Grand Mal Seizures: Anyone found out what's causing your seizures?

My son suffers from Grand Mal seizures and are controlled with Kepra. However, i still have a big concern and was wondering if anyone here has been evaluated by a Neurologist at the Mayo Clinic to find out what is causing the seizures? I would like to know what is involved in the evaluation and diagnostic testing to pin point what may be causing the seizures and if there a cure. Has anyone here found out what is causing your seizures?