Invasive EEG Research Articles

Long-term Stability of Interictal Spike Trajectories in Pediatric Invasive EEG Recordings (P4.5-003)

Long-term Stability of Interictal Spike Trajectories in Pediatric Invasive EEG Recordings (P4.5-003)

Brain-Computer Interface (BCI) Applications in Mapping of Epileptic Brain Networks Based on Intracranial-EEG: An Update.

The main applications of the Brain–Computer Interface (BCI) have been in the domain of rehabilitation, control of prosthetics, and in neuro-feedback. Only a few clinical applications presently exist for the management of drug-resistant epilepsy. Epilepsy surgery can be a life-changing procedure in the subset of millions of patients who are medically intractable. Recording of seizures and localization of the Seizure Onset Zone (SOZ) in the subgroup of “surgical” patients, who require intracranial-EEG (icEEG) evaluations, remain to date the best available surrogate marker of the epileptogenic tissue. icEEG presents certain risks and challenges making it a frontier that will benefit from optimization. Despite the presentation of several novel biomarkers for the localization of epileptic brain regions (HFOs-spikes vs. Spikes for instance), integration of most in practices is not at the prime time as it requires a degree of knowledge about signal and computation. The clinical care remains inspired by the original practices of recording the seizures and expert visual analysis of rhythms at onset. It is becoming increasingly evident, however, that there is more to infer from the large amount of EEG data sampled at rates in the order of less than 1 ms and collected over several days of invasive EEG recordings than commonly done in practice. This opens the door for interesting areas at the intersection of neuroscience, computation, engineering and clinical care. Brain–Computer interface (BCI) has the potential of enabling the processing of a large amount of data in a short period of time and providing insights that are not possible otherwise by human expert readers. Our practices suggest that implementation of BCI and Real-Time processing of EEG data is possible and suitable for most standard clinical applications, in fact, often the performance is comparable to a highly qualified human readers with the advantage of producing the results in real-time reliably and tirelessly. This is of utmost importance in specific environments such as in the operating room (OR) among other applications. In this review, we will present the readers with potential targets for BCI in caring for patients with surgical epilepsy.

Quantitative Signal Characteristics of Electrocorticography and Stereoelectroencephalography: The Effect of Contact Depth.

Patients undergoing epilepsy surgery often require invasive EEG, but few studies have examined the signal characteristics of contacts on the surface of the brain (electrocorticography, ECOG) versus depth contacts, used in stereoelectroencephalography (SEEG). As SEEG and ECOG have significant differences in complication rates, it is important to determine whether both modalities produce similar signals for analysis, to ultimately guide management of medically intractable epilepsy. Twenty-seven patients who underwent SEEG (19), ECOG (6), or both (2) were analyzed for quantitative measures of activity including spectral power and phase-amplitude coupling during approximately 1 hour of wakefulness. The position of the contacts was calculated by coregistering the postoperative computed tomography with a reconstructed preoperative MRI. Using two types of referencing schemes-local versus common average reference-the brain regions where any quantitative measure differed systematically with contact depth were established. Using even the most permissive statistical criterion, few quantitative measures were significantly correlated with contact depth in either ECOG or SEEG contacts. The factors that predicted changes in spectral power and phase-amplitude coupling with contact depth were failing to baseline correct spectral power measures, use of a local rather than common average reference, using baseline correction for phase-amplitude coupling measures, and proximity of other grey matter structures near the region where the contact was located. The signals recorded by ECOG and SEEG have very similar spectral power and phase-amplitude coupling, suggesting that both modalities are comparable from an electrodiagnostic standpoint in delineation of the epileptogenic network.

Impact of withdrawal of antiepileptic medication on the duration of focal onset seizures

PurposeTo systematically evaluate the duration of focal onset seizures under medication withdrawal as a function of drug half-life. MethodsAdults with drug resistant focal epilepsy and invasive electroencephalographic (iEEG) recording between 01/2006 and 06/2016 (n = 128) were identified. Patients with multifocal or unknown epileptic foci were excluded, as well as subclinical seizures, isolated auras, or status epileptic. Antiepileptic drugs (AEDs) were withdrawn upon admission. The seizure duration was determined based on the invasive EEG data, and the latency since start of the monitoring was noted in hours. A negative binomial mixed model was used to compare the seizure durations before and after a cut-off, which was set at 2.5 half-lives of the individual anticonvulsive medication as this is thought to separate therapeutic and ineffective drug levels. ResultsIn total, 70 patients were included in the study and the duration of 672 seizures analyzed. On average, the patients were treated with 2.36 ± 0.78 AEDs. The individual cut-off of 2.5 half-lives was on average reached after 95.02 ± 80.18 h. The seizure frequency (321 vs. 351) and the rate of generalization (15.6% vs. 16.8%) was comparable before and after the individual cut-off point. The mean seizure duration was not statistically significantly prolonged after 2.5 half-lives by a factor of 1.168 for focal onset seizures (p = 0.090) and a factor of 1.091 for secondary generalized seizures (p = 0.545). ConclusionsAlthough AED withdrawal increases the likelihood for epileptic seizures, it did not prolong the seizure duration, nor did it increase the rate of secondary generalization in our study.

Survey of epilepsy and seizure awareness in Manitoba: An evaluation

BackgroundEpilepsy and seizure awareness is gradually improving across Canada. With the strategic proposal for a Comprehensive Epilepsy Program in Manitoba (including formation of a new Pediatric Epilepsy Monitoring Unit (EMU)), a provincial strategy has been recommended outlining a path towards improved access to epilepsy care. We sought to qualify the current state of clinician knowledge and comfort towards diagnosis and management of this condition. MethodsA qualitative online survey (Survey of Epilepsy and Seizure Awareness in Manitoba: An Evaluation (SESAME)), comprised of 36 short-answer questions, was delivered to primary care and specialist physicians in Manitoba. ResultsOne hundred and eight subjects responded across varying medical disciplines. One hundred and one (93.5%) had previously managed patients with epilepsy, and 87 (80.6%) had previously ordered an electroencephalogram (EEG). A total of 63 (59.4%) had referred to a neurologist, with a lower proportion (30, 28.3%) referring specifically to an epileptologist. Only 36 respondents (33.3%) had heard of the International League Against Epilepsy (ILAE) guidelines. A total of 61 (56.5%) were unaware of invasive EEG techniques. Most (85, 78.7%) understood a role for surgery in treating epilepsy, with 12 (11.1%) unaware of surgical therapies beyond vagal nerve stimulation (VNS). Finally, less than half (44.2%) had heard about the Comprehensive Epilepsy Program in Manitoba, with nearly two-thirds (62.8%) indicating that they would like to have more information on epilepsy management. ConclusionsThe SESAME successfully identified strong awareness towards epilepsy, with identifiable lapses in knowledge that will benefit from a formal provincial-wide educational curriculum.

Non-invasive Seizure Localization with Ictal Single-Photon Emission Computed Tomography is Impacted by Preictal/Early Ictal Network Dynamics.

More than one third of children with epilepsy have medically intractable seizures. Promising therapies, including targeted neurostimulation and surgery, depend on accurate localization of the epileptogenic zone. Ictal perfusion Single-Photon Emission Computed Tomography (SPECT) can localize the seizure focus noninvasively, with comparable accuracy to that of invasive EEG. However, multiple factors including seizure dynamics may affect its spatial specificity. Using subtracted ictal from interictal SPECT and scalp EEG from 118 pediatric epilepsy patients (40 of whom had surgery after the SPECT studies), information theoretic measures of association and advanced statistical models, this study investigated the impact of preictal and ictal brain network dynamics on SPECT focality. Network dynamics significantly impacted the SPECT localization ~30 s before to ~45 s following ictal onset. Distributed early ictal connectivity changes, indicative of a rapidly evolving seizure, were negatively associated with SPECT focality. Spatially localized connectivity changes later in the seizure, indicating slower seizure propagation, were positively associated with SPECT focality. In the first ~60 s of the seizure, significantly higher network connectivity was estimated in an area overlapping with the area of hyperperfusion. Finally, ~75% of patients with Engel class 1a/1b outcomes had SPECTs that were concordant with the resected area. Slowly evolving seizures are more likely to be accurately imaged with SPECT, and the identified focus may overlap with brain regions where significant topological changes occur. Measures of preictal/early ictal network dynamics may help optimize the SPECT localization, leading to improved surgical and neurostimulation outcomes in refractory epilepsy.

Predicting state transitions in brain dynamics through spectral difference of phase-space graphs.

Networks are naturally occurring phenomena that are studied across many disciplines. The topological features of a network can provide insight into the dynamics of a system as it evolves, and can be used to predict changes in state. The brain is a complex network whose temporal and spatial behavior can be measured using electroencephalography (EEG). This data can be reconstructed to form a family of graphs that represent the state of the brain over time, and the evolution of these graphs can be used to predict changes in brain states, such as the transition from preictal to ictal in patients with epilepsy. This research proposes objective indications of seizure onset observed from minimally invasive scalp EEG. The approach considers the brain as a complex nonlinear dynamical system whose state can be derived through time-delay embedding of the EEG data and characterized to determine change in brain dynamics related to the preictal state. This method targets phase-space graph spectra as biomarkers for seizure prediction, correlates historical degrees of change in spectra, and makes accurate prediction of seizure onset. A significant trend of normalized dissimilarity over time indicates a departure from the norm, and thus a change in state. Our methods show high sensitivity (90-100%) and specificity (90%) on 241 h of scalp EEG training data, and sensitivity and specificity of 70%-90% on test data. Moreover, the algorithm was capable of processing 12.7 min of data per second on an Intel Core i3 CPU in Matlab, showing that real-time analysis is viable.

Intra-operative cortical motor mapping using subdural grid electrodes in children undergoing epilepsy surgery evaluation and comparison with the conventional extra-operative motor mapping

ObjectivesThe objective of this study was to review our experience with intra-operative “train of five” stimulation using subdural grid for motor mapping in children undergoing epilepsy surgery evaluation. MethodsTwenty consecutive children below 18-years of age with drug-refractory epilepsy who underwent invasive-EEG monitoring using subdural-grid placement and intra-operative motor mapping using direct cortical stimulation by sub-dural grid electrodes (IODCS-SDG) at our institution between January-2016 and June-2017 were reviewed. Stimulation was delivered through the subdural-grid electrodes using a train-of-five pulses and muscle responses were recorded by motor-evoked-potentials (MEPs). Intra-operative direct cortical stimulation delivered through a ball-tipped probe (IODCS-probe) and extra-operative motor-mapping (EODCS-SDG) were also performed. ResultsIODCS-SDG was completed in 20 patients and subsequent EODCS-SDG was done in 17/20 patients. MEP responses were more commonly obtained in the deltoid (19/20), extensor-digitorum-communis (20/20) and first-dorsal-interosseus (19/20). The median thresholds varied between 40 V and 60 V for the six muscle groups. The respective IODCS-probe thresholds tended to be similar. No stimulation-provoked seizures or anaesthesia-related complications were noted during IODCS-SDG. EODCS-SDG could not be completed in 4/17 children and mapping data obtained was frequently inadequate. Nine patients demonstrated 100% concordance between IODCS-SDG and EODCS-SDG for the common mapped body regions. Stimulation-provoked seizures during EODCS-SDG were seen in 6/17 (35.3%) and after-discharges in 7/17 (41.2%) children. ConclusionsIODCS-SDG could be performed safely in children with drug refractory epilepsy undergoing invasive EEG monitoring. SignificanceIODCS-SDG may be a useful adjunct to EODCS-SDG in motor mapping for children.

Seizure outcome after surgery for medically intractable mesial temporal lobe epilepsy and its predictors

To evaluate seizure outcome in patients receiving surgery for chronic medically intractable mesial temporal lobe epilepsy (MTLE) and analyze its possible predictors. This retrospective study was conducted in patients with chronic medically intractable MTLE undergoing anterior temporal lobectomy (ATL) or selective amygdalohippocampectomy (SAH) in our department between September, 2011 and October, 2013. The patients were followed up for 3.5 to 5.5 years, during which the seizure outcome was evaluated according to Engel's classification. The clinical data were collected from the patients to identify the possible predictors that affected the outcome of the patients using Mann-Whitney U test or Kruskal-Wallis test. Atotal of 34 patients were included in this study with a definite diagnosis of chronic medically intractable MTLE after preoperative noninvasive and invasive evaluation. In 4 of these patients, invasive EEG monitoring confirmed that epileptic discharges originated from the bilateral mesial temporal lobe, and hence surgical resection of the epileptogenic zone was not performed. The other 30 patients underwent surgical resection of the epileptogenic zone with ALT or SAH, and favorable outcomes were achieved in 23 (76.7%) of the patients. Of the 7 (23.3%) patients with poor outcomes, 6 patients presented with typical automatism and aura with frequent secondary generalized tonic-clonic seizure, and the other one patient exhibited impaired intelligence. Statistical analysis suggested that the patients without a special disease history (trauma, febrile seizure, or encephalitis) tended to have a more favorable seizure outcome. Surgical interventions can achieve good therapeutic effect on chronic medically intractable MTLE, and patients without a special disease history may have more favorable outcomes after the surgery. SAH via the superior temporal sulcus approach can be a better surgical option for intractable MTLE.

Integrating artificial intelligence with real-time intracranial EEG monitoring to automate interictal identification of seizure onset zones in focal epilepsy

Objective. An ability to map seizure-generating brain tissue, i.e. the seizure onset zone (SOZ), without recording actual seizures could reduce the duration of invasive EEG monitoring for patients with drug-resistant epilepsy. A widely-adopted practice in the literature is to compare the incidence (events/time) of putative pathological electrophysiological biomarkers associated with epileptic brain tissue with the SOZ determined from spontaneous seizures recorded with intracranial EEG, primarily using a single biomarker. Clinical translation of the previous efforts suffers from their inability to generalize across multiple patients because of (a) the inter-patient variability and (b) the temporal variability in the epileptogenic activity. Approach. Here, we report an artificial intelligence-based approach for combining multiple interictal electrophysiological biomarkers and their temporal characteristics as a way of accounting for the above barriers and show that it can reliably identify seizure onset zones in a study cohort of 82 patients who underwent evaluation for drug-resistant epilepsy. Main results. Our investigation provides evidence that utilizing the complementary information provided by multiple electrophysiological biomarkers and their temporal characteristics can significantly improve the localization potential compared to previously published single-biomarker incidence-based approaches, resulting in an average area under ROC curve (AUC) value of 0.73 in a cohort of 82 patients. Our results also suggest that recording durations between 90 min and 2 h are sufficient to localize SOZs with accuracies that may prove clinically relevant. Significance. The successful validation of our approach on a large cohort of 82 patients warrants future investigation on the feasibility of utilizing intra-operative EEG monitoring and artificial intelligence to localize epileptogenic brain tissue. Broadly, our study demonstrates the use of artificial intelligence coupled with careful feature engineering in augmenting clinical decision making.

Investigation of subdural electrode displacement in invasive epilepsy surgery workup using neuronavigation and intraoperative MRI

ABSTRACTObjectives: One of the main obstacles of electrode implantation in epilepsy surgery is the electrode shift between implantation and the day of explantation. We evaluated this possible electrode displacement using intraoperative MRI (iopMRI) data and CT/MRI reconstruction.Methods: Thirteen patients (nine female, four male, median age 26 ± 9.4 years) suffering from drug-resistant epilepsy were examined. After implantation, the position of subdural electrodes was evaluated by 3.0 T-MRI and thin-slice CCT for 3D reconstruction. Localization of electrodes was performed with the volume-rendering technique. Post-implantation and pre-explantation 1.5 T-iopMRI scans were coregistered with the 3D reconstructions to determine the extent of electrode dislocation.Results: Intraoperative MRI at the time of explantation revealed a relevant electrode shift in one patient (8%) of 10 mm. Median electrode displacement was 1.7 ± 2.6 mm with a coregistration error of 1.9 ± 0.7 mm. The median accuracy of the neuronavigation system was 2.2 ± 0.9 mm. Six of twelve patients undergoing resective surgery were seizure free (Engel class 1A, median follow-up 37.5 ± 11.8 months).Conclusion: Comparison of pre-explantation and post-implantation iopMRI scans with CT/MRI data using the volume-rendering technique resulted in an accurate placement of electrodes. In one patient with a considerable electrode dislocation, the surgical approach and extent was changed due to the detected electrode shift.Abbreviations: ECoG: electrocorticography; EZ: epileptogenic zone; iEEG: invasive EEG; iopMRI: intraoperative MRI; MEG: magnetoencephalography; PET: positron emission tomography; SPECT: single photon emission computed tomography; 3D: three-dimensional.

P.014 Survey of epilepsy and seizure awareness in Manitoba: an evaluation (SESAME)

Background: Epilepsy/seizure awareness is improving across Canada. With the formation of a Comprehensive Epilepsy Program in Manitoba (including a new Pediatric Epilepsy Monitoring Unit), a provincial strategy has been proposed outlining a path towards improved access to epilepsy care. We now sought to qualify the current state of clinician knowledge and comfort towards diagnosis and management of this condition. Methods: A qualitative online survey, comprised of 36 short-answer questions, was delivered to primary care and specialist physicians in Manitoba. Results:108 subjects responded, across varying medical disciplines. 101 (93.5%) have previously managed epilepsy patients, and 87 (80.6%) have previously ordered an EEG. A total of 63 (59.4%) have referred to a neurologist, with a lower proportion (30, 28.3%) referring specifically to an epileptologist. 36 respondents (33.3%) have heard of the ILAE guidelines, with 43 (63.2%) reporting refractory epilepsy to be -defined by the failure of 3 (or more) medications. 61 (56.5%) were unaware of invasive EEG techniques. Most (85, 78.7%) understood a role for surgery in treating epilepsy, with 12 (11.1%) unaware of surgical therapies beyond VNS. Conclusions: SESAME successfully identified strong awareness towards epilepsy, with small lapses in knowledge that will benefit from a formal provincial-wide educational curriculum.

Using network analysis to localize the epileptogenic zone from invasive EEG recordings in intractable focal epilepsy.

Treatment of medically intractable focal epilepsy (MIFE) by surgical resection of the epileptogenic zone (EZ) is often effective provided the EZ can be reliably identified. Even with the use of invasive recordings, the clinical differentiation between the EZ and normal brain areas can be quite challenging, mainly in patients without MRI detectable lesions. Consequently, despite relatively large brain regions being removed, surgical success rates barely reach 60–65%. Such variable and unfavorable outcomes associated with high morbidity rates are often caused by imprecise and/or inaccurate EZ localization. We developed a localization algorithm that uses network-based data analytics to process invasive EEG recordings. This network algorithm analyzes the centrality signatures of every contact electrode within the recording network and characterizes contacts into susceptible EZ based on the centrality trends over time. The algorithm was tested in a retrospective study that included 42 patients from four epilepsy centers. Our algorithm had higher agreement with EZ regions identified by clinicians for patients with successful surgical outcomes and less agreement for patients with failed outcomes. These findings suggest that network analytics and a network systems perspective of epilepsy may be useful in assisting clinicians in more accurately localizing the EZ.

F07. Using ultra-high field 7T MRI for evaluation of EEG findings in patients with temporal lobe epilepsy

Introduction Assessment of patients for temporal lobe epilepsy (TLE) surgery requires multimodality input, including anatomical MRI, neuropsychological evaluation, functional neuroimaging, scalp electroencephalography (EEG) and invasive EEG recordings to ensure optimal surgical planning. Often EEG demonstrates abnormal foci that are not detected on 1.5T MRI. Ultra high-field MRI at 7T provides much improved resolution of the brain. We investigated the utility of 7T MRI to detect potential anatomical abnormalities associated with functional abnormalities detected by scalp and/or invasive EEG recordings. Methods Ultra-high-field data were acquired on a 7T neuroimaging optimized MRI scanner for 13 patients with a history of drug resistant TLE during evaluation for epilepsy surgery. All patients had video-EEG telemetry recordings in our Epilepsy Monitoring Unit. Additionally, 9 patients underwent invasive EEG recordings including subdural and/or depth electrodes. Qualitative evaluation of 7T imaging for scan quality and presence of focal abnormalities detected on EEG was performed. The correlation of 7T MRI findings with EEG recordings of focal slowing or interictal epileptic spikes (IEDs), and seizures was performed. Results Assessment of 7T MRI demonstrated concordance with the clinically suspected TLE in 8 out of 13 cases. Among these, 3 exhibited supportive abnormal 7T MRI abnormalities not detected by the clinical 1.5T MRI. Eleven out of 13 cases had scalp and/or invasive electrode EEG findings with no anatomic correlates on 1.5T or 7T MRI. Findings included IEDs localizing to the contralateral temporal lobe in 6 patients, frontal lobes in 3 patients, and parieto-occipital lobes in 2 patients. Qualitative assessment of 7T images did not reveal any focal anatomical abnormalities to account for the EEG findings in these patients. Conclusion To our knowledge, this is the first study to investigate the utility of 7T MRI in combination with scalp and invasive. Qualitative ultra high-field 7T MRI findings show a moderate concordance with clinical data. However, 7T MRI did not reveal focal anatomical findings to account for all the abnormalities detected by the scalp EEG recordings in patients with temporal lobe epilepsy.

T22. Intra-operative motor mapping using subdural grid electrodes in children undergoing invasive EEG monitoring

Introduction Extra-operative motor mapping (EOMM) in the pediatric population can be challenging, especially in young and/or developmentally delayed children, due to lack of cooperation, and higher motor stimulation thresholds. This study examined the feasibility and safety of intra-operative motor mapping (IOMM) using subdural grid electrodes in children undergoing epilepsy surgery evaluation. Methods Twenty consecutive children under18 years of age with drug refractory epilepsy who underwent invasive EEG monitoring using subdural grid placement and intra-operative motor mapping at our institution between December 2015 and June 2017 were enrolled. Stimulation was delivered to the subdural grid electrode using a train of five pulses, with an interstimulus interval of 1.1 ms and a pulse duration of 50 microseconds. Stimulation intensity was commenced at 25 Volts (V) and increased gradually until acceptable motor evoked potential (MEP) waveforms were generated. MEPs were recorded from the contralateral six muscle groups (orbicularis oris, deltoid, extensor digitorum communis, first dorsal interossei, tibialis anterior and abductor halluces). Extra-operative motor mapping (previously published procedure) was also done 3 days after the subdural grid placement. Results IOMM using sub-dural grid electrodes was completed in 20 patients, and simultaneous EOMM was done in 17 patients. The mean age at the time of mapping was 11.7 years (SD 4.2). 13/20 patients had malformations of cortical development. MEP responses were more commonly obtained in the deltoid (19/20), extensor digitorum communis (20/20) and first dorsal inerossei (19/20). The mean threshold varied from 44.5 V to 55.8 V for the six muscle groups. With increasing age, there was a decline in the motor thresholds with a possible exponential relationship. No seizures or anaesthesia related complications were noted. EOMM could not be completed in 4/17 children (3-clinical seizures, 1-limited patient cooperation). The mapping was incomplete in the majority of cases with 1 being the median number of areas mapped (IQR, 1–2). Seizures were seen in 6/17 (35.3%) and after-discharges in 7/17 (41.2%) children. Nine patients demonstrated 100% concordance between the common mapped areas, 4 patients showed 50% concordance and 3 patients showed no concordance between IOMM and EOMM. The median duration of follow up was 10.2 months (IQR, 3.6 to 14.4 months). ILAE seizure outcome 1 was seen in 15 patients (75%) at the last follow up. Post-operative neurological deficits were seen in 11 patients: contralateral motor deficits (6; 2 were transient), contralateral sensory deficits (2), homonymous hemianopia (1) and seizures (3). Conclusion IOMM was found to be feasible and safe procedure in children with drug refractory epilepsy undergoing invasive EEG monitoring using the subdural grid.

Corpus callosum atrophy and post-surgical seizures in temporal lobe epilepsy associated with hippocampal sclerosis

ObjectiveOur aim in this retrospective study was to explore whether corpus callosum atrophy could predict the post-surgical seizure control in patients with temporal lobe epilepsy associated with Hippocampal Sclerosis (HS). MethodsWe used the Corpus Callosum Index (CCI) obtained from best mid-sagittal T2/FLAIR or T1-weighted MRI at two time-points, more than one year apart. CCI has been mainly used in Multiple Sclerosis (MS), but not in epilepsy, so we tested the validity of our results performing a proof of concept cohort, incorporating MS patients with and without epilepsy. Then, we explored this measurement in a well-characterized and long-term cohort of patients with temporal lobe epilepsy associated with HS. ResultsIn the proof of concept cohort (MS without epilepsy n:40, and MS with epilepsy, n:15), we found a larger CCI atrophy rate in MS patients with poor epilepsy control vs. MS without epilepsy (p:0.01). Then, in HS patients (n:74), annualized CCI atrophy rate was correlated with the long-term Engel scale (Rho:0.31, p:0.007). In patients with post-surgical seizure recurrence, a larger CCI atrophy rate was found one year before any seizure relapse. Univariate analysis showed an increased risk of seizure recurrence in males, higher pre-surgical seizure frequency, necessity of invasive EEG monitoring, and higher CCI atrophy rate. Two of these variables were independent predictors in the multivariate analysis, male gender (HR:4.87, p:0.002) and CCI atrophy rate (HR:1.21, p:0.001). ConclusionWe demonstrated that atrophy of the corpus callosum, using the CCI, is related with poor seizure control in two different neurological disorders presenting with epilepsy, which might suggest that corpus callosum atrophy obtained in early post-surgical follow-up, could be a biomarker for predicting recurrences and guiding treatment plans.

A novel non-invasive method for evaluating electroencephalograms on laying hens

The use of electroencephalograms (EEG) to study the avian brain relative to behavior was conducted as early as the 1960's. EEG readings, combined with visual cues, provide the ability to elucidate and correlate behaviors to neurological and physiological changes in a chicken. The use of EEG recordings in animal models require access to the brain to implant electrodes. Having the ability to observe EEG activity on sensible birds without surgical implantation could broaden the research in this area and give further insight related to the hen's state of awareness. The development, construction, and implementation of a minimally invasive EEG electrode placement method is described. After implementation, test animals were exposed to extreme environmental stressors as part of a concurrent depopulation methods study and EEG placement withstood the condition changes and corresponding animal physical activity. Sixteen white commercial laying hens had three monopolar 32-gauge needle electrodes inserted subcutaneously and secured to their head and body. Electrodes were attached to a pre-amplifier which transferred EEG signals to a laptop based recording system. Once the electrodes were in place, the hens were placed in individual treatment/observation chamber then various environmental stressors were applied. Verification that the observed brainwave activity was neural and not muscular was done using a photic stimulation validation test. Behavior observations were recorded to correlate sensible and insensible brainwave activity. The validation test and behavior observations demonstrated the method was successful in measuring EEG in sensible laying hens. The use of a non-surgical method for recording EEG will broaden research capabilities and enhance the understanding of a hen's response its environment, eliminate the need for invasive surgical procedures, and minimizes the confounding components of anesthesia, brain surgery, and recovery. With further refinements, the method could open new avenues in avian behavioral and physiological research.

Lesion focused radiofrequency thermocoagulation of bottom-of-sulcus focal cortical dysplasia type IIb: Conceptional considerations with regard to the epileptogenic zone

Small bottom-of-sulcus focal cortical dysplasias (BOS-FCD) type IIb are intrinsically epileptogenic lesions often responsible for pharmacoresistant epilepsy. They are increasingly well demarcated in vivo from surrounding cortex and white matter by 3 T magnetic resonance imaging (MRI). These facts and frequent seizure freedom after just narrow resections allow questioning the classical concept of epilepsy surgery in which the epileptogenic lesion is generally considered only one part of the epileptogenic zone and the resection volume categorically has to exceed lesion limits.This study approaches this question by analyzing procedures of strongly lesion focused stereotactic radiofrequency thermocoagulation (L-RFTC) applied to BOS-FCD IIb. Seven patients with BOS-FCD IIb were treated, three had invasive EEG recordings prior to L-RFTC, all had intraoperative stereotactic EEG-recordings. Perilesional epileptic discharges (PLD) were documented in all patients. Coagulation was planned based on MRI, the maximum extension beyond lesion limits due to PLD was 4.8 mm. Although in all patients other areas of PLD remained uncoagulated, seizure freedom was achieved in four of five patients with complete lesion coagulation.In summary, due to the minimal extensions of lesion coagulations, current experience with L-RFTC of BOS-FCD IIb is not yet sufficient to rebut the significance of PLD. It encourages, however, further research on even stronger MRI guidance and possibly even ignorance of PLD in BOS-FCD IIb. It appears possible that in some BOS-FCD IIB the complete epileptogenic zone (according to Lüders) might lie inside the MRI visible lesion. This would influence the understanding of the concept of cortical zones.

Intracranial electrodes monitoring improves seizure control and complication outcomes for patients with temporal lobe epilepsy - A retrospective cohort study

BackgroundAnterior temporal lobectomy (ATL) is the standard surgical treatment for temporal lobe epilepsy (TLE), but patients may suffer from recurrent seizures post-surgery. Invasive electrical monitoring plays a critical role in precisely identifying the epileptic foci. This study aimed to evaluate and compare the benefits of long-term invasive electroencephalography (EEG) monitoring and two-stage surgery with the classical approach to examine their effect on post-surgical brain function and complications. Materials and methodsPatients with TLE (N = 198) who underwent epilepsy surgery were retrospectively evaluated. Diagnosis of TLE was confirmed based on clinical grounds (semiology), EEG findings, and magnetic resonance imaging (MRI). Long-term invasive video EEG was performed; epileptiform discharges were recorded. Patients underwent either classical ATL or modified two-step surgery with electrodes implantation. Histopathological examination was performed. The patients were followed up at 1, 3, and 5 years after surgery. ResultsTwenty-three and 175 patients underwent classical ATL and two-stage surgery, respectively. On histopathological examination, inflammation, hippocampal sclerosis, and cortical dysplasia were found to be the leading pathological causes of epileptic foci in both groups. MRI results were not consistent with the pathological findings. Grade II and III Engel scores were more frequent in the ATL group compared to two-stage surgery during follow-up. No postoperative complications were reported in two-stage surgery during follow-up, but one patient had mild hemiplegia in the ATL group. ConclusionsPreoperative invasive monitoring with long-term EEG helps locate the epileptic foci precisely. Postsurgical complications are rare compared to classical ATL, with better prognosis and seizure freedom after surgery.

The Epileptogenic Zone: Concept and Definition.

A "concept" refers to what exists in the mind as a representation (as in something comprehended) or as a formulation (as in a plan). It is generally understood as "any idea of what a thing ought to be" (Merriam-Webster). From that premise, an "idea" cannot be compartmentalized or rigidly defined as exclusively belonging to any single individual or school of thought. The utility of a concept is inherently linked to its adaptability to the needs and conditions of the time. I state this upfront because over the past several decades, the concept of the epileptogenic zone (EZ) has become so crucial to the foundation of major schools of surgical epilepsy that discussions and opinions on the topic have essentially sought to legitimize one view while criticizing the other. This review is not a referendum on any specific definition of the EZ but rather a chronological analysis of the historical evolution of this concept and the invasive EEG tools used to study it. The goal is to highlight common ground necessary to tackle the ever-present challenge of defining the ideal resection for a patient with drug-resistant focal epilepsy.