Stereo electroencephalography in the kingdom of Saudi Arabia.

Epilepsy surgery and intracranial monitoring have a long history in the Kingdom of Saudi Arabia, spanning over 30 years. Stereo-EEG however, is a more recent offering. In this short communication, we discuss how Stereo-EEG has grown in the context of the Kingdom's healthcare model and the Vision 2030 model. We discuss the various positives of this technique and methodology as well as the various challenges that the hospitals offering Stereo-EEG have faced.

Predicting radiofrequency thermocoagulation surgical outcomes in refractory focal epilepsy patients using functional coupled neural mass model.

Objective: The success rate of achieving seizure freedom after radiofrequency thermocoagulation surgery for patients with refractory focal epilepsy is about 20-40%. This study aims to enhance the prediction of surgical outcomes based on preoperative decisions through network model simulation, providing a reference for clinicians to validate and optimize surgical plans. Methods: Twelve patients with epilepsy who underwent radiofrequency thermocoagulation were retrospectively reviewed in this study. A coupled model based on model subsets of the neural mass model was constructed by calculating partial directed coherence as the coupling matrix from stereoelectroencephalography (SEEG) signals. Multi-channel time-varying model parameters of excitation and inhibitions were identified by fitting the real SEEG signals with the coupled model. Further incorporating these model parameters, the coupled model virtually removed contacts destroyed in radiofrequency thermocoagulation or selected randomly. Subsequently, the coupled model after virtual surgery was simulated. Results: The identified excitatory and inhibitory parameters showed significant difference before and after seizure onset (p < 0.05), and the trends of parameter changes aligned with the seizure process. Additionally, excitatory parameters of epileptogenic contacts were higher than that of non-epileptogenic contacts, and opposite findings were noticed for inhibitory parameters. The simulated signals of postoperative models to predict surgical outcomes yielded an area under the curve (AUC) of 83.33% and an accuracy of 91.67%. Conclusion: The multi-channel coupled model proposed in this study with physiological characteristics showed a desirable performance for preoperatively predicting patients' prognoses.

The effect of SEEG on the long-term outcomes of different side anterior temporal lobectomy: A single-center retrospective study.

PURPOSE: Anterior temporal lobectomy (ATL) is the most common surgical treatment for temporal lobe epilepsy (TLE), and Stereoelectroencephalography (SEEG) plays a critical role in precisely localizing the epileptogenic zone (EZ). This study aimed to explore the effect of SEEG on the long-term outcomes of different side ATL. METHODS: From March 2012 to February 2020, a retrospective analysis was conducted on 231 TLE patients who underwent standard ATL surgery. According to the surgical sides and the utilization of SEEG during preoperative evaluation, the patients were categorized into four groups, with a follow-up period exceeding two years. RESULTS: Among the 231 TLE patients, the probability of being seizure-free two years after the surgery was 80.52%, which decreased to 65.65% after five years. There was no significant difference in outcomes between SEEG and non-SEEG patients. For overall and non-SEEG patients, there was no significant difference in short-term outcomes between different surgical sides. However, the long-term outcomes of right ATL patients were significantly better than left. Interestingly, for patients who underwent SEEG, there was no significant difference in both short-term and long-term outcomes between different surgical sides. CONCLUSION: Some TLE patients encounter challenges in localizing the EZ through non-invasive evaluation, necessitating the use of SEEG for precise localization. Furthermore, their seizure outcomes after surgery can be the same with the patients who have a clear epileptogenic zone in non-invasive evaluation. And SEEG patients can achieve a more stable long-term prognosis than non-SSEEG patients.

Sleep-related hypermotor seizures originating from the occipital lobe.

We present two unique cases of sleep-related hypermotor epilepsy (SHE) originating from the occipital lobe. Patients with sleep-related seizures and drug-resistant occipital lobe epilepsy were identified from the ANPHY lab stereo-electroencephalography (SEEG) research database at the Duke Comprehensive Epilepsy Center. We identified two young females with frequent sleep-related focal seizures and occasional focal to bilateral tonic clonic seizures characterized by hypermotor movements. During wakefulness, the semiology also involved an elementary visual aura. They meet the 2016 diagnostic criteria for SHE, and SEEG monitoring with cortical stimulation mapping identified an epileptogenic zone (EZ) within the occipital lobe, with most seizures occurring out of NREM 2 sleep. Responsive neurostimulation devices were implanted, which indicated a trend for event detections in nocturnal periods. Extrafrontal SHE has characteristically been described in the temporal, insular-opercular, and parietal lobes. Here, we demonstrate using SEEG-confirmed EZ identification, that SHE can also originate in the occipital lobe. In patients with sleep-related seizures and hypermotor behavior, occipital lobe seizures thus should not be excluded from the differential diagnosis. Key in identifying this rare localization is non-frontal aura semiology and delay to motor symptoms, which may be supported by a visual field deficit and structural MRI abnormality.

SEEG4D: a tool for 4D visualization of stereoelectroencephalography data.

Epilepsy is a prevalent and serious neurological condition which impacts millions of people worldwide. Stereoelectroencephalography (sEEG) is used in cases of drug resistant epilepsy to aid in surgical resection planning due to its high spatial resolution and ability to visualize seizure onset zones. For accurate localization of the seizure focus, sEEG studies combine pre-implantation magnetic resonance imaging, post-implant computed tomography to visualize electrodes, and temporally recorded sEEG electrophysiological data. Many tools exist to assist in merging multimodal spatial information; however, few allow for an integrated spatiotemporal view of the electrical activity. In the current work, we present SEEG4D, an automated tool to merge spatial and temporal data into a complete, four-dimensional virtual reality (VR) object with temporal electrophysiology that enables the simultaneous viewing of anatomy and seizure activity for seizure localization and presurgical planning. We developed an automated, containerized pipeline to segment tissues and electrode contacts. Contacts are aligned with electrical activity and then animated based on relative power. SEEG4D generates models which can be loaded into VR platforms for viewing and planning with the surgical team. Automated contact segmentation locations are within 1 mm of trained raters and models generated show signal propagation along electrodes. Critically, spatial-temporal information communicated through our models in a VR space have potential to enhance sEEG pre-surgical planning.

Normative atlases of high-frequency oscillation and spike rates under Sevoflurane anesthesia.

OBJECTIVE: We analyzed the dose-dependent effects of Sevoflurane anesthesia on high-frequency oscillations (HFOs) and spike discharges at non-epileptic sites and evaluated their effectiveness in identifying the epileptogenic zone. METHODS: We studied 21 children with drug-resistant focal epilepsy who achieved seizure control after focal resective surgery. Open-source detectors quantified HFO and spike rates during extraoperative and intraoperative intracranial EEG recordings performed before resection. We determined under which anesthetic conditions HFO and spike rates differentiated the seizure onset zone (SOZ) within the resected area from non-epileptic sites. RESULTS: We analyzed 925 artifact-free electrodes, including 867 at non-epileptic sites and 58 at SOZ sites. Higher Sevoflurane doses significantly increased HFO and spike rates at non-epileptic sites, exhibiting spatial variability among different detectors. These biomarkers were elevated in the SOZ more than in non-epileptic sites under 2-4 vol% Sevoflurane anesthesia, with Cohen's d effect sizes above 3.0 and Mann-Whitney U-Test r effect sizes above 0.5. CONCLUSIONS: We provided normative atlases of HFO and spike rates under different Sevoflurane anesthesia conditions. Sevoflurane elevates HFO and spike rates preferentially in the epileptogenic zone. SIGNIFICANCE: Assessing the relative severity of biomarker levels across sites may be relevant for localizing the epileptogenic zone under Sevoflurane anesthesia.

Integrating the 5-SENSE Score for Patient Selection in Vagus Nerve Stimulation for Drug-Resistant Epilepsy.

Addressing the challenge of drug-resistant epilepsy, our study offers a novel perspective by retrospectively applying the 5-SENSE score, initially created for stereoelectroencephalography (SEEG) planning, to evaluate its predictive value in patients undergoing vagus nerve stimulation (VNS) therapy. We conducted a comprehensive preoperative diagnostic work-up, including computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography-CT (PET-CT), video-electroencephalogram (video-EEG), and clinical semiology. We then stratified 76 patients into three groups - low, moderate, and high focality - based on the focality of the seizure-onset zone. Such stratification was made to check the scoring ability in predicting VNS therapy seizure reduction. Our findings demonstrate an association between the extent of focality at the seizure-onset zone and the effectiveness of VNS, which may help to define the role of the 5-SENSE score in patient selection for VNS. This high dispersion of responses in the group with high focality reinforces the idea that outcome estimation is difficult and argues for an individualized strategy in the treatment of drug-resistant epilepsy. A study at the level of the 5-SENSE score indicates the importance of detailed preoperative assessments that may better optimize selection for VNS therapy and further improve clinical outcomes.

Functional mapping of movement and speech using task-based electrophysiological changes in stereoelectroencephalography.

OBJECTIVE: Stereoelectroencephalography (SEEG) has become the predominant method for intracranial seizure localization. When imaging, semiology, and scalp EEG findings are not in full agreement or definitively localizing, implanted SEEG recordings are used to test candidate seizure onset zones (SOZs). Discovered SOZs may then be targeted for resection, laser ablation, or neurostimulation. If an SOZ is eloquent, resection and ablation are both contraindicated, so identifying functional representation is crucial for therapeutic decision-making. The authors present a novel functional brain mapping technique that utilizes task-based electrophysiological changes in SEEG during behavioral tasks and test this in pediatric and adult patients. METHODS: SEEG was recorded in 20 patients with epilepsy who ranged in age from 6 to 39 years (12 female, 18 of 20 patients < 21 years of age) and underwent implanted monitoring to identify seizure onset. Each performed 1) visually cued simple repetitive movements of the hand, foot, or tongue while electromyography was recorded; and 2) simple picture-naming or verb-generation speech tasks while audio was recorded. Broadband changes in the power spectrum of the SEEG recording were compared between behavior and rest. RESULTS: Electrophysiological functional mapping of movement and/or speech areas was completed in all 20 patients. Eloquent representation was identified in both cortex and white matter and generally corresponded to classically described functional anatomical organization as well as other clinical mapping results. Robust maps of brain activity were identified in healthy brain, regions of developmental or acquired structural abnormality, and SOZs. CONCLUSIONS: Task-based electrophysiological mapping using broadband changes in the SEEG signal reliably identifies movement and speech representation in pediatric and adult epilepsy patients.

Epileptic network identification: insights from dynamic mode decomposition of sEEG data.

Objective.For medically-refractory epilepsy patients, stereoelectroencephalography (sEEG) is a surgical method using intracranial electrode recordings to identify brain networks participating in early seizure organization and propagation (i.e. the epileptogenic zone, EZ). If identified, surgical EZ treatment via resection, ablation or neuromodulation can lead to seizure-freedom. To date, quantification of sEEG data, including its visualization and interpretation, remains a clinical and computational challenge. Given elusiveness of physical laws or governing equations modelling complex brain dynamics, data science offers unique insight into identifying unknown patterns within high-dimensional sEEG data. We apply here an unsupervised data-driven algorithm, dynamic mode decomposition (DMD), to sEEG recordings from five focal epilepsy patients (three with temporal lobe, and two with cingulate epilepsy), who underwent subsequent resective or ablative surgery and became seizure free.Approach.DMD obtains a linear approximation of nonlinear data dynamics, generating coherent structures ('modes') defining important signal features, used to extract frequencies, growth rates and spatial structures. DMD was adapted to produce dynamic modal maps (DMMs) across frequency sub-bands, capturing onset and evolution of epileptiform dynamics in sEEG data. Additionally, we developed a static estimate of EZ-localized electrode contacts, termed the higher-frequency mode-based norm index (MNI). DMM and MNI maps for representative patient seizures were validated against clinical sEEG results and seizure-free outcomes following surgery.Main results.DMD was most informative at higher frequencies, i.e. gamma (including high-gamma) and beta range, successfully identifying EZ contacts. Combined interpretation of DMM/MNI plots best identified spatiotemporal evolution of mode-specific network changes, with strong concordance to sEEG results and outcomes across all five patients. The method identified network attenuation in other contacts not implicated in the EZ.Significance.This is the first application of DMD to sEEG data analysis, supporting integration of neuroengineering, mathematical and machine learning methods into traditional workflows for sEEG review and epilepsy surgical decision-making.

Combined value of interictal markers and stimulated seizures to estimate the seizure onset zone in stereoelectroencephalography.

OBJECTIVE: This study was undertaken to investigate the potential of interictal electroencephalographic (EEG) findings and electrically stimulated seizures during stereo-EEG (SEEG) as surrogate markers for the spontaneous seizure onset zone (spSOZ). We hypothesized that combining the localizing information of these markers would allow clinically meaningful estimation of the spSOZ. METHODS: We included all patients (n = 63) who underwent SEEG between January 2013 and March 2020 at Helsinki University Hospital and had spontaneous seizures during the recording. We scored spikes, gamma activity, and background abnormality on each channel visually during a 12-h epoch containing waking state and sleep. Based on semiology, we classified stimulated seizures as typical or atypical/unclassifiable and estimated the stimulated SOZ (stimSOZ) for typical seizures. To assess which markers increased the odds of channel inclusion in the spSOZ, we fitted mixed effects logistic regression models. RESULTS: A combined regression model including the stimSOZ and interictal markers scored during sleep performed better in estimating which channels were part of the spSOZ than models based on stimSOZ (p < .001) or interictal markers (p < .001) alone. Of the individual markers, the effect sizes were greatest for inclusion of a channel in the stimSOZ (odds ratio [OR] = 60, 95% confidence interval [CI] = 37-97, p < .001) and for continuous (OR = 25, 95% CI = 12-55, p < .001) and subcontinuous (OR = 36, 95% CI = 21-64, p < .001) interictal spiking. At the individual level, the model's accuracy to predict spSOZ inclusion varied markedly (median accuracy = 85.7, range = 54.4-100), which was not explained by etiology (p > .05). SIGNIFICANCE: Compared to either marker alone, combining visually rated interictal SEEG markers and stimulated seizures improved prediction of which SEEG channels belonged to the spSOZ. Inclusion in the stimSOZ and continuous or subcontinuous spikes increased the odds of spSOZ inclusion the most. Future studies should investigate whether suboptimal sampling of the true epileptogenic zone can explain the model's poor performance in certain patients.

Investigating current clinical opinions in stereoelectroencephalography-informed epilepsy surgery.

OBJECTIVE: Stereoelectroencephalography (SEEG) is increasingly utilized worldwide in epilepsy surgery planning. International guidelines for SEEG terminology and interpretation are yet to be proposed. There are worldwide differences in SEEG definitions, application of features in epilepsy surgery planning, and interpretation of surgical outcomes. This hinders the clinical interpretation of SEEG findings and collaborative research. We aimed to assess the global perspectives on SEEG terminology, differences in the application of presurgical features, and variability in the interpretation of surgery outcome scores, and analyze how clinical expert demographics influenced these opinions. METHODS: We assessed the practices and opinions of epileptologists with specialized training in SEEG using a survey. Data were qualitatively analyzed, and subgroups were examined based on geographical regions and years of experience. Primary outcomes included opinions on SEEG terminology, features used for epilepsy surgery, and interpretation of outcome scores. Additionally, we conducted a multilevel regression and poststratification analysis to characterize the nonresponders. RESULTS: A total of 321 expert responses from 39 countries were analyzed. We observed substantial differences in terminology, practices, and use of presurgical features across geographical regions and SEEG expertise levels. The majority of experts (220, 68.5%) favored the Lüders epileptogenic zone definition. Experts were divided regarding the seizure onset zone definition, with 179 (55.8%) favoring onset alone and 135 (42.1%) supporting onset and early propagation. In terms of presurgical SEEG features, a clear preference was found for ictal features over interictal features. Seizure onset patterns were identified as the most important features by 265 experts (82.5%). We found similar trends after correcting for nonresponders using regression analysis. SIGNIFICANCE: This study underscores the need for standardized terminology, interpretation, and outcome assessment in SEEG-informed epilepsy surgery. By highlighting the diverse perspectives and practices in SEEG, this research lays a solid foundation for developing globally accepted terminology and guidelines, advancing the field toward improved communication and standardization in epilepsy surgery.

The network is more important than the node: stereo-EEG evidence of neurocognitive networks in epilepsy.

Introduction: Neuropsychological assessment forms an integral part of the presurgical evaluation for patients with medically refractory focal epilepsy. Our understanding of cognitive impairment in epilepsy is based on seminal lesional studies that have demonstrated important structure-function relationships within the brain. However, a growing body of literature demonstrating heterogeneity in the cognitive profiles of patients with focal epilepsy (e.g., temporal lobe epilepsy; TLE) has led researchers to speculate that cognition may be impacted by regions outside the seizure onset zone, such as those involved in the interictal or "irritative" network. Methods: Neuropsychological data from 48 patients who underwent stereoelectroencephalography (SEEG) monitoring between 2012 and 2023 were reviewed. Patients were categorized based on the site of seizure onset, as well as their irritative network, to determine the impact of wider network activity on cognition. Neuropsychological data were compared with normative standards (i.e., z = 0), and between groups. Results: There were very few distinguishing cognitive features between patients when categorized based purely on the seizure onset zone (i.e., frontal lobe vs. temporal lobe epilepsy). In contrast, patients with localized irritative networks (i.e., frontal or temporal interictal epileptiform discharges [IEDs]) demonstrated more circumscribed profiles of impairment compared with those demonstrating wider irritative networks (i.e., frontotemporal IEDs). Furthermore, the directionality of propagation within the irritative network was found to influence the manifestations of cognitive impairment. Discussion: The findings suggest that neuropsychological assessment is sensitive to network activity beyond the site of seizure onset. As such, an overly focal interpretation may not accurately reflect the distribution of the underlying pathology. This has important implications for presurgical work-up in epilepsy, as well as subsequent surgical outcomes.

Development of a stereo-EEG based seizure matching system for clinical decision making in epilepsy surgery.

OBJECTIVE: The proportion of patients becoming seizure-free after epilepsy surgery has stagnated. Large multi-center stereo-electroencephalography datasets can allow comparing new patients to past similar cases and making clinical decisions with the knowledge of how cases were treated in the past. However, the complexity of these evaluations makes the manual search for similar patients impractical. We aim to develop an automated system that electrographically and anatomically matches seizures to those in a database. Additionally, since features that define seizure similarity are unknown, we evaluate the agreement and features among experts in classifying similarity. Approach: We utilized 320 stereo-electroencephalography seizures from 95 consecutive patients who underwent epilepsy surgery. Eight international experts evaluated seizure-pair similarity using a four-level similarity score. As our primary outcome, we developed and validated an automated seizure matching system by employing patient data marked by independent experts. Secondary outcomes included the inter-rater agreement and features for classifying seizure similarity. Main results: The seizure matching system achieved a median area-under-the-curve of 0.76 (interquartile range, 0.1), indicating its feasibility. Six distinct seizure similarity features were identified and proved effective: onset region, onset pattern, propagation region, duration, extent of spread, and propagation speed. Among these features, the onset region showed the strongest correlation with expert scores (Spearman's rho=0.75, p<0.001). Additionally, the moderate inter-rater agreement confirmed the practicality of our approach with an agreement of 73.9% (7%), and Gwet's kappa of 0.45 (0.16). Further, the interoperability of the system was validated on seizures from five centers. Significance: We demonstrated the feasibility and validity of a stereo-electroencephalography seizure matching system across patients, effectively mirroring the expertise of epileptologists. This novel system can identify patients with seizures similar to that of a patient being evaluated, thus optimizing the treatment plan by considering the results of treating similar patients in the past, potentially improving surgery outcome. .

Cognitive outcome after stereo-electroencephalography-guided radiofrequency thermocoagulation in temporal lobe epilepsy.

OBJECTIVE: Stereo-electroencephalography (SEEG)-guided radiofrequency thermocoagulation (RFTC) is being used incrementally in the invasive diagnosis of epilepsy. There is currently a lack of information regarding the potential cognitive consequences of the extended use of this technique. This work describes, for the first time, the cognitive outcomes after RFTC in patients with temporal lobe epilepsy (TLE), evaluated longitudinally and using a control group. METHODS: Forty-eight adult patients with drug-resistant unilateral TLE (30 RFTC-treated patients and 18 controls) were evaluated using a comprehensive neuropsychological protocol at baseline. In the RFTC group, two follow-up assessments were performed at 3 months and 1 year. The control group was reevaluated after 1 year. Two analyses were performed: 1) group-level analyses, in which linear mixed models were applied according to TLE lateralization (intragroup and intergroup [RFTC vs control] comparisons), and 2) individual-level analyses, in which the Reliable Change Index (RCI) algorithm was developed and a 90% CI (cutoff ± 1.64) was used to describe neuropsychological outcomes at 1 year post-RFTC. A memory subanalysis was performed in hippocampal RFTC patients (25/30). A Spearman coefficient study was conducted to determine the correlation between cognitive change and thermocoagulated contacts. RESULTS: Left- and right-sided TLE patients treated with RFTC showed cognitive preservation at baseline. At a group level, the short-term evaluation, including verbal and visual memory, language, and executive functions, showed preservation in these domains and no significant differences compared with baseline. In the long-term follow-up assessment (1 year after RFTC), no significant intragroup changes were found, nor were significant changes found in comparison with the control group. The RCI algorithm showed that significant individual cognitive losses and gains were infrequent. Three patients presented with naming deficits, only 1 (3.3%) of whom showed a clinically significant deficit. Significant gains were more prevalent in executive function tests with a speed component (4/20 left-sided RFTC patients). Twenty-five of the 30 (83%) patients were treated with hippocampal RFTC. No patients experienced significant loss in verbal delayed memory in the left-sided RFTC sample or in visual delayed memory in the right-sided RFTC sample. The correlations between cognitive change and RFTC contacts were mostly nonsignificant. CONCLUSIONS: In the group-level comparisons, discernible cognitive impairment following RFTC was not evidenced. The majority of patients did not exhibit significant individual declines during the 1-year follow-up period. Notably, the procedural intervention yielded no substantial repercussions on memory functioning following hippocampal RFTC. These findings underscore the evidence supporting the cognitive preservation associated with SEEG-guided RFTC.

Simultaneous sampling of both cingulate gyri using a single interhemispheric depth electrode: A technical note.

Background: Simultaneous sampling of the cingulate gyri through a single depth electrode inserted underneath the falx cerebri is clinically useful in certain cases of drug-resistant epilepsy. However, the frequency at which each region of the cingulate gyri - namely, anterior, middle, and posterior - can be simultaneously sampled with a single electrode remains uncertain. Methods: We assessed the anatomical relationship between the falx cerebri and the cingulate gyrus in 50 adults and children. Subsequently, we determined whether an arbitrary line, denoted as A (representing a 5 mm gap between the falx cerebri and corpus callosum necessary for depth electrode insertion), fell within the anterior, middle, or posterior cingulate gyrus. Results: The shape of the falx cerebri and its intersection point with the corpus callosum varied substantially across individuals, with a significant difference between children and adults (P = 0.02). The A line was located in the middle cingulate gyrus in 18 children (72%), while 3 (12%) and 4 (16%) had it located in the posterior and anterior cingulate gyrus, respectively. Among adults, 15 individuals (60%) had the A line in the middle cingulate gyrus, 10 (40%) in the posterior cingulate gyrus, and none in the anterior cingulate gyrus. Conclusion: This study demonstrates the feasibility of simultaneous sampling of both the anterior and middle cingulate gyri in adults and children. Moreover, it represents the first investigation to document the wide interindividual variability in the morphology of the falx cerebri and its association with the cingulate gyrus.

Oscillatory and nonoscillatory sleep electroencephalographic biomarkers of the epileptic network.

OBJECTIVE: In addition to the oscillatory brain activity, the nonoscillatory (scale-free) components of the background electroencephalogram (EEG) may provide further information about the complexity of the underlying neuronal network. As epilepsy is considered a network disease, such scale-free metrics might help to delineate the epileptic network. Here, we performed an analysis of the sleep oscillatory (spindle, slow wave, and rhythmic spectral power) and nonoscillatory (H exponent) intracranial EEG using multiple interictal features to estimate whether and how they deviate from normalcy in 38 adults with drug-resistant epilepsy. METHODS: To quantify intracranial EEG abnormalities within and outside the seizure onset areas, patients' values were adjusted based on normative maps derived from the open-access Montreal Neurological Institute open iEEG Atlas. In a subset of 29 patients who underwent resective surgery, we estimated the predictive value of these features to identify the epileptogenic zone in those with a good postsurgical outcome. RESULTS: We found that distinct sleep oscillatory and nonoscillatory metrics behave differently across the epileptic network, with the strongest differences observed for (1) a reduction in spindle activity (spindle rates and rhythmic sigma power in the 10-16 Hz band), (2) a higher rhythmic gamma power (30-80 Hz), and (3) a higher H exponent (steeper 1/f slope). As expected, epileptic spikes were also highest in the seizure onset areas. Furthermore, in surgical patients, the H exponent achieved the highest performance (balanced accuracy of .76) for classifying resected versus nonresected channels in good outcome patients. SIGNIFICANCE: This work suggests that nonoscillatory components of the intracranial EEG signal could serve as promising interictal sleep candidates of epileptogenicity in patients with drug-resistant epilepsy. Our findings further advance the understanding of epilepsy as a disease, whereby absence or loss of sleep physiology may provide information complementary to pathological epileptic processes.

Safety and accuracy of stereoelectroencephalography for pediatric and young adult patients with prior craniotomy.

OBJECTIVE: The authors assessed the safety and accuracy of stereoelectroencephalography (SEEG) electrode implantation in pediatric patients who had previously undergone craniotomy compared to those without prior cranial surgery. METHODS: The authors performed a retrospective analysis of patients under 25 years of age with medically refractory epilepsy at a single institution who underwent SEEG electrode placement between March 2016 and July 2023. Surgical history and demographic characteristics were collected from the electronic medical records. The coordinates of the anchor bolts and their respective SEEG electrode contacts were manually annotated using postoperative head CT scans. Bolt coordinates were used to calculate the initiated electrode trajectory set by the bolt by using the least-squares method to define a line along the bolt, projected along the length of the electrode. The shortest distance from each electrode contact to this line was calculated to obtain the error measurement. Statistical analysis was conducted using the Kolmogorov-Smirnov test to compare the distribution of errors between groups, the Student t-test was used for continuous variables, and the chi-square/Fisher's exact test was used for categorical variables. RESULTS: Fifty-eight patients underwent a total of 60 SEEG placements and met the inclusion criteria. Eighteen had a history of prior craniotomy and 40 without prior surgery, indicating entirely native cranial bone. Mean age, sex, and mean number of electrodes implanted per surgery were similar between groups. For the electrode contact furthest from the bolt, a mean (IQR) deviation of 1.32 (0.73-2.53) mm was noted for the prior craniotomy group and 1.08 (0.65-1.55) mm for the native bone group (p < 0.0001). A greater number of outliers for the contact furthest from the bolt, defined as > 6 mm from the initiated electrode trajectory, was seen in the prior craniotomy group (p < 0.0001). The complication rate was low and not statistically different between groups. CONCLUSIONS: The authors' analysis draws attention to the effect of the intracranial biomechanical environment along the path of the electrode after traversing past the anchor bolt and found that prior craniotomy was associated with a higher number of contacts with a significant deviation from the initiated trajectory. Despite these deviations, we did not find a difference in the overall low complication rate in both groups. Therefore, the authors conclude that SEEG electrode placement is a safe option in pediatric patients even after prior craniotomy.

Network signatures define consciousness state during focal seizures.

OBJECTIVE: Epilepsy is a common neurological disorder affecting 1% of the global population. Loss of consciousness in focal impaired awareness seizures (FIASs) and focal-to-bilateral tonic-clonic seizures (FBTCSs) can be devastating, but the mechanisms are not well understood. Although ictal activity and interictal connectivity changes have been noted, the network states of focal aware seizures (FASs), FIASs, and FBTCSs have not been thoroughly evaluated with network measures ictally. METHODS: We obtained electrographic data from 74 patients with stereoelectroencephalography (SEEG). Sliding window band power, functional connectivity, and segregation were computed on preictal, ictal, and postictal data. Five-minute epochs of wake, rapid eye movement sleep, and deep sleep were also extracted. Connectivity of subcortical arousal structures was analyzed in a cohort of patients with both SEEG and functional magnetic resonance imaging (fMRI). Given that custom neuromodulation of seizures is predicated on detection of seizure type, a convolutional neural network was used to classify seizure types. RESULTS: We found that in the frontoparietal association cortex, an area associated with consciousness, both consciousness-impairing seizures (FIASs and FBTCSs) and deep sleep had increases in slow wave delta (1-4 Hz) band power. However, when network measures were employed, we found that only FIASs and deep sleep exhibited an increase in delta segregation and a decrease in gamma segregation. Furthermore, we found that only patients with FIASs had reduced subcortical-to-neocortical functional connectivity with fMRI versus controls. Finally, our deep learning network demonstrated an area under the curve of .75 for detecting consciousness-impairing seizures. SIGNIFICANCE: This study provides novel insights into ictal network measures in FASs, FIASs, and FBTCSs. Importantly, although both FIASs and FBTCSs result in loss of consciousness, our results suggest that ictal network changes in FIASs uniquely resemble those that occur during deep sleep. Our results may inform novel neuromodulation strategies for preservation of consciousness in epilepsy.

The surgical interval between robot-assisted SEEG and epilepsy resection surgery is an influencing factor of SSI.

BACKGROUND: In recent years, the development of robotic neurosurgery has brought many benefits to patients, but there are few studies on the occurrence of surgical site infection (SSI) after robot-assisted stereoelectroencephalography (SEEG). The purpose of this study was to collect relevant data from robot-assisted SEEG over the past ten years and to analyze the influencing factors and economic burden of surgical site infection. METHODS: Basic and surgical information was collected for all patients who underwent robot-assisted SEEG from January 2014 to December 2023. Logistic regression was used to analyze the factors influencing SSI according to different subgroups (radiofrequency thermocoagulation or epilepsy resection surgery). RESULTS: A total of 242 subjects were included in this study. The risk of SSI in the epilepsy resection surgery group (18.1%) was 3.5 times greater than that in the radiofrequency thermocoagulation group (5.1%) (OR 3.49, 95% CI 1.39 to 9.05); this difference was statistically significant. SSI rates in the epilepsy resection surgery group were associated with shorter surgical intervals (≤ 9 days) and higher BMI (≥ 23 kg/m2) (6.1 and 5.2 times greater than those in the control group, respectively). Hypertension and admission to the intensive care unit (ICU) were risk factors for SSI in the radiofrequency thermocoagulation group. Patients with SSIs had $21,231 more total hospital costs, a 7-day longer hospital stay, and an 8-day longer postoperative hospital stay than patients without SSI. CONCLUSIONS: The incidence of SSI in patients undergoing epilepsy resection after stereoelectroencephalography was higher than that in patients undergoing radiofrequency thermocoagulation. For patients undergoing epilepsy resection surgery, prolonging the interval between stereoelectroencephalography and epilepsy resection surgery can reduce the risk of SSI; At the same time, for patients receiving radiofrequency thermocoagulation treatment, it is not recommended to enter the ICU for short-term observation if the condition permits.

Stereo-electro-encephalography (SEEG) methodology: technical nuances and insights into image-guided robot-assisted electrode implantation.

An accurate definition of the epileptogenic zone is critical to the success of epilepsy surgery. When noninvasive presurgical studies are insufficient, stereoelectroencephalography (SEEG) becomes indispensable. This study illustrates a systematic approach using an illustrative case of centroparietal epilepsy, detailing the stepwise workup, planning, and image-guided robot-assisted frameless stereotactic implantation of intracerebral electrodes. The video provides insights into technical aspects and a single-center experience. Demonstrating efficacy, safety, and feasibility, SEEG emerges as a valuable procedure for studying drug-resistant focal epilepsy. The video can be found here: https://stream.cadmore.media/r10.3171/2024.4.FOCVID2427.