It's called motor neuron disease. It's a progressive neurological disorder that destroys...

Doctor: It's called motor neuron disease. It's a progressive neurological disorder that destroys the cells in the brain that control essential muscle activity, such as speaking, walking, breathing, swallowing. The signals that muscles must receive in order to move are disrupted. The result is gradual muscle decay. Wasting away. Eventually, the ability to control voluntary movement is lost. Entirely. I'm afraid average life expectancy is two years. There's nothing I can do for you. Stephen Hawking: What about the brain? Doctor: The brain isn't affected. Your thoughts won't change, it's... just that... Well, eventually, no one will know what they are.