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Objective Stereoelectroencephalography (sEEG) is an intracranial encephalography method of expanding use. The need for increased epilepsy surgery access has led to the consideration of sEEG adoption by new or expanding surgical epilepsy programs. Data regarding safety and efficacy are uncommon outside of high‐volume, well‐established centers, which may be less applicable to newer or low‐volume centers. The objective of this study was to add to the sEEG outcomes in the literature from the perspective of a rapidly expanding center. Methods A retrospective chart review of consecutive sEEG cases from January 2016 to December 2019 was performed. Data extraction included demographic data, surgical data, and outcome data, which pertinently examined surgical method, progression to therapeutic procedure, clinically significant adverse events, and Engel outcomes. Results One hundred and fifty‐two sEEG procedures were performed on 131 patients. Procedures averaged 10.5 electrodes for a total of 1603 electrodes. The majority (84%) of patients progressed to a therapeutic procedure. Six clinically significant complications occurred: three retained electrodes, two hemorrhages, and one failure to complete investigation. Only one complication resulted in a permanent deficit. Engel 1 outcome was achieved in 63.3% of patients reaching one‐year follow‐up after a curative procedure. Significance New or expanding epilepsy surgery centers can appropriately consider the use of sEEG. The complication rate is low and the majority of patients progress to therapeutic surgery. Procedural safety, progression to therapeutic intervention, and Engel outcomes are comparable to cohorts from long‐established epilepsy surgery programs.

Background Stereoelectroencephalography (SEEG) allows the identification of deep-seated seizure foci and determination of the epileptogenic zone (EZ) in drug-resistant epilepsy (DRE) patients. We evaluated the accuracy and treatment-associated morbidity of frameless VarioGuide® (VG) neuronavigation-guided depth electrode (DE) implantations. Methods We retrospectively identified all consecutive adult DRE patients, who underwent VG-neuronavigation DE implantations, between March 2013 and April 2019. Clinical data were extracted from the electronic patient charts. An interdisciplinary team agreed upon all treatment decisions. We performed trajectory planning with iPlan® Cranial software and DE implantations with the VG system. Each electrode’s accuracy was assessed at the entry (EP), the centre (CP) and the target point (TP). We conducted correlation analyses to identify factors associated with accuracy. Results The study population comprised 17 patients (10 women) with a median age of 32.0 years (range 21.0–54.0). In total, 220 DEs (median length 49.3 mm, range 25.1–93.8) were implanted in 21 SEEG procedures (range 3–16 DEs/surgery). Adequate signals for postoperative SEEG were detected for all but one implanted DEs (99.5%); in 15/17 (88.2%) patients, the EZ was identified and 8/17 (47.1%) eventually underwent focus resection. The mean deviations were 3.2 ± 2.4 mm for EP, 3.0 ± 2.2 mm for CP and 2.7 ± 2.0 mm for TP. One patient suffered from postoperative SEEG-associated morbidity (i.e. conservatively treated delayed bacterial meningitis). No mortality or new neurological deficits were recorded. Conclusions The accuracy of VG-SEEG proved sufficient to identify EZ in DRE patients and associated with a good risk-profile. It is a viable and safe alternative to frame-based or robotic systems.

Epilepsy is a neurological disorder characterized by recurrent epileptic seizures. Although an increasingly intense research effort has focused on the use of brain signal data to predict or detect epileptic seizures as early as possible, this problem is still computationally challenging. The main challenge is that the patient’s brain signal has strong individual characteristics, and the classification model is easily disturbed by this, which may lead to false predictions, affecting the reliability of the model. Based on the development of brain signal acquisition technology and deep learning, we propose a new type of deep learning model called the Epilepsy Domain Adversarial Neural Network (EDANN) model, which is used to classify epileptic pre-ictal signals. EDANN integrates multiple deep neural networks based on the idea of adversarial learning, which can reduce the impact of the differences between patients on model prediction. The multi-network design in EDANN effectively improves the model training stability and model generalizability. In addition, a unique brain signal processing algorithm is developed to convert signals to data blocks that are ready for pre-ictal classification, and the model may provide an auxiliary diagnosis for early warning of epilepsy. Experimental results on real patient data show that EDANN clearly improved the F1 score by approximately 7.2% compared with the existing models. On a real dataset, our model achieved state-of-the-art results.

Objective: Stereoelectroencephalogram (SEEG) has been widely adapted to detect the electrical activity of patients with epilepsy. Due to the low-quality, large-amount, high-dimensionality characteristics of SEEG data, it is still challenging to comprehensively employ the SEEG signals to automatically and precisely determine the seizure onset zone (SOZ). This is because there is lack of an effective criterion for clinicians to select the target electrodes, which is of great importance for SOZ localization. Methods: We propose a SOZ localization method via analyzing the long-term SEEG monitoring for preoperative planning of epilepsy surgery. Considering that high frequency oscillations can reflect physiological brain activity of epileptic patients, we first extract the high-frequency features of the SEEG signals and utilize the convolutional neural network (CNN) to detect the interictal and seizure segments. Then we propose a novel criterion, namely adaptive high frequency epileptogenicity index (AHFEI), to determine the target electrodes. Results: We compare our SEEG-determined target electrodes with three preoperative planning of successful focal epilepsy resective surgery cases, finding that most localization results of our method are in consistent with clinical successful decision making, while the performance of our method outperforms than the state-of-the-art method for SOZ localization. Conclusion: Our SEEG-determined SOZ localization method can assist clinicians in preliminarily selecting the potential target electrodes according to long-term SEEG data automatically and effectively. Clinical Impact: The proposed automatic SOZ localization method has achieved satisfactory performance in the preliminary study, which has the great potential to be integrated into function-structure fused clinical decision-making system.

Stereo-electroencephalography (SEEG) has gained global popularity in recent years. In Japan, a country in which invasive studies using subdural electrodes (SDEs) have been the mainstream, SEEG has been approved for insurance coverage in 2020 and is expected to gain in popularity. Some concepts supporting SEEG methodology are fundamentally different from that of SDE studies. Clinicians interested in utilizing SEEG in their practice should be aware of those aspects in which they differ. Success in utilizing the SEEG methodology relies heavily on the construction of an a priori hypothesis regarding the putative seizure onset zone (SOZ) and propagation. This article covers the technical and theoretical aspects of SEEG, including the surgical techniques and precautions, hypothesis construction, and the interpretation of the recording, all with the aim of providing an introductory guide to SEEG.

International audience; Interictal electrical source imaging (ESI) encompasses a risk of false localization due to complex relationships between irritative and epileptogenic networks. This study aimed to compare the localizing value of ESI derived from ictal and inter-ictal EEG discharges and to evaluate the localizing value of ESI according to three different subgroups: MRI lesion, presumed etiology and morphology of ictal EEG pattern. We prospectively analyzed 54 of 78 enrolled patients undergoing pre-surgical investigation for refractory epilepsy. Ictal and inter-ictal ESI results were interpreted blinded to- and subse-quently compared with stereoelectroencephalography as a reference method. Anatomical concordance was assessed at a sub-lobar level. Sensitivity and specificity of ictal, inter-ictal and ictal plus inter-ictal ESI were calculated and compared according to the different subgroups. Inter-ictal and ictal ESI sensitivity (84% and 75% respectively) and specificity (38% and 50% respectively) were not statistically different. Regarding the sensitivity, ictal ESI was never higher than inter-ictal ESI. Regarding the specificity, ictal ESI was higher than inter-ictal ESI in malformations of cortical development (MCD) (60% vs. 43%) and in MRI positive patients (49% vs. 30%). Within the ictal ESI analysis, we showed a higher specificity for ictal spikes (59%) and rhythmic discharges > 13 Hz (50%) than rhythmic discharges < 13 Hz (37%) and (ii) for MCD (60%) than in other etiologies (29%). This prospective study demonstrates the relevance of a combined interpretation of distinct inter-ictal and ictal analysis. Inter-ictal analysis gave the highest sensitivity. Ictal analysis gave the highest specificity especially in patients with MCD or a lesion on MRI.

International audience; Stereoelectroencephalography-guided radiofrequency-thermocoagulation (SEEG-guided RF-TC) consists of coupling SEEG investigation with RF-TC stereotactic lesioning directly through the recording electrodes. In this systematic review the surgical technique, indications, and outcomes are described. Maximum accuracy is reached when a frame-based procedure with a robotic assistance and a per-operative vascular X-ray imaging are performed. Monitoring of the lesioning procedure based on the impedance, a sharp modification of which indicates that the thermocoagulation has reached its maximum volume, allows the optimization of the lesion size. The first indication concerns patients in whom a SEEG is required to determine whether surgery is feasible and in whom resection is indeed possible. Even if surgery is performed owing to insufficient efficacy of SEEG-guided RF-TC, the procedure remains interesting owing to its high positive predictive value for good outcome after surgery. The second indication concerns patients in whom phase I non-invasive investigations have concluded to surgical contraindication and who may still undergo SEEG in a purely therapeutic perspective (small deep zones inaccessible to surgery and network nodes of large epileptic networks). Lastly, SEEG-guided RF-TC can be considered as a first-line treatment for periventricular nodular heterotopia (PNH). Independently of indication, the overall seizure-free rate is 23% and the responder rate is 58%. The best results are obtained for PNH (38% seizure-free and 81% responders), while the worst results have been reported for temporal lobe-epilepsy in a dedicated study. The overall complication rate is 2.5%. More evidence is needed to help determine the exact place of SEEG-guided RF-TC in the surgical management algorithm.

International audience; Despite being of primary importance for fundamental research and clinical studies, the relationship between local neural population activity and scalp electroencephalography (EEG) in humans remains largely unknown. Here we report simultaneous scalp and intracerebral EEG responses to face stimuli in a unique epileptic patient implanted with 27 intracerebral recording contacts in the right occipitotemporal cortex. The patient was shown images of faces appearing at a frequency of 6 Hz, which elicits neural responses at this exact frequency. Response quantification at this frequency allowed to objectively relate the neural activity measured inside and outside the brain. The patient exhibited typical 6 Hz responses on the scalp at the right occipitotemporal sites. Moreover, there was a clear spatial correspondence between these scalp responses and intracerebral signals in the right lateral inferior occipital gyrus, both in amplitude and in phase. Nevertheless, the signal measured on the scalp and inside the brain at nearby locations showed a 10-fold difference in amplitude due to electrical insulation from the head. To further quantify the relationship between the scalp and intracerebral recordings, we used an approach correlating time-varying signals at the stimulation frequency across scalp and intracerebral channels. This analysis revealed a focused and right-lateralized correspondence between the scalp and intracerebral recordings that were specific to the face stimulation is more broadly distributed in various control situations. These results demonstrate the interest of a frequency tagging approach in characterizing the electrical propagation from brain sources to scalp EEG sensors and in identifying the cortical sources of brain functions from these recordings.

Epilepsy is a chronic brain disease with dysfunctional brain networks, and electroencephalography (EEG) is an important tool for epileptogenic zone (EZ) identification, with rich information about frequencies. Different frequency oscillations have different contributions to brain function, and cross-frequency coupling (CFC) has been found to exist within brain regions. Cross-channel and inter-channel analysis should be both focused because they help to analyze how epilepsy networks change and also localize the EZ. In this paper, we analyzed long-term stereo-electroencephalography (SEEG) data from 17 patients with temporal lobe epilepsy. Single-channel and cross-channel CFC features were combined to establish functional brain networks, and the network characteristics under different periods and the localization of EZ were analyzed. It was observed that theta–gamma phase amplitude coupling (PAC) within the electrodes in the seizure region increased during the ictal (p < 0.05). Theta–gamma and delta–gamma PAC of cross-channel were enhanced in the early and mid-late ictal, respectively. It was also found that there was a strong cross-frequency coupling state between channels of EZ in the functional network during the ictal, along with a more regular network than interictal. The accuracy rate of EZ localization was 82.4%. Overall, the combination of single-channel and multi-channel cross-band coupling analysis can help identify seizures and localize EZ for temporal lobe epilepsy. Rhythmic coupling reveals a relationship between the functional network and the seizure status of epilepsy.

Introduction: Precise localization of the epileptogenic zone is very essential for the success of epilepsy surgery. Epileptogenicity index (EI) computationally estimates epileptogenicity of brain structures based on the temporal domain parameters and magnitude of ictal discharges. This method works well in cases of mesial temporal lobe epilepsy but it showed reduced accuracy in neocortical epilepsy. To overcome this scenario, in this study, we propose Epileptogenicity Rank (ER), a modified method of EI for quantifying epileptogenicity, that is based on spatio-temporal properties of Stereo EEG (SEEG).Methods: Energy ratio during ictal discharges, the time of involvement and Euclidean distance between brain structures were used to compute the ER. Retrospectively, we localized the EZ for 33 patients (9 for mesial-temporal lobe epilepsy and 24 for neocortical epilepsy) using post op MRI and Engel 1 surgical outcome at a mean of 40.9 months and then optimized the ER in this group.Results: Epileptic network estimation based on ER successfully differentiated brain regions involved in the seizure onset from the propagation network. ER was calculated at multiple thresholds leading to an optimum value that differentiated the seizure onset from the propagation network. We observed that ER < 7.1 could localize the EZ in neocortical epilepsy with a sensitivity of 94.6% and specificity of 98.3% and ER < 7.3 in mesial temporal lobe epilepsy with a sensitivity of 95% and specificity of 98%. In non-seizure-free patients, the EZ localization based on ER pointed to brain area beyond the cortical resections.Significance: Methods like ER can improve the accuracy of EZ localization for brain resection and increase the precision of minimally invasive surgery techniques (radio-frequency or laser ablation) by identifying the epileptic hubs where the lesion is extensive or in nonlesional cases. For inclusivity with other clinical applications, this ER method has to be studied in more patients.

Fruitful progress and change have been accomplished in epilepsy surgery as science and technology advance. Stereotactic electroencephalography (SEEG) was originally developed by Talairach and Bancaud at Hôspital Sainte-Anne in the middle of the 20th century. SEEG has survived, and is now being recognized once again, especially with the development of neurosurgical robots. Many epilepsy centers have already replaced invasive monitoring with subdural electrodes (SDEs) by SEEG with depth electrodes worldwide. SEEG has advantages in terms of complication rates as shown in the previous reports. However, it would be more indispensable to demonstrate how much SEEG has contributed to improving seizure outcomes in epilepsy surgery. Vagus nerve stimulation (VNS) has been an only implantable device since 1990s, and has obtained the autostimulation mode which responds to ictal tachycardia. In addition to VNS, responsive neurostimulator (RNS) joined in the options of palliative treatment for medically refractory epilepsy. RNS is winning popularity in the United States because the device has abilities of both neurostimulation and recording of ambulatory electrocorticography (ECoG). Deep brain stimulation (DBS) has also attained approval as an adjunctive therapy in Europe and the United States. Ablative procedures such as SEEG-guided radiofrequency thermocoagulation (RF-TC) and laser interstitial thermal therapy (LITT) have been developed as less invasive options in epilepsy surgery. There will be more alternatives and tools in this field than ever before. Consequently, we will need to define benefits, indications, and limitations of these new technologies and concepts while adjusting ourselves to a period of fundamental transition in our foreseeable future.

This retrospective description of a surgical series is aimed at reporting on indications, methodology, results on seizures, outcome predictors and complications from a 20-year stereoelectroencephalography (SEEG) activity performed at a single epilepsy surgery centre. Prospectively collected data from a consecutive series of 742 SEEG procedures carried out on 713 patients were reviewed and described. Long-term seizure outcome of SEEG-guided resections was defined as a binomial variable: absence (ILAE classes 1–2) or recurrence (ILAE classes 3–6) of disabling seizures. Predictors of seizure outcome were analysed by preliminary uni/bivariate analyses followed by multivariate logistic regression. Furthermore, results on seizures of these subjects were compared with those obtained in 1128 patients operated on after only non-invasive evaluation. Survival analyses were also carried out, limited to patients with a minimum follow-up of 10 years. Resective surgery has been indicated for 570 patients (79.9%). Two-hundred and seventy-nine of 470 patients operated on (59.4%) were free of disabling seizures at least 2 years after resective surgery. Negative magnetic resonance and post-surgical lesion remnant were significant risk factors for seizure recurrence, while type II focal cortical dysplasia, balloon cells, glioneuronal tumours, hippocampal sclerosis, older age at epilepsy onset and periventricular nodular heterotopy were significantly associated with seizure freedom. Twenty-five of 153 patients who underwent radio-frequency thermal coagulation (16.3%) were optimal responders. Thirteen of 742 (1.8%) procedures were complicated by unexpected events, including three (0.4%) major complications and one fatality (0.1%). In conclusion, SEEG is a safe and efficient methodology for invasive definition of the epileptogenic zone in the most challenging patients. Despite the progressive increase of MRI-negative cases, the proportion of seizure-free patients did not decrease throughout the years.

International audience; Objective: The stereo electroencephalogram (SEEG) recordings are the sate of the art tool used in pre-surgical evaluation of drug-unresponsive epileptic patients. Coupled with SEEG, electrical cortical stimulation (CS) offer a complementary tool to investigate the lesioned/healthy brain regions and to identify the epileptic zones with precision. However, the propagation of this stimulation inside the brain masks the cerebral activity recorded by nearby multi-contact SEEG electrodes. The objective of this paper is to propose a novel filtering approach for suppressing the CS artifact in SEEG signals using time, frequency as well as spatial information.Methods: The method combines spatial filtering with tunable-Q wavelet transform (TQWT). SEEG signals are spatially filtered to isolate the CS artifacts within a few number of sources/components. The artifacted components are then decomposed into oscillatory background and sharp varying transient signals using tunable-Q wavelet transform (TQWT). The CS artifact is assumed to lie in the transient part of the signal. Using prior known time-frequency information of the CS artifacts, we selectively mask the wavelet coefficients of the transient signal and extract out any remaining significant electro-physiological activity.Results: We have applied our proposed method of CS artifact suppression on simulated and real SEEG signals with convincing performance. The experimental A. Bhattacharyya 2 results indicate the effectiveness of the proposed approach.Conclusion: The proposed method suppresses CS artifacts without affecting the background SEEG signal. Significance: The proposed method can be applied for suppressing both low and high frequency CS artifacts and outperforms current methods from the literature. Index Terms cortical stimulation, SEEG, tunable-Q wavelet transform, subspace correlation approach, blind source separation.

Dual-tasking is extremely prominent nowadays, despite ample evidence that it comes with a performance cost: the Dual-Task (DT) cost. Neuroimaging studies have established that tasks are more likely to interfere if they rely on common brain regions, but the precise neural origin of the DT cost has proven elusive so far, mostly because fMRI does not record neural activity directly and cannot reveal the key effect of timing, and how the spatio-temporal neural dynamics of the tasks coincide.Recently, DT electrophysiological studies in monkeys have recorded neural populations shared by the two tasks with millisecond precision to provide a much finer understanding of the origin of the DT cost. We used a similar approach in humans, with intracranial EEG, to assess the neural origin of the DT cost in a particularly challenging naturalistic paradigm which required accurate motor responses to frequent visual stimuli (task T1) and the retrieval of information from long-term memory (task T2), as when answering passengers’ questions while driving.We found that T2 elicited neuroelectric interferences in the gamma-band (>40 Hz), in key regions of the T1 network including the Multiple Demand Network. They reproduced the effect of disruptive electrocortical stimulations to create a situation of dynamical incompatibility, which might explain the DT cost. Yet, participants were able to flexibly adapt their strategy to minimize interference, and most surprisingly, reduce the reliance of T1 on key regions of the executive control network – the anterior insula and the dorsal anterior cingulate cortex – with no performance decrement.HIGHLIGHTS- First direct evidence in humans of neural interferences between two tasks.- First explanation of the Dual-Task cost at the neural level in humans.- First Dual-Tasking study with intracranial EEG in naturalistic conditions.

Objectives: We recently introduced a navigated, robot-driven laser beam craniotomy for use with stereoelectroencephalography (SEEG) applications. This method was intended to substitute the hand-held electric power drill in an ex vivo study. The purpose of this in vivo non-recovery pilot study was to acquire data for the depth control unit of this laser device, to test the feasibility of cutting bone channels, and to assess dura perforation and possible cortex damage related to cold ablation.Methods: Multiple holes suitable for SEEG bone channels were planned for the superior portion of two pig craniums using surgical planning software and a frameless, navigated technique. The trajectories were planned to avoid cortical blood vessels using magnetic resonance angiography. Each trajectory was converted into a series of circular paths to cut bone channels. The cutting strategy for each hole involved two modes: a remaining bone thickness mode and a cut through mode (CTR). The remaining bone thickness mode is an automatic coarse approach where the cutting depth is measured in real time using optical coherence tomography (OCT). In this mode, a pre-set measurement, in mm, of the remaining bone is left over by automatically comparing the bone thickness from computed tomography with the OCT depth. In the CTR mode, the cut through at lower cutting energies is managed by observing the cutting site with real-time video.Results: Both anesthesia protocols did not show any irregularities. In total, 19 bone channels were cut in both specimens. All channels were executed according to the planned cutting strategy using the frameless navigation of the robot-driven laser device. The dura showed minor damage after one laser beam and severe damage after two and three laser beams. The cortex was not damaged. As soon as the cut through was obtained, we observed that moderate cerebrospinal fluid leakage impeded the cutting efficiency and interfered with the visualization for depth control. The coaxial camera showed a live video feed in which cut through of the bone could be identified in 84%.Conclusion: Inflowing cerebrospinal fluid disturbed OCT signals, and, therefore, the current CTR method could not be reliably applied. Video imaging is a candidate for observing a successful cut through. OCT and video imaging may be used for depth control to implement an updated SEEG bone channel cutting strategy in the future.

Objective Stereotactic electroencephalography (SEEG) has been widely used to explore the epileptic network and localize the epileptic zone in patients with medically intractable epilepsy. Accurate anatomical labeling of SEEG electrode contacts is critically important for correctly interpreting epileptic activity. We present a method for automatically assigning anatomical labels to SEEG electrode contacts using a 3D‐segmented cortex and coregistered postoperative CT images. Method Stereotactic electroencephalography electrode contacts were spatially localized relative to the brain volume using a standard clinical procedure. Each contact was then assigned an anatomical label by clinical epilepsy fellows. Separately, each contact was automatically labeled by coregistering the subject's MRI to the USCBrain atlas using the BrainSuite software and assigning labels from the atlas based on contact locations. The results of both labeling methods were then compared, and a subsequent vetting of the anatomical labels was performed by expert review. Results Anatomical labeling agreement between the two methods for over 17 000 SEEG contacts was 82%. This agreement was consistent in patients with and without previous surgery (P = .852). Expert review of contacts in disagreement between the two methods resulted in agreement with the atlas based over manual labels in 48% of cases, agreement with manual over atlas‐based labels in 36% of cases, and disagreement with both methods in 16% of cases. Labels deemed incorrect by the expert review were then categorized as either in a region directly adjacent to the correct label or as a gross error, revealing a lower likelihood of gross error from the automated method. Significance The method for semi‐automated atlas‐based anatomical labeling we describe here demonstrates potential to assist clinical workflow by reducing both analysis time and the likelihood of gross anatomical error. Additionally, it provides a convenient means of intersubject analysis by standardizing the anatomical labels applied to SEEG contact locations across subjects.

Highlights • Radiofrequency ablation (RFA) was selected over other minimally invasive surgical option due to utility of using already implanted sEEG electrodes. • We describe 4 patients who underwent combined RFA of seizure onset area and spread regions. • All 4 patients had favorable outcome with at least 50% improvement in seizures. • No permanent deficits were observed with network RFA., Radiofrequency ablation (RFA) is a minimally invasive procedure for drug-resistant focal epilepsy. Although well tolerated, seizure outcomes are less favorable than standard resection. RFA is commonly performed following stereoencephalography (sEEG) identification of the seizure onset zone (SOZ). We hypothesized RFA outcomes can improve by adding RFA of seizure spread regions to the SOZ as identified by sEEG, an approach we term network RFA. Four patients underwent network RFA at our institution from 8/2017 to 9/2019. There were two Engel IB outcomes and two Engel III outcomes. The median follow-up length was 25.5 months (range 17–35). No permanent neurological deficits occurred. Etiologies consisted of polymicrogyria (1), mixed malformation of cortical development (MCD) (2), and cryptogenic (1). This study provides descriptive results regarding the efficacy and safety of network RFA. Network RFA can be considered in patients with focal epilepsies with large MCDs that may not be amenable to standard resection.

Highlights • Anterior insular stimulation produces reproducible episodes of emotional crying. • This is due to activation of complex neural network with its connectivity to the anterior cingulate cortex. • This study increases our understanding of the complex functionality of the insula., Stereo-EEG (sEEG) is an invasive recording technique used to localize the seizure-onset zone for epilepsy surgery in people with drug-resistant focal seizures. Pathological crying reflects disordered emotional expression and the anterior insula is known to play a role in empathy and socio-emotional processing. We describe a patient where electrical stimulation mapping (ESM) of the anterior insula during sEEG generated pathological crying and profound sadness that was time-locked to the electrical stimulus. We evaluated a 35-year-old left-handed female for repeat epilepsy surgery. The patient had drug resistant focal impaired awareness seizures despite a previous left temporal neocortical resection informed by an invasive study using subdural grid and strip electrodes seven years earlier. She was studied invasively with 10 sEEG electrodes sampling temporal, occipital, and insular targets. In the process of functional mapping, stimulation of the anterior insular cortex provoked tearful crying with sad affect, reproducible upon repeat stimulation. Our case is unique in demonstrating transitory pathological crying with profound sadness provoked by ESM of the left anterior insula. Furthermore we demonstrate repeated time-synched crying from electrical stimulation, which supports the hypothesis that the anterior insula in the brain plays an important role in the biology of emotion, as implicated by previous studies.

International audience; Purpose: Frontal seizures are organized according to anatomo-functional subdivisions of the frontal lobe. Prefrontal seizures have been the subject of few detailed studies to date. The objective of this study was to identify subcategories of prefrontal seizures based on seizure onset quantification and to look for semiological differences.Methods: Consecutive patients who underwent stereoelectroencephalography (SEEG) for drug-resistant prefrontal epilepsy between 2000 and 2018 were included. The different prefrontal regions investigated in our patients were dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC), dorsomedial prefrontal cortex (DMPFC), ventromedial prefrontal cortex (VMPFC), and orbitofrontal cortex (OFC). The seizure onset zone (SOZ) was determined from one or two seizures in each patient, using the epileptogenicity index (EI) method. The presence or absence of 16 clinical ictal manifestations was analyzed. Classification of prefrontal networks was performed using the k-means automatic classification method.Results: A total of 51 seizures from 31 patients were analyzed. The optimal clustering was 4 subgroups of prefrontal seizures: a "pure DLPF" group, a "pure VMPF" group, a "pure OFC" group, and a "global prefrontal" group. The first 3 groups showed a mean EI considered epileptogenic (>0.4) only in one predominant structure, while the fourth group showed a high mean EI in almost all prefrontal structures. The median number of epileptogenic structures per seizure (prefrontal or extrafrontal) was 5 for the "global prefrontal" group and 2 for the other groups. We found that the most common signs were altered consciousness, automatisms/stereotypies, integrated gestural motor behavior, and hyperkinetic motor behavior. We found no significant difference in the distribution of ictal signs between the different groups.Conclusion: Our study showed that although most prefrontal seizures manifest as a network of several anatomically distinct structures, we were able to determine a sublobar organization of prefrontal seizure onset with four groups.

International audience; Purpose: Posttraumatic epilepsy (PTE) is a common cause of drug-resistant epilepsy, especially in young adults. Nevertheless, such patients are not common candidates for intracranial presurgical evaluation. We investigated the role of stereoelectroencephalography (SEEG) in defining epileptogenicity and surgical strategy in patients with PTE.Methods: We analyzed ictal SEEG recordings from 18 patients. We determined the seizure onset zone (SOZ) by quantifying the epileptogenicity of the sampled structures, using the \"epileptogenicity index\" (EI). We also identified seizure onset patterns (SOPs) through visual and frequency analysis. Postsurgical outcome was assessed by Engel's classification.Results: The SOZ in PTE was most often located in temporal lobes, followed by frontal lobes. The SOZ was network-organized in the majority of the cases. Half of the SOP did not contain fast discharges. Half of the recordings showed SOZ that were less extensive than the posttraumatic lesions seen on brain magnetic resonance imaging (MRI). All but one operated patient benefited from tailored cortectomy. Only 3 patients were contraindicated for surgical resection due to bilateral epileptogenicity. The overall surgical outcome was good in majority of patients (67% Engel I).Conclusion: Despite the potential risk of bilateral or multifocal epilepsy, patients with PTE may benefit from presurgical assessment in well-selected cases. In this context, SEEG allows guidance of tailored resections adapted to the SOZ.

Localization of the epileptogenic zone (EZ) is crucial in the surgical treatment of focal epilepsy. Recently, EEG studies have revealed that the EZ exhibits abnormal connectivity, which has led investigators to now consider connectivity as a biomarker to localize the EZ. Further, abnormal connectivity of the EZ may provide an explanation for the impact of focal epilepsy on more widespread brain networks involved in typical cognition and development. Stereo-electroencephalography (sEEG) is a well-established method for localizing the EZ that has recently been applied to examine altered brain connectivity in epilepsy. In this manuscript, we review recent computational methods for identifying the EZ using sEEG connectivity. Findings from previous sEEG studies indicate that during interictal periods, the EZ is prone to seizure generation but concurrently receives inward connectivity preventing seizures. At seizure onset, this control is lost, allowing seizure activity to spread from the EZ. Regulatory areas within the EZ may be important for subsequently ending the seizure. After the seizure, the EZ appears to regain its influence on the network, which may be how it is able to regenerate epileptiform activity. However, more research is needed on the dynamic connectivity of the EZ in order to build a biomarker for EZ localization. Such a biomarker would allow for patients undergoing sEEG to have electrode implantation, localization of the EZ, and resection in a fraction of the time currently needed, preventing patients from having to endure long hospital stays and induced seizures.

Measuring connectivity in the human brain involves innumerable approaches using both noninvasive (fMRI, EEG) and invasive (intracranial EEG or iEEG) recording modalities, including the use of external probing stimuli, such as direct electrical stimulation. To examine how different measures of connectivity correlate with one another, we compared ‘passive’ measures of connectivity during resting state conditions to the more ‘active’ probing measures of connectivity with single pulse electrical stimulation (SPES). We measured the network engagement and spread of the cortico-cortico evoked potential (CCEP) induced by SPES at 53 out of 104 total sites across the brain, including cortical and subcortical regions, in patients with intractable epilepsy (N=11) who were undergoing intracranial recordings as a part of their clinical care for identifying seizure onset zones. We compared the CCEP network to functional, effective, and structural measures of connectivity during a resting state in each patient. Functional and effective connectivity measures included correlation or Granger causality measures applied to stereoEEG (sEEGs) recordings. Structural connectivity was derived from diffusion tensor imaging (DTI) acquired before intracranial electrode implant and monitoring (N=8). The CCEP network was most similar to the resting state voltage correlation network in channels near to the stimulation location. In contrast, the distant CCEP network was most similar to the DTI network. Other connectivity measures were not as similar to the CCEP network. These results demonstrate that different connectivity measures, including those derived from active stimulation-based probing, measure different, complementary aspects of regional interrelationships in the brain.

Highlights • SEEG is feasible with little to no skull to anchor a bolt. • To the best of our knowledge, this is the first report describing SEEG electrode placement with no skull bone., Stereo electroencephalogram (SEEG) electrode placement with cranially fixed guide bolts is recognized as one of the most accurate and safest implantation strategies to sample deep and buried cortex during certain clinical scenarios involving epilepsy surgery. Bone thickness of less than 2 mm is a relative contraindication to SEEG. Here, we describe a case drug-resistant focal epilepsy where prior craniotomies, infections and radiation therapy yielded limited skull bone requiring invasive EEG monitoring. Due to the inability to use bolts over areas with limited skull bone, we successfully utilized a combination of the standard and a modified SEEG techniques for implantation and stabilization of intracranial electrodes without complications. This strategy enabled optimal intracranial EEG monitoring and surgical management of the patient’s drug-resistant focal seizures.

For epileptic patients requiring resective surgery, a modality called stereo-electroencephalography (SEEG) may be used to monitor the patient's brain signals to help identify epileptogenic regions that generate and propagate seizures. SEEG involves the insertion of multiple depth electrodes into the patient's brain, each with 10 or more recording contacts along its length. However, a significant fraction (≈ 30% or more) of the contacts typically reside in white matter or other areas of the brain which can not be epileptogenic themselves. Thus, an important step in the analysis of SEEG recordings is distinguishing between electrode contacts which reside in gray matter vs. those that do not. MRI images overlaid with CT scans are currently used for this task, but they take significant amounts of time to manually annotate, and even then it may be difficult to determine the status of some contacts. In this paper we present a fast, automated method for classifying contacts in gray vs. white matter based only on the recorded signal and relative contact depth. We observe that bipolar referenced contacts in white matter have less power in all frequencies below 150 Hz than contacts in gray matter, which we use in a Bayesian classifier to attain an average area under the receiver operating characteristic curve of 0.85 ± 0.079 (SD) across 29 patients. Because our method gives a probability for each contact rather than a hard labeling, and uses a feature of the recorded signal that has direct clinical relevance, it can be useful to supplement decision-making on difficult to classify contacts or as a rapid, first-pass filter when choosing subsets of contacts from which to save recordings.

Seizure semiology represents the dynamic clinical expression of seizures and is an important behavioral data source providing clues to cerebral organization. It is produced through interactions between electrical seizure discharge and physiologic and pathologic brain networks. Semiology is described in spatial and temporal terms; its expression depends on spatial (localization) and temporal (eg, discharge frequency, synchrony) characteristics of cerebral electrical activity. Stereoelectroencephalography studies of electroclinical correlations, including with quantified signal analysis, have helped elucidate several semiological patterns. Future research could help improve pattern recognition of complex semiological patterns, possibly using deep learning methods in a multiscale, multimodal modelization framework.

The refractory seizures have significant impact on the quality of life and increase long term neurologic and non-neurologic complications. Implantation of Stereotactic Electroencephalography (SEEG) leads is one of the newer surgical techniques intended to localize seizure foci with higher accuracy than the conventional methods. Most of the commonly utilized anesthetic agents depress EEG waveforms affecting intra operative monitoring during these surgeries. Hence, the anesthetic goals include a stable induction and maintenance with agents which have minimal effect on EEG. This article discusses the peri-operative considerations of multiple anti-epileptic medications, recent advances in anesthetic management, and important post-operative concerns.

Many outstanding studies have reported promising results in seizure forecasting, one of the most challenging predictive data analysis problems. This is mainly because electroencephalogram (EEG) bio-signal intensity is very small, in $\mu \text{V}$ range, and there are significant sensing difficulties given physiological and non-physiological artifacts. Today the process of accurate epileptic seizure identification and data labeling is done by neurologists. The current unpredictability of epileptic seizure activities together with the lack of reliable treatment for patients living with drug resistant forms of epilepsy creates an urgency for research into accurate, sensitive and patient-specific seizure forecasting. Most seizure forecasting algorithms use only labeled data for training purposes. As the seizure data is labeled manually by neurologists, preparing the labeled data is expensive and time consuming, making the best use of the data critical. In this article, we propose an approach that can make use of not only labeled EEG signals but also the unlabeled ones which are more accessible. We use the short-time Fourier transform on 28-s EEG windows as a pre-processing step. A generative adversarial network (GAN) is trained in an unsupervised manner where information of seizure onset is disregarded. The trained Discriminator of the GAN is then used as a feature extractor. Features generated by the feature extractor are classified by two fully-connected layers (can be replaced by any classifier) for the labeled EEG signals. This semi-supervised patient-specific seizure forecasting method achieves an out-of-sample testing area under the operating characteristic curve (AUC) of 77.68%, 75.47% and 65.05% for the CHB-MIT scalp EEG dataset, the Freiburg Hospital intracranial EEG dataset and the EPILEPSIAE dataset, respectively. Unsupervised training without the need for labeling is important because not only it can be performed in real-time during EEG signal recording, but also it does not require feature engineering effort for each patient. To the best of our knowledge, this is the first application of GAN to seizure forecasting.

International audience; In this study, we seek to analyze the determinants of the intracranial EEG seizure onset pattern and the impact of the seizure onset pattern in predicting postsurgical seizure outcome. Methods: To this end, we analyzed 820 seizures from 252 consecutive patients explored by SEEG (total of 2148 electrodes) including various forms of focal refractory epilepsies. We used a reproducible method combining visual and time-frequency analyses. Results: We described eight seizure onset patterns: low-voltage fast activity (LVFA), preictal spiking followed by LVFA, burst of poly-spikes followed by LVFA, slow wave/DC shift followed by LVFA, theta/alpha sharp waves, beta sharp waves, rhythmic spikes/spike-waves and delta-brush. LVFA occurred in 79% of patients. The seizureonset pattern was significantly associated with: 1) underlying etiology (burst of polyspikes followed by LVFA with the presence of a focal cortical dysplasia, LVFA with malformation of cortical development, post-vascular and undetermined epilepsies); 2) spatial organization of the epileptogenic zone (burst of poly-spikes followed by LVFA with focal organization, slow wave/DC shift followed by LVFA with network organization); 3) post-surgical seizure outcome (better outcome when LVFA present). Significance: This study demonstrates that the main determinants of the seizure onset pattern are the underlying etiology and the spatial organization of the epileptogenic zone. Concerning the post-surgical seizure outcome, the main determinant factor is the spatial organization of the epileptogenic zone, but the seizure onset pattern plays also a role, conferring better prognosis when LVFA was present.

Purpose: Stereotactic EEG (SEEG) recordings are considered to be the best choice for preoperative invasive evaluation when the epilepsy of the patient is suspected to originate in deep-sited anatomical structures and standard electro-clinical examinations are not conclusive. The interictal epileptic discharges (IEDs) occurring in these recordings in general are abundant compared to ictal discharges, but difficult to interpret due to complex underlying network interactions. Method: A framework is developed to model the spatiotemporal net-work interactions underlying the IEDs. To identify the highly synchronized neural activity underlying these discharges, the variation in correlation over time of the SEEG signals is related to the occurrence of the IEDs using the general linear model [van Houdt et al., 2012]. Subsequently, it is assessed whether the brain regions that reflect highly synchronized neural activity are either independent or interacting within an epileptic network. Independent component analysis is applied followed by clustering of the spatial distributions of the independent components. The spatial distributions of the spike clusters are visualized together with the estimated time delays against the patients’ brain anatomy [Meesters et al., 2015]. Results: The analysis framework was evaluated for five patients who underwent SEEG recordings prior to successful epilepsy surgery. The spatial distribution of the spike cluster that was related to the MRI-visible brain lesions coincided with the seizure onset zone of these patients. Unraveling of the complex network interactions underlying the IEDs of two more patients without satisfactory surgical outcome indicated that an alternative and plausible resection strategy could have been considered. Conclusion: The analysis framework applied to IEDs is considered a valuable additional tool to the current seizure assessment approach, which might lead to a more successful outcome of epilepsy surgery. Acknowledgement: This study is part of the DeNeCor-project that has received funding from the ENIAC Joint Undertaking (grant no. 324257).

Object The objective of the study is to investigate and report our experience with extra operative intracranial EEG monitoring for evaluation of epilepsy surgery among elderly (≥ 60 years) patients. Methods After IRB approval, we searched our prospectively maintained epilepsy surgery database to find patients who underwent eiEEG at the age of 60 years or older. Electronic medical records were reviewed to extract clinical and surgery-related information. Patients who underwent resective epilepsy surgery after eiEEG and had at least 1 year of clinical follow-up were assessed for seizure outcome. Categorical and continuous variables were compared using Pearson chi-square and Student's t-test, respectively. Results A total of 21 patients, with 13 (62%) women, underwent eiEEG in our center at the age of 60 years or older. The mean age at time of implantation was 63.8 ± 2.7 years. Sub-dural grids (SDG) were implanted in five (24%) patients, whereas sixteen (76%) patients underwent stereo-EEG (SEEG) implantation. Median number of contacts in SDG were 106 (56–136) and depth electrodes in SEEG were 12 (9–14). There were 2 complications, including one mortality due to intracerebral hemorrhage. Sixteen (76%) patients underwent respective epilepsy surgery after eiEEG and eleven (69%) achieved Engel class I outcome on the last follow-up [mean follow-up duration of 2.7 (± 1.8) years]. Conclusion We noticed an increased utilization of eiEEG in elderly patients after the introduction of SEEG at our center. Overall, we found that eiEEG can help achieve good seizure outcomes in the elderly population. However, the one eiEEG-related mortality serves a word of caution about the potential risks in this population., Highlights • First report on extra operative intracranial EEG (eiEEG) monitoring use in the elderly • Twenty-one elderly patients underwent eiEEG at the mean age of 63.8 ± 2.7 years. • Sixteen (76%) underwent surgery after eiEEG and 11 (69%) achieved Engel class I outcome. • Utilization of eiEEG increased after the introduction of stereo EEG (SEEG) at our center.

Objective In the detection of seizure onset zones, arterial spin labeling (ASL) can overcome the limitations of positron emission tomography (PET) with 18F-fluorodeoxyglucose (18F-FDG), which is invasive, expensive, and radioactive. PET/magnetic resonance (MR) systems have been introduced that allow simultaneous performance of ASL and PET, but comparisons of these techniques with stereoelectroencephalography (SEEG) and comparisons among the treatment outcomes of these techniques are still lacking. Here, we investigate the effectiveness of ASL compared with that of SEEG and their outcomes in localizing mesial temporal lobe epilepsy (MTLE) and assess the correlation between simultaneously acquired PET and ASL. Methods Between October 2016 and August 2017, we retrospectively studied 12 patients diagnosed with pure unilateral MTLE. We extracted and quantitatively computed values for ASL and PET in the bilateral hippocampus. SEEG findings and outcome were considered the gold standard of lateralization. Finally, the bilateral asymmetry index (AI) was calculated to assess the correlation between PET and ASL. Results Our results showed that hypoperfusion in the hippocampus detected using ASL matched the SEEG-defined epileptogenic zone in this series of patients. The mean normalized voxel value of ASL in the contralateral hippocampus was 0.97 ± 0.19, while in the ipsilateral hippocampus, it was 0.84 ± 0.14. Meanwhile, significantly decreased perfusion and metabolism were observed in these patients (Wilcoxon, p, Highlights • ASL has been increasingly used in presurgical evaluations in epilepsy recent years. • Comparisons of ASL and PET with a PET/MR system using SEEG and treatment outcomes as gold-standard are still lacking. • Decreased perfusion consistent with hypometabolism and SEEG was observed with ASL. • ASL offers an effective non-invasive alternative to PET in evaluation of MTLE.

International audience; Rapid individuation of conspecifics' faces is ecologically important in the human species, whether the face belongs to a familiar or unfamiliar individual. Here we tested a large group (N = 69) of epileptic patients implanted with intracerebral electrodes throughout the ventral occipito-temporal cortex (VOTC). We used a frequency-tagging visual stimulation paradigm optimized to objectively measure face individuation with direct neural recordings. This enabled providing an extensive map of the significantly larger neural responses to upright than to inverted unfamiliar faces, i.e. reflecting visual face individuation processes that go beyond physical image differences. These high-level face individuation responses are both distributed and anatomically confined to a strip of cortex running from the inferior occipital gyrus all along the lateral fusiform gyrus, with a large right hemispheric dominance. Importantly, face individuation responses are limited anteriorly to the bilateral anterior fusiform gyrus and surrounding sulci, with a near absence of significant responses in the extensively sampled temporal pole. This large-scale mapping provides original evidence that face individuation is supported by a distributed yet anatomically constrained population of neurons in the human VOTC, and highlights the importance of probing this function with face stimuli devoid of associated semantic, verbal and affective information.

There is currently a replication crisis in many fields of neuroscience and psychology, with some estimates claiming up to 64% of research in psychological science is not reproducible. Three common culprits which have been suspected to cause the failure to replicate such studies are small sample sizes, “hypothesizing after the results are known,” and “p-hacking.” Here, we introduce accurate stimulus timing as an additional possibility. Accurate stimulus onset timing is critical to almost all psychophysical research. Auditory, visual, or manual response time stimulus onsets are typically sent through wires to various machines that record data such as: eye gaze positions, electroencephalography, stereo electroencephalography, and electrocorticography. These stimulus onsets are collated and analyzed according to experimental condition. If there is variability in the temporal accuracy of the delivery of these onsets to external systems, the quality of the resulting data and scientific analyses will degrade. Here, we describe an approximately $200 Arduino based system and associated open-source codebase which achieved a 5.34 microsecond delay from the inputs to the outputs while electrically opto-isolating the connected external systems. Using an oscilloscope, the device is configurable for different environmental conditions particular to each laboratory (e.g. light sensor type, screen type, speaker type, stimulus type, temperature, etc). This low-cost open-source project delivered electrically isolated stimulus onset Transistor-Transistor Logic triggers with a median precision of 5.34 microseconds and was successfully tested with 7 different external systems that record eye and neurological data.

Contains fulltext : 221812pub.pdf (Publisher’s version ) (Closed access) Contains fulltext : 221812pre.pdf (Author’s version preprint ) (Open Access) We report a comprehensive mapping of the human ventral occipito-temporal cortex (VOTC) for selective responses to frequency-tagged faces or landmarks (houses) presented in rapid periodic trains of objects, with intracerebral recordings in a large sample (N = 75). Face-selective contacts are three times more numerous than house-selective contacts and show a larger amplitude, with a right hemisphere advantage for faces. Most importantly, these category-selective contacts are spatially dissociated along the lateral-to-medial VOTC axis, respectively, consistent with neuroimaging evidence. At the minority of "overlap" contacts responding selectively to both faces and houses, response amplitude to the two categories is not correlated, suggesting a contribution of distinct populations of neurons responding selectively to each category. The medio-lateral dissociation also extends into the underexplored anterior temporal lobe (ATL). In this region, a relatively high number of intracerebral recording contacts show category-exclusive responses (i.e., without any response to baseline visual objects) to faces but rarely to houses, in line with the proposed role of this region in processing people-related semantic information. Altogether, these observations shed novel insight on the neural basis of human visual recognition and strengthen the validity of the frequency-tagging approach coupled with intracerebral recordings in epileptic patients to understand human brain function. 18 p.

The subjective inner experience of mental imagery is among the most ubiquitous human experiences in daily life. Elucidating the neural implementation underpinning the dynamic construction of mental imagery is critical to understanding high-order cognitive function in the human brain. Here, we applied a frequency-tagging method to isolate the top-down process of speech mental imagery from bottom-up sensory-driven activities and concurrently tracked the neural processing time scales corresponding to the two processes in human subjects. Notably, by estimating the source of the magnetoencephalography (MEG) signals, we identified isolated brain networks activated at the imagery-rate frequency. In contrast, more extensive brain regions in the auditory temporal cortex were activated at the stimulus-rate frequency. Furthermore, intracranial stereotactic electroencephalogram (sEEG) evidence confirmed the participation of the inferior frontal gyrus in generating speech mental imagery. Our results indicate that a disassociated neural network underlies the dynamic construction of speech mental imagery independent of auditory perception.

Stereoelectroencephalography (SEEG) is a diagnostic procedure in which multiple electrodes are stereotactically implanted within predefined areas of the brain to identify the seizure onset zone, which needs to be removed to achieve remission of focal epilepsy. Computer-assisted planning (CAP) has been shown to improve trajectory safety metrics and generate clinically feasible trajectories in a fraction of the time needed for manual planning. We report a prospective validation study of the use of EpiNav (UCL, London, UK) as a clinical decision support software for SEEG. Thirteen consecutive patients (125 electrodes) undergoing SEEG were prospectively recruited. EpiNav was used to generate 3D models of critical structures (including vasculature) and other important regions of interest. Manual planning utilizing the same 3D models was performed in advance of CAP. CAP was subsequently employed to automatically generate a plan for each patient. The treating neurosurgeon was able to modify CAP generated plans based on their preference. The plan with the lowest risk score metric was stereotactically implanted. In all cases (13/13), the final CAP generated plan returned a lower mean risk score and was stereotactically implanted. No complication or adverse event occurred. CAP trajectories were generated in 30% of the time with significantly lower risk scores compared to manually generated. EpiNav has successfully been integrated as a clinical decision support software (CDSS) into the clinical pathway for SEEG implantations at our institution. To our knowledge, this is the first prospective study of a complex CDSS in stereotactic neurosurgery and provides the highest level of evidence to date. Electronic supplementary material The online version of this article (10.1007/s13311-019-00774-9) contains supplementary material, which is available to authorized users.

We aimed to assess stereoelectroencephalography (SEEG) seizure-onset and interictal patterns associated with MRI-negative epilepsy and investigate their possible links with histology, extent of the epileptogenic zone (EZ) and surgical outcome. We retrospectively analysed a cohort of 59 consecutive MRI-negative surgical candidates, who underwent SEEG recordings followed by cortectomy between 2000 and 2016. Most of the eight distinct seizure-onset patterns could be encountered both in confirmed focal cortical dysplasia (FCD) and in histologically non-specific or normal cases. We found strong correlation (p = 0.008) between seizure-onset pattern and histology for: (1) slow-wave/DC-shift prior to low voltage fast activity (LVFA), associated with normal/non-specific histology, and (2) bursts of polyspikes prior to LVFA, exclusively observed in FCD. Three interictal patterns were identified: periodic slow-wave/gamma burst, sub-continuous rhythmic spiking and irregular spikes. Both “periodic” patterns were more frequent in but not specific to FCD. Surgical outcome depended on the EZ complete removal, regardless electrophysiological features. Histologically normal and FCD-associated epileptogenic zones share distinct interictal and ictal electrophysiological phenotypes, with common patterns between FCD subtypes and between dysplastic and apparently normal brain. Some specific seizure-onset patterns seem to be predictive of the underlying histology and may help to detect an MRI-invisible FCD.

Présentation Poster. Abstract published in Neurophysiologie Clinique 49(3):196-197, June 2019; International audience; Contexte: Les épilepsies focales structurelles pharmacorésistantes avec crises pariétales représentent seulement 5 % des séries chirurgicales et moins de 10 % dans notre série de patients explorés en SEEG à Nancy. Ce sont des épilepsies de diagnostic difficile du fait de leur rareté et d’une symptomatologie riche témoignant d’une implication extrapariétale. Le diagnostic localisateur des crises peut donc être retardé voire conduire à une localisation erronée de la zone épileptogène.Objectifs: À partir des corrélations anatomo-électrocliniques en SEEG, déterminer les signes critiques associés à la décharge critique pariétale initiale et à la propagation pariétale et extrapariétale.Méthodes: Étude de deux patients implantés en SEEG présentant une épilepsie pariétale pharmacorésistante. Analyse de l’activité paroxystique enregistrée et de la clinique lors de la crise enregistrée en simultanée en vidéo.Résultats: La première patiente présente une symptomatologie sensitive unilatérale associée à une décharge limitée au cortex post-central. Le second patient présente une activité motrice dystonique et hyperkinétique concomitante d’une décharge pariétale avec une propagation lente intrapariétale (26 s) puis secondairement une propagation extrapariétale asymétrique (frontal ipsilatéral), contrairement aux crises frontales qui se caractérisent par une propagation bilatérale rapide.Conclusion: Ces deux observations permettent de mettre évidence un pattern électroclinique orientant vers le lobe pariétal aussi bien au niveau des signes que de la dynamique. Ces conclusions sont à confirmer sur une série de patient plus importante.

Although a number of experimental and clinical studies have pointed out participation or an even more prominent role of basal ganglia in focal seizures, the mode of interaction between cortical and striatal signals remains unclear. In the present study, we took stereoelectroencephalographic (SEEG) recordings in drug-resistant epilepsy patients, to qualitatively and quantitatively analyse the ictal striatum activity as well as its synchronization with cerebral cortex. Eleven patients who underwent SEEG evaluation were prospectively included if they fulfilled two inclusion criteria: (i) at least one orthogonal intracerebral electrode contact explored the basal ganglia, in either their putaminal or caudate part; and (ii) at least two SEEG seizures were recorded. Cortical and subcortical regions of interest were defined and different periods of interest were analysed. SEEG was visually inspected and h2 non-linear correlation analysis performed to study functional connectivity between cortical region of interest and striatum. Six correlation indices were calculated. Two main patterns of striatal activation were recorded: the most frequent was characterized by an early alpha/beta activity that started within the first 5 s after seizure onset, sometimes concomitant with it. The second one was characterized by late, slower, theta/delta activity. A significant difference in h2 correlation indices was observed during the preictal and seizure onset period compared to background for global striatal index, mesio-temporal/striatal index, latero-temporal/striatal index, insular/striatal index, prefrontal/striatal index. In addition, a significant difference in h2 correlation indices was observed during the seizure termination period compared to all the other periods of interest for the six indices calculated. These results indicate that cortico-striatal synchronization can arise from the start of focal seizures. Depending on the ictal frequency pattern, desynchronization can occur later, but a late and terminal hypersynchronization progressively takes over. These changes in synchronization level between cortical and striatal activity might be part of an endogenous mechanism controlling the duration of abnormal oscillations within the striato-thalamo-cortical loop and thereby their termination. Pathophysiology of basal ganglia in focal seizures appears to be much more interlinked with the cortex than expected. Beyond the stereotypical features they could imprint to seizure semiology, their role in strengthening mechanisms underlying cessation of ictal propagation should inspire new rationales for deep brain stimulation in patients with intractable focal epilepsies.

International audience; Stereo-electroencephalography (SEEG) is used in clinical routine as a golden standard for precisely delineating the epileptic before surgical resection. In recent years it has been demonstrated that the SEEG setup is also eligible for Electrical Source Imaging (ESI), usually achieved from noninvasive measurements such as EEG/MEG. We found out that the principal burden for reliable localization from SEEG comes from the particular implantations of the electrode shafts in cluster, yielding a partial vision of the cerebral activity around the implanted zones. There is evidence that a compromise between the number of electrodes, their spatial repartition, and their distance to the source has to be reached toward successful ESI from SEEG. We then introduce a spatial conditioning criteria aiming at adequately describing these requirements on the sensor configuration. Under supervised simulation with known source position, we identify eligible value of this criteria yielding globally the highest source localization performance. Subsequently, the strategy is assessed under a realistic simulation framework, demonstrating the relevance of our local approach.

International audience; During presurgical evaluation of pharmacoresistant partial epilepsies, stereoelectroencephalography (SEEG) records interictal and ictal activities directly but is inherently limited in spatial sampling. In contrast, scalp-EEG and MEG are less sensitive but provide a global view on brain activity. Therefore, recording simultaneously these three modalities should provide a better understanding of the underlying brain sources by taking advantage of the different sensitivities of the three recording techniques. We performed trimodal EEG-MEG-SEEG recordings in a 19-year-old woman with pharmacoresistant cryptogenic posterior cortex epilepsy. Sub-continuous and highly focal spikes that were not visible at the surface were marked on SEEG by an epileptologist. Surface signals, MEG and scalp-EEG, were then averaged locked on SEEG spikes. MEG sources were reconstructed based on a moving dipole approach (Brainstorm software). This analysis revealed source within the left occipital pole, located posteriorly to the SEEG leads presenting the maximal number of spikes, in a region not explored by SEEG. In summary, simultaneous recordings provide a new framework for obtaining a view on brain signals that is both local and global, thereby overcoming the inherent SEEG limited spatial sampling.

The extent to which faces and written words share neural circuitry in the human brain is actively debated. Here we compared face-selective and word-selective responses in a large group of patients (N = 37) implanted with intracerebral depth electrodes in the ventral occipito-temporal cortex (VOTC). Both face-selective (i.e., significantly different responses to faces vs. nonface visual objects) and word-selective (i.e., significantly different responses to words vs. pseudofonts) neural activity is isolated through frequency-tagging. Critically, this sensitive approach allows to objectively quantify category-selective neural responses and disentangle them from general visual responses. About 70% of significant contacts show either only face-selectivity or only word-selectivity, with the expected right and left hemispheric dominance, respectively. Spatial dissociations are also found within core regions of face and word processing, with a medio-lateral dissociation in the fusiform gyrus (FG) and surrounding sulci, while a postero-anterior dissociation is found in the inferior occipital gyrus (IOG). Only 30% of the significant contacts show both face- and word-selective responses. Critically, in these contacts, across the VOTC or in the FG and surrounding sulci, between-category selective-amplitudes (faces vs. words) showed no-to-weak correlations, despite strong correlations in both the within-category selective amplitudes (face-face, word-word) and the general visual responses to words and faces. Overall, we conclude that category-selectivity for faces and written words is largely dissociated in the human VOTC.Significance StatementIn modern human societies, faces and written words have become arguably the most significant stimuli of the visual environment. Despite extensive research in neuropsychology, electroencephalography and neuroimaging over the past three decades, whether these two types of visual signals are recognized by similar or dissociated processes and neural networks remains unclear. Here we provide an original contribution to this outstanding scientific issue by directly comparing frequency-tagged face- and word-selective neural responses in a large group of epileptic patients implanted with intracerebral electrodes covering the ventral occipito-temporal cortex. While general visual responses to words and faces show significant overlap, the respective category-selective responses are neatly dissociated in spatial location and magnitude, pointing to largely dissociated processes and neural networks.

Objective 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 drug-resistant epilepsy. Methods The epileptogenic zone (EZ) was defined by SEEG analysis based on the Epileptogenicity Index. Interictal spikes, ripples (80–250 Hz) and fast ripples (FR, 250-330 Hz) 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.