Amyotrophic lateral sclerosis (ALS) is a neurological disease that affects nerve cells that are responsible for controlling voluntary muscles, such as the muscles used for speaking, walking, and breathing.
Over time, these cells die, leading to muscle weakness and eventually paralysis.
The exact cause of ALS is still unknown, but researchers believe a combination of genetic and environmental factors may play a role.
About 10% of ALS cases are hereditary, while the other 90% are considered sporadic.