What is ALS?

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a neurological disease that attacks the nerve cells responsible for controlling voluntary muscles. ALS can progress quickly after the onset of symptoms.

With ALS, nerve cells (or neurons) located in the brain, brainstem and spinal cord gradually degenerate over time. The neurons are important communication links between the nervous system and voluntary muscles. The upper motor neurons (in the brain) talk to lower motor neurons (in the spinal cord), which relay the messages to other parts of the body like arms and legs, fingers and toes.

As these neurons break down and die, they stop transmitting messages to muscles. Because the muscles are unable to get instructions, they gradually weaken and show signs of atrophy (wasting away).

Over time, ALS affects most voluntary muscles in the body. In later stages, the muscles used for breathing are affected. Assistance with breathing, such as using a ventilator, usually becomes necessary.

ALS does not affect a person's ability to see, smell, taste, hear, or recognize touch. Patients typically maintain control of eye muscles and bladder and bowel functions.

Learn more about ALS, including:

Causes of ALS
Diagnosing ALS
Stages of ALS
Risk factors of ALS

Who gets ALS?

Every year an estimated 5,600 Americans are diagnosed with ALS. It is one of the most common neuromuscular diseases worldwide, and as many as 30,000 Americans have ALS. People of all races and ethnic backgrounds are affected. It commonly strikes people between 40 and 70 years of age, but younger and older people also can develop the disease. Men are affected more often than women.

Progression of ALS

Even though ALS affects motor neurons in the brain, it does not usually affect a person's mind or intelligence. Several recent studies, however, suggest that some patients may experience depression and problems with decision-making and memory.

When muscles used for breathing degenerate to the point that they fail, patients lose the ability to breathe without assistance from a mechanical ventilator. Respiratory failure is most common 3 to 5 years after the onset of symptoms.

Among ALS patients:

• 20% live for 5 years or more
• 10% live for 10 years or more
• 5% live for 20 years

Why is ALS called Lou Gehrig's disease?

ALS is commonly associated with baseball legend Lou Gehrig, who was diagnosed with the disease in 1939. Other notable people who have been diagnosed with ALS include: theoretical physicist Stephen Hawking, jazz composer Charles Mingus, British actor David Niven, creator of Sesame Street Jon Stone, and former Vice President of the United States Henry Wallace.