Sandrine Aubert

From mesial temporal lobe to temporoperisylvian seizures: A quantified study of temporal lobe seizure networks

Purpose:  The determination of epileptogenic structures in partial epilepsy is crucial in the context of epilepsy surgery. In this study we have quantified the “epileptogenicity” of mesial temporal lobe structures (M), lateral neocortical regions (L), and extratemporal perisylvian structures (ET) in patients with temporal lobe epilepsy (TLE), in order to classify the brain networks involved in seizure generation.

Déjà-vu in temporal lobe epilepsy: Metabolic pattern of cortical involvement in patients with normal brain MRI

To contribute to the identification of brain regions involved in déjà-vu, we studied the metabolic pattern of cortical involvement in patients with seizures of temporal lobe origin presenting with or without déjà-vu. Using voxel-based analysis of 18FDG-PET brain scans, we compared glucose metabolic rate of 8 patients with déjà-vu, 8 patients without déjà-vu, and 20 age-matched healthy subjects. Patients were selected after comprehensive non-invasive presurgical evaluation, including normal brain MRI and surface electroclinical features compatible with unilateral temporal lobe epilepsy (TLE). Patients with and without déjà-vu did not differ in terms of age, gender, epilepsy lateralization, epilepsy onset, epilepsy duration, and other subjective ictal manifestations. TLE patients with déjà-vu exhibited ipsilateral hypometabolism of superior temporal gyrus and of parahippocampal region, in the vicinity of perirhinal/entorhinal cortex, in comparison either to healthy subjects or to TLE patients without déjà-vu (p<0.05 FDR-corrected). By contrast, no difference was found between patient subgroups for hypometabolism of hippocampus and amygdala. At an individual-level, in comparison to healthy subjects, hypometabolism of both parahippocampal region and superior temporal gyrus was present in 7/8 patients with déjà-vu. Hippocampal metabolism was spared in 3 of these 7 patients. These findings argue for metabolic dysfunction of a medial-lateral temporal network in patients with déjà-vu and normal brain MRI. Within the medial temporal lobe, specific involvement of the parahippocampal region, often in the absence of hippocampal impairment, suggests that the feeling of familiarity during seizures greatly depends on alteration of the recognition memory system.

Clinical, neuropsychological, and metabolic characteristics of transient epileptic amnesia syndrome

Transient epileptic amnesia (TEA) is a recently individualized syndrome occurring in adult patients that includes epileptic seizures with amnestic features and interictal memory disturbances.

Seizure-onset patterns in focal cortical dysplasia and neurodevelopmental tumors: Relationship with surgical prognosis and neuropathologic subtypes.

The study of intracerebral electroencephalography (EEG) seizure‐onset patterns is crucial to accurately define the epileptogenic zone and guide successful surgical resection. It also raises important pathophysiologic issues concerning mechanisms of seizure generation. Until now, several seizure‐onset patterns have been described using distinct recording methods (subdural, depth electrode), mostly in temporal lobe epilepsies or with heterogeneous neocortical lesions.

Intraoperative monitoring in pediatric orthopedic spinal surgery: three hundred consecutive monitoring cases of which 10% of patients were younger than 4 years of age.

Study Design. Analysis of a prospective series of 300 consecutive cases undergoing intraoperative monitoring in pediatric orthopedic spinal surgery, of which 10% were children younger than 4 years. Objective. Determine feasibility and performance of intraoperative monitoring in children younger than 4 years. Analyze distinct physiopathologic mechanisms of relevant alerts. Summary of Background Data. There are few studies in the literature concerning the intraoperative monitoring of children younger than 4 years. During childhood, the development of sensori-motor pathways is dominated by two coexisting phenomena, which have opposite effects: maturation decreasing latencies and height increasing them. Methods. We used intraoperative somatosensory-evoked potentials and neurogenic mixed evoked potentials with a flexible bipolar epidural electrode. Uniform total intravenous anesthesia was used. Results. Values of sensitivity and specificity of the monitoring showed slight differences between patients younger than 4 years versus older patients. There was no false-negative outcome. Various tendencies were highlighted. There were more true positive alerts for secondary etiologies than for idiopathic ones, for revision spinal surgeries than for index ones, and for boys than for girls. There were no more true positive alerts for children younger than 4 years than for older patients whereas the proportion of hemivertebrae was obviously greater for the younger group. Relevant monitoring alerts were more frequent in case of kyphoscoliosis. This is highlighted in case reports. Conclusion. In some cases of kyphoscoliosis, during a posterior-based vertebral column resection, monitoring changes were corrected by positioning a rod that allowed correction of the position of the spine in the sagittal plane. Intraoperative spinal cord monitoring can be performed in children younger than 4 years and allows real-time assessment of spinal functional integrity.

Reading epilepsy from the dominant temporo-occipital region.

Background Reading epilepsy is a rare form of epilepsy, classified among idiopathic, age- and localisation-related (partial) epilepsies as a reflex epilepsy syndrome. Seizures usually consist of myoclonic jerks restricted to the jaw. However, distinct ictal features including visual symptoms and paroxysmal a- or dyslexia are described in some patients. The anatomical substrate of ictogenesis in reading epilepsy remains poorly understood. Methods The authors report here the case of a primary reading epilepsy for which ictal semiology was characterised by visual symptoms and dyslexia, investigated by MRI, interictal high-resolution EEG and PET, ictal video-EEG and SPECT. Brain MRI was normal. Interictal high-resolution EEG was performed with 64 scalp channels, a realistic head model and different algorithms to solve the inverse problem. Results Interictal source localisations highlighted the left occipito-temporal junction. Interictal PET demonstrated bilateral occipito-temporal hypometabolism with left-sided predominance. Ictal EEG showed a rhythmic discharge in left temporo-parieto-occipital junction channels, with left occipito-temporal predominance. MRI fusion of the coregistered subtraction between ictal and interictal SPECT individualised relative hyperperfusion affecting (a) the left occipito-parietal junction area, (b) the left lateral middle and inferior temporal gyri and (c) the left inferior frontal area. Conclusion Besides reading-induced myoclonic jerks of the jaw, a second variant of reading epilepsy exists with clearly partial seizures manifested by visual symptoms and a- or dyslexia. These seizures originate from the occipito-temporal region of the dominant hemisphere, corresponding to the posterior part of the neural network that underlies the function of reading.

18FDG-PET in different subtypes of temporal lobe epilepsy: SEEG validation and predictive value.

The objective of the study was to characterize interictal 18‐fluorodeoxyglucose–positron emission tomography (18FDG‐PET) whole‐brain voxel‐based metabolic patterns among distinct subtypes of temporal lobe epilepsy (TLE), as defined by stereo–electroencephalography (SEEG) and to determine predictive value of PET result on postoperative outcome.

Responders to vagus nerve stimulation (VNS) in refractory epilepsy have reduced interictal cortical synchronicity on scalp EEG.

EEG desynchronization has been proposed to be an important mechanism for antiepileptic effect of vagus nerve stimulation (VNS) but has never been clearly documented in human. The aim of this study was to evaluate impact of VNS on the synchronicity of interictal EEG rhythms. We estimated synchronization between scalp EEG signals using phase lag index (PLI) in 19 patients with chronic VNS therapy. We estimated changes in synchronization between ON and OFF phases and between responder (R) and non-responder (NR) patients. We found that R have a lower global level of synchronization (EEG broadband) than NR (p<0.0001) In addition, ON periods were characterized by lower values in comparison with OFF periods (p<0.001). R had significantly lower global synchronization levels in delta and alpha frequency bands (p<0.0001). Patients responding to VNS have thus a lower level of broadband EEG synchronization than non-responders. Estimating changes of synchronization level is thus a promising tool for predicting response to VNS.

Réseaux épileptogènes associés aux dysplasies corticales et aux tumeurs dysembryoplasiques neuroépithéliales

Introduction Dans la plupart des cas d’epilepsies partielles pharmaco- resistantes, le probleme-cle est la determination precise de la topographie et de l’extension de la Zone Epileptogene (ZE). Objectifs et methodes Nous avons donc utilise un outil recemment mis au point (Bartolomei et al, Brain 2008), permettant de quantifier l’epileptogenicite de differentes structures intracerebrales ; il s’agit de l’Index d’Epileptogenicite (IE), qui analyse les parametres spectraux et temporels de la decharge epileptique. Cette methode permet de mesurer la capacite qu’a une structure cerebrale donnee a generer des decharges rapides et le temps qu’elle met a etre impliquee dans la crise. Cet IE a ete calcule chez 36 patients explores par electrodes intracerebrales (SEEG), et presentant une epilepsie partielle pharmaco-resistante lesionnelle (sur dysplasie corticale focale, ou lesion developpementale type DNET). Resultats Dans notre population, 31 % des patients avaient une seule structure epileptogene (ZE d’organisation focale), alors que 61 % avaient une organisation regionale (en reseau) de leur ZE et 8 % une organisation bilaterale de celle-ci. Par ailleurs, plus le nombre de structures presentant un IE etait eleve, moins le resultat post-operatoire etait satisfaisant. Discussion et conclusion Ainsi, dans le cas des epilepsies lesionnelles, la determination de l’IE peut s’averer utile pour quantifier l’epileptogenicite relative de differentes structures cerebrales, pour determiner l’extension de la ZE, et pour potentiellement optimiser l’etendue de la resection chirurgicale.