Information from ALS Society of Ontario

ALS stands for Amyotrophic Lateral Sclerosis, sometimes called Lou Gehrig's disease. It is a rapidly progressive and fatal neuromuscular disease that is characterized by degeneration of a select group of nerve cells and pathways (motor neurons) in the brain and spinal cord. This loss of motor neurons leads to progressive paralysis of the voluntary muscles. The heart is not a voluntary muscle, and therefore, remains unaffected by the disease. However, since breathing is controlled voluntarily by the chest muscles, death usually occurs when the chest muscles are no longer able to help the lungs achieve adequate oxygenation. Generally, there is little impairment of the brain or the senses.

more info at:

http://www.alsont.ca/about-als/