EEG source localization of the epileptogenic focus in patients with refractory temporal lobe epilepsy, dipole modelling revisited.

EEG source localization of epileptic brain activity is of diagnostic importance in the presurgical evaluation in patients with refractory epilepsy. Localization of the epileptogenic foci by visual inspection of the scalp EEG only is a qualitative and subjective procedure and may be difficult. Techniques such as dipole modelling allow to analyse the characteristics of the generators of the electric activity inside the brain in a quantitative and objective way. Interictal and ictal dipole modelling reveal different types of spike voltage fields and dipole sources. The published literature shows conflicting evidence in different study populations in terms of results and reliability of localization. The reliability of dipole models has been questioned, especially in case of deep mesial temporal lobe sources. In order to validate dipole modelling, comparisons between dipole localizations and intracerebral fields, recorded with depth-electrodes, were made. When interpreting results of dipole modelling, the intrinsic limitations of this technique should be taken into account.