Another Episode

I'm almost positive my husband has a form of epilepsy - very scary. What's worse is that no doctor has been able to explain or diagnose it. Last week was the most recent of his tonic-clonic/'grand mal' seizures. He only has one (or 2 in succession) every 8 months or so. Every test he has had, CT, MRI, EEG, EKG has all been completely normal. We went to a neurologist once, she made him do some weird exercises and pronounced him fine...then charged us over $200 for her 10 minutes. Almost every seizure has happened while he was sleeping, all except one. We used to think it was related to dehydration, sunstroke or a prior medical issue that was depriving him of sleep - not so. I don't know how to proceed, he is terrified that any further investigation will lead to them pulling his license for good. Yes, it terrifies him and me that it could happen on the road - but currently his job depends on it. I feel like the medical system has let us down by giving up. I work in a medical environment, I feel like I should do something, but I don't know what.