Table 1

Cortical zones defined in presurgical evaluation

Cortical zoneDefinition
Symptomatogenic zoneThe 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 zoneThe area of cortex from which clinical seizures actually originate.
Epileptogenic zoneThe 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 zoneThe area of cortex that generates interictal electrographic spikes
Epileptogenic lesionThe macroscopic lesion seen on the MR scan that is causing the epileptic seizures.