Stereoelectroencephalography in children and adolescents with difficult-to-localize refractory focal epilepsy

Prevalence of Temporal Lobe Epilepsy (TLE) Subtypes and Response to Resective Surgery in Patients with Presumed TLE Undergoing Limbic and Paralimbic Network Exploration with Stereo-Electrodes

Background/Objectives: Temporal lobe epilepsy (TLE) responds well to surgical treatment, although a considerable percentage of patients experience seizure recurrence after resection. Relapse from the contralateral mesial temporal lobe, extratemporal lobe epilepsy mimicking TLE, or temporal plus epilepsy might account for surgical failures. Methods: We included patients with a pre-implantation hypothesis suggesting TLE, who underwent stereo-EEG (SEEG) evaluation at our institution and had an individual SEEG exploration paradigm with at least twelve stereo-electrodes placed to sixteen brain regions allowing exploration of limbic and paralimbic networks. We analyzed the prevalence of TLE subtypes based on ictal onset localization with SEEG and response to resective surgery. Results: Twenty-four subjects met the inclusion criteria. Seven patients had unilateral mesial temporal epilepsy (UMTE), five had bilateral mesial temporal epilepsy (BMTE), five had unilateral neocortical temporal epilepsy (UNTE), six had temporal-plus epilepsy (TPE), one had extratemporal epilepsy (ETE). The number of patients who underwent destructive surgeries and surgical outcomes are as follows: UMTE-all seven patients, Engel I; BMTE- three out of five, Engel I, III, and IV, respectively; UNTE-three out of five, Engel I; TLE mimic (ETE)-one, Engel I; TPE-all six patients, Engel I-three, Engel III-two, Engel IV-one. Conclusions: In our study, UMTE was the most frequent TLE subtype (29%), and all patients proceeded to resective surgery with good outcomes. TPE comprised a substantial component (25%) of this cohort with initially presumed TLE, who had a notable proportion of unfavorable outcomes. Larger studies are needed to create guidelines for rational counseling of patients with presumed TLE regarding surgical outcomes.

Applications and Predictors of Outcomes Following Stereo-Electroencephalography in Pediatric Patients With Drug-Resistant Epilepsy

AIMS

This study aims to evaluate the role of stereo-electroencephalography (SEEG) in managing pediatric patients with drug-resistant epilepsy. We further explore prognostic factors influencing surgical outcomes following SEEG-guided resective or disconnective surgery.

METHODS

A retrospective review was conducted on pediatric patients who underwent SEEG at the Pediatric Epilepsy Center, Peking University First Hospital, between July 2017 and July 2022. Univariate and multivariate analyses identified key predictors for SEEG-guided surgery. Kaplan-Meier survival analysis was employed to estimate the seizure-free rate, and further statistical tests were applied to evaluate factors associated with seizure outcomes.

RESULTS

Among the 148 children included in this study, 102 underwent SEEG-guided resective/disconnective surgery. Multivariate regression identified age at surgery (p < 0.05, 95% CI 0.190-0.997) as an independent predictor for selecting resective/disconnective surgery. The seizure-free rate in patients who underwent SEEG-guided surgery was 69.6%. Multivariate regression confirmed that total resection with lesional MRI (p < 0.05, 95% CI 0.012-0.186) and FCD type II (p < 0.05, 95% CI 0.051-0.851) were strong predictors of seizure freedom.

CONCLUSIONS

SEEG plays a crucial role in pediatric epilepsy surgery, particularly in children under 6 years old. Total resection with lesional MRI and FCD type II was the most favorable prognostic predictor for achieving seizure freedom in children undergoing SEEG-guided surgery.

Safety, Accuracy, and Efficacy of Robot-Assisted Stereo Electroencephalography in Children of Different Ages

BACKGROUND AND OBJECTIVES

Aimed to investigate the safety, accuracy, and efficacy of stereo electroencephalography (SEEG) in children of various ages, with particular emphasis on those younger than 3 years. There is limited guidance regarding whether SEEG can conducted on very young children.

METHODS

This retrospective study was conducted between July 2018 and August 2022. It involved 88 patients who underwent 99 robot-assisted SEEG procedures at our center. The patients were categorized into 3 groups based on their age at the time of the robot-assisted SEEG procedures: group 1 (3 years and younger, n = 28), group 2 (age 3-6 years, n = 27), and group 3 (older than 6 years, n = 44). Clinical data, SEEG demographics, complications, and seizure outcomes were analyzed.

RESULTS

A total of 675 electrodes were implanted, with an average of 6.82 ± 3.47 (2.00-16.00) electrodes per patient (P = .052). The average target point error for the 675 electrodes was 1.93 ± 1.11 mm, and the average entry point error was 1.30 ± 0.97 mm (P = .536 and P = .549, respectively). The overall percentage of complications was 6.06% (P = .879). No severe or long-term neurologic impairment was observed. Of the total 99 procedures included in this study, 78 were admitted for epilepsy surgery for the first time, while 9 patients were treated twice and 1 patient was treated 3 times. There were 21 radiofrequency thermocoagulation and 78 second-stage resective procedures performed after SEEG. There was no statistically significant difference in Engel class I outcomes among the patients who underwent SEEG in the 3 age groups (P = .621).

CONCLUSION

Robot-assisted SEEG were demonstrated to be safe, accurate, and efficient across different age groups of children. This technique is suitable for children younger than 3 years who have indications for SEEG placement.

Learning Curve in Robotic Stereoelectroencephalography: Single Platform Experience

BACKGROUND

Learning curve, training, and cost impede widespread implementation of new technology. Neurosurgical robotic technology introduces challenges to visuospatial reasoning and requires the acquisition of new fine motor skills. Studies detailing operative workflow, learning curve, and patient outcomes are needed to describe the utility and cost-effectiveness of new robotic technology.

METHODS

A retrospective analysis was performed of pediatric patients who underwent robotic stereoelectroencephalography (sEEG) with the Medtronic Stealth Autoguide. Workflow, total operative time, and time per electrode were evaluated alongside target accuracy assessed via error measurements and root sum square. Patient demographics and clinical outcomes related to sEEG were also assessed.

RESULTS

Robot-assisted sEEG was performed in 12 pediatric patients. Comparison of cases over time demonstrated a mean operative time of 363.3 ± 109.5 minutes for the first 6 cases and 256.3 ± 59.1 minutes for the second 6 cases, with reduced operative time per electrode (P = 0.037). Mean entry point error, target point error, and depth point error were 1.82 ± 0.77 mm, 2.26 ± 0.71 mm, and 1.27 ± 0.53 mm, respectively, with mean root sum square of 3.23 ± 0.97 mm. Error measurements between magnetic resonance imaging and computed tomography angiography found computed tomography angiography to be more accurate with significant differences in mean entry point error (P = 0.043) and mean target point error (P = 0.035). The epileptogenic zone was identified in 11 patients, with therapeutic surgeries following in 9 patients, of whom 78% achieved an Engel class I.

CONCLUSIONS

This study demonstrated institutional workflow evolution and learning curve for the Autoguide in pediatric sEEG, resulting in reduced operative times and increased accuracy over a small number of cases. The platform may seamlessly and quickly be incorporated into clinical practice, and the provided workflow can facilitate a smooth transition.

[Safety of robot-assisted implantation of deep electrodes for invasive stereo-EEG monitoring]

Robot-assisted implantation of deep electrodes for stereo-EEG monitoring has become popular in recent years in patients with drug-resistant epilepsy. However, there are still few data on safety of this technique.

OBJECTIVE

To assess the incidence of complications in patients with drug-resistant epilepsy undergoing robot-assisted implantation of stereo-EEG electrodes.

MATERIAL AND METHODS

We retrospectively studied the results of implantation of stereo-EEG electrodes in 187 patients with drug-resistant epilepsy. All patients underwent non-invasive preoperative examination (video-EEG, MRI, PET, SPECT, MEG). In case of insufficient data, stereo-EEG monitoring was prescribed. We determined electrode insertion trajectory using a robotic station and MR images. Implantation of electrodes was carried out using a Rosa robot (Medtech, France). All patients underwent invasive EEG monitoring after implantation.

RESULTS

There were 11.25±3 electrodes per a patient. Implantation of one electrode took 7.5±4.9 min. Postoperative MRI revealed electrode malposition in 2.3% of cases. None was associated with complications. The complication rate per electrode was 0.6%. Complications affected stereo-EEG monitoring only in 3 cases (1.6%). The mortality rate was 0.5%. Bilateral implantation (p=0.005), insular (p=0.040) and occipital (p=0.045) deep electrode implantation were associated with lower incidence of complications. Longer duration of the procedure influenced the incidence of electrode placement in the lateral ventricle (p=0.028), and implantation in the frontal lobe was more often associated with epidural placement of electrodes (p=0.039).

CONCLUSION

Robot-assisted implantation of stereo-EEG electrodes is a safe procedure with minimal risk of complications. Rare electrode malposition does not usually affect invasive monitoring.

Accuracy of Depth Electrodes is Not Time-Dependent in Robot-Assisted Stereoelectroencephalography in a Pediatric Population

BACKGROUND AND OBJECTIVES

Robot-assisted stereoelectroencephalography (sEEG) is steadily supplanting traditional frameless and frame-based modalities for minimally invasive depth electrode placement in epilepsy workup. Accuracy rates similar to gold-standard frame-based techniques have been achieved, with improved operative efficiency. Limitations in cranial fixation and placement of trajectories in pediatric patients are believed to contribute to a time-dependent accumulation of stereotactic error. Thus, we aim to study the impact of time as a marker of cumulative stereotactic error during robotic sEEG.

METHODS

All patients between October 2018 and June 2022 who underwent robotic sEEG were included. Radial errors at entry and target points as well as depth and Euclidean distance errors were collected for each electrode, excluding those with errors over 10 mm. Target point errors were standardized by planned trajectory length. ANOVA and error rates over time were analyzed using GraphPad Prism 9.

RESULTS

Forty-four patients met inclusion criteria for a total of 539 trajectories. Number of electrodes placed ranged from 6 to 22. Average root mean squared error was 0.45 ± 0.12 mm. Average entry, target, depth, and Euclidean distance errors were 1.12 ± 0.41 mm, 1.46 ± 0.44 mm, -1.06 ± 1.43 mm, and 3.01 ± 0.71 mm, respectively. There was no significant increased error with each sequential electrode placed (entry error P -value = .54, target error P -value = .13, depth error P -value = .22, Euclidean distance P -value = .27).

CONCLUSION

No decremental accuracy over time was observed. This may be secondary to our workflow which prioritizes oblique and longer trajectories first and then into less error-prone trajectories. Further study on the effect of level of training may reveal a novel difference in error rates.

Safety profile of subdural and depth electrode implantations in invasive EEG exploration of drug-resistant focal epilepsy

PURPOSE

To analyze the safety profile of subdural and depth electrode implantation in a large monocentric cohort of patients of all ages undergoing intracranial EEG exploration because of drug resistant focal epilepsy diagnosed and implanted by a constant team of epileptologists and neurosurgeons.

METHODS

We retrospectively analyzed data from 452 implantations in 420 patients undergoing invasive presurgical evaluation at the Freiburg Epilepsy Center from 1999 to 2019 (n = 160 subdural electrodes, n = 156 depth electrodes and n = 136 combination of both approaches). Complications were classified as hemorrhage with or without clinical manifestations, infection-associated and other complications. Furthermore, possible risk factors (age, duration of invasive monitoring, number of electrode contacts used) and changes in complication rates during the study period were analyzed.

RESULTS

The most frequent complications in both implantation groups were hemorrhages. Subdural electrode explorations caused significantly more symptomatic hemorrhages and required more operative interventions (SDE 9.9%, DE 0.3%, p < 0.05). Hemorrhage risk was higher for grids with 64 contacts than for smaller grids (p < 0.05). The infection rate was very low (0,2%). A transient neurological deficit occurred in 8.8% of all implantations and persisted for at least 3 months in 1.3%. Transient, but not persistent neurological deficits were more common in patients with implanted subdural electrodes than in the depth electrode group.

CONCLUSION

The use of subdural electrodes was associated with a higher risk of hemorrhage and transient neurological symptoms. However persistent deficits were rare with either approach, demonstrating that intracranial investigations using either subdural electrodes or depth electrodes carry acceptable risks in patients with drug-resistant focal epilepsy.

Invasive Intracranial Electroencephalogram (EEG) Monitoring for Epilepsy in the Pediatric Patient With a Shunt

The use of invasive intracranial electroencephalogram (EEG) monitoring in the patient with a cerebrospinal fluid (CSF) diversionary shunt presents a conundrum -- the presence of a percutaneous electrode passing into the intracranial compartment presents a pathway for entry of pathogens to which a chronically implanted device like a shunt is especially susceptible to infection. In this case report, we describe the clinical and radiological features, medical and surgical management, and treatment outcomes of pediatric patients with shunted hydrocephalus who underwent invasive intracranial monitoring over an eight-year period. Three cases of children undergoing invasive intracranial monitoring were included in this study. Invasive monitoring for each patient occurred over three to six days. In each case, invasive intracranial monitoring was completed successfully, without resulting infection or shunt malfunction. While the second procedure was complicated by the formation of a pneumocephalus, there was no associated midline shift, and invasive intracranial monitoring was completed without incidence. Each patient received further surgery that successfully reduced seizure frequency. This study suggests that, while children with CSF diversionary shunts are at an inherently increased risk for infection and other complications, invasive intracranial monitoring is a relatively safe and feasible option in these patients. Future studies should explore the optimal duration for intracranial monitoring in pediatric patients with chronically implanted devices.

Does Stereoelectroencephalography Add Value in Patients with Lesional Epilepsy?

OBJECTIVE

Stereoelectroencephalography (SEEG) has gained popularity as an invasive monitoring modality for epileptogenic zone (EZ) localization. The need and indications for SEEG in patients with evident brain lesions or associated abnormalities on imaging is debated. We report our experience with SEEG as a presurgical evaluation tool for patients with lesional epilepsy.

METHODS

A retrospective cohort study was performed of 131 patients with lesional or magnetic resonance imaging abnormality-associated medically refractory focal epilepsy who underwent resections from 2010 to 2017. Seventy-one patients had SEEG followed by resection, and 60 had no invasive recordings. Volumetric analysis of resection cavities from 3T magnetic resonance imaging was performed.

RESULTS

Mean lesion and resection volumes for SEEG and non-SEEG were 16.2 (standard deviation [SD] = 29) versus 23.7 cm3 (SD = 38.4) and 28.1 (SD = 23.2) versus 43.6 cm3 (SD = 43.5), respectively (P = 0.009). Comparing patients with seizure recurrence and patients who remained seizure free, significantly associated variables with seizure recurrence included mean number of failed antiseizure medications (6.86 [SD = 0.32] vs. 5.75 [SD = 0.32]; P = 0.01) and in SEEG patients the mean number of electrodes implanted (8.1 [SD = 0.8] vs. 5.0 [SD = 0.8]; P = 0.005). After multivariate analysis, only failed numbers of medication remained significantly associated with seizure recurrence.

CONCLUSIONS

Seizure outcomes did not correlate with final resection volume after SEEG evaluation. SEEG evaluation presurgically can be used to maintain the efficacy of resection and decrease the volume and subsequent risk of extensive tissue removal. We believe that this technology allows resective surgery to proceed in a subpopulation of patients with lesional epilepsy who may otherwise not have been considered surgical candidates.

Stereoelectroencephalography before 2 years of age

OBJECTIVE

Stereoelectroencephalography (SEEG) is a widely used technique for localizing seizure onset zones prior to resection. However, its use has traditionally been avoided in children under 2 years of age because of concerns regarding pin fixation in the immature skull, intraoperative and postoperative electrode bolt security, and stereotactic registration accuracy. In this retrospective study, the authors describe their experience using SEEG in patients younger than 2 years of age, with a focus on the procedure’s safety, feasibility, and accuracy as well as surgical outcomes.

METHODS

A retrospective review of children under 2 years of age who had undergone SEEG while at Children’s Hospital of Philadelphia between November 2017 and July 2021 was performed. Data on clinical characteristics, surgical procedure, imaging results, electrode accuracy measurements, and postoperative outcomes were examined.

RESULTS

Five patients younger than 2 years of age underwent SEEG during the study period (median age 20 months, range 17–23 months). The mean age at seizure onset was 9 months. Developmental delay was present in all patients, and epilepsy-associated genetic diagnoses included tuberous sclerosis (n = 1), KAT6B (n = 1), and NPRL3 (n = 1). Cortical lesions included tubers from tuberous sclerosis (n = 1), mesial temporal sclerosis (n = 1), and cortical dysplasia (n = 3). The mean number of placed electrodes was 11 (range 6–20 electrodes). Bilateral electrodes were placed in 1 patient. Seizure onset zones were identified in all cases. There were no SEEG-related complications, including skull fracture, electrode misplacement, hemorrhage, infection, cerebrospinal fluid leakage, electrode pullout, neurological deficit, or death. The mean target point error for all electrodes was 1.0 mm. All patients proceeded to resective surgery, with a mean follow-up of 21 months (range 8–53 months). All patients attained a favorable epilepsy outcome, including Engel class IA (n = 2), IC (n = 1), ID (n = 1), and IIA (n = 1).

CONCLUSIONS

SEEG can be safely, accurately, and effectively utilized in children under age 2 with good postoperative outcomes using standard SEEG equipment. With minimal modification, this procedure is feasible in those with immature skulls and guides the epilepsy team’s decision-making for early and optimal treatment of refractory epilepsy through effective localization of seizure onset zones.

Stereo-Encephalographic Presurgical Evaluation of Temporal Lobe Epilepsy: An Evolving Science

Drug-resistant epilepsy is present in nearly 30% of patients. Resection of the epileptogenic zone has been found to be the most effective in achieving seizure freedom. The study of temporal lobe epilepsy for surgical treatment is extensive and complex. It involves a multidisciplinary team in decision-making with initial non-invasive studies (Phase I), providing 70% of the required information to elaborate a hypothesis and treatment plans. Select cases present more complexity involving bilateral clinical or electrographic manifestations, have contradicting information, or may involve deeper structures as a part of the epileptogenic zone. These cases are discussed by a multidisciplinary team of experts with a hypothesis for invasive methods of study. Subdural electrodes were once the mainstay of invasive presurgical evaluation and in later years most Comprehensive Epilepsy Centers have shifted to intracranial recordings. The intracranial recording follows original concepts since its development by Bancaud and Talairach, but great advances have been made in the field. Stereo-electroencephalography is a growing field of study, treatment, and establishment of seizure pattern complexities. In this comprehensive review, we explore the indications, usefulness, discoveries in interictal and ictal findings, pitfalls, and advances in the science of presurgical stereo-encephalography for temporal lobe epilepsy.

Virtual reality-based 3-dimensional localization of stereotactic EEG (SEEG) depth electrodes and related brain anatomy in pediatric epilepsy surgery

INTRODUCTION

The increasing use of stereoelectroencephalography (SEEG) in the USA and the need for three-dimensional (3D) appreciation of complex spatial relationships between implanted stereotactic EEG depth electrodes and surrounding brain and cerebral vasculature are a challenge to clinicians who are used to two-dimensional (2D) appreciation of cortical anatomy having been traditionally trained on 2D radiologic imaging. Virtual reality and its 3D renderings have grown increasingly common in the multifaceted practice of neurosurgery. However, there exists a paucity in the literature regarding this emerging technology in its utilization of epilepsy surgery.

METHODS

An IRB-approved, single-center retrospective study identifying all SEEG pediatric patients in which virtual reality was applied was observed.

RESULTS

Of the 46 patients identified who underwent an SEEG procedure, 43.5% (20/46) had a 3D rendering (3DR) of their SEEG depth electrodes. All 3DRs were used during patient-family education and discussion among the Epilepsy multidisciplinary team meetings, while 35% (7/20) were used during neuronavigation in surgery. Three successful representative cases of its application were presented.

DISCUSSION

Our institution's experience regarding virtual reality in the 3D representation of SEEG depth electrodes and the application to pre-surgical planning, patient-family education, multidisciplinary communication, and intraoperative neuronavigation demonstrate its applicability in comprehensive epilepsy patient care.

The role of stereo-electroencephalography to localize the epileptogenic zone in children with nonlesional brain magnetic resonance imaging

OBJECTIVE

This study aimed to assess the clinical outcome and outcome predictive factors in pediatric epilepsy patients evaluated with stereo-electroencephalography (SEEG).

METHODS

Thirty-eight patients who underwent SEEG implantation at the Pediatric Epilepsy Center in New York Presbyterian Hospital between June 2014 and December 2019 were enrolled for retrospective chart review. Postoperative seizure outcomes were evaluated in patients with at least 12-months follow up. Meta-analysis was conducted via electronic literature search of data reported from 2000 to 2020 to evaluate significant surgical outcome predictors for SEEG evaluation in the pediatric population.

RESULTS

In the current case series of 25 postsurgical patients with long-term follow up, 16 patients (64.0%) were seizure free. An additional 7 patients (28.0%) showed significant seizure improvement and 2 patients (8.0%) showed no change in seizure activity. Patients with nonlesional magnetic resonance imaging (MRI) achieved seizure freedom in 50% (5/10) of cases. By comparison, 73% (11/15) of patients with lesional MRI achieved seizure freedom. Out of 12 studies, 158 pediatric patients were identified for inclusion in a meta-analysis of the effectiveness of SEEG. Seizure freedom was reported 54.4% (n = 86/158) of patients at last follow up. Among patients with nonlesional MRI, 45% (n = 24) achieved seizure freedom compared with patients with lesional MRI findings (61.2%, n:= 60) (p = 0.02). The risk for seizure recurrence was 2.15 times higher [95% confidence interval [CI] 1.06-4.37, p = 0.033] in patients diagnosed with nonlesional focal epilepsy compared to those with lesional epilepsy [ 1.49 (95% CI 1.06-2.114, p = 0.021].

CONCLUSION

Evaluation by SEEG implantation in pediatric epilepsy is effective in localizing the epileptogenic zone with favorable outcome. Presence of a non-lesional brain MRI was associated with lower chances of seizure freedom. Further research is warranted to improve the efficacy of SEEG in localizing the epileptogenic zone in pediatric patients with non-lesional brain MRI.

Stereoelectroencephalography in the very young: Case report

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To the best of our knowledge this is the youngest reported patient implanted with SEEG.

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Accurate and safe SEEG surgery may be feasible in patients as young as 17 months-old.

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Robotic SEEG with standard tools may be effectively used in this very young population.

Stereoelectroencephalography (SEEG) is an increasingly popular invasive monitoring approach to epilepsy surgery in patients with drug-resistant epilepsies. The technique allows a three-dimensional definition of the epileptogenic zones (EZ) in the brain. It has been shown to be safe and effective in adults and older children but has been used sparingly in children less than two years old due to concerns about pin fixation in thin bone, registration accuracy, and bolt security. As such, most current series of pediatric invasive EEG explorations do not include young participants, and, when they do, SEEG is often not utilized for these patients. Recent national survey data further suggests SEEG is infrequently utilized in very young patients. We present a novel case of SEEG used to localize the EZ in a 17-month-old patient with thin cranial bone, an open fontanelle, and severe drug-resistant epilepsy due to tuberous sclerosis complex (TSC), with excellent accuracy, surgical results, and seizure remission.

Magnetic resonance-guided laser interstitial thermal therapy for pediatric periventricular nodular heterotopia-related epilepsy

OBJECTIVE

Periventricular nodular heterotopia (PVNH) is a result of disrupted neuronal migration from the ventricular system and can be a rare cause of refractory focal epilepsy. The goal of this case series was to describe the treatment of pediatric PVNH-related epilepsy with MR-guided laser interstitial thermal ablation.

METHODS

Patients treated at a single institution with MR-guided laser interstitial thermal therapy (MRgLITT) for PVNH-related epilepsy were identified. Preoperative and postoperative seizure outcomes and procedural information were evaluated.

RESULTS

Five children with PVNH treated with MRgLITT were reviewed; 1 child was treated twice. Three patients were female; the median age was 10.9 years. Five of 6 treatments were preceded by stereoelectroencephalography phase II monitoring. Three children experienced unilateral PVNH, and 2 had bilateral seizures. The median number of seizures recorded during phase II monitoring was 2; the median number of ablation targets was 2 (range 1-4). All patients experienced a decrease in seizure frequency; 4 patients (80%) had an Engel class ≤ III at the last follow-up (range I-IV). One child experienced right hemianopia posttreatment.

CONCLUSIONS

This case series investigation has illustrated a novel, minimally invasive approach for treating pediatric PVNH-related epilepsy. Further study of this technique with comparison with other surgical techniques is warranted.

Surgically treatable adult epilepsy: a changing patient population. Experience from a level 4 epilepsy center

OBJECTIVE

Invasive monitoring has long been utilized in the evaluation of patients for epilepsy surgery, providing localizing information to guide resection. Stereoelectroencephalography (SEEG) was introduced at the authors' level 4 epilepsy surgery program in 2013, with responsive neurostimulation (RNS) becoming available the following year. The authors sought to characterize patient demographics and epilepsy-related variables before and after SEEG introduction to understand whether differences emerged in their patient population. This information will be useful in understanding how SEEG, possibly in conjunction with RNS availability, may have changed practice patterns over time.

METHODS

This is a retrospective cohort study of consecutive patients who underwent surgery for epilepsy from 2006 to 2018, comprising 7 years before and 5 years after the introduction of SEEG. The authors performed univariate analyses of patient characteristics and outcomes and used generalized estimating equations logistic regression for predictive analysis.

RESULTS

A total of 178 patients were analyzed, with 109 patients in the pre-SEEG cohort and 69 patients in the post-SEEG cohort. In the post-SEEG cohort, more patients underwent invasive monitoring for suspected bilateral seizure onsets (40.6% vs 22.0%, p = 0.01) and extratemporal seizure onsets (68.1% vs 8.3%, p < 0.0001). The post-SEEG cohort had a higher proportion of patients with seizures arising from eloquent cortex (14.5% vs 0.9%, p < 0.001). Twelve patients underwent RNS insertion in the post-SEEG group versus none in the pre-SEEG group. Fewer patients underwent resection in the post-SEEG group (55.1% vs 96.3%, p < 0.0001), but there was no significant difference in rates of seizure freedom between cohorts for those patients having undergone a follow-up resection (53.1% vs 59.8%, p = 0.44).

CONCLUSIONS

These findings demonstrate that more patients with suspected bilateral, eloquent, or extratemporal epilepsy underwent invasive monitoring after adoption of SEEG. This shift occurred coincident with the adoption of RNS, both of which likely contributed to increased patient complexity. The authors conclude that their practice now considers invasive monitoring for patients who likely would not previously have been candidates for surgical investigation and subsequent intervention.

Early implementation of stereoelectroencephalography in children: a multiinstitutional case series

OBJECTIVE

Pediatric stereoelectroencephalography (SEEG) has been increasingly performed in the United States, with published literature being limited primarily to large single-center case series. The purpose of this study was to evaluate the experience of pediatric epilepsy centers, where the technique has been adopted in the last several years, via a multicenter case series studying patient demographics, outcomes, and complications.

METHODS

A retrospective cohort methodology was used based on the STROBE criteria. ANOVA was used to evaluate for significant differences between the means of continuous variables among centers. Dichotomous outcomes were assessed between centers using a univariate and multivariate logistic regression.

RESULTS

A total of 170 SEEG insertion procedures were included in the study from 6 different level 4 pediatric epilepsy centers. The mean patient age at time of SEEG insertion was 12.3 ± 4.7 years. There was no significant difference between the mean age at the time of SEEG insertion between centers (p = 0.3). The mean number of SEEG trajectories per patient was 11.3 ± 3.6, with significant variation between centers (p < 0.001). Epileptogenic loci were identified in 84.7% of cases (144/170). Patients in 140 cases (140/170, 82.4%) underwent a follow-up surgical intervention, with 47.1% (66/140) being seizure free at a mean follow-up of 30.6 months. An overall postoperative hemorrhage rate of 5.3% (9/170) was noted, with patients in 4 of these cases (4/170, 2.4%) experiencing a symptomatic hemorrhage and patients in 3 of these cases (3/170, 1.8%) requiring operative evacuation of the hemorrhage. There were no mortalities or long-term complications.

CONCLUSIONS

As the first multicenter case series in pediatric SEEG, this study has aided in establishing normative practice patterns in the application of a novel surgical technique, provided a framework for anticipated outcomes that is generalizable and useful for patient selection, and allowed for discussion of what is an acceptable complication rate relative to the experiences of multiple institutions.

The Missed Value of Underutilizing Pediatric Epilepsy Surgery: A Systematic Review

Pediatric epilepsy surgery is underutilized. Only 1%-11% of children with drug resistant epilepsy (DRE) undergo surgical treatment, or less than half of those estimated to benefit. We conducted a systematic review of articles published in PubMed, EMBASE, and Web of Science in order to study the factors related to surgery underutilization as well as the impact on both the individual and the healthcare system. Our review demonstrates multiple factors leading to underutilization, including family misconceptions about epilepsy surgery, lack of provider knowledge, as well as systemic health disparities. While the upfront cost of epilepsy surgery is significant, the long-term financial benefits and reduced health resource utilization tilt the economic advantage in favor of surgery in children with DRE. Additionally, timely interventions improve seizure and cognitive outcomes with low risk of complications. Further interventions are needed at the levels of family, provider, and the healthcare system to increase access to pediatric epilepsy surgery.

Smaller Knife, Fewer Seizures? Recent Advances in Minimally Invasive Techniques in Pediatric Epilepsy Surgery

Children with drug-resistant epilepsy are at high risk for developmental delay, increased mortality, psychiatric comorbidities, and requiring assistance with activities of daily living. Despite the advent of new and effective pharmacologic therapies, about one in 5 children will develop drug-resistant epilepsy, and most of these children continue to have seizures despite trials of other medication. Epilepsy surgery is often a safe and effective option which may offer seizure freedom or at least a significant reduction in seizure burden in many children. However, despite published evidence of safety and efficacy, epilepsy surgery remains underutilized in the pediatric population. Patient and family fears about the risks of surgery may contribute to this gap. Less invasive surgical techniques may be more palatable to children with epilepsy and their caregivers. In this review, we present recent advances in minimally invasive techniques for the surgical treatment of epilepsy as well as intriguing possibilities for the future. We describe the indications for, benefits of, and limits to minimally-invasive techniques including Stereo-encephalography, laser interstitial thermal ablation, deep brain stimulation, focused ultrasound, stereo-encephalography-guided radiofrequency ablation, endoscopic disconnections, and responsive neurostimulation.

Long-term mood, quality of life, and seizure freedom in intracranial EEG epilepsy surgery

OBJECTIVES

To determine the long-term outcomes in patients undergoing intracranial EEG (iEEG) evaluation for epilepsy surgery in terms of seizure freedom, mood, and quality of life at St. Vincent's Hospital, Melbourne.

METHODS

Patients who underwent iEEG between 1999 and 2016 were identified. Patients were retrospectively assessed between 2014 and 2017 by specialist clinic record review and telephone survey with standardized validated questionnaires for: 1) seizure freedom using the Engel classification; 2) Mood using the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E); 3) Quality-of-life outcomes using the QOLIE-10 questionnaire. Summary statistics and univariate analysis were performed to investigate variables for significance.

RESULTS

Seventy one patients underwent iEEG surgery: 49 Subdural, 14 Depths, 8 Combination with 62/68 (91.9%) of those still alive, available at last follow-up by telephone survey or medical record review (median of 8.2 years). The estimated epileptogenic zone was 62% temporal and 38% extra-temporal. At last follow-up, 69.4% (43/62) were Engel Class I and 30.6% (19/62) were Engel Class II-IV. Further, a depressive episode (NDDI-E > 15)was observed in 34% (16/47), while a 'better quality of life' (QOLIE-10 score < 25) was noted in 74% (31/42). Quality of life (p < 0.001) but not mood (p = 0.24) was associated with seizure freedom.

SIGNIFICANCE

Long-term seizure freedom can be observed in patients undergoing complex epilepsy surgery with iEEG evaluation and is associated with good quality of life.

Stereo-electroencephalography (SEEG) in pediatric epilepsy: Utility in children with and without prior epilepsy surgery failure

BACKGROUND

When noninvasive modalities fail to adequately localize the seizure onset zone (SOZ) in children with medically refractory epilepsy, invasive interrogation with stereo-electroencephalography (SEEG) or subdural electrodes may be required. Our center utilizes SEEG for invasive monitoring in a carefully selected population of children, many of whom have seizures despite a prior surgical resection. We describe the cohort of patients who underwent SEEG in the first 5 years of its employment in our institution, almost half of which had a history of a failed epilepsy surgery.

METHODS

We retrospectively reviewed the records of the first 44 consecutive children who underwent SEEG at Nicklaus Children's Hospital (Miami, Florida), a large, level 4 epilepsy referral center. Patient demographic, clinical, radiographic, and electrophysiological information was collected prospectively. Student's t-test was used for sampling of means and analysis of variance (ANOVA) for evaluation of variance beyond 2 means; chi-square test of independence was used to assess the relationship between categorical variables.

RESULTS

There were 44 patients in this cohort, of whom 17 (38.6 %) were male. The mean age of seizure onset was 6.2 years. Twenty-one patients (47.7 %) had previously failed an epilepsy surgery. Patients with a history of prior epilepsy surgery failure were older at SEEG implantation (17.6 vs. 13.7 years; p = 0.043), were more likely to have SEEG for identification of resection margins (9 vs. 4; p = 0.034), and had fewer electrodes placed (5.9 vs. 7.5; p = 0.016). No difference was seen in complication rates between groups with only 3/297 electrodes placed associated with complications, all of which were minor. Post-SEEG, 29 (65.9 %) patients underwent focal resection, 7 patients had VNS insertion, 3 underwent RNS placement, and 5 had no further intervention. The majority of patients that underwent resection in both groups experienced an improvement in seizures (Engel class I-III), reported by 13/15 (86.7 %) in those naive to surgery and 10/14 (71.4 %) in those with prior surgical failure. Seizure-freedom was much lower in those with prior epilepsy surgery, seen in only 4/14 (28.6 %) versus 8/15 (53.3 %).

CONCLUSION

Our data supports current literature on SEEG as a safe and effective method of electrophysiological evaluation in children naive to surgery and adds that it is a safe technique in children with a history of failed epilepsy surgery. There was no difference in complication rates, which were <1 % in both groups. A favorable outcome was seen in the majority of patients in both groups; the seizure freedom rate, however, was much lower in those with prior epilepsy surgery.

Variation in pediatric stereoelectroencephalography practice among pediatric neurosurgeons in the United States: survey results

OBJECTIVE

Stereoelectroencephalography (SEEG) has become widespread in the United States during the past decade. Many pediatric neurosurgeons practicing SEEG may not have had experience with this technique during their formal training, and the literature is mostly limited to single-center series. As a result, implementation of this relatively new technique may vary at different institutions. The authors hypothesized that aspects of SEEG experience, techniques, and outcomes would vary widely among programs across the country.

METHODS

An electronic survey with 35 questions addressing the categories of training and experience, technique, electrode locations, and outcomes was sent to 128 pediatric epilepsy surgeons who were potential SEEG users.

RESULTS

Sixty-one pediatric fellowship-trained epilepsy surgeons in the United States responded to the survey. Eighty-nine percent were actively using SEEG in their practice. Seventy-two percent of SEEG programs were in existence for less than 5 years, and 68% were using SEEG for > 70% of their invasive monitoring. Surgeons at higher-volume centers operated on younger patients (p < 0.001). Most surgeons (70%) spent 1-3 hours per case planning electrode trajectories. Two-thirds of respondents reported a median implant duration of 5-7 days, but 16% reported never having an implant duration > 5 days, and 16% reported having had implants stay in place for > 4 weeks. The median response for the median number of electrodes initially implanted was 12 electrodes, although 19% of respondents reported median implants of 5-8 electrodes and 17% reported median implants of 15-18 electrodes. Having a higher volume of SEEG cases per year was associated with a higher median number of electrodes implanted (p < 0.001). Most surgeons found SEEG helpful in defining an epileptic network and reported that most of their SEEG patients undergo focal surgical treatment.

CONCLUSIONS

SEEG has been embraced by the pediatric epilepsy surgery community. Higher case volume is correlated with a tendency to place more electrodes and operate on younger patients. For most parameters addressed in the survey, responses from surgeons clustered around a norm, though additional findings of substantial variations highlight differences in implementation and philosophy among pediatric epilepsy programs.

VarioGuide® frameless neuronavigation-guided stereoelectroencephalography in adult epilepsy patients: technique, accuracy and clinical experience

Background

Stereoelectroencephalography (SEEG) allows the identification of deep-seated seizure foci and determination of the epileptogenic zone (EZ) in drug-resistant epilepsy (DRE) patients. We evaluated the accuracy and treatment-associated morbidity of frameless VarioGuide® (VG) neuronavigation-guided depth electrode (DE) implantations.

Methods

We retrospectively identified all consecutive adult DRE patients, who underwent VG-neuronavigation DE implantations, between March 2013 and April 2019. Clinical data were extracted from the electronic patient charts. An interdisciplinary team agreed upon all treatment decisions. We performed trajectory planning with iPlan® Cranial software and DE implantations with the VG system. Each electrode’s accuracy was assessed at the entry (EP), the centre (CP) and the target point (TP). We conducted correlation analyses to identify factors associated with accuracy.

Results

The study population comprised 17 patients (10 women) with a median age of 32.0 years (range 21.0–54.0). In total, 220 DEs (median length 49.3 mm, range 25.1–93.8) were implanted in 21 SEEG procedures (range 3–16 DEs/surgery). Adequate signals for postoperative SEEG were detected for all but one implanted DEs (99.5%); in 15/17 (88.2%) patients, the EZ was identified and 8/17 (47.1%) eventually underwent focus resection. The mean deviations were 3.2 ± 2.4 mm for EP, 3.0 ± 2.2 mm for CP and 2.7 ± 2.0 mm for TP. One patient suffered from postoperative SEEG-associated morbidity (i.e. conservatively treated delayed bacterial meningitis). No mortality or new neurological deficits were recorded.

Conclusions

The accuracy of VG-SEEG proved sufficient to identify EZ in DRE patients and associated with a good risk-profile. It is a viable and safe alternative to frame-based or robotic systems.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00701-021-04755-w.

Rapidly spreading seizures arise from large-scale functional brain networks in focal epilepsy

It remains unclear whether epileptogenic networks in focal epilepsy develop on physiological networks. This work aimed to explore the association between the rapid spread of ictal fast activity (IFA), a proposed biomarker for epileptogenic networks, and the functional connectivity or networks of healthy subjects. We reviewed 45 patients with focal epilepsy who underwent electrocorticographic (ECoG) recordings to identify the patients showing the rapid spread of IFA. IFA power was quantified as normalized beta-gamma band power. Using published resting-state functional magnetic resonance imaging databases, we estimated resting-state functional connectivity of healthy subjects (RSFC-HS) and resting-state networks of healthy subjects (RSNs-HS) at the locations corresponding to the patients' electrodes. We predicted the IFA power of each electrode based on RSFC-HS between electrode locations (RSFC-HS-based prediction) using a recently developed method, termed activity flow mapping. RSNs-HS were identified using seed-based and atlas-based methods. We compared IFA power with RSFC-HS-based prediction or RSNs-HS using non-parametric correlation coefficients. RSFC and seed-based RSNs of each patient (RSFC-PT and seed-based RSNs-PT) were also estimated using interictal ECoG data and compared with IFA power in the same way as RSFC-HS and seed-based RSNs-HS. Spatial autocorrelation-preserving randomization tests were performed for significance testing. Nine patients met the inclusion criteria. None of the patients had reflex seizures. Six patients showed pathological evidence of a structural etiology. In total, we analyzed 49 seizures (2-13 seizures per patient). We observed significant correlations between IFA power and RSFC-HS-based prediction, seed-based RSNs-HS, or atlas-based RSNs-HS in 28 (57.1%), 21 (42.9%), and 28 (57.1%) seizures, respectively. Thirty-two (65.3%) seizures showed a significant correlation with either seed-based or atlas-based RSNs-HS, but this ratio varied across patients: 27 (93.1%) of 29 seizures in six patients correlated with either of them. Among atlas-based RSNs-HS, correlated RSNs-HS with IFA power included the default mode, control, dorsal attention, somatomotor, and temporal-parietal networks. We could not obtain RSFC-PT and RSNs-PT in one patient due to frequent interictal epileptiform discharges. In the remaining eight patients, most of the seizures showed significant correlations between IFA power and RSFC-PT-based prediction or seed-based RSNs-PT. Our study provides evidence that the rapid spread of IFA in focal epilepsy can arise from physiological RSNs. This finding suggests an overlap between epileptogenic and functional networks, which may explain why functional networks in patients with focal epilepsy frequently disrupt.

[Stereoelectroencephalography (seeg): a brief historical review of modern deep electrode implantation methods used for diagnosis and treatment of epilepsy]

More than 30% of patients with symptomatic epilepsy are resistant to drug therapy and therefore surgical treatment is the method of choice for such patients. Search and localization of the epileptogenic zone and all parts of the neural networks involved in stereotypic seizures are the most important objectives of pre-surgical evaluation and the prerequisite for the successful surgery. In the last decade, stereotactic implantation of multiple intracerebral multi-contact electrodes (SEEG) has been increasingly used for this purpose. The article includes a brief history of SEEG and a description of the major techniques for stereotactic implantation of electrodes. Information on accuracy (errors and deviations from planned target) and on complications are summarized. The data on the clinical value of the method and how these data affected the results of subsequent treatment are highlighted. The method of thermocoagulation and its results are briefly considered.

Standard work tools for dynamic stereoelectroencephalography using ROSA: naming convention and perioperative planning

OBJECTIVE

The grid-based orthogonal placement of depth electrodes (DEs), initially defined by Jean Talairach and Jean Bancaud, is known as stereo-electroencephalography (sEEG). Although acceptance in the United States was initially slow, advances in imaging and technology have spawned a proliferation of North American epilepsy centers offering sEEG. Despite publications highlighting minimal access techniques and varied indications, standard work for phase I targeted DE has not been defined. In this article, the authors propose the term "dynamic sEEG" and define standard work tools and related common data elements to promote uniformity in the field.

METHODS

A multidisciplinary approach from July to August 2016 resulted in the production of 4 standard work tools for dynamic sEEG using ROSA: 1) a 34-page illustrated manual depicting a detailed workflow; 2) a planning form to collocate all the phase I data; 3) a naming convention for DEs that encodes the data defining it; and 4) a reusable portable perioperative planning and documentation board. A retrospective review of sEEG case efficiency was performed comparing those using standard work tools (between July 2016 and April 2017) with historical controls (between March 2015 and June 2016). The standard work tools were then instituted at another epilepsy surgery center, and the results were recorded.

RESULTS

The process for dynamic sEEG was formally reviewed, including anesthesia, positioning, perioperative nursing guidelines, surgical steps, and postoperative care for the workflow using cranial fixation and ROSA-guided placement. There was a 40% improvement in time per electrode, from 44.7 ± 9.0 minutes to 26.9 ± 6.5 minutes (p = 0.0007) following the development and use of the manual, the naming convention, and the reusable portable perioperative planning and documentation board. This standardized protocol was implemented at another institution and yielded a time per electrode of 22.3 ± 4.4 minutes.

CONCLUSIONS

The authors propose the term dynamic sEEG for stereotactic depth electrodes placed according to phase I workup data with the intention of converting to ablation. This workflow efficiency can be optimized using the standard work tools presented. The authors also propose a novel naming convention that encodes critical data and allows portability among providers. Use of a planning form for common data elements optimizes research, and global adoption could facilitate multicenter studies correlating phase I modality and seizure onset zone identification.

Non-lesional mesial temporal lobe epilepsy requires bilateral invasive evaluation

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Bilateral ictal onsets may lead to surgery failure in mesial temporal lobe epilepsy.

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Bitemporal SEEG seizures were recorded despite of unilateral non-invasive tests.

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Patients with non-lesional MTLE need bitemporal invasive evaluation before resection.

Purpose

Mesial temporal lobe epilepsy (MTLE) usually responds well to surgical treatment, although in non-lesional cases up to 50% of patients experience seizure relapse. The possibility of bilateral independent seizure onset should be considered as a reason for epilepsy surgery failure.

Methods

In a cohort of 177 patients who underwent invasive presurgical evaluation with stereo-tactically placed electrodes in two level four epilepsy centers, 29 had non-lesional MTLE. Invasive evaluation results are described.

Results

Among 29 patients with non-lesional MRI and mesial temporal lobe seizure onset recorded during stereo-EEG (SEEG) evaluation, four patients with unilateral preimplantation hypothesis had independent bilateral mesial temporal seizures on SEEG despite of unilateral non-invasive evaluation data. Three of these patients were treated with bitemporal responsive neurostimulator system (RNS). Independent bilateral mesial temporal seizures have been confirmed on RNS ECoG (electrocorticography). The fourth patient underwent right anterior temporal lobectomy.

Conclusion

We propose that patients with non-lesional mesial temporal lobe epilepsy would benefit from bilateral invasive evaluation of mesial temporal structures to predict those patients who would be at most risk for surgical failure. Neurostimulaiton could be an initial treatment option for patients with independent bitemporal seizure onset.

Contributions of Robotics to the Safety and Efficacy of Invasive Monitoring With Stereoelectroencephalography

The purpose of this review is to provide a discussion of the history and utility of robotics in invasive monitoring for epilepsy surgery using stereoelectroencephalography (sEEG). The authors conducted a literature review of available sources to describe how the advent of surgical robotics has improved the efficacy and ease of performing sEEG surgery. The sEEG method integrates anatomic, electrographic, and clinical information to test hypotheses regarding the localization of the epileptogenic zone (EZ) and has been used in Europe since the 1950s. One of the primary benefits of robot-assisted sEEG implantation techniques is the ability to seamlessly transition between both orthogonal and oblique trajectory types using a single technique. Based on available information, it is our view that, when applied appropriately, robotic sEEG can have a low rate of complications and many advantages over both non-robotic sEEG implantation and traditional craniotomy-based invasive monitoring methods.

Advances in the Surgical Management of Epilepsy: Drug-Resistant Focal Epilepsy in the Adult Patient

Pharmacoresistant seizures occur in nearly one-third of people with epilepsy. Medial temporal lobe and lesional epilepsy are the most favorable surgically remediable epileptic syndromes. Successful surgery may render the patient seizure-free, reduce antiseizure drug(s) adverse effects, improve quality of life, and decrease mortality. Surgical management should not be considered a procedure of "last resort." Despite the results of randomized controlled trials, surgery remains an underutilized treatment modality for patients with drug-resistant epilepsy (DRE). Important disparities affect patient referral and selection for surgical treatment. This article discusses the advances in surgical treatment of DRE in adults with focal seizures.

Individualized stereoelectroencephalography evaluation and navigated resection in medically refractory pediatric epilepsy

Pediatric patients frequently require invasive exploration with intracranial electrodes to achieve high-resolution delineation of the epileptogenic zones (EZ). We intend to discuss the efficacy and safety of stereoelectroencephalophraphy (SEEG) monitoring in pediatric patients with difficulty to localize the EZ. We retrospectively analyzed presurgical findings, SEEG data, resections, and outcomes of a series of 72 consecutive pediatric patients (<18 yrs) who had medically refractory epilepsy and received SEEG recording between January 2015 and September 2019. There were 20 girls and 52 boys with a mean age of 10.13 ± 4.11 years old (range: 1.8-18 years). Twenty-seven patients (37.5%) had nonlesional magnetic resonance imagings (MRIs). In total, 744 electrodes were implanted for an average of 10.33 ± 2.53 (range: 3-18) electrodes per patient. Twenty-eight explorations were unilateral (17 left and 11 right), and 44 explorations were bilateral (12 of which was predominately one side). The average monitoring period in days for the SEEG was 8.99 ± 5.79 (range: 3-25) days. The EZ could be located in 67 (94.4%) patients for the initial implantation according to SEEG monitoring. Lobectomy was performed in 12 patients (17.9%), of those anterior temporal lobectomy (ATL) was performed in 8 cases (11.9%) and insular plus was 2 cases (3.0%), multilobectomy resections in 15 cases (22.4%), tailored cortical resections in 37 cases (55.2%), and corpus callosotomy plus in 2 cases (3.0%). The average follow-up was 18.1 ± 7.53 months (range: 6-54). Forty-three of 67 patients (64.2%) were Engel class I, 12 patients (17.9%) were Engel class II, 10 patients (14.9%) were Engel class III, and an additional 2 patients (3.0%) were Engel class IV. In the SEEG implantation series, no child experienced serious or permanent morbidity. One patient (1.4%) experienced symptomatic intracranial hemorrhage (ICH), and 3 patients (4.2%) experienced asymptomatic ICH. There were no postimplantation infections or other postoperative complications associated with the SEEG. Several common complications related to resection surgery were included in this series with zero mortality. Of the 6 patients in whom we performed a second surgery, 4 of them subsequently became seizure-free (66.7%) after undergoing the second resection with SEEG evaluation. Stereoelectroencephalophraphy is a safe and efficient methodology to identify the EZ in particularly complex cases of focal medically refractory epilepsy for pediatric patients, even in infancy and early childhood. Seizure outcomes of SEEG-guided resection surgery are desirable. We recommend SEEG evaluations and even a more aggressive resection in certain pediatric patients who failed initial resection with realistic chances to benefit from reoperation.

Robotic Stereotactic Assistance (ROSA) for Pediatric Epilepsy: A Single-Center Experience of 23 Consecutive Cases

Robotic assisted neurosurgery has become increasingly utilized for its high degree of precision and minimally invasive approach. Robotic stereotactic assistance (ROSA^®) for neurosurgery has been infrequently reported in the pediatric population. The goal of this case series was to describe the clinical experience, anesthetic and operative management, and treatment outcomes for pediatric patients with intractable epilepsy undergoing ROSA^® neurosurgery at a single-center institution. Patients who underwent implantation of stereoelectroencephalography (SEEG) leads for intractable epilepsy with ROSA^® were retrospectively evaluated between August 2016 and June 2018. Demographics, perioperative management details, complications, and preliminary seizure outcomes after resective or ablative surgery were reviewed. Nineteen children who underwent 23 ROSA^® procedures for SEEG implantation were included in the study. Mean operative time was 148 min. Eleven patients had subsequent resective or ablative surgery, and ROSA^® was used to assist with laser probe insertion in five patients for seizure foci ablation. In total, 148 SEEG electrodes were placed without any perioperative complications. ROSA^® is minimally invasive, provides superior accuracy for electrode placement, and requires less time than traditional surgical approaches for brain mapping. This emerging technology may improve the perioperative outcomes for pediatric patients with intractable epilepsy since large craniotomies are avoided; however, long-term follow-up studies are needed.

Planning stereoelectroencephalography using automated lesion detection: Retrospective feasibility study

Objective

This retrospective, cross‐sectional study evaluated the feasibility and potential benefits of incorporating deep‐learning on structural magnetic resonance imaging (MRI) into planning stereoelectroencephalography (sEEG) implantation in pediatric patients with diagnostically complex drug‐resistant epilepsy. This study aimed to assess the degree of colocalization between automated lesion detection and the seizure onset zone (SOZ) as assessed by sEEG.

Methods

A neural network classifier was applied to cortical features from MRI data from three cohorts. (1) The network was trained and cross‐validated using 34 patients with visible focal cortical dysplasias (FCDs). (2) Specificity was assessed in 20 pediatric healthy controls. (3) Feasibility of incorporation into sEEG implantation plans was evaluated in 34 sEEG patients. Coordinates of sEEG contacts were coregistered with classifier‐predicted lesions. sEEG contacts in seizure onset and irritative tissue were identified by clinical neurophysiologists. A distance of <10 mm between SOZ contacts and classifier‐predicted lesions was considered colocalization.

Results

In patients with radiologically defined lesions, classifier sensitivity was 74% (25/34 lesions detected). No clusters were detected in the controls (specificity = 100%). Of the total 34 sEEG patients, 21 patients had a focal cortical SOZ, of whom eight were histopathologically confirmed as having an FCD. The algorithm correctly detected seven of eight of these FCDs (86%). In patients with histopathologically heterogeneous focal cortical lesions, there was colocalization between classifier output and SOZ contacts in 62%. In three patients, the electroclinical profile was indicative of focal epilepsy, but no SOZ was localized on sEEG. In these patients, the classifier identified additional abnormalities that had not been implanted.

Significance

There was a high degree of colocalization between automated lesion detection and sEEG. We have created a framework for incorporation of deep‐learning–based MRI lesion detection into sEEG implantation planning. Our findings support the prospective evaluation of automated MRI analysis to plan optimal electrode trajectories.

Postoperative outcomes following pediatric intracranial electrode monitoring: A case for stereoelectroencephalography (SEEG)

BACKGROUND

For patients with medically refractory epilepsy, intracranial electrode monitoring can help identify epileptogenic foci. Despite the increasing utilization of stereoelectroencephalography (SEEG), the relative risks or benefits associated with the technique when compared with the traditional subdural electrode monitoring (SDE) remain unclear, especially in the pediatric population. Our aim was to compare the outcomes of pediatric patients who received intracranial monitoring with SEEG or SDE (grids and strips).

METHODS

We retrospectively studied 38 consecutive pediatric intracranial electrode monitoring cases performed at our institution from 2014 to 2017. Medical/surgical history and operative/postoperative records were reviewed. We also compared direct inpatient hospital costs associated with the two procedures.

RESULTS

Stereoelectroencephalography and SDE cohorts both showed high likelihood of identifying epileptogenic zones (SEEG: 90.9%, SDE: 87.5%). Compared with SDE, SEEG patients had a significantly shorter operative time (118.7 versus 233.4 min, P < .001) and length of stay (6.2 versus 12.3 days, P < .001), including days spent in the intensive care unit (ICU; 1.4 versus 5.4 days, P < .001). Stereoelectroencephalography patients tended to report lower pain scores and used significantly less narcotic pain medications (54.2 versus 197.3 mg morphine equivalents, P = .005). No complications were observed. Stereoelectroencephalography and SDE cohorts had comparable inpatient hospital costs (P = .47).

CONCLUSION

In comparison with subdural electrode placement, SEEG results in a similarly favorable clinical outcome, but with reduced operative time, decreased narcotic usage, and superior pain control without requiring significantly higher costs. The potential for an improved postoperative intracranial electrode monitoring experience makes SEEG especially suitable for pediatric patients.

Robot-assisted versus manual navigated stereoelectroencephalography in adult medically-refractory epilepsy patients

OBJECTIVE

Stereoelectroencephalography (SEEG) has experienced a recent growth in adoption for epileptogenic zone (EZ) localization. Advances in robotics have the potential to improve the efficiency and safety of this intracranial seizure monitoring method. We present our institutional experience employing robot-assisted SEEG and compare its operative efficiency, seizure reduction outcomes, and direct hospital costs with SEEG performed without robotic assistance using navigated stereotaxy.

METHODS

We retrospectively identified 50 consecutive adult SEEG cases at our institution in this IRB-approved study, of which 25 were navigated with image guidance (hereafter referred to as "navigated") (02/2014-10/2016) and 25 were robot-assisted (09/2016-12/2017). A thorough review of medical/surgical history and operative records with imaging and trajectory plans was done for each patient. Direct inpatient costs related to each technique were compared.

RESULTS

Most common seizure etiologies for patients undergoing navigated and robot-assisted SEEG included non-lesional and benign temporal lesions. Despite having a higher mean number of leads-per-patient (10.2 ± 3.5 versus 7.2 ± 2.6, P = 0.002), robot-assisted cases had a significantly shorter mean operative time than navigated cases (125.5±48.5 versus 173.4±84.3 min, P = 0.02). Comparison of robot-assisted cases over the study interval revealed no significant difference in mean operative time (136.4±51.4 min for the first ten cases versus 109.9±75.8 min for the last ten cases, P = 0.25) and estimated operative time-per-lead (13.4±6.0 min for the first ten cases versus 12.9±7.7 min for the last ten cases, P = 0.86). The mean depth, radial, target, and entry point errors for robot-assisted cases were 2.12±1.89, 1.66±1.58, 3.05±2.02 mm, and 1.39 ± 0.75 mm, respectively. The two techniques resulted in equivalent EZ localization rate (navigated 88 %, robot-assisted 96 %, P = 0.30). Common types of epilepsy surgery performed consisted of implantation of responsive neurostimulation (RNS) device (56 %), resection (19.1 %), and laser ablation (23.8 %) for navigated SEEG. For robot-assisted SEEG, either RNS implantation (68.2 %) or laser ablation (22.7 %) were performed or offered. A majority of navigated and robot-assisted patients who underwent epilepsy surgery achieved either Engel Class I (navigated 36.8 %, robot-assisted 31.6 %) or II (navigated 36.8 %, robot-assisted 15.8 %) outcome with no significant difference between the groups (P = 0.14). Direct hospital cost for robot-assisted SEEG was 10 % higher than non-robotic cases.

CONCLUSION

This single-institutional study suggests that robotic assistance can enhance efficiency of SEEG without compromising safety or precision when compared to image guidance only. Adoption of this technique with uniform safety and efficacy over a short period of time is feasible with favorable epilepsy outcomes.

Comparison of Functional Deficit Zone Defined by FDG PET to the Epileptogenic Zones Described in Stereo-Electroencephalograph in Drug-Resistant Epileptic Patients Treated by Surgery

INTRODUCTION

The purpose of presurgical assessment is to delimit the epileptogenic zone and the functional deficit zone with a brain MRI, an electroencephalograph or even a stereo-electroencephalograph (SEEG), neuropsychological evaluation, and a cerebral FDG PET. Several studies concur that the hypometabolism of FDG PET seems to be consistent with epileptogenic zones. We compared the functional deficit zone defined by FDG PET with the results of the SEEG, for each cluster electrode contact (CEC) located in the gray matter.

METHODS

The electrode diagram of the 15 patients (486 CECs) operated on for drug-resistant epilepsy was merged with MRI and FDG PET. The metabolisms of FDG PET and SEEG were compared using a logistic regression test.

RESULTS

The presence of hypometabolism resulted in a significantly higher risk of being in the seizure onset zone and the irritative zone, particularly when it was intense. Of the deeply hypometabolic CECs, 47% were in the seizure onset zone and 76% in the irritative zone. Normal metabolism resulted in a significantly higher probability of being in the healthy zone.

CONCLUSIONS

This study demonstrated an association between the presence of normal metabolism and the location of CECs in the healthy zone, and between the presence of pathological metabolism and the location of CECs in the seizure onset zone and the irritative zone, with metabolism abnormalities progressively more present and more intense near the seizure onset zone.

Stereoelectroencephalography in Pediatric Epilepsy Surgery

Stereoelectroencephalography (SEEG) is an invasive technique used during the surgical management of medically refractory epilepsy. The utility of SEEG rests in its ability to survey the three-dimensional organization of the epileptogenic zone as well as nearby eloquent cortices. Once concentrated to specialized centers in Europe and Canada, the SEEG methodology has gained worldwide popularity due to its favorable morbidity profile, superior coverage of deep structures, and ability to perform multilobar explorations without the need for craniotomy. This rapid shift in practice represents both a challenge and an opportunity for pediatric neurosurgeons familiar with the subdural grid approach. The purpose of this review is to discuss the indications, technique, and safety of long-term SEEG monitoring in children. In addition to reviewing the conceptual and technical points of the diagnostic evaluation, attention will also be given to SEEG-based interventions (e.g., radiofrequency thermo-coagulation).

Robot-assisted stereoelectroencephalography in children

OBJECTIVEThe goal in the study was to describe the clinical outcomes associated with robot-assisted stereoelectroencephalography (SEEG) in children.METHODSThe authors performed a retrospective, single-center study in consecutive children with medically refractory epilepsy who were undergoing robot-assisted SEEG. Kaplan-Meier survival analysis was used to calculate the probability of seizure freedom. Both univariate and multivariate methods were used to analyze the preoperative and operative factors associated with seizure freedom.RESULTSFifty-seven children underwent a total of 64 robot-assisted procedures. The patients' mean age was 12 years, an average of 6.4 antiepileptic drugs (AEDs) per patient had failed prior to implantation, and in 56% of the patients the disease was considered nonlesional. On average, children had 12.4 electrodes placed per implantation, with an implantation time of 9.6 minutes per electrode and a 10-day postoperative stay. SEEG analysis yielded a definable epileptogenic zone in 51 (89%) patients; 42 (74%) patients underwent surgery, half of whom were seizure free at last follow-up, 19.6 months from resection. In a multivariate generalized linear model, resective surgery, older age, and shorter SEEG-related hospital length of stay were associated with seizure freedom. In a Cox proportional hazards model including only the children who underwent resective surgery, older age was the only significant factor associated with seizure freedom. Complications related to bleeding were the major contributors to morbidity. One patient (1.5%) had a symptomatic hemorrhage resulting in a permanent neurological deficit.CONCLUSIONSThe authors report one of the largest pediatric-specific SEEG series demonstrating that the modern surgical management of medically refractory epilepsy in children can lead to seizure freedom in many patients, while also highlighting the challenges posed by this difficult patient population.

Invasive EEG-electrodes in presurgical evaluation of epilepsies: Systematic analysis of implantation-, video-EEG-monitoring- and explantation-related complications, and review of literature

INTRODUCTION

Stereoelectroencephalography (sEEG) is a diagnostic procedure for patients with refractory focal epilepsies that is performed to localize and define the epileptogenic zone. In contrast to grid electrodes, sEEG electrodes are implanted using minimal invasive operation techniques without large craniotomies. Previous studies provided good evidence that sEEG implantation is a safe and effective procedure; however, complications in asymptomatic patients after explantation may be underreported. The aim of this analysis was to systematically analyze clinical and imaging data following implantation and explantation.

RESULTS

We analyzed 18 consecutive patients (mean age: 30.5 years, range: 12-46; 61% female) undergoing invasive presurgical video-EEG monitoring via sEEG electrodes (n = 167 implanted electrodes) over a period of 2.5 years with robot-assisted implantation. There were no neurological deficits reported after implantation or explantation in any of the enrolled patients. Postimplantation imaging showed a minimal subclinical subarachnoid hemorrhage in one patient and further workup revealed a previously unknown factor VII deficiency. No injuries or status epilepticus occurred during video-EEG monitoring. In one patient, a seizure-related asymptomatic cross break of two fixation screws was found and led to revision surgery. Unspecific symptoms like headaches or low-grade fever were present in 10 of 18 (56%) patients during the first days of video-EEG monitoring and were transient. Postexplantation imaging showed asymptomatic and small bleedings close to four electrodes (2.8%).

CONCLUSION

Overall, sEEG is a safe and well-tolerated procedure. Systematic imaging after implantation and explantation helps to identify clinically silent complications of sEEG. In the literature, complication rates of up to 4.4% in sEEG and in 49.9% of subdural EEG are reported; however, systematic imaging after explantation was not performed throughout the studies, which may have led to underreporting of associated complications.

Outcome after individualized stereoelectroencephalography (sEEG) implantation and navigated resection in patients with lesional and non-lesional focal epilepsy

BACKGROUND

Refined localization of the epileptogenic zone (EZ) in patients with pharmacoresistant focal epilepsy proceeding to resective surgery might improve postoperative outcome. We here report seizure outcome after stereo EEG (sEEG) evaluation with individually planned stereotactically implanted depth electrodes and subsequent tailored resection.

METHODS

A cohort of consecutive patients with pharmacoresistant focal epilepsy, evaluated with a non-invasive evaluation protocol and invasive monitoring with personalized, stereotactically implanted depth electrodes for sEEG was analyzed. Co-registration of post-implantation CT scan to presurgical MRI data was used for 3D reconstructions of the patients' brain surface and mapping of neurophysiology data. Individual multimodal 3D maps of the EZ were used to guide subsequent tailored resections. The outcome was rated according to the Engel classification.

RESULTS

Out of 914 patients who underwent non-invasive presurgical evaluation, 85 underwent sEEG, and 70 were included in the outcome analysis. Median follow-up was 31.5 months. Seizure-free outcome (Engel class I A-C, ILAE class 1-2) was achieved in 83% of the study cohort. Patients exhibiting lesional and non-lesional (n = 42, 86% vs. n = 28, 79%), temporal and extratemporal (n = 45, 80% vs. n = 25, 84%), and right- and left-hemispheric epilepsy (n = 44, 82% vs. n = 26, 85%) did similarly well. This remains also true for those with an EZ adjacent to or distant from eloquent cortex (n = 21, 86% vs. n = 49, 82%). Surgical outcome was independent of resected tissue volume.

CONCLUSION

Favourable post-surgical outcome can be achieved in patients with resistant focal epilepsy, using individualized sEEG evaluation and tailored navigated resection, even in patients with non-lesional or extratemporal focal epilepsy.

Frameless robot-assisted stereoelectroencephalography for refractory epilepsy in pediatric patients: accuracy, usefulness, and technical issues

BACKGROUND

Stereoelectroencephalography (SEEG) is an effective technique to help to locate and to delimit the epileptogenic area and/or to define relationships with functional cortical areas. We intend to describe the surgical technique and verify the accuracy, safety, and effectiveness of robot-assisted SEEG in a newly created SEEG program in a pediatric center. We focus on the technical difficulties encountered at the early stages of this program.

METHODS

We prospectively collected SEEG indication, intraoperative events, accuracy calculated by fusion of postoperative CT with preoperative planning, complications, and usefulness of SEEG in terms of answering preimplantation hypothesis.

RESULTS

Fourteen patients between the ages of 5 and 18 years old (mean 10 years) with drug-resistant epilepsy were operated on between April 2016 and April 2018. One hundred sixty-four electrodes were implanted in total. The median entry point localization error (EPLE) was 1.57 mm (1-2.25 mm) and the median target point localization error (TPLE) was 1.77 mm (1.2-2.6 mm). We recorded seven intraoperative technical issues. Two patients suffered complications: meningitis without demonstrated germ in one patient and a right frontal hematoma in the other. In all cases, the SEEG was useful for the therapeutic decision-making.

CONCLUSION

SEEG has been useful for decision-making in all our pediatric patients. The robotic arm is an accurate tool for the insertion of the deep electrodes. Nevertheless, it is an invasive technique not risk-free and many problems can appear at the beginning of a robotic arm-assisted SEEG program that must be taken into account beforehand.

Robot-guided pediatric stereoelectroencephalography: single-institution experience

OBJECTIVEStereoelectroencephalography (SEEG) has increased in popularity for localization of epileptogenic zones in drug-resistant epilepsy because safety, accuracy, and efficacy have been well established in both adult and pediatric populations. Development of robot-guidance technology has greatly enhanced the efficiency of this procedure, without sacrificing safety or precision. To date there have been very limited reports of the use of this new technology in children. The authors present their initial experience using the ROSA platform for robot-guided SEEG in a pediatric population.METHODSBetween February 2016 and October 2017, 20 consecutive patients underwent robot-guided SEEG with the ROSA robotic guidance platform as part of ongoing seizure localization and workup for medically refractory epilepsy of several different etiologies. Medical and surgical history, imaging and trajectory plans, as well as operative records were analyzed retrospectively for surgical accuracy, efficiency, safety, and epilepsy outcomes.RESULTSA total of 222 leads were placed in 20 patients, with an average of 11.1 leads per patient. The mean total case time (± SD) was 297.95 (± 52.96) minutes and the mean operating time per lead was 10.98 minutes/lead, with improvements in total (33.36 minutes/lead vs 21.76 minutes/lead) and operative (13.84 minutes/lead vs 7.06 minutes/lead) case times/lead over the course of the study. The mean radial error was 1.75 (± 0.94 mm). Clinically useful data were obtained from SEEG in 95% of cases, and epilepsy surgery was indicated and performed in 95% of patients. In patients who underwent definitive epilepsy surgery with at least a 3-month follow-up, 50% achieved an Engel class I result (seizure freedom). There were no postoperative complications associated with SEEG placement and monitoring.CONCLUSIONSIn this study, the authors demonstrate that rapid adoption of robot-guided SEEG is possible even at a SEEG-naïve institution, with minimal learning curve. Use of robot guidance for SEEG can lead to significantly decreased operating times while maintaining safety, the overall goals of identification of epileptogenic zones, and improved epilepsy outcomes.

Safety and efficacy of stereoelectroencephalography in pediatric focal epilepsy: a single-center experience

OBJECTIVE

Patients with medically refractory localization-related epilepsy (LRE) may be candidates for surgical intervention if the seizure onset zone (SOZ) can be well localized. Stereoelectroencephalography (SEEG) offers an attractive alternative to subdural grid and strip electrode implantation for seizure lateralization and localization; yet there are few series reporting the safety and efficacy of SEEG in pediatric patients.

METHODS

The authors review their initial 3-year consecutive experience with SEEG in pediatric patients with LRE. SEEG coverage, SOZ localization, complications, and preliminary seizure outcomes following subsequent surgical treatments are assessed.

RESULTS

Twenty-five pediatric patients underwent 30 SEEG implantations, with a total of 342 electrodes placed. Ten had prior resections or ablations. Seven had no MRI abnormalities, and 8 had multiple lesions on MRI. Based on preimplantation hypotheses, 7 investigations were extratemporal (ET), 1 was only temporal-limbic (TL), and 22 were combined ET/TL investigations. Fourteen patients underwent bilateral investigations. On average, patients were monitored for 8 days postimplant (range 3-19 days). Nearly all patients were discharged home on the day following electrode explantation. There were no major complications. Minor complications included 1 electrode deflection into the subdural space, resulting in a minor asymptomatic extraaxial hemorrhage; and 1 in-house and 1 delayed electrode superficial scalp infection, both treated with local wound care and oral antibiotics. SEEG localized the hypothetical SOZ in 23 of 25 patients (92%). To date, 18 patients have undergone definitive surgical intervention. In 2 patients, SEEG localized the SOZ near eloquent cortex and subdural grids were used to further delineate the seizure focus relative to mapped motor function just prior to resection. At last follow-up (average 21 months), 8 of 15 patients with at least 6 months of follow-up (53%) were Engel class I, and an additional 6 patients (40%) were Engel class II or III. Only 1 patient was Engel class IV.

CONCLUSIONS

SEEG is a safe and effective technique for invasive SOZ localization in medically refractory LRE in the pediatric population. SEEG permits bilateral and multilobar investigations while avoiding large craniotomies. It is conducive to deep, 3D, and perilesional investigations, particularly in cases of prior resections. Patients who are not found to have focally localizable seizures are spared craniotomies.

Stereoelectroencephalography in children: a review

Stereoelectroencephalography (SEEG) is an intracranial diagnostic measure that has grown in popularity in the United States as outcomes data have demonstrated its benefits and safety. The main uses of SEEG include 1) exploration of deep cortical/sulcal structures; 2) bilateral recordings; and 3) 3D mapping of epileptogenic zones. While SEEG has gradually been accepted for treatment in adults, there is less consensus on its utility in children. In this literature review, the authors seek to describe the current state of SEEG with a focus on the more recent technology-enabled surgical techniques and demonstrate its efficacy in the pediatric epilepsy population.