Undescended testicle in my four year old epileptic papillion?

I have a Papillon too. He is my BABY!! I can only imagine what you are feeling. What I would do, is do a lot of research online, get a lot of opinions from vets. Go to vet chat rooms and blogs. Maybe find some info on canine epilepsy. Maybe he'd be better of not getting neutered? Do A LOT of research before making the decision.