Amyotrophic lateral sclerosis (a-my-o-TROE-fik LAT-ur-ul skluh-ROE-sis), or ALS, is a progressive nervous system disease that affects nerve cells in the brain and spinal cord, causing loss of muscle control.
ALS is often called Lou Gehrig’s disease, after the baseball player who was diagnosed with it. Doctors usually don’t know why ALS occurs. Some cases are inherited.
ALS often begins with muscle twitching and weakness in a limb, or slurred speech. Eventually, ALS affects control of the muscles needed to move, speak, eat and breathe. There is no cure for this fatal disease.
Signs and symptoms of ALS vary greatly from person to person, depending on which neurons are affected. It generally begins with muscle weakness that spreads and gets worse over time. Signs and symptoms might include:
- Difficulty walking or doing normal daily activities
- Tripping and falling
- Weakness in your legs, feet or ankles
- Hand weakness or clumsiness
- Slurred speech or trouble swallowing
- Muscle cramps and twitching in your arms, shoulders and tongue
- Inappropriate crying, laughing or yawning
- Cognitive and behavioral changes
ALS often starts in the hands, feet or limbs, and then spreads to other parts of your body. As the disease advances and nerve cells are destroyed, your muscles get weaker. This eventually affects chewing, swallowing, speaking and breathing.
There’s generally no pain in the early stages of ALS, and pain is uncommon in the later stages. ALS doesn’t usually affect your bladder control or your senses.
ALS affects the nerve cells that control voluntary muscle movements such as walking and talking (motor neurons). ALS causes the motor neurons to gradually deteriorate, and then die. Motor neurons extend from the brain to the spinal cord to muscles throughout the body. When motor neurons are damaged, they stop sending messages to the muscles, so the muscles can’t function.
ALS is inherited in 5% to 10% of people. For the rest, the cause isn’t known.
Researchers continue to study possible causes of ALS. Most theories center on a complex interaction between genetic and environmental factors.
Established risk factors for ALS include:
- Heredity. Five to 10 percent of the people with ALS inherited it (familial ALS). In most people with familial ALS, their children have a 50-50 chance of developing the disease.
- Age. ALS risk increases with age, and is most common between the ages of 40 and the mid-60s.
- Sex. Before the age of 65, slightly more men than women develop ALS. This sex difference disappears after age 70.
- Genetics. Some studies examining the entire human genome found many similarities in the genetic variations of people with familial ALS and some people with noninherited ALS. These genetic variations might make people more susceptible to ALS.
Environmental factors, such as the following, might trigger ALS.
- Smoking. Smoking is the only likely environmental risk factor for ALS. The risk seems to be greatest for women, 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 single agent or chemical has been consistently associated with ALS.
- Military service. Studies indicate that people who have served in the military are at higher risk of ALS. It’s unclear what about military service might trigger the development of ALS. It might include exposure to certain metals or chemicals, traumatic injuries, viral infections, and intense exertion.
As the disease progresses, ALS causes complications, such as:
Over time, ALS paralyzes the muscles you use to breathe. You might need a device to help you breathe at night, similar to what someone with sleep apnea might wear. For example, you may be given a bilevel positive airway pressure (BiPAP) device to help with your breathing at night. This type of device supports your breathing through a mask worn over your nose, your mouth or both.
Some people with advanced ALS choose to have a tracheostomy — a surgically created hole at the front of the neck leading to the windpipe (trachea) — for full-time use of a respirator that inflates and deflates their lungs.
The most common cause of death for people with ALS is respiratory failure. On average, death occurs within 3 to 5 years after symptoms begin. However, some people with ALS live 10 or more years.
Most people with ALS develop trouble speaking. This usually starts as occasional, mild slurring of words, but becomes more severe. Speech eventually becomes difficult for others to understand, and people with ALS often rely on other communication technologies to communicate.
People with ALS can develop malnutrition and dehydration from damage to the muscles that control swallowing. 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.
Some people with ALS have problems with memory and decision-making, and some are eventually diagnosed with a form of dementia called frontotemporal dementia.