I once had a dog who suddenly lost the ability to walk... and somehow I figured out it was myasthenia gravis... I read that if they gave the dog a certain drug and it could walk, it confirmed it. The vets kept telling me it couldn't be... It took forever to convince the vet to try it... He gave her the shot, and she got up and walked... We were all stunned... She took the pills for a while, then it never came back. She lived another 6 years... and walked right up til the end.
I know it probably has nothing to do with what happened to your dog, but I thought I'd share it with you...
There are no guarantees that your dog won't have another seizure, but it's possible it won't happen again... I'm really sorry you're going through it... You have enough to deal with... :hug: