There's a correspondence between epilepsy and autism. If you have one you are more likely to have another. I don't know that we really have proof that one causes the other. My best guess around why they are connected is that they both involve over active neurology.
I've known kids who have just epilepsy. The one's who came into my care had memory loss after a seizure, which impacted their ability to learn. They really didn't have autistic features. There where some things that they would insist on, reutine wise, but there was always a logical to other people based on what triggers their symptoms. Or in once case, based on the mental age she maintained. (The same as she was before the seizures started - about 2. Two year olds look a lot like autistic kids sometimes. It's just normal development.)