From all the research I did on-line this morning, it seems you can join certain branches of the military if you had a diagnosis of Epilepsy as long as you have not had a seizure within 5 years, you are medication free, and you pass with a normal EEG (done when going through the medical evaluations while applying).
They will also require all your records that relate to this to show proof of your seizures and when the last one was, when the last time you were prescribed pills, etc...they will not just take your word that you haven't had a seizure and you are medication free.
I will contact my friend at the retention center this afternoon to see what he says on the specific requirement for this situation, but it'll be an Army answer and I won't be sure of the other branches.