My husband has epilepsy, caused by a cortical dysplasia---abnormal brain tissue--which also causes him to have AS behaviors. My understanding is that the disruption of brain function caused by an electrical storm in the brain can, over time, cause AS behaviors. This is especially so depending on the severity and frequency of the seizures, as well as where in the brain the seizures are mostly occurring.
In my husband's case, the lesion and the focal point of his severe and recurrent seizures are in the left frontal and parietal lobes, exactly where speech and language develop. It's no wonder that he has AS behaviors.
From what I have read, there is a link between epilepsy and autism. (Many doctors consider Asperger's to be a form of autism. My husband's doctors in Spain call it Autismo Asperger's.) Not everyone with autism has epilepsy, but a good percentage of people with epilepsy are on the spectrum.