(CNN) Amyotrophic Lateral Sclerosis, more commonly known as ALS, is a progressive, neurodegenerative disease . It affects the nerve cells in the brain and spinal cord that make the muscles of both the upper and lower body work. Those nerve cells lose their ability to initiate and control muscle movement, which leads to paralysis and death. People with the condition lose control of muscle movement, eventually losing their ability to eat, speak, walk and, ultimately, breathe. Its most famous sufferer was famed physicist Stephen Hawking, who died on Wednesday at the age of 76. ALS is also called Lou Gehrig's disease, named after the famous baseball player who retired in 1939 because of the condition. Other notable sufferers actor David Niven, NBA Hall of Famer George Yardley and jazz musician Charles Mingus. Little is known about the causes of the disease, and there is currently no cure. The condition is slightly more common in men than women. Unusually lo