More often than not antiepileptic drugs, like Dilantin, Lamictal, Keppra, Valproic acid, Phenobarbitol, Tegretol, etc. alter the underlying brain processes just enough to increase the difficulty for any seizure process to occur. This is how anticonvulsants effectively manage epilepsy.

Taking an anticonvulsant is similar to taking an antihypertensive (medication to treat high blood pressure) and thereby managing all the adverse effects of high blood pressure. For most people who have seizures antiepileptic medication protects them from having seizures, and so protects them from the adverse effects of recurrent seizures.

However, for some people, anticonvulsant medication alone is not effective enough to prevent their seizures.

Often this is because the seizure network (group of dancers who often prefer to march in step rather than perform the complex ballet dance) is so abnormal that medication, even at toxic doses, does not reduce the likelihood of seizure manifestation enough.

Theoretically, if enough medication is delivered to the epileptic network, it will be controlled. However, such high levels of medication will affect the normal brain networks, causing adverse side effects such as lethargy, imbalance, nausea, and other problems that are unacceptable. The problem is one of getting the medication just to the area of the brain where it is needed, which is not yet possible.

Since the medications go everywhere in the body and throughout the brain in a non-selective manner, the medication affects the normal brain areas as well as the abnormal regions. Fortunately, the abnormal epileptic network is often so abnormal, that it does not contribute to normal brain function. That is, this abnormal area where the seizure begins, does not do anything that is important to everyday function, so it can be removed without causing a loss of normal function. This is the fundamental concept of epilepsy surgery.