Intracranial video-EEG Research Articles

Combining three-phase EEG pattern and ipsilateral isolated eye deviation to predict seizure focus in the frontal interhemispheric fissure

ObjectiveIdentification of seizure focus on the interhemispheric fissure (IHF) is often challenging at the step of scalp video-EEG monitoring on preoperative evaluations. We previously reported ictal three-phase EEG patterns (3Ph-EEG) and isolated eye deviation (isolated ED) to side of the seizure focus during seizures, each of which is available for identifying the seizure focus for frontal IHF (F-IHF). This study aimed to evaluate the accuracy of predicting the F-IHF focus using a combination of 3Ph-EEG and isolated ED in patients with frontal lobe epilepsy and the accuracy of predicting lateralization of the F-IHF focus using the predominance of findings. MethodsWe collected 15 patients diagnosed with frontal lobe epilepsy showing clinical seizures arising only from the frontal lobe, from 131 patients with intracranial video-EEG performed between January 2012 and December 2019. All 15 patients were classified into the IHF group (n = 7) and the extra-IHF group (n = 8) based on intracranial video-EEG. We statistically evaluated the accuracies of predicting F-IHF onset using combinations of 3Ph-EEG and isolated ED on scalp-EEG: 1) 3Ph-EEG (+); 2) isolated ED (+); 3) 3Ph-EEG (+) and/or isolated ED (+); and 4) 3Ph-EEG (+) and isolated ED (+). We also evaluated the accuracy of predicting focus lateralization using 3Ph-EEG and isolated ED. ResultsBoth 3Ph-EEG (+) and isolated ED (+) demonstrated good accuracy for identifying F-IHF foci. They showed identical sensitivities of 71.4 %, with odds ratios of 7.5 for 3Ph-EEG (+) and 17.5 for isolated ED (+), respectively. Only the combination of 3Ph-EEG (+) and/or isolated ED (+) showed significant associations (p = 0.007). This combination demonstrated the highest sensitivity (100 %) and modified odds ratio (39.0), indicating that all patients in the IHF group exhibited at least one of the following: 3Ph-EEG or isolated ED. The combination of 3Ph-EEG (+) and isolated ED (+) offered one of the highest specificities, at 87.5 %. To predict lateralization with the F-IHF focus, both the predominant side for the third phase of 3Ph-EEG (n = 5) and the direction of isolated ED (n = 5) were perfectly concordant with the F-IHF focus side (100 % for both). ConclusionThe combination of 3Ph-EEG and isolated ED can detect the IHF seizure focus with higher sensitivity in patients with frontal lobe epilepsy compared with using each method individually. Moreover, the absence of these two features eliminated the possibility of an F-IHF focus. Based on 3Ph-EEG and the direction of isolated ED, the focus side could presume lateralization of the F-IHF focus. Combining 3Ph-EEG and ipsilateral isolated ED at presurgical evaluation may help in designating locations for intracranial EEG electrodes.

Mapping interictal discharges using intracranial EEG-fMRI to predict postsurgical outcomes.

Various subjective and objective methods have been proposed to identify which interictal epileptiform discharge (IED)-related EEG-fMRI results are more likely to delineate seizure generating tissue in patients with drug-resistant focal epilepsy for the purposes of surgical planning. In this intracranial EEG-fMRI study, we evaluated the utility of these methods to localize clinically relevant regions pre-operatively and compared the extent of resection of these areas to post-operative outcome. Seventy patients admitted for intracranial video-EEG monitoring were recruited for a simultaneous intracranial EEG-fMRI study. For all analyses of blood oxygen level-dependent responses associated with IEDs, an experienced epileptologist identified the most Clinically Relevant brain activation cluster using available clinical information. The Maximum cluster (the cluster with the highest z-score) was also identified for all analyses and assigned to one of three confidence levels (low, medium, or high) based on the difference of the peak z-scores between the Maximum and Second Maximum cluster (the cluster with the second highest peak z-value). The distance was measured and compared between the peak voxel of the aforementioned clusters and the electrode contacts where the interictal discharge and seizure onset were recorded. In patients who subsequently underwent epilepsy surgery, the spatial concordance between the aforementioned clusters and the area of resection was determined and compared to post-operative outcome. We evaluated 106 different IEDs in 70 patients. Both subjective (identification of the Clinically Relevant cluster) and objective (Maximum cluster much more significant than the second maximum cluster) methods of culling non-localizing EEG-fMRI activation maps increased the spatial concordance between these clusters and the corresponding IED or seizure onset zone contacts. However, only the objective methods of identifying medium and high confidence maps resulted in a significant association between resection of the peak voxel of the Maximum cluster and post-operative outcome. Resection of this area was associated with good post-operative outcomes but was not sufficient for seizure freedom. On the other hand, we found that failure to resect the medium and high confidence Maximum clusters was associated with a poor post-surgical outcome (negative predictive value = 1.0, sensitivity = 1.0). Objective methods to identify higher confidence EEG-fMRI results are needed to localize areas necessary for good post-operative outcomes. However, resection of the peak voxel within higher confidence Maximum clusters is not sufficient for good outcomes. Conversely, failure to resect the peak voxel in these clusters is associated with a poor post-surgical outcome.

Candidate Selection for Implantation: Noninvasive Predictors of Seizure Onset Zone Focality and Surgical Outcome in People with Drug-Resistant Epilepsy Evaluated by Intracranial Video-EEG Monitoring—A Retrospective Cohort Study

Objectives. People with drug-resistant epilepsy are potential candidates for epilepsy surgery, a subset of whom requires intracranial video-EEG monitoring (IVEM) to determine the seizure onset zone (SOZ). The purpose of this study is to investigate noninvasive predictors of SOZ focality and surgical outcome in order to optimise case selection for this procedure. Materials and Methods. We performed a retrospective cohort study of patients who underwent IVEM at our centre from January 2006 to July 2021. We applied a multivariate logistic regression model to estimate the effect of potential noninvasive data as influencing factors for both SOZ focality and surgical outcome. A focal SOZ included a sublobar onset on IVEM, and a good surgical outcome was defined as Engel class I. Results. A total of 783 underwent a presurgical evaluation, 102 of them with IVEM. Ninety-seven patients were included in the SOZ focality analysis, and 64 were included in the surgical outcome analysis. The presence of focal to bilateral tonic-clonic seizures ( p = 0.03 ) and generalised interictal epileptiform discharges (IEDs) during scalp EEG ( p = 0.02 ) predicted a nonfocal SOZ. A weekly ( p = 0.01 ) or daily seizure frequency ( p < 0.01 ), focal to bilateral tonic-clonic seizures ( p = 0.01 ), nonlesional MRI ( p < 0.01 ), and multifocal ( p = 0.02 ) or generalised IEDs ( p < 0.01 ) were associated with a poor surgical outcome. Conclusions. A high seizure frequency, positive history of focal to bilateral tonic-clonic seizures, nonlesional MRI, and generalised and multifocal IEDs are noninvasive factors that may aid in selecting candidates for IVEM.

Seizure focus in the frontal interhemispheric fissure leads to ipsilateral isolated eye deviation

ObjectiveFew studies have examined the localization of seizures presenting with ictal eye deviation (ED) in the absence of other motor symptoms. We aimed to investigate differences in the localization of the ictal onset zone (IOZ) between patients with isolated ED and those with ED plus head turning (HT) during focal seizures. MethodsWe reviewed intracranial video-EEG data for 931 seizures in 80 patients with focal onset epilepsy in whom the IOZ could be confirmed. The 233 seizures in 49 patients with ED were classified into two semiological groups based on initial ED and the presence/absence of HT: (1) isolated ED (i.e., ED without HT), and (2) ED + HT (i.e., ED with HT). We analyzed the localization and lateralization of IOZs in each semiological group. We performed multivariate logistic regression analysis using a mixed-effects to determine the associations between IOZs and isolated ED/ED + HT. ResultsA total of 183 IOZs in 24 patients were included in the isolated ED group, while a total of 143 IOZs in 31 patients were included in the ED + HT group. Sixty-eight IOZs of eight patients in the isolated ED group were located in the ipsilateral frontal interhemispheric fissure (F-IHF). Only ipsilateral F-IHF was significantly associated with isolated ED (odds ratio [OR], 2.43; 95% confidence interval [CI], 0.37–4.49; P = 0.021). The contralateral lateral frontal cortex (latF) (P = 0.007) and ipsilateral mesial temporal region (mT) (P = 0.029) were significantly associated with ED + HT. ConclusionThe present study is the first to demonstrate that seizures with an F-IHF focus tend to present with initial ipsilateral isolated ED. This finding may aid in identifying the seizure focus in patients with isolated ED prior to resection.

Semiological differences of focal onset bilateral motor (convulsive) seizure between mesial temporal lobe epilepsy and neocortical epilepsy

ObjectiveWe investigated the semiology of focal onset bilateral motor (convulsive) seizure (FBMS) in patients with intractable focal epilepsy who underwent epilepsy surgery to understand its value in localizing the origin of the seizure. MethodsThe study included 20 patients who underwent resective surgery after intracranial video-EEG monitoring (iEEG) with a favorable seizure outcome (Engel class I), and had at least one FBMS during iEEG. The diagnosis was mesial temporal lobe epilepsy (MTLE) for 7 patients and neocortical epilepsy (NE) for 13 patients (lateral temporal lobe, 3; posterior cortex, 6; frontal lobe, 3; perirolandic, 1). Videotaped FBMSs were carefully analyzed. ResultsA generalized tonic phase appeared in all 7 patients with MTLE, but was absent in 6 of the 13 patients with NE (P = .044). Tonic cry was more frequently observed in MTLE than in NE (P = .012). Facial tonicity preceding limb tonicity was more frequently seen in patients with MTLE (P = .001). ConclusionNotably, patients with MTLE and those with NE showed semiological differences during bilateralization. FBMS includes not only focal to bilateral tonic-clonic seizure but also focal to bilateral clonic seizure.

RTTBD-like activity in association with hippocampal ictal discharges in patients with temporal lobe epilepsy.

To determine clinical and intracranial EEG correlates of rhythmic temporal theta bursts of drowsiness (RTTBD) and assess its clinical significance in patients with temporal lobe epilepsy (TLE). A retrospective review of simultaneous scalp and intracranial video-EEG recordings from 28 patients with TLE was evaluated for epilepsy surgery. Scalp RTTBD patterns were identified and their clinical and intracranial EEG correlates were then determined on video-EEG recording using depth and subdural electrodes. Thirty-one RTTBD patterns on scalp EEG were observed in six (21%) of the 28 patients. Five (16%) of the RTTBD patterns occurred during wakefulness and 26 (84%) occurred during drowsiness and light sleep. The mean duration of RTTBD was 10 seconds (range: 3-28seconds). RTTDB consistently correlated with hippocampal ictal discharges and was time-locked to the hippocampal seizures in which the ictal discharges evolved into rhythmic theta frequency (4-7-Hz) range. Ictal automatisms were observed during five (16%) RTTBD patterns, while cognitive impairment was observed in four (13%) of the 31 RTTBD patterns. Our findings show that scalp EEG correlates of hippocampal ictal discharges can resemble RTTBD and may be associated with ictal symptoms and cognitive impairment, indicating that RTTBD may rarely be an ictal EEG pattern in patients with TLE.

Outcomes of stereoelectroencephalography exploration at an epilepsy surgery center.

Epilepsy surgery is offered in resistant focal epilepsy. Non-invasive investigations like scalp video EEG monitoring (SVEM) help delineate epileptogenic zone. Complex cases may require intracranial video EEG monitoring (IVEM). Stereoelectroencephalography (SEEG)-based intracerebral electrode implantation has better spatial resolution, lower morbidity, better tolerance, and superiority in sampling deep structures. Our objectives were to assess IVEM using SEEG with regard to reasoning behind implantation, course, surgical interventions, and outcomes. Seventy-two admissions for SEEG from January 2014 to December 2018 were included in the study. Demographic and clinical data were retrospectively collected. The cohort comprised of 69 adults of which 34 (47%) had lesional MRI. Reasons for SEEG consideringall cases includednon-localizing ictal onset (76%), ictal-interictal discordance (21%), discordant semiology (17%), proximity to eloquent cortex (33%), nuclear imaging discordance (34%), and discordance with neuropsychology (19%). Among lesional cases, additional reasons included SVEM discordance (68%) and dual or multiple pathology (47%). Forty-eight patients (67%) were offered resective surgery, and 41 underwent it. Twenty-three (56%) had at least one year post-surgical follow-up of which 14 (61%) had Engels class I outcome. Of the remaining 23 who were continued on medical management, 4 (17%) became seizure-free and 12 (51%) had reduction in seizure frequency. SEEG monitoring is an important and safe tool for presurgical evaluation with good surgical and non-surgical outcomes. Whether seizure freedom following non-surgical management could be related to SEEG implantation, medication change, or natural course needs to be determined.

Clinical implications of scalp ictal EEG pattern in patients with temporal lobe epilepsy

ObjectiveTo determine the clinical implications of scalp ictal EEG pattern in patients with temporal lobe epilepsy (TLE). MethodsScalp EEG ictal patterns were retrospectively determined in 27 consecutive patients with medically refractory temporal lobe epilepsy who underwent phase-1 scalp video-EEG and phase-2 simultaneous scalp and intracranial video-EEG recordings for pre-surgical evaluation. ResultsOf the 192 temporal lobe seizures recorded during phase-1 and phase-2 scalp video-EEG studies, 124 (65%) seizures were associated with theta/alpha (5–9 Hz) ictal onset pattern, and 68 (35%) seizures were associated with delta (2–5 Hz) ictal onset pattern. Fourteen (52%) patients had exclusively theta/alpha ictal onset, 3 (11%) patients had exclusively delta ictal onset, and 10 (37%) patients had mixed theta/alpha and delta ictal onsets. MTLE was observed in 26 patients who had 124 seizures with theta/alpha ictal onset and 59 seizures with delta ictal onset. LTLE was observed in one patient who had 9 seizures with delta ictal onset. Scalp ictal EEG pattern was not significantly correlated with postsurgical seizure outcomes. ConclusionsBoth scalp delta and theta/alpha ictal onset patterns can be commonly found in patients with MTLE. SignificanceScalp delta ictal onset is not a unique EEG pattern for LTLE as commonly believed.

The epileptogenic zone in pharmaco-resistant temporal lobe epilepsy with amygdala enlargement.

Temporal lobe epilepsy with amygdala enlargement (TLE-AE) has been considered a subtype of TLE. We evaluated the epileptogenic zone in patients with TLE-AE, who underwent intracranial video-EEG (ivEEG) and/or intraoperative electrocorticography (ioECoG) as well as epilepsy surgery. Eleven patients with TLE-AE were enrolled and investigated based on seizure profile, volumetric MRI, the Wechsler Memory Scale-Revised (WMS-R), the location of seizure onset zone (SOZ) and irritative zone (IZ) based on ivEEG (n=8), the location of interictal epileptiform discharges (IEDs) based on ioECoG (11), surgical procedure, and seizure outcome. The mean age at seizure onset was 34.9 years (range: 23-57). The mean duration of seizures was 5.0 years (range: 1-10). The number of AEDs was 2.3 (range: 1-5). The mean seizure frequency was nine per month (range: 1-30/month). All patients presented with focal impaired awareness seizures with (n=9) and without (2) secondary generalized convulsions. Volumetric MRI analysis showed unilateral enlarged amygdala with statistical significance (p<0.01). None of the patients' hippocampi had any abnormality based on MRI. Pre-operative mean verbal, visual, and delayed recall scores based on the WMS-R were over 100. The SOZ and IZ were identified in both the amygdala and hippocampus in seven patients and in only the amygdala in one patient based on ivEEG. IEDs were identified in the hippocampus in six patients and in both the amygdala and hippocampus in four patients based on ioECoG. All 11 patients underwent anterior temporal lobectomy, including amygdala resection, with multiple hippocampal transections (dominant hemisphere: seven patients) and resection (non-dominant hemisphere: three patients). Nine (81.8%) of 11 patients achieved seizure freedom with a mean follow-up of 26 months (range: 12-47). Post-operative WMS-R results did not show any significant deterioration, with a mean follow-up of 15 months (range: 12-24). The resected amygdala showed no histopathological abnormality. The epileptogenic zone of TLE-AE involves both the amygdala and hippocampus. ivEEG may be needed to explore the SOZ in normal hippocampus in addition to enlarged amygdala. Amygdala resection and multiple hippocampal transections may control the epileptogenic limbic system and save memory function in patients with TLE-AE.

A comprehensive clinico-pathological and genetic evaluation of bottom-of-sulcus focal cortical dysplasia in patients with difficult-to-localize focal epilepsy.

We comprehensively studied the clinical presentation, stereo-EEG and MRI findings, histopathological diagnosis, and brain somatic mutations in a retrospective series of drug-resistant patients with difficult-to-localize epilepsy due to focal cortical dysplasia at the bottom of a sulcus (BOS-FCD). We identified 10 patients with BOS-FCD from the Cleveland Clinic epilepsy surgery database submitted for intracranial video-EEG monitoring. Brain MRI, including voxel-based morphometric analysis and surgical tissue submitted for histopathology, was reviewed. Paraffin tissue samples from five patients were made available for targeted next-generation sequencing. Postsurgical follow-up was available in nine patients. BOS-FCD was identified in the superior frontal sulcus in six patients, inferior frontal sulcus in one patient, central sulcus in one patient, and intraparietal sulcus in two patients. All patients had stereotyped seizures. Intracranial EEG recordings identified ictal onset at the BOS-FCD in all 10 patients, whereas ictal scalp EEG had a localizing value in only six patients. Complete resection was achieved by lesionectomy or focal corticectomy in nine patients. Histopathologically, six patients had FCD type IIb and three had FCD type IIa. Next-generation sequencing analysis of DNA extracted from lesion-enriched (micro-dissected) tissue from five patients with FCD type II led to the identification of a germline frameshift insertion in DEPDC5, introducing a premature stop in one patient. Eight out of nine patients with available follow-up were completely seizure-free (Engel Class IA) after a mean follow-up period of six years. Our results confirm previous studies classifying difficult-to-localize BOS-FCD into the emerging spectrum of FCD ILAE type II mTORopathies. Further studies with large patient numbers and ultra-deep genetic testing may help to bridge the current knowledge gap in genetic aetiologies of FCD.

Sleep, Circadian Rhythms, and Epilepsy.

There is a known interrelationship between sleep and epilepsy. This review highlights the recent findings regarding interactions between sleep and circadian rhythms and the manifestations of epilepsy and surgical treatments for refractory epilepsy. CLOCK gene expression may be reduced within the epileptogenic focus in patients with refractory epilepsy. Interictal epileptiform discharges during NREM and especially REM sleep may lateralize to the epileptogenic hemisphere. Intracranial video EEG monitoring and EEG from implanted responsive neurostimulator devices confirm scalp video EEG findings of a nocturnal peak for interictal epileptiform discharges. Successful epilepsy surgery may improve sleep macrostructure and quality. Sleep outcomes in people with epilepsy undergoing epilepsy surgery and neurostimulator implantation may provide innovative understandings into the associations between sleep and epilepsy. These associations may then provide novel therapeutic options targeting sleep and circadian pathways to improve seizure control and improve the quality of life for patients with this debilitating disorder.

Cognitive tasks and human ambulatory electrocorticography using the RNS System

BackgroundElectrocorticography studies are typically conducted in patients undergoing video EEG monitoring, but these studies are subject to confounds such as the effects of pain, recent anesthesia, analgesics, drug changes, antibiotics, and implant effects. New methodTechniques were developed to obtain electrocorticographic (ECoG) data from freely moving subjects performing navigational tasks using the RNS® System (NeuroPace, Inc., Mountain View, CA), a brain-responsive neurostimulation medical device used to treat focal onset epilepsy, and to align data from the RNS System with cognitive task events with high precision. These subjects had not had recent surgery, and were therefore not confounded by the perioperative variables that affect video EEG studies. ResultsTask synchronization using the synchronization marker technique provides a quantitative measure of clock uncertainty, and can align data to task events with less than 4 ms of uncertainty. Hippocampal ECoG activity was found to change immediately before an incorrect response to a math problem compared to hippocampal activity before a correct response. In addition, subjects were found to have variable but significant changes in theta band power in the hippocampus during navigation compared to when subjects were not navigating. We found that there is theta–gamma phase-amplitude coupling in the right hippocampus while subjects stand still during a navigation task. Comparison with existing methodsAn alignment technique described in this study improves the upper bound on task-ECoG alignment uncertainty from approximately 30 ms to under 4 ms. The RNS System is one of the first platforms capable of providing untethered ambulatory ECoG recording in humans, allowing for the study of real world instead of virtual navigation. Compared to intracranial video EEG studies, studies using the RNS System platform are not subject to confounds caused by the drugs and recent surgery inherent to the perioperative environment. Furthermore, these subjects provide the opportunity to record from the same electrodes over the course of many years. ConclusionsThe RNS System enables us to study human navigation with unprecedented clarity. While RNS System patients have fewer electrodes implanted than video EEG patients, the lack of external artifact and confounds from recent surgery make this system a useful tool to further human electrophysiology research.

Advanced dynamic statistical parametric mapping with MEG in localizing epileptogenicity of the bottom of sulcus dysplasia

ObjectiveTo investigate whether advanced dynamic statistical parametric mapping (AdSPM) using magnetoencephalography (MEG) can better localize focal cortical dysplasia at bottom of sulcus (FCDB). MethodsWe analyzed 15 children with diagnosis of FCDB in surgical specimen and 3 T MRI by using MEG. Using AdSPM, we analyzed a ±50 ms epoch relative to each single moving dipole (SMD) and applied summation technique to estimate the source activity. The most active area in AdSPM was defined as the location of AdSPM spike source. We compared spatial congruence between MRI-visible FCDB and (1) dipole cluster in SMD method; and (2) AdSPM spike source. ResultsAdSPM localized FCDB in 12 (80%) of 15 children whereas dipole cluster localized six (40%). AdSPM spike source was concordant within seizure onset zone in nine (82%) of 11 children with intracranial video EEG. Eleven children with resective surgery achieved seizure freedom with follow-up period of 1.9 ± 1.5 years. Ten (91%) of them had an AdSPM spike source in the resection area. ConclusionAdSPM can noninvasively and neurophysiologically localize epileptogenic FCDB, whether it overlaps with the dipole cluster or not. SignificanceThis is the first study to localize epileptogenic FCDB using MEG.

Three phase-ictal scalp EEG patterns in patients with seizures arising from the cortex facing the interhemispheric fissure

ObjectiveIctal scalp EEG patterns have been reported to vary across onset regions. We assessed the sequential EEG changes during seizure events on scalp EEG, and tested our hypothesis that patients with focal seizures arising from the cortex facing the interhemispheric fissure (IHF cortex) would be specifically characterized by 3 phase-EEG patterns (3Ph-EEG). MethodsPatient inclusion criteria were: 1) focal epilepsy and 2) ictal onset records on scalp and intracranial video-EEG. Patients were classified into one of the three groups: the IHF group, mesial temporal (MT) group, or lateral convexity (LC) group, based on the localization of the ictal onset zone (IOZ) on intracranial video-EEG. We defined 3Ph-EEG on ictal scalp EEG as follows: phase 1, brief spike/fast wave burst; phase 2, diffuse attenuation; and phase 3, focal rhythmic activity with evolution. We determined if the occurrence ratios of 3Ph-EEG and each of the three phases differed between the groups (IHF and others). ResultsWe studied 36 patients aged 8–59 years (mean, 30 years). Ten patients were classified as IHF, 16 as MT, and 10 as LC group from 303 ictal events on intracranial EEG. 193 seizures on scalp EEG consisted of 79 seizures in IHF; 58 in MT; 56 in LC group. Sixty-nine seizures (92%) in nine patients (90%) in IHF group showed 3Ph-EEG, whereas none of the seizures in MT and LC groups showed the 3Ph-EEG. Multivariate logistic regression analysis suggested that the presence of 3Ph-EEG (p < 0.01) and phase 2 (p = 0.03) components were predictive of IHF scalp EEG onset. SignificanceThe 3Ph-EEG may be observed preferentially in patients with focal seizures from IHF cortex. Observation of the ictal phases on scalp EEG may warrant consideration of intracranial EEG sampling for the presurgical evaluation.

Intracranial video-EEG monitoring in presurgical evaluation of patients with refractory epilepsy

ObjectiveReviewing our experience in intracranial video-EEG monitoring in the presurgical evaluation of patients with refractory epilepsy. MethodsWe report on 62 out of 202 (31%) patients with refractory epilepsy, who underwent a long term video-EEG monitoring (LTM). The epileptogenic zone (EZ) was localised either based on the results of LTM or after intracranial EEG recordings from depth, subdural or foramen ovale electrodes. The decision on the location of the electrodes was based upon semiology of the seizures, EEG findings and the lesions visualised in MRI brain scan. Intraoperative corticography was carried out before and right after the resection of the seizure onset zone. ResultsThe video-EEG monitoring could localise EZ in 43 (69%) cases based. The remaining patients underwent invasive diagnostics: 10 (53%) had intracerebral depth electrodes, 6 (31%) depth and subdural and 3 (16%) foramen ovale electrodes. Intracranial video EEG recordings showed seizure focus in all the patients. Ten of them had EZ in mesial temporal structures, 4 in accessory motor area, 3 at the base of the frontal lobe and 2 in parietal lobe. There was one case of an asymptomatic intracerebral haematoma at the electrode. All patients were subsequently operated on. In 15 (79%) cases the seizures subsided (follow-up from 2 to 5 years), in 4 (21%) they decreased. ConclusionsThe intracranial EEG is required in all patients with normal MRI (so-called nonlesional cases) in whom EZ is suspected to be located in the hippocampus, insula or in the basal parts of the frontal lobe.

Postsurgical outcome in patients with olfactory auras and drug-resistant epilepsy.

We investigated the clinical features associated with olfactory auras in patients with drug-resistant epilepsy and also hypothesized that this type of aura may predict worse postsurgical outcome in patients with drug-resistant temporal lobe epilepsy (TLE). In this retrospective analysis, data from all patients with drug-resistant epilepsy who underwent epilepsy surgery were reviewed. Patients were prospectively registered in a database from 1986 through 2016. We assessed outcome in the first 5years after surgery to produce a Kaplan-Meier estimate of seizure recurrence. Post-surgical outcome was classified into two groups; 1) seizure-free, with or without auras; or 2) relapse of complex partial or secondarily generalized seizures. We also investigated the clinical features of patients with TLE and olfactory auras compared with those without olfactory auras. We studied 1186 patients. Thirty-seven patients (3.1%) reported olfactory auras with their seizures. Thirty-two patients had temporal lobe surgery. Intracranial video-EEG recording was performed in four patients. Three patients with lateral temporal neocortical seizures reported olfactory auras with their seizures; two of them were seizure-free after surgery. There were no significant clinical differences between patients with TLE and olfactory auras compared with those without. Seizure outcome after surgery was not significantly different between these two groups (p=0.3; Cox-Mantel test). The rarity of olfactory auras makes it difficult to propose new diagnostic and treatment strategies. A multicenter approach, which can enroll more patients, is needed to devise better therapies for patients with drug-resistant epilepsy and this symptom.

Increased subcortical oligodendroglia‐like cells in pharmacoresistant focal epilepsy in children correlate with extensive epileptogenic zones

Cortical resections in epilepsy surgery tend to involve multiple lobes in children, compared to adults, partly due to underlying pathology. Oligodendroglia-like cells (OLCs) have been observed in surgical specimens from children with pharmacoresistant epilepsy. We hypothesize that OLCs recruit multiple-lobe epileptogenic zones in pediatric pharmacoresistant focal epilepsy. We examined the surgical specimens from 30 children who underwent epilepsy surgery (1.8- to 16.9-years-old; mean age 9.7 years). Immunohistochemical assays of OLCs were performed using Olig2, which is a marker of OLC. OLC populations in three sites (gray matter, gray-white matter junction, and white matter) were counted. We also performed immunohistochemical staining with neuronal nuclear antigen (NeuN) and glial fibrillary acidic protein (GFAP) for neuronal and astroglial markers, respectively. NeuN- and GFAP-positive cells were distinguished from OLCs. OLC results were compared with seizure types, scalp and intracranial video-electroencephalography (EEG), magnetic resonance imaging (MRI), surgical resection area, histopathologic diagnosis, and seizure outcome. Histopathologic diagnosis consisted of 14 cases of focal cortical dysplasia (FCD; type I; 4, type II; 9, type III; one); 6 cases of oligodendrogliosis; 6 cases of astrocytic gliosis; 2 cases of hyaline protoplasmic astrocytopathy; and 2 cases of tuberous sclerosis. Fifteen children (50%) underwent multiple-lobe resections after intracranial video-EEG. There was a positive correlation between the number of resected electrodes and the OLC population in the white matter (correlation coefficient 0.581, p = 0.001) and at the gray-white matter junction- (correlation coefficient 0.426, p = 0.027). OLC populations in both areas were increased significantly in nine children with epileptic spasms (ES) (gray-white matter junction [p = 0.021] and white matter [p = 0.025]), and nine nonfocal ictal scalp EEG findings (gray-white matter junction [p = 0.04] and white matter [p = 0.042]). The OLC population in white matter was significantly increased in children with 11 nonfocal interictal scalp EEG findings (p = 0.01), with 15 multiple-lobe resections (p = 0.028). Pharmacoresistant epilepsy in children with increased OLCs presented with nonfocal epileptiform discharges on scalp EEG and ES, and they required multiple-lobe resections. We found increased populations of subcortical OLCs in the extensive epileptogenic zone.

Coprolalia as a manifestation of epileptic seizures.

The aim of this study was to investigate the lateralizing and localizing value of ictal coprolalia and brain areas involved in its production. A retrospective search for patients manifesting ictal coprolalia was conducted in our EMU database. Continuous video-EEG recordings were reviewed, and EEG activity before and during coprolalia was analyzed using independent component analysis (ICA) technique and was compared to the seizures without coprolalia among the same patients. Nine patients were evaluated (five women), eight with intracranial video-EEG recordings (icVEEG). Four had frontal or temporal lesions, and five had normal MRIs. Six patients showed impairment in the language functions and five in the frontal executive tasks. Two hundred six seizures were reviewed (60.7% from icVEEG). Ictal coprolalia occurred in 46.6% of them, always associated with limbic auras or automatisms. They arose from the nondominant hemisphere in five patients, dominant hemisphere in three, and independently from the right and left hippocampus-parahippocampus in one. Electroencephalographic activity always involved orbitofrontal and/or mesial temporal regions of the nondominant hemisphere when coprolalia occurred. Independent component analysis of 31 seizures in seven patients showed a higher number of independent components in the nondominant hippocampus-parahippocampus before and during coprolalia and in the dominant lateral temporal region in those seizures without coprolalia (p=0.009). Five patients underwent surgery, and all five had an ILAE class 1 outcome. Ictal coprolalia occurs in both males and females with temporal or orbitofrontal epilepsy and has a limited lateralizing value to the nondominant hemisphere but can be triggered by seizures from either hemisphere. It involves activation of the paralimbic temporal-orbitofrontal network.

Rapid eye movement sleep reveals epileptogenic spikes for resective surgery in children with generalized interictal discharges.

Epilepsy surgery can be successful in children with extensive congenital or early acquired focal or hemispheric brain lesion on magnetic resonance imaging (MRI) despite generalized interictal epileptiform discharges (IEDs). The aim of this study was to assess if rapid eye movement (REM) sleep reduced generalized IEDs and revealed lateralized IEDs to identify the epileptogenic hemisphere in children with generalized IEDs and normal/subtle changes on MRI. We studied 20 children with generalized IEDs on scalp electroencephalography (EEG) and normal/subtle changes on MRI who underwent intracranial video-EEG for epilepsy surgery. We assessed a minimum of 100 IEDs during REM, non-REM, and wakefulness, and assigned the distribution (generalized, left, or right hemisphere) to each IED. The number of lobes in the resected areas and seizure outcome were compared between 20 children with generalized IEDs and a comparison group of 28 children without generalized IEDs. The mean occurrence rate of generalized IEDs during REM (37%) was significantly lower than that during non-REM (67%, p < 0.001) and wakefulness (54%, p = 0.003). The number of children whose largest number of IEDs was lateralized in REM was significantly higher than that in non-REM (15 vs. 3 children, 75% vs. 15%, p < 0.001). The hemisphere with lateralized IEDs among three states corresponded with the surgical side in 16 children with generalized IEDs. Seventeen children (85%) with generalized IEDs and 27 (96%) without generalized IEDs underwent resective surgery. Multilobar resection was required for 16 children (94%) with generalized IEDs more frequently than 7 children (26%) without generalized IEDs (p < 0.001). Thirteen children (77%) with generalized IEDs and 19 (73%) without generalized IEDs were seizure-free with a mean of 3.3 years of follow-up. Our study demonstrates the importance of assessing REM in children with generalized IEDs as it reveals lateralized epileptogenic spikes. Seizure freedom may be achieved with multilobar resection in these children with generalized IEDs and normal/subtle changes on MRI. Generalized IEDs in children with normal/subtle changes on MRI should not preclude surgical resection.

A multi-modality approach to identifying primary generalized epilepsy that can mimic focal epilepsy

Introduction: Evaluating the suitability for surgery in patients with epilepsy requires determining if the epilepsy is focal or generalized. Presurgical workups can indicate focal epilepsy in certain cases of generalized epilepsy (GE). The purpose of this study was to identify distinctive features which characterize patients with primary GE that mimics focal epilepsy. Method: We retrospectively identified 19 children with generalized interictal discharges during scalp video-EEG (SVEEG) and underwent invasive monitoring and/or epilepsy surgery. Two children did not undergo resective surgery due to final diagnosis of primary GE (Group A). Seventeen children underwent a resective surgery (Group B). Scalp video-EEG, MEG, MRI, and intracranial video EEG (IVEEG) were reviewed. Results: On (SVEEG), the frequency of generalized spike-and-waves (GSW) was 3Hz in Group A and 1.5-2.5Hz in Group B. Group A had only absence seizures , whereas 80% in Group B had multiple types of seizures. Both groups had lateralized MEG dipoles. One patient in Group A had a focal MRI abnormality. In Group A, IVEEG showed GSW of 3 Hz frequency with inconsistent leading. In Group B, IVEEG showed consistent localization of ictal and interictal high frequency oscillations. Conclusion: Children with generalized 3 Hz spike-and-waves and only absence seizures may be a contraindication of resective surgery even though some presurgical workup shows focality.