal tap (also called lumbar puncture), used to collect a sample of the fluid around the brain and spinal cord for analysis
- genetic tests, to look for disease-associated mutations
- blood or urine tests, to check for other potential causes of symptoms.
Types of ALS
ALS is commonly classified into two main types, familial and sporadic, based on whether or not the person has a family history of the disease.
Disease manifestations and symptoms are broadly comparable between the two ALS types, though there can be a lot of variability even among patients with the same form of the disease. On average, people with familial ALS tend to experience disease onset at a younger age and have faster symptom progression than those with sporadic disease.
Familial ALS
Familial ALS, diagnosed in about 10% of ALS patients, refers to cases in which the disorder affects multiple relatives within the same biological family. Because this form of ALS runs in families, it has a greater genetic contribution, with about 60% of patients having a known disease-causing mutation.
The most commonly mutated genes in people with familial ALS are C9ORF72, SOD1, FUS, and TARDBP. However, not everyone who inherits an ALS-associated mutation will develop the condition — other factors, such as environmental exposures and lifestyle also are known to play a role.
Sporadic ALS
In the majority of ALS cases, patients have no known family history of the disease. This is found for about 90% of patients and is referred to as sporadic ALS.
In these cases, lifestyle habits and environmental factors are believed to play a more important role than genetics. Nonetheless, about 10% of people with sporadic ALS have a known disease-associated mutation.
Other types
Apart from the classification based on family history, other systems may be used to classify ALS. The most common is classification based on disease onset — that is, the first symptoms that a patient experiences.
About two-thirds of patients have limb-onset disease, in which the first ALS symptoms affect the muscles in the hands or feet. The other third of patients have bulbar-onset disease, where the first symptoms affect muscles around the jaw and throat.
In addition to these main ALS types, there are rarer forms of the disease, including juvenile ALS and an ALS-like disorder originally detected in the Pacific island of Guam that shares symptoms with other diseases.
How common is ALS?
The incidence of ALS, or the number of new cases per year, is estimated to be about two per 100,000 people — this means that, on average, someone is newly diagnosed with the disease every 90 minutes. About 5,000 people are diagnosed every year in the U.S.
This incidence increases with age, typically starting in the 40s and increasing until around age 80. However, ALS can occur as early as during childhood.
The prevalence, or the number of people living with ALS, varies among geographic locations, but is estimated to be somewhere between four and nine individuals per 100,000 people. The U.S. Centers for Disease Control and Prevention estimates that, as of 2017, there were approximately 25,000 people with ALS living in the U.S.
ALS life expectancy
Life expectancy and survival rates in ALS vary depending on which symptoms first appear and how quickly the disease progresses. The average ALS life expectancy is about two to five years after the initial appearance of symptoms.
However, about 20% of ALS patients will survive more than five years after disease onset, and about 10% will survive for a decade after the disease first appears. A minority of patients, about 5%, may survive with ALS for 20 years or longer.
Because ALS can make it difficult or impossible to move around, swallow, or speak, many people living with ALS rely on supportive equipment and care to help them maintain health and function in day-to-day life. This may include ventilators or feeding tubes to support breathing and nutrition, wheelchairs or other mobility aids to help get around, and adaptive communication devices to help make their thoughts known.
ALS News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
FAQs about ALS
There’s no known exact cause of amyotrophic lateral sclerosis (ALS), but its symptoms are due to the progressive dysfunction and death of motor neurons. A number of ALS risk factors, including genetics, environmental exposures, and lifestyle habits, have been identified.
Amyotrophic lateral sclerosis (ALS) is characterized by progressive muscle weakness. Usually, the first symptoms include weakness in the hands or feet, causing problems with writing, gripping objects, or walking. In about one-third of patients, however, the first symptoms affect muscles around the mouth and throat, usually manifesting as issues speaking or swallowing.
Amyotrophic lateral sclerosis (ALS) most commonly manifests between the ages of 55 and 75, and the disease is more common in men than women. Other risk factors for ALS include a family history of the disease, smoking, excessive exercise, and exposures to toxins like pesticides.
In the early disease stages, people with amyotrophic lateral sclerosis (ALS) often struggle with activities that require fine hand motor skills, like writing or buttoning a shirt. As the disease progresses, muscle weakness becomes more severe and spreads throughout the body, with most patients eventually progressing to have little or no ability to move under their own power. People with ALS often experience difficulty eating and speaking, and breathing problems are common.
The average life expectancy for someone with amyotrophic lateral sclerosis (ALS) is about two to five years after the initial onset of symptoms. However, it is estimated that about 20% of ALS patients live more than five years after symptom onset, and about 10% will live past 10 years.
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