The most common epilepsy surgery is the temporal lobectomy where a part of the temporal lobe is removed. That's the most common area where seizures come from in the brain. Risks of removing that include problems with memory, problems with speech. Risks of surgery include infection, stroke, things like that. Those are very rare, less than 1% for major complications. Most people feel that they have a little bit of trouble with their memory or speech, but they are not unable to speak for the most part.
In addition, in the process of determining if someone is a candidate for surgery, testing is done to make sure that we know exactly where the seizures are coming from and whether there is a higher risk to memory or speech so that we can discuss that with the patient and determine whether or not that's the appropriate treatment.