P.Z.
I had the same thing happen when my daughter was an infant. She was sleeping in daddy's arms and I noticed she had an involuntary movement that I thought was a seizure. I didn't notice if her eyes were rolled back because it only lasted a matter of seconds and she woke as soon as I picked her up out of daddy's arms. We took her to the doctor, had an EEG done, worried a ton and the test showed nothing. About 6 months later, she had a cold with a low grade fever. She was asleep in her crib and when I went in to check on her, she was having a Fibril Seizure. That's when I realized that the first incident wasn't a seizure at all. Her body simply jerked involuntarily while she was sleeping. This happens to all of, even adults.
Also, remember what others have already said... Seizures can be controlled with medication and people who have them can lead happy normal lives. I know it's scary, but try and stay grounded and try not to worry about what is still unknown.
I hope your sons test results are OK. You will be in my thoughts and prayers. Please keep us updated.