Stereoelectroencephalography in the presurgical evaluation of focal epilepsy in infancy and early childhood

De novo cerebral pseudoaneurysm formation: a rare delayed complication of stereotactic electroencephalography in children

OBJECTIVE

To describe the rare complication of cerebral pseudoaneurysm formation following stereotactic electroencephalography (sEEG) lead implantation in children.

METHODS

A retrospective chart review of all pediatric patients undergoing sEEG procedures between 2015 and 2020 was performed. Cases of pseudoaneurysm were identified and reviewed.

RESULTS

Cerebral pseudoaneurysms were identified in two of 58 total cases and 610 implanted electrodes. One lesion was detected 1 year after sEEG explantation and required craniotomy and clipping. The other was detected 3 months post-explantation and underwent coil embolization. Neither patient had any neurologic deficits associated with the pseudoaneurysm before or after treatment.

CONCLUSIONS

Pseudoaneurysm formation post-sEEG explantation is rare and likely underreported. Routine, post-explantation/treatment imaging is warranted to detect this rare but potentially lethal complication.

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.

Pediatric Neurostimulation and Practice Evolution

Since the late nineteenth century, the prevailing view of epilepsy surgery has been to identify a seizure focus in a medically refractory patient and eradicate it. Sadly, only a select number of the many who suffer from uncontrolled seizures benefit from this approach. With the development of safe, efficient stereotactic methods and targeted surgical therapies that can affect deep structures and modulate broad networks in diverse disorders, epilepsy surgery in children has undergone a paradigmatic evolutionary change. With modern diagnostic techniques such as stereo electroencephalography combined with closed loop neuromodulatory systems, pediatric epilepsy surgery can reach a much broader population of underserved patients.

Implications of intracranial hemorrhage associated with stereo-EEG

OBJECTIVE

Intracranial hemorrhage (ICH) is a known complication during stereo-electroencephalography (sEEG) however true rates remain unknown. We provide a comprehensive review of ICH during sEEG regardless of clinical symptoms. Secondly, we analyzed sEEG recordings to identify electrographic correlates of ICH.

METHODS

This is a retrospective study of patients undergoing sEEG between January 2016 and April 2022 at the Mayo Clinic in Rochester. We reviewed medical records and imaging studies to identify ICH. We analyzed ICH by type, electrode trajectories, timing, sEEG findings and outcomes.

RESULTS

There were a total of 201 sEEG implants, of which 23 (11%) cases or 0.9% electrodes implanted had evidence of ICH. The majority of affected patients (82%) were either asymptomatic or had mild clinical neurological manifestations. In 90% of patients who proceeded with surgical treatments, outcomes were favorable. The most common sEEG finding in contacts in proximity of ICH was either focal slowing with interictal discharges or focal electrographic seizures.

CONCLUSIONS

ICH associated with sEEG is likely under-reported in literature. We present electroencephalographic correlates of ICH that may aid identification of ICH in the course of performing sEEG monitoring.

SIGNIFICANCE

Our data provides clinically relevant information on potential risks and outcomes of ICH. Furthermore, our findings aid identification of ICH during sEEG.

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.

Stereoelectroencephalography followed by combined electrode removal and MRI-guided laser interstitial thermal therapy or open resection: a single-center series in pediatric patients with medically refractory epilepsy

OBJECTIVE

Stereoelectroencephalography (SEEG) and MRI-guided laser interstitial thermal therapy (MRgLITT) have emerged as safe, effective, and less invasive alternatives to subdural grid placement and open resection, respectively, for the localization and treatment of medically refractory epilepsy (MRE) in children. Reported pediatric experience combining these complementary techniques is limited, with traditional workflows separating electrode removal and ablation/resection. The authors describe the largest reported series of pediatric epilepsy patients who underwent MRgLITT following SEEG contrasted with a cohort that underwent craniotomy following SEEG, combining ablation/resection with electrode explantation as standard practice.

METHODS

The medical records of all patients with MRE who had undergone SEEG followed by MRgLITT or open resection/disconnection at Boston Children's Hospital between November 2015 and December 2020 were retrospectively reviewed. Primary outcome variables included surgical complication rates, length of hospital stay following treatment, and Engel classification at the last follow-up.

RESULTS

Of 74 SEEG patients, 27 (median age 12.1 years, 63% female) underwent MRgLITT and 47 (median age 12.1 years, 49% female) underwent craniotomy. Seventy patients (95%) underwent SEEG followed by combined electrode removal and treatment. Eight MRgLITT cases (30%) and no open cases targeted the insula (p < 0.001). Complication rates did not differ, although trends toward more subdural/epidural hematomas, infarcts, and permanent unanticipated neurological deficits were evident following craniotomy, whereas a trend toward more temporary unanticipated neurological deficits was seen following MRgLITT. The median duration of hospitalization after treatment was 3 and 5 days for MRgLITT and open cases, respectively (p = 0.078). Seizure outcomes were similar between the cohorts, with 74% of MRgLITT and craniotomy patients attaining Engel class I or II outcomes (p = 0.386) at the last follow-up (median 1.1 and 1.9 years, respectively).

CONCLUSIONS

MRgLITT and open resection following SEEG can both effectively treat MRE in pediatric patients and generally can be performed in a two-surgery workflow during a single hospitalization. In appropriately selected patients, MRgLITT tended to be associated with shorter hospitalizations and fewer complications following treatment and may be best suited for focal deep-seated targets associated with relatively challenging open surgical approaches.

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.

Safety and Efficacy of Stereoelectroencephalography in Pediatric Epilepsy Surgery

Stereoelectroencephalography (SEEG) is the preoperative assessment of choice when the epileptogenic zone (EZ) is unclear in patients requiring surgery for severe, drug-refractory epilepsy. There are relatively little data on the safety and efficacy of SEEG in the pediatric epilepsy population. We, therefore, investigated the insertional complications, rate of successful identification of the EZ, and long-term seizure outcomes following surgery after SEEG in children. This was a retrospective study of drug-resistant pediatric epilepsy patients treated with surgery between 2005 and 2020 and who underwent presurgical SEEG. Rationale for and coverage of SEEG, identification of the EZ, and ultimate seizure outcome following SEEG-tailored resections were collected and analyzed. Thirty patients (15 male, mean age: 12.4 ± 5 years) who underwent SEEG were studied. SEEG-related complications occurred in one case (3%). A total of 190 multicontact electrodes (mean: 7.0 ± 2.5 per patient) were implanted across 30 insertions capturing 440 electrographic seizures (mean: 17.5 ± 27.6 per patient). The most common rationale for SEEG was normal magnetic resonance imaging with surface EEG that failed to identify the EZ (17/30; 57%). SEEG identified a putative EZ in all cases, resulting in SEEG-tailored resections in 25/30 (83%). Freedom from disabling seizures was achieved following resections in 20/25 cases (80%) with 5.9 ± 4.0 years of postoperative follow-up. SEEG is a safe and effective way to identify the EZ in the presurgical evaluation of children with refractory epilepsy and permits effective and long-lasting SEEG-tailored resections.

Robot-assisted stereoelectroencephalography in young children: technical challenges and considerations

Robot-assisted stereoelectroencephalography (sEEG) is frequently employed to localize epileptogenic zones in patients with medically refractory epilepsy (MRE). Its methodology is well described in adults, but less so in children. Given the limited information available on pediatric applications, the objective is to describe the unique technical challenges and considerations of sEEG in the pediatric population. In this report, we describe our institutional experience with the technical aspects of robot-assisted sEEG in an exclusively pediatric epilepsy surgery unit, focusing on pre-, intra-, and post-operative nuances that are particular to the pediatric population. The pediatric population presents several unique challenges in sEEG, including reduced skull thickness relative to adults, incomplete neurologic development, and often special behavioral considerations. Pre-operative selection of putative epileptogenic zones requires careful multidisciplinary decision-making. Intraoperative attention to nuances in positioning, clamp selection, registration, and electrode placement are necessary. Activity considerations and electrode migration and removal are key post-operative considerations. Robot-assisted sEEG is a valuable tool in the armamentarium of techniques to characterize MRE. However, special considerations must be given to the pediatric population to optimize safety and efficacy.

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.

Epilepsy Surgery: Special Circumstances

Epilepsy surgery has proven to be very effective in treating refractory focal epilepsies in children, producing seizure freedom or partial seizure control well beyond any other medical or dietary therapies. While surgery is mostly utilized in certain clinical phenotypes, either based on the location such as temporal lobe epilepsy, or based on the presence of known epileptogenic lesions such as focal cortical dysplasia, tumors or hemimegalencephaly, there is a growing body of evidence to support the role of surgery in other patients' cohorts that were classically not thought of as surgical candidates. These include patients with rare genetic disorders, electrical status epilepticus in sleep, status epilepticus and the very young patients. Furthermore, epilepsy surgery is not considered as a "last resort" as seizure and cognitive outcomes of surgery are considerably better when done earlier rather than later in relation to the time of onset of epilepsy and age of surgery especially in the context of known focal cortical dysplasia. This article examines the accumulating evidence of the utility of epilepsy surgery in these special circumstances.

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.

Pediatric stereo-electroencephalography: effects of robot assistance and other variables on seizure outcome and complications

OBJECTIVE

The safety of stereo-electroencephalography (SEEG) has been investigated; however, most studies have not differentiated pediatric and adult populations, which have different anatomy and physiology. The purpose of this study was to assess SEEG safety in the pediatric setting, focusing on surgical complications and the identification of patient and surgical risk factors, if any. The authors also aimed to determine whether robot assistance in SEEG was associated with a change in practice, surgical parameters, and clinical outcomes.

METHODS

The authors retrospectively studied all SEEG cases performed in their department from December 2014 to March 2020. They analyzed both demographic and surgical variables and noted the types of surgery-related complications and their management. They also studied the clinical outcomes of a subset of the patients in relation to robot-assisted and non-robot-assisted SEEG.

RESULTS

Sixty-three children had undergone 64 SEEG procedures. Girls were on average 3 years younger than the boys (mean age 11.1 vs 14.1 years, p < 0.01). The overall complication rate was 6.3%, and the complication rate for patients with left-sided electrodes was higher than that for patients with right-sided electrodes (11.1% vs 3.3%), although the difference between the two groups was not statistically significant. The duration of recording was positively correlated to the number of implanted electrodes (r = 0.296, p < 0.05). Robot assistance was associated with a higher number of implanted electrodes (mean 12.6 vs 7.6 electrodes, p < 0.0001). Robot-assisted implantations were more accurate, with a mean error of 1.51 mm at the target compared to 2.98 mm in nonrobot implantations (p < 0.001). Clinical outcomes were assessed in the first 32 patients treated (16 in the nonrobot group and 16 in the robot group), 23 of whom proceeded to further resective surgery. The children who had undergone robot-assisted SEEG had better eventual seizure control following subsequent epilepsy surgery. Of the children who had undergone resective epilepsy surgery, 42% (5/12) in the nonrobot group and 82% (9/11) in the robot group obtained an Engel class IA outcome at 1 year (χ2 = 3.885, p = 0.049). Based on Kaplan-Meier survival analysis, the robot group had a higher seizure-free rate than the nonrobot group at 30 months postoperation (7/11 vs 2/12, p = 0.063). Two complications, whose causes were attributed to the implantation and head-bandaging steps, required surgical intervention. All complications were either transient or reversible.

CONCLUSIONS

This is the largest single-center, exclusively pediatric SEEG series that includes robot assistance so far. SEEG complications are uncommon and usually transient or treatable. Robot assistance enabled implantation of more electrodes and improved epilepsy surgery outcomes, as compared to those in the non-robot-assisted cases.

Functional characteristics of the human primary somatosensory cortex: An electrostimulation study

The common knowledge of the functional organization of the human primary somatosensory cortex (S1) had been primarily established by Penfield who electrically stimulated the exposed surface [referred as Brodmann area (BA)1] of S1 under neurosurgical conditions. Nevertheless, the functional information regarding the deep surface (BA 2 and 3) of S1 is poorly understood. We retrospectively analyzed all the clinical manifestations induced by extra-operative cortical electrical stimulation (ES) in 33 patients with medically intractable epilepsy who underwent stereo-electroencephalography (SEEG) monitoring for presurgical assessment. Demographic and clinical data were gathered and evaluated to delineate the determinants of the occurrence of positive responses, types of responses, and size of body regions involved. The stimulation of 244 sites in S1 yielded 198 positive sites (81.1%), most of which were located in the sulcal cortex. In multivariable analyses, no clinical or demographic factors predicted the occurrence of responses or their threshold levels. The size of body region involved in the responses had ordinal association with the stimulated BA sites (p < 0.001). Various types of responses elicited from the S1 were documented and classified, and the predictors of those responses were also assessed. Our analysis revealed the functional characteristics of the entire S1 and proved the multiplicity of functions of S1.

Language Mapping Using Stereo Electroencephalography: A Review and Expert Opinion

Stereo-electroencephalography (sEEG) is a method that uses stereotactically implanted depth electrodes for extra-operative mapping of epileptogenic and functional networks. sEEG derived functional mapping is achieved using electrical cortical stimulations (ECS) that are currently the gold standard for delineating eloquent cortex. As this stands true especially for primary cortices (e.g., visual, sensitive, motor, etc.), ECS applied to higher order brain areas determine more subtle behavioral responses. While anterior and posterior language areas in the dorsal language stream seem to share characteristics with primary cortices, basal temporal language area (BTLA) in the ventral temporal cortex (VTC) behaves as a highly associative cortex. After a short introduction and considerations about methodological aspects of ECS using sEEG, we review the sEEG language mapping literature in this perspective. We first establish the validity of this technique to map indispensable language cortices in the dorsal language stream. Second, we highlight the contrast between the growing empirical ECS experience and the lack of understanding regarding the fundamental mechanisms underlying ECS behavioral effects, especially concerning the dispensable language cortex in the VTC. Evidences for considering network architecture as determinant for ECS behavioral response complexities are discussed. Further, we address the importance of designing new research in network organization of language as this could enhance ECS ability to map interindividual variability, pathology driven reorganization, and ultimately identify network resilience markers in order to better predict post-operative language deficit. Finally, based on a whole body of available studies, we believe there is strong evidence to consider sEEG as a valid, safe and reliable method for defining eloquent language cortices although there have been no proper comparisons between surgical resections with or without extra-operative or intra-operative language mapping.

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.

Stimulation Mapping Using Stereoelectroencephalography: Current and Future Directions

Electrical stimulation mapping (ESM) using stereoelectroencephalography (SEEG) is an essential component in the workup of surgical epilepsy. Since the initial application of ESM in the mid-1960s, it remains unparalleled in defining eloquent brain areas and delimiting seizure foci for the purposes of surgical planning. Here, we briefly review the current state of SEEG stimulation, with a focus on the techniques used for identifying the epileptogenic zone and eloquent cortex. We also summarize clinical data on the efficacy of SEEG stimulation in surgical outcomes and functional mapping. Finally, we briefly highlight future applications of SEEG ESM, including novel functional mapping approaches, identifying rare seizure semiologies, neurophysiologic investigations for understanding cognitive function, and its role in SEEG-guided radiofrequency thermal coagulation.

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.

Comparison of narcotic pain control between stereotactic electrocorticography and subdural grid implantation

INTRODUCTION

The choice of subdural grid (SDG) or stereoelectroencephalography (sEEG) for patients with epilepsy can be complex and in some cases overlap. Comparing postoperative pain and narcotics consumption with SDG or sEEG can help develop an intracranial monitoring strategy.

MATERIALS AND METHODS

A retrospective study was performed for adult patients undergoing SDG or sEEG monitoring. Numeric Rating Scale (NRS) was used for pain assessment. Types and dosage of the opioids were calculated by converting into milligram morphine equivalents (MME). Narcotic consumption was analyzed at the following three time periods: I. the first 24 h of implantation; II. from the second postimplantation day to the day of explantation; and III. the days following electrode removal to discharge.

RESULTS

Forty-two patients who underwent SDG and 31 patients who underwent sEEG implantation were analyzed. After implantation, average NRS was 3.7 for SDG and 2.2 for sEEG (P < .001). After explantation, the NRS was 3.5 for SDG and 1.4 in sEEG (P < .001). Sixty percent of SDG patients and 13% of sEEG patients used more than one opioid in period III (P < .001). The SDG group had a significantly higher MME throughout the three periods compared with the sEEG group: period I: 448 (SDG) vs. 205 (sEEG) mg, P = .002; period II: 377 (SDG) vs. 102 (sEEG) mg, P < .001; and period III: 328 (SDG) vs. 75 (sEEG) mg; P = .002. Patients with the larger SDG implantation had the higher NRS (P = .03) and the higher MME at period I (P = .019). There was no correlation between the number of depth electrodes and pain control in patients with sEEG.

CONCLUSIONS

Patients undergoing sEEG had significantly less pain and required fewer opiates compared with patients with SDG. These differences in perioperative pain may be a consideration when choosing between these two invasive monitoring options.

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.

Preoperative evaluation and surgical management of infants and toddlers with drug-resistant epilepsy

OBJECTIVE Despite perioperative risks, epilepsy surgery represents a legitimate curative or palliative treatment approach for children with drug-resistant epilepsy (DRE). Several factors characterizing infants and toddlers with DRE create unique challenges regarding optimal evaluation and management. Epilepsy surgery within children < 3 years of age has received moderate attention in the literature, including mainly case series and retrospective studies. This article presents a systematic literature review and explores multidisciplinary considerations for the preoperative evaluation and surgical management of infants and toddlers with DRE. METHODS The study team conducted a systematic literature review based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, targeting studies that investigated children < 3 years of age undergoing surgical treatment of DRE. Using the PubMed database, investigators selected peer-reviewed articles that reported seizure outcomes with or without developmental outcomes and/or perioperative complications. Studies were eliminated based on the following exclusion criteria: sample size < 5 patients; and inclusion of patients > 3 years of age, when demographic and outcomes data could not be separated from the cohort of patients < 3 years of age. RESULTS The study team identified 20 studies published between January 1990 and May 2017 that satisfied eligibility criteria. All selected studies represented retrospective reviews, observational studies, and uncontrolled case series. The compiled group of studies incorporated 465 patients who underwent resective or disconnective surgery (18 studies, 444 patients) or vagus nerve stimulator insertion (2 studies, 21 patients). Patient age at surgery ranged between 28 days and 36 months, with a mean of 16.8 months (1.4 years). DISCUSSION The study team provided a detailed summary of the literature review, focusing on the etiologies, preoperative evaluation, surgical treatments, seizure and developmental outcomes, and potential for functional recovery of infants and toddlers with DRE. Additionally, the authors discussed special considerations in this vulnerable age group from the perspective of multiple disciplines. CONCLUSIONS While presenting notable challenges, pediatric epilepsy surgery within infants and toddlers (children < 3 years of age) offers significant opportunities for improved seizure frequency, neuro-cognitive development, and quality of life. Successful evaluation and treatment of young children with DRE requires special consideration of multiple aspects related to neurological and physiological immaturity and surgical morbidity.

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).

Magnetic resonance-guided laser interstitial thermal therapy for the treatment of non-lesional insular epilepsy in pediatric patients: thermal dynamic and volumetric factors influencing seizure outcomes

PURPOSE

To investigate the safety and efficacy of stereoelectroencephalography (sEEG) directed magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) in medically refractory insular epilepsy in pediatric patients, define the relationship between ablation volumes and seizure control, and analyze the relationship between thermal energy and ablation volumes.

METHODS

A single-institution, retrospective review of pediatric patients with insular epilepsy who underwent sEEG directed MRgLITT over a 10-month period was performed. Perioperative, imaging, and outcome data were analyzed. Seizure outcomes were determined based on Engel score (Engel I versus Engel II-IV). Insula and ablation volumes were measured, and the proportion of insula volume ablated was calculated. Thermal energy was calculated in joules.

RESULTS

Four patients underwent sEEG directed MRgLITT of insular epileptogenic foci. The ablation volume was higher in patients with Engel I outcome (3.93 cm³) compared to Engel II-IV outcome (1.02 cm³). The proportion of ablation to insula volume was lowest in patients with Engel II-IV outcome (25.09%). The mean energy requirement to create a unit volume of ablation in the insula is 1205.86 J. A linear trend was noted between thermal ablation energy and ablation volume (R² = 0.884). Over a mean follow-up period of 104 days, three patients were seizure-free (Engel I), and one patient saw significant improvement in seizure frequency (Engel III).

CONCLUSIONS

The proportion of insula ablated, as well as the volume of ablation, are related to seizure outcome with increasing ablation volumes corresponding to improved seizure control. Further analysis of insula laser ablation thermal dynamics and volumes is needed.

Accuracy of robot-assisted versus optical frameless navigated stereoelectroencephalography electrode placement in children

OBJECTIVE The aim of this study was to compare the accuracy of optical frameless neuronavigation (ON) and robot-assisted (RA) stereoelectroencephalography (SEEG) electrode placement in children, and to identify factors that might increase the risk of misplacement. METHODS The authors undertook a retrospective review of all children who underwent SEEG at their institution. Twenty children were identified who underwent stereotactic placement of a total of 218 electrodes. Six procedures were performed using ON and 14 were placed using a robotic assistant. Placement error was calculated at cortical entry and at the target by calculating the Euclidean distance between the electrode and the planned cortical entry and target points. The Mann-Whitney U-test was used to compare the results for ON and RA placement accuracy. For each electrode placed using robotic assistance, extracranial soft-tissue thickness, bone thickness, and intracranial length were measured. Entry angle of electrode to bone was calculated using stereotactic coordinates. A stepwise linear regression model was used to test for variables that significantly influenced placement error. RESULTS Between 8 and 17 electrodes (median 10 electrodes) were placed per patient. Median target point localization error was 4.5 mm (interquartile range [IQR] 2.8–6.1 mm) for ON and 1.07 mm (IQR 0.71–1.59) for RA placement. Median entry point localization error was 5.5 mm (IQR 4.0–6.4) for ON and 0.71 mm (IQR 0.47–1.03) for RA placement. The difference in accuracy between Stealth-guided (ON) and RA placement was highly significant for both cortical entry point and target (p < 0.0001 for both). Increased soft-tissue thickness and intracranial length reduced accuracy at the target. Increased soft-tissue thickness, bone thickness, and younger age reduced accuracy at entry. There were no complications. CONCLUSIONS RA stereotactic electrode placement is highly accurate and is significantly more accurate than ON. Larger safety margins away from vascular structures should be used when placing deep electrodes in young children and for trajectories that pass through thicker soft tissues such as the temporal region. ABBREVIATIONS CTA = CT angiography; IQR = interquartile range; MEG = magnetoencephalography; ON = optical frameless neuronavigation; RA = robot-assisted; SEEG = stereoelectroencephalography.

Neuroimaging methods in Epilepsy of Temporal Origin

Background:

Temporal Lobe Epilepsy (TLE) comprises the most common form of symptomatic refractory focal epilepsy in adults. Accurate lateralization and localization of the epileptogenic focus are a significant prerequisite for determining surgical candidacy once the patient has been deemed medically intractable. Structural MR imaging, clinical, electrophysiological, and neurophysiological data have an established role in the localization of the epileptogenic foci. Nevertheless, hippocampal sclerosis cannot be detected on MR images in more than 30% of patients with TLE, and the presurgical assessment remains controversial. </P><P> Discussion: In the last years, advanced MR imaging techniques, such as 1H-MRS, DWI, DTI, DSCI, and fMRI, may provide valuable additional information regarding the physiological and metabolic characterization of brain tissue. MR imaging has shifted towards functional and molecular imaging, thus, promising to improve the accuracy regarding the lateralization and the localization of the epileptogenic focus. Additionally, nuclear medicine studies, such as SPECT and PET imaging modalities, have become an asset for the decoding of brain function and activity, and can be diagnostically helpful as well, since they provide valuable data regarding the altered metabolic activity of the seizure foci.

Conclusion:

Overall, advanced MRI, SPECT, and PET imaging techniques are increasingly becoming an essential part of TLE diagnostics, when the epileptogenic area is not identified on structural MRI or when structural MRI, clinical, and electrophysiological findings are not in concordance.

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.

Early outcomes of stereoelectroencephalography followed by MR-guided laser interstitial thermal therapy: a paradigm for minimally invasive epilepsy surgery

OBJECTIVE

Stereoelectroencephalography (sEEG) and MR-guided laser interstitial thermal therapy (MRgLITT) have both emerged as minimally invasive alternatives to open surgery for the localization and treatment of medically refractory lesional epilepsy. Although some data are available about the use of these procedures individually, reports are almost nonexistent on their use in conjunction. The authors’ aim was to report early outcomes regarding efficacy and safety of sEEG followed by MRgLITT for localization and ablation of seizure foci in the pediatric population with medically refractory lesional epilepsy.

METHODS

A single-center retrospective review of pediatric patients who underwent sEEG followed by MRgLITT procedures was performed. Demographic, intraoperative, and outcome data were compiled and analyzed.

RESULTS

Four pediatric patients with 9 total lesions underwent sEEG followed by MRgLITT procedures between January and September 2017. The mean age at surgery was 10.75 (range 2–21) years. Two patients had tuberous sclerosis and 2 had focal cortical dysplasia. Methods of stereotaxy consisted of BrainLab VarioGuide and ROSA robotic guidance, with successful localization of seizure foci in all cases. The sEEG procedure length averaged 153 (range 67–235) minutes, with a mean of 6 (range 4–8) electrodes and 56 (range 18–84) contacts per patient. The MRgLITT procedure length averaged 223 (range 179–252) minutes. The mean duration of monitoring was 6 (range 4–8) days, and the mean total hospital stay was 8 (range 5–11) days. Over a mean follow-up duration of 9.3 (range 5.1–16) months, 3 patients were seizure free (Engel class I, 75%), and 1 patient saw significant improvement in seizure frequency (Engel class II, 25%). There were no complications.

CONCLUSIONS

These early data demonstrate that sEEG followed by MRgLITT can be used safely and effectively to localize and ablate epileptogenic foci in a minimally invasive paradigm for treatment of medically refractory lesional epilepsy in pediatric populations. Continued collection of data with extended follow-up is needed.

Methodology, outcome, safety and in vivo accuracy in traditional frame-based stereoelectroencephalography

Background

Stereoelectroencephalography (SEEG) is an established diagnostic technique for the localization of the epileptogenic zone in drug-resistant epilepsy. In vivo accuracy of SEEG electrode positioning is of paramount importance since higher accuracy may lead to more precise resective surgery, better seizure outcome and reduction of complications.

Objective

To describe experiences with the SEEG technique in our comprehensive epilepsy center, to illustrate surgical methodology, to evaluate in vivo application accuracy and to consider the diagnostic yield of SEEG implantations.

Methods

All patients who underwent SEEG implantations between September 2008 and April 2016 were analyzed. Planned electrode trajectories were compared with post-implantation trajectories after fusion of pre- and postoperative imaging. Quantitative analysis of deviation using Euclidean distance and directional errors was performed. Explanatory variables for electrode accuracy were analyzed using linear regression modeling. The surgical methodology, procedure-related complications and diagnostic yield were reported.

Results

Seventy-six implantations were performed in 71 patients, and a total of 902 electrodes were implanted. Median entry and target point deviations were 1.54 mm and 2.93 mm. Several factors that predicted entry and target point accuracy were identified. The rate of major complications was 2.6%. SEEG led to surgical therapy of various modalities in 53 patients (69.7%).

Conclusions

This study demonstrated that entry and target point localization errors can be predicted by linear regression models, which can aid in identification of high-risk electrode trajectories and further enhancement of accuracy. SEEG is a reliable technique, as demonstrated by the high accuracy of conventional frame-based implantation methodology and the good diagnostic yield.

New Techniques and Progress in Epilepsy Surgery

While open surgical resection for medically refractory epilepsy remains the gold standard in current neurosurgical practice, modern techniques have targeted areas for improvement over open surgical resection. This review focuses on how a variety of these new techniques are attempting to address these various limitations. Stereotactic electroencephalography offers the possibility of localizing deep epileptic foci, improving upon subdural grid placement which limits localization to neocortical regions. Laser interstitial thermal therapy (LITT) and stereotactic radiosurgery can minimally or non-invasively ablate specific regions of interest, with near real-time feedback for laser interstitial thermal therapy. Finally, neurostimulation offers the possibility of seizure reduction without needing to ablate or resect any tissue. However, because these techniques are still being evaluated in current practice, there are no evidence-based guidelines for their use, and more research is required to fully evaluate their proper role in the current management of medically refractory epilepsy.

Recent developments in the surgical management of paediatric epilepsy

Among the 1% of children affected by epilepsy, failure of pharmacological therapy and early age of seizure onset can lead to worse long-term cognitive outcomes, mental health disorders and impaired functional status. Surgical management often improves functional and cognitive outcomes in children with medically refractory epilepsy, especially when seizure remission is achieved. However, surgery remains underused in children with drug-resistant epilepsy, creating a large treatment gap. Several recent innovations have led to considerable improvement in surgical technique, including the recent development of minimally invasive diagnostic and therapeutic techniques such as stereotactic EEG, transcranial magnetic stimulation, MRI-guided laser ablation, as well as novel paradigms of neurostimulation. This article discusses the current landscape of surgical innovation in the management of paediatric epilepsy, leading to a paradigm shift towards minimally invasive therapy and closing the treatment gap in children suffering from drug-resistant seizures.

Robot-assisted procedures in pediatric neurosurgery

OBJECTIVE

During the last 3 decades, robotic technology has rapidly spread across several surgical fields due to the continuous evolution of its versatility, stability, dexterity, and haptic properties. Neurosurgery pioneered the development of robotics, with the aim of improving the quality of several procedures requiring a high degree of accuracy and safety. Moreover, robot-guided approaches are of special interest in pediatric patients, who often have altered anatomy and challenging relationships between the diseased and eloquent structures. Nevertheless, the use of robots has been rarely reported in children. In this work, the authors describe their experience using the ROSA device (Robotized Stereotactic Assistant) in the neurosurgical management of a pediatric population.

METHODS

Between 2011 and 2016, 116 children underwent ROSA-assisted procedures for a variety of diseases (epilepsy, brain tumors, intra- or extraventricular and tumor cysts, obstructive hydrocephalus, and movement and behavioral disorders). Each patient received accurate preoperative planning of optimal trajectories, intraoperative frameless registration, surgical treatment using specific instruments held by the robotic arm, and postoperative CT or MR imaging.

RESULTS

The authors performed 128 consecutive surgeries, including implantation of 386 electrodes for stereo-electroencephalography (36 procedures), neuroendoscopy (42 procedures), stereotactic biopsy (26 procedures), pallidotomy (12 procedures), shunt placement (6 procedures), deep brain stimulation procedures (3 procedures), and stereotactic cyst aspiration (3 procedures). For each procedure, the authors analyzed and discussed accuracy, timing, and complications.

CONCLUSIONS

To the best their knowledge, the authors present the largest reported series of pediatric neurosurgical cases assisted by robotic support. The ROSA system provided improved safety and feasibility of minimally invasive approaches, thus optimizing the surgical result, while minimizing postoperative morbidity.

SEEG assistant: a 3DSlicer extension to support epilepsy surgery

Background

In the evaluation of Stereo-Electroencephalography (SEEG) signals, the physicist’s workflow involves several operations, including determining the position of individual electrode contacts in terms of both relationship to grey or white matter and location in specific brain regions. These operations are (i) generally carried out manually by experts with limited computer support, (ii) hugely time consuming, and (iii) often inaccurate, incomplete, and prone to errors.

Results

In this paper we present SEEG Assistant, a set of tools integrated in a single 3DSlicer extension, which aims to assist neurosurgeons in the analysis of post-implant structural data and hence aid the neurophysiologist in the interpretation of SEEG data. SEEG Assistant consists of (i) a module to localize the electrode contact positions using imaging data from a thresholded post-implant CT, (ii) a module to determine the most probable cerebral location of the recorded activity, and (iii) a module to compute the Grey Matter Proximity Index, i.e. the distance of each contact from the cerebral cortex, in order to discriminate between white and grey matter location of contacts. Finally, exploiting 3DSlicer capabilities, SEEG Assistant offers a Graphical User Interface that simplifies the interaction between the user and the tools. SEEG Assistant has been tested on 40 patients segmenting 555 electrodes, and it has been used to identify the neuroanatomical loci and to compute the distance to the nearest cerebral cortex for 9626 contacts. We also performed manual segmentation and compared the results between the proposed tool and gold-standard clinical practice. As a result, the use of SEEG Assistant decreases the post implant processing time by more than 2 orders of magnitude, improves the quality of results and decreases, if not eliminates, errors in post implant processing.

Conclusions

The SEEG Assistant Framework for the first time supports physicists by providing a set of open-source tools for post-implant processing of SEEG data. Furthermore, SEEG Assistant has been integrated into 3D Slicer, a software platform for the analysis and visualization of medical images, overcoming limitations of command-line tools.

Utility of Stereoelectroencephalography in Children with Dysembryoplastic Neuroepithelial Tumor and Cortical Malformation

BACKGROUND

Uncontrolled seizures in children can contribute to irreversible cognitive impairment and developmental delay, in addition to placing them at risk for sudden unexplained death in epileptic patients (SUDEP). Since its introduction at Saint Ann Hospital in Paris in the 1960s, stereoelectroencephalography (SEEG) is increasingly being utilized at epilepsy centers in the United States as an invasive tool to help localize the seizure focus in drug-resistant focal epilepsy.

INDICATIONS

Children with symptomatic epilepsy, commonly due to cortical dysplasia and dysembryoplastic neuroepithelial tumor (DNET), may benefit from SEEG investigation. The arrangement of SEEG electrodes is individually tailored based on the suspected location of the epileptogenic zone (EZ). The implanted depth electrodes are used to electrically stimulate the corresponding cortices to obtain information about the topography of eloquent cortex and EZ. Morbidity: Surgical morbidity in these children undergoing SEEG investigation is low, but not negligible. The number of electrodes directly correlates with the risk of intraoperative complication. Thus a risk and benefit analysis needs to be carefully considered for each patient. Neurodiagnostic technology: Both during and after the SEEG electrode implantation, the intraoperative monitoring and EEG technologists play a vital role in the successful monitoring of the patient.

CONCLUSION

SEEG is an important tool in the process of epilepsy surgery in children with symptomatic epilepsy, commonly due to cortical dysplasia and DNET.

Lesional cerebellar epilepsy: a review of the evidence

Classical teaching in epileptology localizes the origins of focal seizures solely in the cerebral cortex, with only inhibitory effects attributed to subcortical structures. However, electrophysiological and neuroimaging studies over the last decades now provide evidence for an initiation of epileptic seizures within subcortical structures. Intrinsic epileptogenicity of hypothalamic hamartoma has already been established in recognition of subcortical epilepsy, whereas a seizure-generating impact of dysplastic cerebellar lesions remains to be clarified. Herein, we examine the supportive evidence and clinical presentation of cerebellar seizures and review therapy options.

Current and Emerging Surgical Therapies for Severe Pediatric Epilepsies

The use of epilepsy surgery in various medically resistant epilepsies is well established. For patients with intractable pediatric epilepsy, the role of intracranial electrodes, resective surgery, hemispherectomy, corpus callosotomy, neurostimulation, and multiple subpial transections continues to be very effective in select cases. Newer treatment and diagnostic methods include laser thermal ablation, minimally invasive surgeries, stereo electroencephalography, electrocorticography, and other emerging techniques. This article will review the established and emerging surgical therapies for severe pediatric epilepsies, their respective indications and overall efficacy.