I just found this out recently, even though it happened almost 16 years ago. Diagnosed with Lou Gehrig's Disease at age 20, Jason Becker, one of the greatest guitarists on the planet lost his ability play his guitar, and just about everything else, including walking and speaking. This guy was soooooooooooooooo good. His technique was amazing. He had just landed a gig with David Lee Roth
in 1990 or so for his 'Little Ain't Enough' tour when he began to feel weakness in his hands and legs. Ussually this disease kills people within three to five years, but Jason is still alive today, his condition remaining stable since 1997. I just picked up his CD Rasberry Jams, which is a pile of his old demos and unreleased tunes. These days he's still composing using a computer and other musicians. The guy is trully inspiring.
Just in case you think you're having a bad day..
Check out this documentary.