IANAMD. Go to medical doctor and get a NMR. It provides a lot of information and is very little invasive. Perhaps it's not a tumor but a small cerebral stroke or some other cerebral problem. It may be easy to cure with the correct medication + diet. Even if it's a tumor, some of them are easier to treat than others.
Meanwhile, driving a car seam to be potentially dangerous.
Agree. While it's possible he's still fully functional and able to drive during these episodes (maybe even likely -- a driver having a full-on seizure or in some kind of black-out would crash pretty quickly) it's not worth taking a chance of killing someone or yourself.
Meanwhile, driving a car seam to be potentially dangerous.