Stephen Hawking was diagnosed with amyotrophic lateral sclerosis, or Lou Gehrig's Disease, in 1963. Doctors told Hawking that he would live only two more years as a result of this motor neuron disease, but he is still alive as of August 2014.
When motor neurones die, the brain can't control the muscles used for walking, talking, swallowing or breathing. These muscles begin to atrophy, and the legs and arms appear smaller.
Despite having a motor neurone disease, Stephen Hawking completed his college education and received many honorary degrees. In 2009, he became the Lucasian Professor at Cambridge, which is a position previously held by Sir Isaac Newton in 1663. Hawking's brilliance has been compared to that of Einstein.