See the recent thread "myasthenia buzz" for a relevant discussion:
http://neurotalk.psychcentral.com/sh...yasthenia+buzz
Everything you describe sounds like typical MG symptoms except the difficulty concentrating and trouble with words. Could that be happening to you just as a result of the extreme fatigue you're feeling?
As for the connection with altitude...who knows. I'm always looking for triggers for my flare-ups, and it's tricky. Sometimes I think I've identified one, but the next time the supposed trigger happens, I'm fine. The altitude shift may very well have set you off, or it may be a total coincidence. The best way to find out is to keep a detailed journal.
Abby