chronic fatigue syndrome
"I was diagnosed with CFS 18 years ago.  When it gets really bad, I have major cognitive problems, memory loss, confusion and my speech even becomes more simple (small words less educated). I've  been on modafinal (provigil) for over 6 years.  Had to slightly up my dose about 3 years ago.  I can hold a job and function well provided I don't over do it.  My brain just "clicks" better again.  Closer to normal.   Slight side effect of nausea similar to morning sickness for about 3 hours after taking is well worth the benefit"