ALS

Although respiratory support can ease problems with breathing and prolong survival, it does not affect the progression of ALS. Most people with ALS die from respiratory failure, usually within three to five years from the onset of symptoms. The median survival time from onset to death is around 39 months, and only 4% survive longer than 10 years. Physicist Stephen Hawking has lived with the disease for more than 50 years, though he is an unusual case.

 

http://en.wikipedia.org/wiki/Amyotrophic_lateral_sclerosis