Table 1.

Definition of some commonly used terminology in stereo-encephalography (SEEG) study.

Concept	Definition	Example
Lesional Zone (LZ)	Site(s) of permanent slow background activity, independent of seizure recurrence.	Tumor, stroke, gliosis, etc.,
Irritative zone (IZ)	Site(s) of abnormal interictal paroxysmal activities. Waveforms may be various and complex. Rarely focal in TLE but spread within cortico-cortical networks.	Spikes, sharp waves, spike and waves, low voltage fast activity.
Second Irritative Zone	A zone that is spatially distinct from the seizure onset and occurrence dependent on primary spikes.	Frequently seen in Temporal lobe epilepsy as synchronic spikes. (See Figure 1).
Epileptogenic Zone (EZ)	Site(s) of “primary organization” of ictal discharge. Triggering this area with cortical stimulation will in theory cause a seizure.
High Frequency Oscillation (HFO)	High frequency interictal and ictal activity in gamma range that has high correlation with the epileptogenic tissue and zone (27)	Seen frequently in focal cortical dysplasia and lesional epilepsy
Afterdischarges (AD)	A seizure pattern following single or repetitive electrical stimulations of a discrete area of the brain by using intracerebral electrodes.	No specific pattern seen; EEG finding is similar to IZ.