Amyotrophic Lateral Sclerosis (ALS), also called motor neuron disease and Lou Gehrig’s Disease, affects about two out of every 100,000 people worldwide. When a person has ALS, their motor neurons - the cells responsible for all voluntary muscle control in the body - lose function and die. Fernando G. Vieira shares what we know (and don't know) about ALS. Lesson by Fernando G. Vieira, animation by Artrake Studio.