Amyotrophic lateral sclerosis (ALS) is a debilitating and progressive neurodegenerative disease that affects the nerve cells responsible for controlling muscle movements. The disease is also known as Lou Gehrig's disease, named after a famous baseball player who was diagnosed with it in 1939. Other synonyms for ALS include motor neuron disease, which encompasses a group of conditions characterized by the death of motor neurons that control voluntary muscle movements. ALS is also referred to as Charcot disease, named after the French neurologist Jean-Martin Charcot, who first described the disease in detail in 1869. Regardless of what it's called, ALS remains a devastating condition that currently has no cure.