UNASSIGNED: 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.
UNASSIGNED: 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.
UNASSIGNED: 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%.
UNASSIGNED: The multi-channel coupled model proposed in this study with physiological characteristics showed a desirable performance for preoperatively predicting patients\' prognoses.

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.

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.

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).
CONCLUSIONS: 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.

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.

UNASSIGNED: 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.
UNASSIGNED: 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.
UNASSIGNED: 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.
UNASSIGNED: 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.

UNASSIGNED: 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.
UNASSIGNED: 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.
UNASSIGNED: 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.
UNASSIGNED: 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.

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.
CONCLUSIONS: 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.

BACKGROUND: Stereoelectroencephalography (SEEG) is a procedure used to localize the epileptogenic zone in patients with medically refractory epilepsy, involving the stereotactic implantation of electrodes into brain parenchyma. Magnetic Resonance Imaging (MRI), Digital Subtraction Angiography, and Computed Tomography have been used preoperatively to prevent Intracranial Hemorrhage (ICH) by identifying electrode-vessel conflicts (EVC\'s) on planned electrode trajectories. There is variation in the use of Digital Subtraction Angiography and non-invasive sequences for vascular planning. Digital Subtraction Angiography provides high spatial resolution, but carries risks of arterial dissection, groin and retroperitoneal hematoma, and a 0.5-1.9% risk of stroke. Our group has incorporated Intravenous Cone Beam Computed Tomography (CBCT A/V) Brain into our SEEG workflow, given its effective implementation in other neurosurgical domains. Primary aims include validating the safety of our CBCT A/V sequence for SEEG planning and determining if CBCT A/V is comparable to other modalities in detecting EVC\'s. Secondary aims include elucidating the relationship of conflicting vessel calibre with ICH incidence in SEEG using CBCT A/V imaging.
METHODS: A single-center retrospective study was conducted of 20 patients who underwent preoperative CBCT A/V Brain and MRI Brain with gadolinium enhancement, encompassing 273 electrode implantations from August 2020 - July 2023. The incidence and grade of post-implant, post-explant symptomatic ICH and asymptomatic ICH was noted. The total number of EVC\'s identifiable on MRI and CBCT A/V was recorded, along with average diameter of conflicting vessels.
RESULTS: Across 20 patients and 273 implanted electrodes, there were four ICH events, where two were symptomatic and two were asymptomatic. The mean diameter of EVC\'s across all patients was 1.4 mm (±0.5). A significant difference (P < 0.0001) was observed between the number of EVC\'s that CBCT A/V could identify (20) compared to MRI (6). Two EVC\'s were identified in the region of two symptomatic ICH\'s, with the mean diameter of these conflicted vessels being 1.5 mm (±0.4). The two symptomatic ICH-associated EVC\'s were observed on CBCT A/V but not MRI.
CONCLUSIONS: In our series, CBCT A/V demonstrates an acceptable safety profile for SEEG planning compared to other imaging modalities. CBCT A/V identified significantly more EVC\'s compared to MRI, including those contributing to transient symptomatic intracranial hemorrhage. A conflicting vessel calibre of less than 1.2 mm on CBCT A/V did not contribute to ICH in our SEEG series.

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.