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Amyotrophic Lateral Sclerosis (ALS)

Amyotrophic Lateral Sclerosis (ALS)

Table of Contents

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What causes ALS?

The causes of the vast majority of ALS cases are still unknown. Investigators theorize that some individuals may be genetically predisposed to developing the disease but do so only after coming into contact with an environmental trigger. The interaction of genetics and environment may hold clues as to why some individuals develop ALS.

Although the majority of ALS cases are sporadic, meaning there is no family history of the disease, about 10% of cases are familial, meaning the disease runs in the family. A common misconception is that only familial ALS is "genetic." Actually, both familial and sporadic ALS can stem from genetic causes, and some people who have a diagnosis of sporadic ALS may carry ALS-causing genetic mutations that can be passed on to offspring. A genetic counselor can help people with ALS understand inheritance and any associated risks for family members.

For a more detailed discussion of possible causes of sporadic ALS and the genetics of familial ALS, please see Causes/Inheritance.

What are the symptoms of ALS?

ALS results in muscles that are reduced in size (atrophic), weak, and soft, or muscles that are stiff, tight, and spastic. Muscle twitches and cramps are common. Symptoms may begin anywhere in the body, including in the limbs, the bulbar region (the area supplied by the motor neurons in the brainstem) or, rarely, in the diaphragm that supports breathing. Symptoms may be limited to a single body region or may affect more than one region. When ALS begins in the bulbar motor neurons the muscles used for swallowing and speaking are affected first.

As ALS progresses, symptoms become more widespread, and some muscles become profoundly weak while others are weakened or unaffected. In late-stage ALS, most voluntary muscles become unusable, either from severe weakness or increased tone.

The involuntary muscles, such as those that control the heart, gastrointestinal tract and bowel, bladder, and sexual functions are not directly affected by ALS. Sensations, such as vision, hearing, and touch, are also unaffected.

In many cases, ALS does not affect a person's thinking ability. However, a small subset of individuals will develop frontotemporal dementia manifested as behavioral abnormalities and a severe language disorder. An additional 30-40% of people with ALS develop some degree of executive function disorder.

For more information on ALS symptoms, see Signs and Symptoms and Medical Management.

Join the National ALS Registry. With your help, we can advance research. Learn More.

What is the life expectancy in ALS?

Each person's disease course is unique.

From the time of diagnosis, most individuals will live for three to five years. Around 30% of ALS patients are alive beyond five years after diagnosis, and 10-20% of patients survive 10 years or more. Survival beyond 20 years is possible but rare. Factors associated with more favorable survival rates include a younger age, male gender, and limb rather than bulbar symptom onset.

For more information on the disease course, see Medical Management.

What can be done about ALS?

Medical interventions and technology have vastly improved the quality of life for people with ALS by assisting with breathing, nutrition, mobility, and communication. Proper management of symptoms, and proactive use of medical interventions and equipment, can make a positive difference in day-to-day living and potentially may lengthen life.

In 1995, the glutamate blocker riluzole (Rilutek) became the first treatment approved by the U.S. Food and Drug Administration (FDA) to treat ALS. In people with ALS, the neuronal signaling molecule glutamate accumulates abnormally in the brain and causes death of motor neurons. Rilutek blocks the release of glutamate, thereby protecting motor neurons from cell death. Alternative formulations of Rilutek have been developed, to potentially increase accessibilty for individuals who have difficulty swallowing. Tiglutek, an oral liquid formulation of Rilutek was approved in 2018 and, Exservan, an oral formulation of Rilutek that dissolves on the tongue, was approved in the US in 2021. For more information, see press releases for Tiglutik approval and Exservan approval.

Dextromethorphan HBr and quinidine sulfate (Nuedexta) was approved in 2010, for treatment of pseudobulbar affect (PBA), a condition experienced by 15-45% ALS patients. PBA is manifested as exaggerated or inappropriate emotional responses including laughter and crying that is unwanted by the individual.

On May 5, 2017, the FDA approved edaravone (Radicava) for the treatment of ALS. Radicava is an intravenous (IV) therapy for adults. For more information, see FDA Approves Radicava to Treat ALS. On May 12, 2022, the FDA granted approval to oral edaravone (RADICAVA ORS) for the treatment of ALS. Radicava is thought to protect neurons from the damage caused by oxidative stress in people with ALS.

Most recently, on April 25, 2023, the FDA granted accelerated approval of tofersen (Qalsody) for the treatment of ALS associated with mutation in the superoxide dismutase 1 (SOD1) gene (SOD1-ALS). Qalsody is the first therapy to target a genetic cause of ALS. Qalsody is administered once monthly intrathecally.

What is the status of ALS research?

A number of strategies and approaches are being tested around the world, both in the laboratory and in human clinical trials. MDA's basic science program is constantly pursuing new avenues of research to understand the underlying causes of ALS, with a sharp focus on developing treatments.

One of the most significant breakthroughs in the last decade has been the discovery of a number of genes that, when flawed, cause ALS. In fact, the genes responsible for causing the majority of the familial forms of ALS are now known — with some of these genes also having been found to be involved in sporadic ALS. Identification of these genes is crucial to moving research forward because it allows researchers to better understand the causes of ALS and design therapies to target them. For details about current ALS research, go to Research and Clinical Trials.

MDA takes a big-picture perspective on neuromuscular diseases, including ALS, so we can work across conditions to find effective treatments and cures.

With our collective strength, we encourage early diagnosis and action, support families in hometowns across the country, and uncover research breakthroughs to help everyone with ALS live longer, stronger lives.

Additional reading

  • Feldman EL, Goutman SA, Petri S, Mazzini L, Savelieff MG, Shaw PJ, Sobue G. Amyotrophic lateral sclerosis. Lancet. 2022 Oct 15;400(10360):1363-1380. doi: 10.1016/S0140-6736(22)01272-7. Epub 2022 Sep 15. PMID: 36116464; PMCID: PMC10089700.
  • Siddique N, Siddique T. Amyotrophic Lateral Sclerosis Overview. 2001 Mar 23 [Updated 2023 Sep 28]. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2025. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1450/

Last revised August 2025

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