night seizures

My father suffered an aneurysm in 1997. It occured at night and resulted in him having a seizure. He underwent surgery and the anuerysm was clamped (with a titanium clip of some sore) and he has been on anti-seizure medication since then.

He does however still have seizures at night, and recently they have been happening more frequently (approximately every 6 to 8 weeks). After the seizure (while he is still unconcious) he has trouble breathing - he doesn't/can't breath through his nose and his tongue and excess saliva make it very difficult for him to breath through his mouth (he really struggles unless someone pulls his mouth open and moves his tongue out the way).

He has also recently started going on business trips which require him to stay overnight. Our family is of course worried what would happen if he has a seizure and there isn't anybody there to help him.

I would really appreciate any information about how to prevent these seizures happening, especially diet related info (eg. does Aspartame increase the chance of seizure), and what we should we do after he has an episode. I would also like to know if there is any reason why they only occur at night, and if it is possible that he could have a seizure during the day.

I would greatly appreciate any help.
Thanks.