Epileptogenic zone

Epilelptogenic Zone (EZ) was originally defined in the ‘50s by Jean Bancaud and Jean Talairach as “the site of the beginning and of primary organization of the epileptic seizures” (La règion <>). This definition has been slightly updated throughout the years by some other authors: Luders H.O., Engel J., Munari C. defined it in ’93 “as the area of cortex that is necessary and sufficient for initiating seizures and whose removal (or disconnection) is necessary for complete abolition of seizures”. EZ must be defined using non invasive and invasive investigations able to provide information about the spatio-temporal structure of the ictal discharge. In fact, the seizure is originated by a paroxysmal dynamic activity that spreads in many directions (“crise comme un ensemble de signes dèterminès essentiellement par une activitè paroxystique dynamique à trajectoire le plus souvent multidirectionelle”). Non invasive investigations should include clinical history, neurological exam, MRI and video-EEG monitoring. Moreover, other neuro-radiological and neuro-physiological modalities can be adopted, such as CT, SPECT, PET, EEG-fMRI, MEG. In about one third of the subjects an invasive recording methodology, such as video-SEEG monitoring, must be performed in order to define tridimensionally the EZ. The definition of the epileptic zone is a crucial step in presurgical evaluation of patient with drug-resistant focal epilepsy.