Evidence for spreading seizure as a cause of theta-alpha activity electrographic pattern in stereo-EEG seizure recordings.

Intracranial electroencephalography is a standard tool in clinical evaluation of patients with focal epilepsy. Various early electrographic seizure patterns differing in frequency, amplitude, and waveform of the oscillations are observed. The pattern most common in the areas of seizure propagation is the so-called theta-alpha activity (TAA), whose defining features are oscillations in the θ - α range and gradually increasing amplitude. A deeper understanding of the mechanism underlying the generation of the TAA pattern is however lacking. In this work we evaluate the hypothesis that the TAA patterns are caused by seizures spreading across the cortex. To do so, we perform simulations of seizure dynamics on detailed patient-derived cortical surfaces using the spreading seizure model as well as reference models with one or two homogeneous sources. We then detect the occurrences of the TAA patterns both in the simulated stereo-electroencephalographic signals and in the signals of recorded epileptic seizures from a cohort of fifty patients, and we compare the features of the groups of detected TAA patterns to assess the plausibility of the different models. Our results show that spreading seizure hypothesis is qualitatively consistent with the evidence available in the seizure recordings, and it can explain the features of the detected TAA groups best among the examined models

Indications and limits of stereoelectroencephalography (SEEG)

International audienceEpilepsy surgery is now an accepted treatment to achieve seizure control in carefully selected patients, both children and adults, suffering from drug-resistant focal epilepsy. Although surgical strategies can often be defined on the basis of non-invasive diagnostic procedures, and despite the recent advances in this field, an increasing number of more complex cases requires invasive EEG (iEEG) to provide precise information on the localization of the epileptogenic zone (EZ), its relationships with eloquent cortex (EC), and the feasibility of a tailored surgical resection. Stereoelectroencephalography (SEEG) is one of the iEEG techniques currently used in the presurgical work-up, and it is well-distinguished from other invasive techniques, such as subdural grids and strips. SEEG depth electrodes enable exploration of deeply located structures and lesions, and of buried cortex, which are not easily assessable by subdural or other iEEG methods. Simultaneous recording of SEEG signals from deep and superficial brain structures allows, when the position of each electrode is precisely determined, delineation of a three-dimensional, spatial and temporal organization of epileptic activities. In the following chapter we discuss some specific indications (temporal or extra-temporal, lesional or non-lesional epilepsies) as well as the limits of the SEEG technique, with respect to some epileptological issues during presurgical evaluation

Anatomical electroclinical correlations during an SEEG-recorded seizure with autoscopic hallucination

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Anatomical electroclinical correlations during an SEEG-recorded seizure with autoscopic hallucination

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Comparaison du métabolisme cérébrale de la TEP cérébrale au 18F-FDG aux zones d’épileptogénicité de la SEEG chez les patients opérés pour épilepsie pharmacorésistante

Introduction Le bilan pré-chirurgical des patients épileptiques souffrant d’une forme réfractaire au traitement médical a pour objectif de délimiter la zone épileptogène (zone minimale à réséquer pour obtenir une disparition complète des crises). Il comprend une IRM cérébrale, une électroencéphalographie (EEG) voire une stéréo-EEG (SEEG), une TEP-TDM cérébrale au 18F-FDG et un bilan neuropsychologique. La SEEG est un examen invasif comprenant certains risques (chirurgicaux, infectieux, hémorragiques…). Des études ont trouvé des concordances entre l’hypométabolisme cérébral de la TEP au 18F-FDG à l’échelle d’une aire cérébrale et les résultats de la SEEG. Nous avons comparé le métabolisme de la TEP cérébrale au 18F-FDG en regard de chaque plot d’électrode de la SEEG situé dans la substance grise aux zones d’épileptogénicité décrites à la SEEG chez 15 patients opérés pour épilepsie réfractaire au traitement médical, afin d’évaluer si les variations fines du métabolisme étaient liées à ces zones. Matériels Parmi tous les patients opérés à Strasbourg pour épilepsie réfractaire au traitement médical entre février 2014 et décembre 2016, nous avons inclus les 15 patients qui avaient réalisé une TEP cérébrale au 18F-FDG, une IRM cérébrale et pour lesquels nous avons obtenu une relecture complète de la SEEG. Le suivi postopératoire était d’au moins un an. Le schéma des électrodes de SEEG a été fusionné avec l’IRM cérébrale et la TEP cérébrale au 18F-FDG. Pour chaque groupement de plots d’électrodes (GPE) situé dans la substance grise, le métabolisme de la TEP a été noté sur une échelle de 1 à 4 (hypométabolisme intense, hypométabolisme modéré, métabolisme normal, hypermétabolisme) et l’épileptogénicité a été analysée sur la SEEG et classée en 4 catégories (zone d’initiation, zone irritative, zone de propagation, zone saine). Un test de régression logistique a comparé le métabolisme de la TEP et les zones SEEG. Résultats/Conclusion La comparaison du métabolisme des 486 GPE aux zones d’épileptogénicité a permis de mettre en évidence une association entre la présence d’un métabolisme pathologique et la localisation des GPE dans les zones d’initiation et irritative et entre un métabolisme normal et la localisation des GPE dans la zone saine, avec des anomalies métaboliques progressivement plus présentes et plus intenses à proximité de la zone d’initiation. Les GPE hypermétaboliques ne semblaient pas être liées à une zone particulière décrite à la SEEG

Atonic seizures in children with surgically remediable epilepsy: a motor system seizure phenotype?

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Atonic seizures in children with surgically remediable epilepsy: a motor system seizure phenotype?

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VEP atlas: An anatomic and functional human brain atlas dedicated to epilepsy patients

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High Frequency Oscillations and spikes running down after SEEG-guided thermocoagulations in the epileptogenic network of periventricular nodular heterotopia

International audienceObjective: Epilepsy associated with Periventricular Nodular Heterotopia (PNH) is characterized by complex relationships between the heterotopic and the normotopic cortex during the interictal state and at seizure onset. High frequency oscillations (HFO) have been proposed as a marker of epileptogenicity that might reflect disease activity. The effects of thermocoagulations on epileptogenicity in this context remain unknown. We aimed to investigate the interictal HFO-and spike profiles of different cortical structures before and after two consecutive SEEG-guided thermocoagulations, in correlation with seizure outcome, in a patient with PNH-related drugresistant epilepsy. Methods: The epileptogenic zone (EZ) was defined by SEEG analysis based on the Epileptogenicity Index. Interictal spikes, ripples (80-250Hz) and fast ripples (FR, 250-330Hz) were analyzed within the heterotopia, the temporal neocortex and the hippocampus. Results: The SEEG recordings revealed a distributed EZ involving the heterotopia and the posterior temporal neocortex. Both structures were targeted by thermocoagulations. Background spikes, ripples and FR-rates were significantly higher in PNH compared to the normotopic cortex. A drastic reduction of spikes (by over 80%) and absence of FR were demonstrated both in the PNH and in the neocortex during the second SEEG exploration 6 months after the first thermocoagulation, whereas no significant difference was observed in the posterior hippocampus. Ripples were significantly reduced by the first and suppressed by the second thermocoagulation within the three structures. Seizures relapsed after two months but decreased in frequency after the first thermocoagulation. Sustained seizure-freedom was achieved only after the second procedure. Conclusions: Our data demonstrate the running down of interictal HFO and spikes within the epileptogenic network following thermocoagulations of heterotopic and normotopic sites involved at seizure onset. This dynamics was in good correlation with significantly improved seizure control. Significance: Combination of ictal and different interictal markers of epileptogenicity, including HFO and spike analysis, is important to get the full picture of the epileptogenic zone and could help to evaluate the disease activity