Center for ALS Research and Therapy

What is ALS?

Amyotrophic lateral sclerosis (ALS), commonly known as Lou Gehrig's disease, is a neurodegenerative disease without a cure or effective treatments. According to the ALS Association, approximately 5,600 people in the U.S. are diagnosed with ALS each year. It is estimated that as many as 30,000 Americans may have the disease at any given time, with approximately 300 in San Diego County alone.

ALS is characterized by a progressive degeneration of motor nerve cells in the brain (upper motor neurons) and spinal cord (lower motor neurons). When the motor neurons can no longer send impulses to the muscles, the muscles begin to waste away (atrophy), causing muscle weakness.

Unable to function, the muscles gradually weaken, and often twitch as they waste away. Eventually the ability of the brain to start and control voluntary movement is lost.  Individuals with ALS lose their strength and the ability to move their arms, legs, and body. When muscles in the diaphragm and chest wall fail, individuals lose the ability to breathe without ventilatory support. 

The disease does not affect a person's ability to move their eyes or to see, smell, taste, hear, or recognize touch, and it does not usually impair a person’s thinking or other cognitive abilities.  However, several recent studies suggest that a small percentage of patients may experience problems with memory or decision-making, and there is growing evidence that some may even develop a form of dementia. 

The cause of ALS is not known, and scientists do not yet know why ALS strikes some people and not others. ALS is often referred to as a syndrome because the disease becomes apparent in various patterns. ALS occurs rarely as an inherited disease.