Objectives In patients with mesial temporal lobe epilepsy (mTLE) and normal MRI, anterior temporal lobectomy sparing the hippocampus might be considered because of the risk of post-operative memory deficit. However, it is unclear whether some patients with normal MRI and non-invasive EEG and semiological pattern highly suggestive of mesial temporal seizures demonstrate a seizure onset network sparing the hippocampus, potentially warranting surgery. Methods A retrospective study of 17 patients with mTLE epilepsy and normal MRI who underwent SEEG. Only patients whose non-invasive presurgical data suggested an unilateral mesial temporal epileptogenic zone (EZ), as defined by combination of ictal semiology and ictal EEG during scalp video-EEG, were included. SEEG data were analyzed using both visual and quantitative approaches. Two EZ organization were defined: (i) EZ involved the hippocampus at the onset of the ictal discharge (HIP group): (ii) patients in whom a delay>1sec was observed between the seizure onset and the involvement of the hippocampus (nHIP group). Non-invasive clinical and functional imaging data, as well as post-operative outcomes, were compared across groups. Results Eleven patients were included in HIP group and 6 in the nHIP group. In the nHIP group, the maximal epileptogenicity was in the amygdala in five patients and in the entorhinal cortex in one. The hippocampus normalized interictal spiking activity was not different between groups. None of the patients characteristics collected during the non-invasive presurgical workup was associated with the SEEG-based organization of the EZ. Twelve patients underwent a surgical resection, including temporal cortectomy sparing hippocampus in six. Seizure and neuropsychological post-operative outcomes were similar. Conclusion In patients with MRI-normal mTLE, SEEG should be included in the surgical decision-making process because seizure organization cannot be predicted from non-invasive investigations. When hippocampus is not included in the EZ, temporal resection sparing the hippocampus can be considered.

Background: Visceral and emotional sensations (VES) are frequently reported during epileptic seizures. To date, the underlying mechanisms and the location of brain areas involved in the processing of these sensations remain unclear. The aim of our study is to characterize the type and frequency of VES evoked by electrical stimulations performed all over the cortical mantle and to assess whether they might be related to specific brain structures. Methods : We reviewed 12,088 bipolar stimulations performed in 203 patients using stereotactically implanted depth electrodes, during the presurgical evaluation of drug-refractory epilepsy, at Neurological Hospital in Lyon (France). VES were divided into viscero-sensitive (feelings in the throat, thorax or abdomen), viscero-vegetative (flush, nausea, feeling of tachycardia and dyspnea) and viscero-psychic sensations (fear, anxiety). Univariate analysis and then conditional logistic regression were used to assess the association between VES and localization of the stimulated contacts. Results : 543 stimulations evoked VES (4.26%). Stimulations of insulo-limbic structures (amygdala, anterior and posterior insula, anterior and mid-cingulate cortex, hippocampus and parahippocampus) were significantly more associated with VES than those of extra limbic structures (p<0.0001). Preferential implication of certain brain structures, depending on the type of visceral responses was evidenced: temporo-mesial structures (amygdala, hippocampus and parahippocampus) and insula for viscero-sensitive sensations; amygdala, insula and mid-cingulate cortex for viscero-vegetative sensations; temporo-mesial structures and anterior cingulate cortex for emotional sensations. Conclusion : These data can help to localize the epileptogenic zone in seizures with visceral sensations, and also bring insights in the discussion on the mechanisms of interoception.

Medically treated patients suffering from tuberous sclerosis complex (TSC) have less than 30% chance of achieving a sustained remission. Both the international TSC consensus conference in 2012, and the panel of European experts in 2012 and 2018 have concluded that surgery should be considered for medically refractory TSC patients. However, surgery remains currently underutilized in TSC. Case series, meta-analyses and guidelines all agree that a 50 to 60% chance of long-term seizure freedom can be achieved after surgery in TSC patients and a presurgical work-up should be done as early as possible after failure of two appropriate AEDs. The presence of infantile spasms, the second most common seizure type in TSC, had initially been a barrier to surgical planning but is now no longer considered a contraindication for surgery in TSC patients. TSC patients undergoing presurgical evaluation range from those with few tubers and good anatomo-electro-clinical correlations to patients with a significant “tuber burden” in whom the limits of the epileptogenic zone is much more difficult to define. Direct surgery is often possible in patients with a good electro-clinical and MRI correlation. For more complex cases, invasive monitoring is often mandatory and bilateral investigations can be necessary. Multiple non-invasive tools have been shown to be helpful in determining the placement of these invasive electrodes and in planning the resection scheme. Additionally, at an individual level, multimodality imaging can assist in identifying the epileptogenic zone. Increased availability of investigations that can be performed without sedation in young and/or cognitively impaired children such as MEG and HR EEG would most probably be of great benefit in the TSC population. Of those selected for invasive EEG, rates of seizure freedom following surgery are close to cases where invasive monitoring is not required, strengthening the important and efficient role of intracranial investigations in drug-resistant TSC associated epilepsy.

Epilepsy related to malformations of cortical development is frequently drug resistant or requires heavy medication, therefore surgery is key in their management. The role of stereotactic surgery has recently changed the diagnosis and treatment of focal cortical dysplasias (FCD), hypothalamic hamartomas (HH) and periventricular nodular heterotopias (PNH). In HH, radiosurgery using Gammaknife® leads to 60 % of seizure control and is associated with excellent neuropsychological results without significant endocrine function impairment. The seizure control rate is even higher (more than 80 %) with monopolar multiple stereotactic thermocoagulations and Laser interstitial Thermal Therapy (LiTT). While the first technique is associated with a 2 % complications rate (but with excellent neuropsychological outcomes), the latest has up to 22 % side effects in some series. All three of these techniques have encouraging results, but controlled studies are still lacking to provide evidence-based new therapeutic algorithms. With regard to the PNH, surgical management has long been limited by the depth of the lesions and their close anatomical relations with the functional brain connectome. Stereotactic approaches required to perform a SEEG, to locate the part of the PNH responsible for the seizure onset, are later followed by a stereotactic lesioning procedure, therefore doubling the bleeding risk. That is why SEEG-guided radiofrequency-thermocoagulation (SEEG guided-RF-TC), which makes it possible to perform these two steps in a single procedure, was considered as a promising option. A recent meta-analysis confirmed this intuition and reported 38 % of seizure-free patients and 81 % of responders with only 0.3 % of complications, making this approach the first treatment line, followed by LiTT. Among the multiple advances in the FCD identification by non-invasive investigations, a new modality of per-operative diagnostic procedure, the three-dimensional electrocorticography may lead to simplify the preoperative investigation and enhance the accuracy of FCD delineation. Evidence is nevertheless still insufficient to validate this promising concept. Conventional surgical resection has also been concerned by significant conceptual advances during the past few years, in particular with the development of the hodotopic approach, initially in oncologic surgery. Associated with a better understanding of neuroplasticity in epilepsy and the setting up of functional mapping during SEEG or during awake surgery, the possibility of surgical resections grew up. A short-term perspective in this field, when surgical resection remains impossible, would be to target crucial nodes of the epileptic network, distinct from the core functional connectome.

Electrical stimulations of the insula performed during stereo-electro-encephalography (SEEG) reproduce the ictal symptoms observed during the development of insular seizures and are also a unique opportunity to provide a functional mapping of the insular cortex. We provide here a functional mapping of the insular cortex obtained by electrical stimulation, based on our previous work and a review of literature. The most frequent responses to insula stimulation were somatosensory sensations followed by visceral responses. Then, in decreasing order of frequency, auditory sensations, vestibular illusions, speech impairment, gustato-olfactory sensations and motor reactions were evoked. A bipolar organization could be evidenced with a posterior part assigned to somatosensory functions and notably to pain perception; and an anterior part assigned to visceral functions. Although some degree of spatial segregation could be evidenced, there was a clear spatial overlap between the representations of the different types of responses. These data provide a better understanding of physiological insular functions, insula seizures semiology and a prediction of post-surgical deficits. Insula is the only cortical region where stimulations demonstrate such a multi-modal representation, perhaps supporting its integrative functions of polymodal inputs.

After the early attempts of intra-operative electrocorticography and insulectomy in the 1950s, the notion of insular lobe seizures was largely forgotten for decades. It is only since the late 1990s that the recent technique of stereo-electroencephalography (SEEG) enabled preoperative diagnosis of insular origin seizures and thus gave rise to a renewed interest for this ill-defined electroclinical entity. Owing to the multiple functional roles of insula and its extensive connectivity with adjacent as well as distant brain structures, insular lobe seizures present with a combination or series of diverse subjective and objective symptoms. In this review, we summarize current knowledge on the semiology of insular origin seizures. The following two distinct forms of clinical presentation have been recognized: 1) Seizures with predominant insulo-perisylvian symptoms, most notably paraesthesia and cervico-laryngeal discomfort. The former typically involves a large/bilateral cutaneous territory and can be perceived as cold, hot, or painful sensations. The latter ranges from slight dyspnea to strong sensation of strangulation. Other symptoms include epigastric discomfort/nausea, hypersalivation, auditory, vestibular, gustatory, and aphasic symptoms. 2) Nocturnal hyperkinetic seizures with/without tonic elevation of upper limbs, masquerading as fronto-mesial seizures. Patients are usually not fully aware of their symptoms despite preserved contact and organized behavior to others. Ipsilateral eye blinking can be observed. These two patterns often occur in succession or simultaneously. This characteristic combination and progression of ictal symptoms orients us strongly towards an insular origin of seizure, a better understanding of which is a crucial key to further optimize modern SEEG strategy.

Le but de cette étude pilote est d’évaluer l’intérêt et la faisabilité d’une nouvelle méthode, l’électro-corticographie tridimensionnelle (3D-ECoG), pour définir en peropératoire les limites de la zone épileptogène lorsque celle-ci est en rapport avec une dysplasie corticale focale (DCF) de type II. De 2015 à 2016, tous les patients du CHU de Lyon présentant une épilepsie focale pharmaco-résistante en rapport avec une DCF de type II ont été inclus. La DCF était suspectée sur le bilan préopératoire non invasif ou lors d’une SEEG. Le critère de jugement principal était la survenue, sur les bases de la 3D-ECoG, d’une modification du schéma de résection prévu lors du bilan préopératoire. Les critères secondaires d’évaluation étaient la faisabilité de la technique (obtention sous anesthésie avec un protocole AIVOC au propofol de la signature électrophysiologique de la DCF de type II) et la sécurité (survenue de complication). Cinq patients ont été inclus dont quatre avaient bénéficié d’une stéréo-électro-encéphalographie (SEEG) avant la chirurgie. Trois patients ont bénéficié d’une cartographie fonctionnelle réalisée en peropératoire. Le schéma de résection a été modifié chez quatre des cinq patients suite à la réalisation de la 3D-ECoG (extension de la zone réséquée). Dans tous les cas, la signature électrophysiologique de la DCF de type II a pu être enregistrée durant la 3D-ECoG. Par ailleurs la résection de la zone épileptogène n’a été limitée chez aucun patient dans les suites de la cartographie fonctionnelle peropératoire. Aucune complication n’est survenue. Le diagnostic de DCF de type II a été confirmé par l’analyse anatomopathologique chez tous les patients. Cette étude pilote suggère un intérêt de la 3D-ECoG pour la définition peropératoire des zones épileptogènes en rapport avec une DCF de type II ainsi que le caractère faisable et sûr de cette technique et encourage donc la poursuite des recherches dans cette direction.

Objective: In this study we investigated the electrical characteristics of seizures recorded by stereo EEG (SEEG) in a cohort of patients with bitemporal lobe epilepsy (BTLE), in the attempt to verify the presence/absence of different seizure patterns and to identify good surgical candidates.Methods: We retrospectively reviewed 14 consecutive patients with medically refractory BTLE confirmed by scalp video-EEG (VEEG) recording of bitemporal independent or non-lateralizing seizure onset. All patients had a comprehensive evaluation including history and neurologic examination, MRI, scalp VEEG and SEEG monitoring. Neuropsychological, Wada testing and FDG-PET were performed in most patients. When temporal lobe resection was performed (7 cases), the postoperative follow-up was of at least 1 year.Results: Intracranial EEG (SEEG) revealed that only 4/14 (29%) patients were suffering of unilateral TLE. Two groups of patients with distinct SEEG patterns of seizures were identified: a temporo-mesial origin of seizures was the only SEEG pattern observed in 8 patients (Group 1); in 6 patients seizures originated from multiple onset zones in mesial and lateral temporal cortex or from extra-temporal cortex (Group 2). All patients of group 1 (except one who refused surgery) underwent surgery and had a favorable outcome (6 Engel class I; one Engel's class II). The side of surgery was not necessarily the one responsible for the majority of recorded seizures. It was chosen on the basis of MRI findings and consistency of data from presurgical functional investigations, mostly memory assessment and Wada test.Significance: In patients with suspected BTLE, SEEG proved to be useful in identifying the origin of seizures. Good surgical outcome can be obtained after unilateral resection in patients with bilateral independent seizure onsets or sequential mesial temporal involvement on SEEG if the side of surgery is chosen considering multimodal data. (C) 2016 Elsevier B.V. All rights reserved.

Motor cortex stimulation for pain relief has shown its usefulness but also its limits. In the search for new targets, one can stimulate relatively high (e.g. DLPFC) or low level cortical areas. The posterior insula-medial operculum is one of the earliest areas to process nociceptive information but is a difficult target. We addressed its stimulation along two experimental lines: tDCS and intra-cranial stimulation.

The hippocampus is a structure frequently involved in epilepsy, especially in partial drug-resistant forms. In addition, some hippocampal pathologies are associated with specific types of epilepsy presenting specific clinical courses and requiring specific treatments. Considering these major implications for treatment, morphological investigations of the hippocampus are crucial for epileptic patients. Indeed, discovery of hippocampal sclerosis may (depending on the clinical and electrophysiological findings) lead to the diagnosis of mesial temporal lobe epilepsy (MTLE). If the diagnosis of MTLE is retained in a case of drug-resistance, surgery may be proposed without invasive phase II investigations such as stereoelectroencephalograpy. In other instances, hippocampal abnormalities may be associated with epilepsy, but without the same value for localizing the ictal onset zone. Hippocampal dysgenesis is a strong argument for non-temporo-mesial ictal onset ipsilateral to the malformation. We describe here the specific MRI modalities adapted for hippocampal investigations and the radiological signs of hippocampal pathologies associated with epilepsy (especially hippocampal sclerosis and hippocamal dysgenesis). Hippocampus morphological investigations in epilepsy require specific MRI modalities and appropriate knowledge of the specific signs of each pathology. Careful analysis is crucial since the results may have a major impact on the therapeutic management of epileptic patients.

The Wada test was adapted from the procedure described by Wada in 1964. It still has a role in the prognostic evaluation of memory disorders after mesial temporal lobectomy. The test consists of injecting a short-acting anesthetic into one hemisphere, under continuous EEG monitoring and during carotid catheterization, to verify the function of contralateral structures. Intracranial EEG recordings deliver signals with few artifacts, and which are quite specific of the zone explored. Three types of electrodes are in common use: (a) foramen ovale (FO) electrodes: electrodes can be inserted directly, without any stereotactic procedure, to provide easy and comparative EEG recordings of the lower and middle portions of the temporal lobe close to the hippocampus. These allow validation of the temporal lobe origin of seizures using FO electrodes recording coupled with scalp EEG; (b): subdural strip or grip electrodes. This relatively aggressive technique carries infectious and hemorrhagic risks and does not allow the exploration of deep cortical structures. However, it permits precise functional cortical mapping via electrical stimulation because of dense and regular positioning of electrodes over the cortical convexity; (c) stereotactically implanted depth electrodes (stereo-electroencephalography [SEEG]). Electrodes are individually planned and inserted within the brain parenchyma through small burr holes. This technique is less aggressive than subdural grid exploration. However it offers relatively limited spatial sampling that may be less well adapted to precise functional evaluation. It allows recording from deep cortical structures and can be argued to be the gold standard of presurgical EEG exploration.

L’électroencéphalogramme (EEG) permet une analyse fonctionnelle du signal électrique cérébral et constitue l’examen de référence pour analyser les processus électrophysiologiques sous-tendant l’épilepsie mais également de nombreux autres dysfonctionnements du système nerveux central. Les examens d’imagerie morphologique apportent des renseignements complémentaires de l’EEG mais ne peuvent se substituer à cet outil d’analyse fonctionnelle. L’EEG a de plus l’avantage d’être non invasif, facile à réaliser et à contrôler quand un suivi est nécessaire, y compris au lit du patient. Face à l’évolution des connaissances, des techniques et des indications, une actualisation des recommandations sur l’EEG a été jugée nécessaire par la Société de Neurophysiologie Clinique de Langue Française (SNCLF) et la Ligue Française contre l’Épilepsie (LFCE). Cet article aborde la méthodologie adoptée pour ce travail de recommandations, précise les différentes thématiques détaillées dans les chapitres suivants et reprend les fiches synthétiques de recommandation de chacun de ces chapitres ainsi que des propositions de rédaction du compte-rendu d’EEG. La revue de la littérature n’a pas permis d’apporter une réponse à certaines questions pour lesquelles un avis d’experts a cependant été exprimé par le groupe de travail et de lecture en complément des recommandations.

Electroencephalography allows the functional analysis of electrical brain cortical activity and is the gold standard for analyzing electrophysiological processes involved in epilepsy but also in several other dysfunctions of the central nervous system. Morphological imaging yields complementary data, yet it cannot replace the essential functional analysis tool that is EEG. Furthermore, EEG has the great advantage of being non-invasive, easy to perform and allows control tests when follow-up is necessary, even at the patient's bedside. Faced with the advances in knowledge, techniques and indications, the Société de Neurophysiologie Clinique de Langue Française (SNCLF) and the Ligue Française Contre l'Épilepsie (LFCE) found it necessary to provide an update on EEG recommendations. This article will review the methodology applied to this work, refine the various topics detailed in the following chapters. It will go over the summary of recommendations for each of these chapters and underline proposals for writing an EEG report. Some questions could not be answered by the review of the literature; in those cases, an expert advice was given by the working and reading groups in addition to the guidelines.

Purpose: In recent years, there have been series analysing the electro-clinical correlations of insular epilepsy in adult populations. In contrast, the ictal semiology in children with insular epilepsy is poorly described. Considering that early and successful surgery may greatly improve the cognitive outcome and quality of life, it is worthwhile to deepen our knowledge of insular epilepsy in children.Methods: We retrospectively evaluated ten children with drug-resistant focal insular epilepsy who had been consecutively explored with stereoelectroencephalography (SEEG), followed by individually tailored resective surgery that included part of the insula in all cases. A detailed anatomo-electro-clinical analysis of non-invasive EEG and SEEG data was performed. At least one of the electrodes explored the insular cortex. SEEG analysis confirmed that the insular cortex was included in the ictal onset zone.Results: Epilepsy onset was mostly during the first year of life, characterized by subtle seizures as well as spasms and myoclonic seizures. Later on, neurovegetative signs and asymmetric tonic and hypermotor seizures (HMS) dominated the ictal semiology. The epileptogenic zone was frequently wider than insular with frontal and central predominance. In eight patients, the tailored resection included a lesion. In seven patients, an Engel class 1 outcome as well as neuropsychological and behavioural improvement was obtained.Conclusions: SEEG is feasible and useful in children with drug-resistant insular epilepsy which is often characterized by autonomic symptoms as the initial symptoms and should be suspected in cases with HMS, asymmetric tonic seizures and even asymmetric spasms. Early propagation is mostly frontal and central. Analysis of a larger population is required to refine these findings. (C) 2014 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

Background: Previous literature includes numerous reports of acute stereotactic ablation for epilepsy Most reports focus on amygdalotomies or amygdalohippocampotomies, some others focus on various extra-limbic targets. These stereotactic techniques proved to have a less favourable outcome than that of standard surgery, so that their rather disappointing benefit/risk ratio explains why they have been largely abandoned.However, depth electrode recordings may be required in some cases of epilepsy surgery to delineate the best region of cortical resection. We usually implant depth electrodes according to Talairach's stereo electroencephalography (SEEG) methodology Using these chronically implanted depth electrodes, we are able to perform radiofrequency (RF)-thermolesions of the epileptic foci. This paper reports the technical data required to perform such multiple cortical thermolesions, as well as the results in terms of seizure outcome in a group of 41 patients.Technical data: Lesions are placed in the cortex areas showing either a low amplitude fast pattern or spike-wave discharges at the onset of the seizures. Interictal paroxysmal activities are not considered for planning thermocoagulation sites. All targets are first functionally evaluated using electrical stimulation. Only those showing no clinical response to stimulation are selected for thermolesion, including sites located inside or near primary functional area.Lesions are performed using 120 mA bipolar current (Soy), applied for 10-30 sec. Each thermocoagulation produces a 5-7 mm diameter cortical lesion. A total of 2-31 lesions were performed in each of the 41 patients. Lesions are placed without anaesthesia.Results: 20 patients (48.7%) experienced a seizure frequency decrease of at least 50% that was more than 80% in eight of them. One patient was seizure free after RF thermocoagulation. in 21 patients, no significant reduction of the seizure frequency was observed. Amongst the characteristics of the disease (age and sex of the patient, lobar localization of the EZ) and the characteristics of the thermocoagulations (topography lateralization, number, morphology of the lesions on MRI) no factor was significantly linked to the outcome. However, the best results were clearly observed in epilepsies symptomatic of a cortical development malformation (CDM), with 67% of responders in this group of 20 patients (p = 0.052). Three transient post-procedure side-effects, consisting of paraesthetic sensations in the mouth (2 cases), and mild apraxia of the hand, were observed.Conclusion: SEEG-guided-RF-thermolesioning is a safe technique. Our results indicate that such lesions can lead to a significant reduction of seizure frequency Our experience suggests that SEEG-guided RF thermocoagulation should be dedicated to drug-resistant epileptic patients for whom conventional resection surgery is risky or contra-indicated on the basis of invasive pre-surgical evaluation, particularly those suffering from epilepsy symptomatic of cortical development malformation.