Can Epileptologists Without Access to Intracranial EEG Use Reliably the International League Against Epilepsy Classification of the Localization-Related Epileptic Syndromes?

Abstract

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.

Specific Epileptic Syndromes Are Rare Even in Tertiary Epilepsy Centers: A Patient‐oriented Approach to Epilepsy Classification

“…Although MRI results were available in 70% of the adults and 80% of the children, the etiology of the epilepsy was unknown in more than half of the patients in both groups. Other studies found even higher rates (6,17,21–23,28). This is probably due to the higher percentage of patients with MRI examination and the use of dedicated MRI protocols reviewed by expert neuroradiologists (29).…”

Syndromic Diagnosis at the Epilepsy Clinic: Role of MRI in Lobar Epilepsies

“…The topographic diagnosis of LE in this study did not include ILAE sites but included the four major lobes, the rolandic cortex, and the TPO junctional cortex, because a further localization to ILAE sites usually required the use of intracranial electrodes. Rektor et al (24) reported a good agreement between epileptologists with or without access to the intracranial EEG recordings for the localization of the epileptogenic region to major lobes, but a large discrepancy was observed in the localization to more restricted sites. The rolandic cortex was included because seizures originating from this region were readily identifiable clinically, and many patients reported both primary motor and somatosensory symptoms together.…”

“…Over the past decade, magnetic resonance imaging (MRI) has exerted a great impact on the practice of epilepsy management. MRI may detect lesions in 50% to 74% of patients with LE attending an epilepsy clinic (17,18), and the presence of lesions in MRI may provide reliable evidence of seizure origin as well as other important clinical information such as etiology, surgical accessibility and outcome, prognosis, or responses to drug therapy (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29). However, no attempt to incorporate MRI features into the current ICEES has yet been systematically undertaken.…”