ALS (amyotrophic lateral sclerosis) is a progressive disease that destroys the motor neurons responsible for voluntary movement, gradually taking away the ability to walk, talk, eat, and eventually breathe. The average survival time after diagnosis is about three years, though roughly 20% of people live five years or more and about 10% live beyond a decade. What happens along the way varies from person to person, but the overall trajectory follows a recognizable pattern.
How Motor Neurons Break Down
Your brain controls voluntary movement through two sets of motor neurons working in relay. Upper motor neurons in the brain collect and translate the brain’s commands, then pass those signals down the spinal cord. Lower motor neurons in the spinal cord carry the signal the rest of the way to individual muscles. ALS attacks both sets.
As these neurons deteriorate, the electrical signals that tell muscles to contract become weaker, less frequent, and eventually stop altogether. Without regular stimulation, muscles begin to waste away. Researchers have identified several mechanisms driving this breakdown, including a buildup of stress inside the cell’s protein-processing machinery and the loss of proteins that normally protect neuron health. But the damage is irreversible: once a motor neuron dies, the muscle fibers it controlled can no longer be activated.
Where Symptoms Start
ALS doesn’t show up the same way in everyone. About two-thirds of people experience what’s called limb-onset ALS, where the first problems appear in the arms or legs. Early signs include muscle cramps or stiffness, twitching (fasciculations), weakness in the hands or feet, and loss of grip strength. You might notice trouble buttoning a shirt, writing with a pen, tripping while walking, or losing your balance in situations that never used to be a problem.
The remaining third develop bulbar-onset ALS, which first affects the muscles of the face, jaw, throat, and tongue. Early symptoms include slurred speech, difficulty chewing and swallowing, excessive choking, and changes in voice quality. Words become harder to form. Speech may sound harsh, hoarse, or strained, and the voice may lose its range and volume.
Regardless of where it starts, the disease eventually spreads to other regions. Someone who first noticed weakness in their hand will, over time, develop difficulty speaking or swallowing, and vice versa.
How the Disease Progresses
ALS moves outward from its point of origin. A person with weakness in one hand will typically see it spread to the other hand, then to the arms, and eventually to the legs or trunk. The pace varies considerably. Some people experience a slow decline over many years, while others lose function within months.
In the middle stages, everyday independence shrinks. Tasks that require fine motor control become impossible first. Walking grows unreliable, then requires assistive devices, then a wheelchair. Speech becomes increasingly difficult to understand, and many people eventually rely on communication devices that track eye movement or other small muscle signals. Swallowing difficulties make eating slower, riskier, and less nutritious, and many people eventually need a feeding tube to maintain adequate nutrition.
Throughout all of this, the senses remain intact. ALS does not affect the ability to see, hear, smell, taste, or feel touch. The mind is largely preserved too, which is part of what makes the disease so difficult: people remain aware of what’s happening to their bodies.
Cognitive and Behavioral Changes
That said, ALS isn’t purely a motor disease. More than 50% of people with ALS experience some degree of changes in thinking or behavior, and roughly 8 to 14% meet the full diagnostic criteria for frontotemporal dementia. These changes can include difficulty with planning and decision-making, reduced social awareness, apathy, impulsive behavior, and repetitive actions or speech. For caregivers, these cognitive shifts can be as challenging to manage as the physical symptoms, particularly when the person with ALS has difficulty recognizing that their behavior has changed.
Why Breathing Fails
Respiratory failure is the primary cause of death in ALS. Breathing depends on the diaphragm, a large dome-shaped muscle beneath the lungs, along with the intercostal muscles between the ribs and several accessory muscles in the neck and chest. ALS affects all of them.
The nerve cells that control the diaphragm sit in the cervical spinal cord, a region that tends to be affected early in the disease. As the diaphragm weakens, accessory muscles try to compensate, but they don’t have the capacity to fully replace it, especially since ALS progressively damages those muscles too. The result is that the body can’t take in enough oxygen or expel enough carbon dioxide.
Weakness in the expiratory muscles creates a second problem: an ineffective cough. Without the ability to forcefully clear the airways, mucus builds up, and the risk of respiratory infection rises sharply. Most people with ALS will eventually use noninvasive ventilation, a mask-based breathing support that helps maintain oxygen levels and offload the work of weakened respiratory muscles. Some choose invasive ventilation through a tracheostomy, which can extend life significantly but requires full-time care.
What Causes ALS
For the vast majority of people, the cause remains unknown. About 90 to 95% of cases are classified as sporadic, meaning there’s no clear family history. The remaining 5 to 10% are familial, with an inherited genetic mutation passed down from a parent. About two-thirds of people with familial ALS carry mutations in known ALS-related genes, though more genes likely remain to be discovered. Interestingly, about 10% of people with sporadic ALS also carry a mutation in a gene linked to the disease, blurring the line between the two categories.
Available Treatments
There is no cure for ALS, but several medications can slow the disease or manage specific symptoms. Riluzole, the first drug approved for ALS, works by reducing levels of a chemical signal called glutamate that can become toxic to nerve cells in excess. It modestly extends survival. Radicava, approved in 2017, is designed to slow physical decline by neutralizing unstable molecules that damage cells during normal energy production. It’s available as an IV infusion or an oral liquid.
In 2023, the FDA approved a genetically targeted therapy called Qalsody for the small subset of people whose ALS is caused by a specific gene mutation. It works by blocking the production of a toxic protein at the genetic level, representing a fundamentally different approach from earlier treatments. A fourth medication, Nuedexta, treats a specific symptom called pseudobulbar affect, which causes involuntary episodes of laughing or crying that don’t match how the person actually feels. Recent evidence suggests it may also help with speech and swallowing function.
The Role of Specialized Care Teams
Because ALS affects so many body systems, the most effective care comes from a multidisciplinary team rather than a single doctor. These teams typically include a neurologist, physical therapist, occupational therapist, respiratory therapist, dietitian, speech therapist, social worker, and sometimes a neuropsychologist. The goal is to keep a person safe, healthy, and as independent as possible for as long as possible.
Research consistently shows that people who receive care through multidisciplinary ALS clinics experience better quality of life, better mental health, and even improved survival compared to those who see specialists separately. Part of the benefit is practical: instead of juggling appointments across multiple offices, everything happens in coordinated visits. But the larger benefit is that each new challenge, whether it’s a weakening grip, worsening speech, or declining lung function, gets addressed proactively rather than reactively. As needs evolve, the team can bring in home health providers, equipment specialists, and assistive technology experts to adapt the living environment to the person’s current abilities.