Our first show dog started seizures at about 3 years old, and his episodes were about 4 to 5 months apart. A good friend and trained but not a practicing Vet told us to get a urinalysis. Our Vet said it would be useless. Our friend insisted that we insist, and we found triple phosphate crystals suggesting a metabolic imbalance. In the blood work up they found eosinophills (spelling is wrong I'm sure) that suggested allergies. We started cooking rice and liver for him to eat. We put Brie on Benadryl at first, then changed to a prescription antihistamine for the allergies. We went about 8 years seizure free. Old age brought them back on.
Make sure your dog didn't get into any bug spray or other poisons. 12 years old is not the normal for idiopathic epilepsy to start, so I'm thinking there must be something else that triggered it. Oh, we also found that stress usually triggered seizures in Brie. Almost every time my wife left town for a convention, he would seizure the second day she got back. It is scary to see this, and you feel sooo helpless. I do remember laying on top of Brie on the floor at the Vet's office one time when he was having a cluster of grand mal seizures. We were blocking the front door. It was the only time our Vet actually saw him have a seizure. These can be very dangerous.
Do you have a trusted friend or family member that can be with your dog while you are gone? Oh, and there is a Yahoo list for people who have dogs that have seizures. We think it is called Epi-L. My wife said to google ocular compression and try that. It is possible that there is a tumor that could be causing the problem.
Will keep your pup in our prayers. Jim.