Localization of ictal onset zones in Lennox–Gastaut syndrome (LGS) based on information theoretical time delay analysis of intracranial electroencephalography (iEEG)

Precise localization of ictal onset zones is of great clinical importance for successful surgery in patients with intractable drug-resistant epilepsy. Time delay analysis has been one of the most reliable and most widely used computational electroencephalogram (EEG) analysis methods for localizing ictal onset zones. However, the majority of previous studies have only been applied to the localization of ictal onset zones in focal epilepsy. In the present study, we analyzed intracranial EEG (iEEG) recordings acquired from patients with Lennox–Gaustaut syndrome (LGS), which is a type of intractable, pediatric, secondary generalized epilepsies with bilaterally synchronous ictal epileptiform discharges. To estimate the ictal onset zones from ictal iEEG recordings, we estimated time delays among iEEG signals based on the information theoretical approach. The results of the time delay analysis applied to the iEEG data of four successfully treated LGS patients corresponded well with the surgical resection areas identified by experienced epileptologists and multiple neuroimaging modalities, suggesting that the time delay analysis may provide useful information on the precise locations of ictal onset zones prior to epilepsy surgery in LGS patients.