Cortical zones defined in presurgical evaluation
| Cortical zone | Definition |
| Symptomatogenic zone | The area of cortex which, when activated by an epileptiform discharge, produces the initial ictal symptoms; it is usually an area of eloquent cortex, and may be outside the epileptogenic zone. |
| Seizure onset zone | The area of cortex from which clinical seizures actually originate. |
| Epileptogenic zone | The area of cortex that is necessary for the generation of seizures, and must be removed (or disconnected) to render patients seizure-free after surgery; it may be larger than the seizure onset zone and the epileptogenic lesion. |
| Irritative zone | The area of cortex that generates interictal electrographic spikes |
| Epileptogenic lesion | The macroscopic lesion seen on the MR scan that is causing the epileptic seizures. |