Our lab started having those when she was about 3, 5 years ago now. The first one took us by grand surprise as well. She's been on potassium bromide ever since and we travel with a handful of valium pills.

The bromide is not toxic to the liver but above a certain level, she turns into nervous Nellie. It took a while to fine tune the dose, but she'd now been seizure free for 3 years (crossing fingers...) and the neurotic behavior is at a tolerable level.