Due to excitement and/or fear - especially when my neighbor started his Harley. My Collies don't like noise at all.
He was not on meds for it, I changed his diet to raw food (turkey necks, pork loin and chuck roast, with various organs), and hasn't had a seizure since. I believe grains have some connection to seizures. I belong to a canine seizure email list, and many many dogs have stopped seizing when the diet is changed to something more species appropriate. Grains are full of pesticides, and some grains are genetically modified, the safety has yet to be proven.
A dog that has seizures is considered unhealthy, so I've stopped vaccinating him, using the "unhealthy" excuse. I will titer him for rabies when he's due and use that to avoid any more jabs. He also has the genetic Collie defect that doesn't allow him to process certain drugs properly, like heartworm prevention. So he's truly unhealthy. BTW, our county hasn't seen a case of rabies in any species for over 50 years.
There are raw food mixes, where the bones are ground up with the meat and organs, since your pup has chewing problems.
As a side benefit of raw food, the mosquitoes don't hover around the dogs anymore either. I no longer give heartworm prevention because of the defect. I test every 6 months.
I suggest you join this Yahoo group:
[email protected]On edit: They don't get fleas anymore, either, since switching to raw. I no longer have to treat with a preventive, which is a neurotoxin, the absolute wrong thing for a dog with seizures.