Amyotrophic lateral sclerosis (ALS)

Date Updated: 03/17/2026

Overview

Amyotrophic lateral sclerosis (a-my-o-TROE-fik LAT-ur-ul skluh-ROE-sis) is a nervous system disease that affects nerve cells in the brain and spinal cord. Also known as ALS, the disease leads to muscle weakness and gets worse over time.

ALS often begins with muscle twitching and weakness in an arm or leg, trouble swallowing, or slurred speech. Eventually ALS affects the muscles needed to move, speak, eat and breathe. There is no cure for this fatal disease, but research into new therapies is ongoing.

ALS is often called Lou Gehrig's disease after the baseball player who was diagnosed with it. The exact cause of the disease is still not known. In a small percentage of people, ALS is inherited from a parent.

Symptoms

Symptoms of amyotrophic lateral sclerosis (ALS) vary from person to person. They depend on which nerve cells are affected. ALS generally begins with muscle weakness that spreads and gets worse over time.

Symptoms might include:

Trouble walking or doing usual daily activities.
Tripping and falling.
Weakness in the legs, feet or ankles.
Hand weakness or clumsiness.
Slurred speech or trouble swallowing.
Weakness related to muscle cramps and twitching in the arms, shoulders and tongue.
Crying, laughing or yawning at inappropriate times.
Thinking or behavioral changes.

ALS often starts in the hands, feet, arms or legs. Then it spreads to other parts of the body. Muscles get weaker as more nerve cells die. This eventually affects chewing, swallowing, speaking and breathing.

There's generally no pain in the early stages of ALS, and pain is not common in the later stages. ALS doesn't usually affect bladder function or the senses, such as taste, smell, touch and hearing.

Causes

A genetic cause is found in about 10% of people with amyotrophic lateral sclerosis (ALS). For the rest, the cause is not known.

ALS affects the nerve cells that allow voluntary muscle movements such as walking and talking. These nerve cells are called motor neurons. One group of motor neurons extends from the brain to the spinal cord to muscles throughout the body. They're referred to as upper motor neurons. The second group extends from the spinal cord to muscles throughout the body. They're called lower motor neurons.

ALS causes both groups of motor neurons to gradually deteriorate and then die. When motor neurons are damaged, they stop sending messages to the muscles. As a result, the muscles can't function.

Researchers continue to study possible causes of ALS. Most theories center on a complex interaction between genes and factors in the environment.

Risk factors

Established risk factors for amyotrophic lateral sclerosis (ALS) include:

Genetics. For about 10% of people with ALS, a gene that caused the disease was passed down from a family member. This is called hereditary ALS. In most people with hereditary ALS, their children have a 50% chance of inheriting the gene.
Age. Risk rises with age up to age 75. ALS is most common between the ages of 60 and the mid-80s.
Sex assigned at birth. Before the age of 65, slightly more men than women get ALS. This difference disappears after age 70.

Environmental factors, such as the following, have been linked to a higher risk of ALS.

Smoking. Evidence supports that smoking is an environmental risk factor for ALS. Women who smoke seem to be at even higher risk, particularly after menopause.
Environmental toxin exposure. Some evidence suggests that exposure to lead or other substances in the workplace or at home might be linked to ALS. Much study has been done, but no agent or chemical has been consistently linked to ALS.
Military service. Studies indicate that people who have served in the military are at higher risk of ALS. It's not clear what about military service might trigger ALS. It might include exposure to certain metals or chemicals, traumatic injuries, viral infections or intense exertion.

Complications

As the disease progresses, amyotrophic lateral sclerosis (ALS) causes complications that may include:

Trouble breathing

Over time, ALS leads to weakness of the muscles used to breathe. People with ALS might need a device such as a mask ventilator to help them breathe at night. The device is similar to what someone with sleep apnea might wear. This type of device supports the person's breathing through a mask worn over the nose, the mouth or both.

Some people with advanced ALS choose to have a tracheostomy. This is a surgically created hole at the front of the neck leading to the windpipe. A ventilator may work better on a tracheostomy than on a mask.

The most common cause of death for people with ALS is breathing failure. On average, people with ALS die 3 to 5 years after symptoms begin. However, some people with ALS live 10 years or longer.

Trouble speaking

Most people with ALS have weakness of the muscles used to form speech. This usually starts with slower speech and occasional slurring of words. It then becomes harder to speak clearly. This can progress to the point that others can't understand the person's speech. Other forms of communication and technology are used to communicate.

Trouble eating

People with ALS may have weakness of the muscles involved with swallowing. This can lead to malnutrition and dehydration. They are also at higher risk of getting food, liquids or saliva into the lungs, which can cause pneumonia. A feeding tube can reduce these risks and ensure proper hydration and nutrition.

Dementia

Some people with ALS have problems with language and decision-making. Some are eventually diagnosed with a form of dementia called frontotemporal dementia.

Prevention

There's no way to prevent ALS. Experts don't know exactly what causes the disease in most people. Researchers are actively studying the genes and other factors related to ALS.

Diagnosis

Amyotrophic lateral sclerosis (ALS) can be hard to diagnose early because it can have symptoms similar to other diseases. Tests to rule out other conditions or help diagnose ALS might include:

Electromyogram (EMG). A needle is inserted through the skin into various muscles. The test records the electrical activity of the muscles when they contract and when they're at rest. This can determine if there is a problem with the muscles or nerves.
Nerve conduction study. This study measures your nerves' ability to send impulses to muscles in different areas of the body. This test can determine if you have nerve damage. EMG and nerve conduction studies are almost always done together.
Magnetic resonance imaging (MRI). Using radio waves and a powerful magnetic field, an MRI produces detailed images of the brain and spinal cord. An MRI can reveal spinal cord tumors, herniated disks in the neck or other conditions that might be causing your symptoms. The highest resolution cameras may sometimes see ALS changes themselves.
Blood and urine tests. Analyzing samples of your blood and urine in the laboratory might help eliminate other possible causes of your symptoms. Serum neurofilament light levels, which are measured from blood samples, are generally high in people with ALS. The test can help make a diagnosis early in the disease.
Spinal tap, also known as a lumbar puncture. This involves removing a sample of spinal fluid for lab testing. Spinal fluid is removed using a small needle inserted between two bones in the lower back. This test doesn't diagnose ALS but may reveal another cause of symptoms.
Muscle biopsy. If your healthcare professional believes you may have a muscle disease rather than ALS, you might undergo a muscle biopsy. While you're under local anesthesia, a small piece of muscle is removed and sent to a lab for analysis.
Nerve biopsy. If your healthcare professional believes you may have a nerve disease rather than ALS, you might undergo a nerve biopsy. While you're under local anesthesia, a small piece of nerve is removed and sent to a lab for analysis.

Treatment

Treatments can't reverse the damage of amyotrophic lateral sclerosis (ALS), but they can slow the progression of symptoms. They also can help prevent complications and make you more comfortable and independent.

You might need a team of healthcare professionals and doctors trained in many areas to provide your care. The team works together to select the right treatment for you, with a focus on improving your quality of life. You have the right to choose or refuse any of the treatments suggested.

Medicines

The Food and Drug Administration has approved these medicines for treating ALS:

Riluzole (Tiglutik). Taken by mouth, this medicine can add three months to life expectancy. It can cause side effects such as dizziness, gastrointestinal conditions and liver problems. Your healthcare professional typically monitors your liver function and complete blood counts with blood draws while you're taking the medicine.
Edaravone (Radicava). This medicine may reduce the speed of decline in daily functioning. It's given through a vein in your arm or by mouth as a liquid. The effect on life span isn't yet known. Side effects can include bruising, headache and trouble walking. This medicine is given daily for two weeks each month.
Tofersen (Qalsody). This medicine is approved for people with ALS who have a gene change, known as a mutation, in the SOD1 gene. Your healthcare professional injects this medicine into the cerebrospinal fluid during a spinal tap. Side effects of tofersen may include headache, fatigue, joint pain and injection site pain.

Your healthcare professional also might prescribe treatments for relief of other symptoms, including:

Muscle cramps and spasms.
Constipation.
Fatigue and trouble sleeping.
Excessive saliva and phlegm.
Pain.
Depression.
Outbursts of laughing or crying.
An urgent need to urinate.
Leg swelling.

Therapies

When ALS affects your ability to breathe, speak and move, therapies and other forms of support can help.

Breathing care. Most people with ALS eventually have more trouble breathing as muscles weaken. Your healthcare professional might test your breathing regularly and provide devices to assist your breathing at night.

You might choose to use a machine with a mask that can easily be applied and removed. This is known as noninvasive ventilation. Common names for these machines with a mask are BiPAP and CPAP. Some people eventually have surgery that creates a hole at the front of the neck leading to the windpipe. This is called a tracheostomy. A tube inserted into the hole connects to a respirator to help the person breathe. Sometimes people with ALS who have a tracheostomy also have a type of surgery called a laryngectomy. This surgery prevents food from entering the lungs.
Physical therapy. A physical therapist can address pain, walking, mobility, bracing and equipment needs that help you stay independent. Practicing low-impact exercises can help you maintain your cardiovascular fitness, muscle strength and range of motion for as long as possible.

Regular exercise also can help improve your sense of well-being. Appropriate stretching can help prevent pain and help your muscles function at their best.

A physical therapist also can help you overcome weakness by using a brace, walker or wheelchair. The therapist might suggest devices such as ramps that make it easier for you to get around.
Occupational therapy. An occupational therapist can help you find ways to remain independent despite hand and arm weakness. Adaptive equipment can help you perform activities such as dressing, grooming, eating and bathing.

An occupational therapist also can help you modify your home to allow accessibility if you have trouble walking safely.
Speech therapy. A speech therapist can teach you adaptive techniques to make your speech more understandable. Speech therapists also can help you find other ways to communicate. These may include using a smartphone app, alphabet board, or pen and paper.

Ask your therapist about the possibility of recording your own voice to be used by a text-to-speech application.
Nutritional support. Your team typically works with you and your family members to ensure you are eating foods that are easier to swallow and meet your nutritional needs. You might choose to have a feeding tube placed when it becomes too hard to swallow.
Psychological and social support. Your team might include a social worker to help with financial issues, insurance, and getting equipment and paying for devices you need. Psychologists, social workers and others may provide emotional support for you and your family.

Potential future treatments

Based on the current understanding of amyotrophic lateral sclerosis (ALS), researchers are conducting clinical studies on promising medicines and treatments.

Coping and support

Learning you have amyotrophic lateral sclerosis (ALS) can be devastating. The following tips may help you and your family cope:

Take time to grieve. The news that you have a fatal condition that reduces your mobility and independence is hard to hear. You and your family may go through a period of mourning and grief after diagnosis.
Be hopeful. Your team can help you focus on your abilities and healthy living. Some people with ALS live much longer than the 3 to 5 years usually associated with this condition. Some live 10 years or more. Maintaining an optimistic outlook can help improve quality of life for people with ALS.
Think beyond the physical changes. Many people with ALS lead rewarding lives despite physical limitations. Try to think of ALS as only one part of your life, not your entire identity.
Join a support group. You might find comfort in a support group with others who have ALS. Loved ones helping with your care might benefit from a support group of other ALS caregivers. Find support groups in your area by talking to your healthcare professional or by contacting the ALS Association.
Make decisions now about your future medical care. Planning for the future means you can make your own decisions about your life and your care. It also lessens the burden for your loved ones. With the help of your healthcare professional, hospice nurse or social worker, you can decide whether you want certain life-extending procedures.

You also can decide where you want to spend your final days. You might consider hospice care options. Planning for the future can help you and your loved ones calm anxieties.
Consider getting involved in ALS research. ALS research is working toward finding a cure for ALS. Consider joining a clinical trial, providing samples for research and joining the National ALS Registry. The registry is open to all people with ALS. Many institutions collect samples for research to better understand the disease.

Preparing for an appointment

Your healthcare professional may be the first to recognize the symptoms of amyotrophic lateral sclerosis (ALS). You may be referred to a doctor trained in nervous system conditions, known as a neurologist, to establish a diagnosis.

What you can do

You might need several tests to diagnose your condition. These strategies can help the process.

Keep a symptom diary. Before you see a neurologist, start using a calendar or notebook to jot down when and how you notice symptoms. Record information about your symptoms related to walking, hand coordination, speech, swallowing or other muscle movements. Your notes might show a pattern that's helpful for your diagnosis.
Find a neurologist and care team. An integrated care team led by your neurologist usually is most appropriate for ALS care. Your team members typically communicate with each other and are familiar with your needs.

What to expect from your doctor

Your healthcare professional will likely review your family's medical history and your symptoms. A physical and neurological exam might include testing your:

Reflexes.
Muscle strength.
Muscle size and tone.
Senses of touch and sight.
Coordination.
Balance.
Speaking.