My MC is an otherwise more or less healthy young man, in his late teens when this story is set. He has tonic-clonic seizures triggered by severe stress and accompanied by an aura. In canon it isn't clear how long he's been having seizures, but general fanon is that it's from a traumatic brain injury when he was younger. The setting the story takes place in isn't quite a recognizable historical period
Short of surgery/something like trephining, the only thing I can see being suggested for him is to avoid what triggers his seizures. This seems like a good idea, but it isn't very doable given his inherently stressful living situation. He's a very unhappy and angry young man, but connected to people of importance -- people have probably suggested it's something akin to possession, but not too loudly.
Terms googled: "treatment + epilepsy", "premodern treatment epilepsy", "historical treatment epilepsy", "renaissance + epilepsy" and (I know this is in no way comprehensive, but) a lot of Wikipedia. Most of the information I can find either relates to the stigmatization of epileptics, which is upsetting but not helpful, or more recent, if still not up to date, options for medication.
I apologize for my ignorance on this subject, any help would be appreciated!