Can epileptologists without access to intracranial EEG use reliably the International League Against Epilepsy classification of the localization-related epileptic syndromes? A stereo-electroencephalographic study.

The goal of the present study was to investigate the reliability of clinical and electroencephalographic (EEG) criteria for the classification of localization-related epileptic syndromes as listed in the Proposals of Revised Classification of Epilepsies and Epileptic Syndromes 1989 (ICE). ICE distinguishes between multiple syndromes within epilepsies of a given lobe. Intracranial recordings were the main element in the development of the revised ICE. Considering that most epilepsy centers have no access to such invasive techniques for precise anatomic localization, it was of interest to assess how accurately the seizure origin could be determined from the scalp EEG and clinical data as reported in ICE. In this retrospective study, we compared the accuracy of the topographic diagnosis made by two groups of physicians evaluating the same patients-one group with and the other without access to results of stereo-EEG (SEEG). Medical files of 87 patients with intractable localization-related epilepsy were analyzed: 38 with frontal, 37 with temporal, 10 with parietal, and 2 with occipital lobe epilepsy were included in the study. All patients underwent previous SEEG and successful cortectomy. Minimum follow-up was 5 years. In most cases, noninvasive techniques and criteria suggested by ICE allowed topographic diagnosis of focal epilepsies according to brain lobe involvement. More detailed diagnosis, localizing the origin of critical activity within a lobe, was often unreliable. Further data are required for a definition of the epileptogenic zone. A spatiotemporal evaluation of critical events, including the intracranial EEG recording, remains the best method for topographic diagnosis of localization-related epilepsy.