Spatio-temporal characteristics of paroxysmal interictal events in human temporal lobe epilepsy

A spatio-temporal mapping technique was applied to stereotactically-implanted depth electrode recordings (SEEG). This technique was used to study the interictal activity in 13 epileptic patients with temporal lobe epilepsies during the pre-surgical evaluation of their epileptogenic zone prior to surgery. The method further provided the precise localization of distinct interictal activities in each explored structure. The high sensitivity of the technique is showed and has demonstrated the evidence of multiple sources during one single sequence of interictal activity. The stability of such an activity was also demonstrated in each patient. A temporal relationship existed between the activity recorded in different structures. Paroxysmal interictal activity thus appeared as an ordered and successive activation of different interictal foci overlapping each other. In this way it was possible to distinguish two different types of activities; primary foci that are activated independently of each other, and secondary foci activated by the primary foci. Finally, in addition to the source localization of interictal activity, the problem of detection and discrimination of the different components must be considered.