Amyotrophic lateral sclerosis is a type of motor neuron disease. ALS, sometimes called Maladie de Charcot, is a progressive, fatal, neurodegenerative disease caused by the degeneration of motor neurons, the nerve cells in the central nervous system that control voluntary muscle movement. The condition is frequently called Lou Gehrig's Disease in North America, after the New York Yankees baseball icon who was diagnosed with the disease in 1939 and died from it in 1941, at age thirty-seven. Today, famous physicist Stephen Hawking is likely the best-known living ALS patient. The disorder causes muscle weakness and atrophy throughout the body as both the upper and lower motor neurons degenerate, ceasing to send messages to muscles.