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.
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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.