Validation and Safety Profile of a Novel, Noninvasive Fiducial Attachment for Stereotactic Robotic-Guided Stereoelectroencephalography: A Case Series.

BACKGROUND AND OBJECTIVES: We developed, tested, and validated a novel, noninvasive, Leksell G frame-based fiducial attachment, for use in stereotactic registration for stereoelectroencephalography (sEEG). Use of the device increased the number of fixed reference points available for registration, while obviating the need for additional scalp incisions. We report here on our experience and safety profile of using the device. METHODS: We collected registration data using the fiducial device across 25 adult and pediatric patients with epilepsy consecutively undergoing robotic-guided sEEG for invasive epilepsy monitoring, treated between May 2022 and July 2023. ROSA One Brain was used for trajectory planning and electrode implantation. Postoperative clinical and radiographic data were computed and quantified, including mean registration error for all patients. Entry point, target point (TP), and angular errors were measured. Descriptive statistics and correlation coefficients for error were calculated. RESULTS: Twenty-five patients underwent robotic-guided sEEG implantation (11 patients, bilateral; 10 patients, left unilateral; 4 patients, right). The mean number of electrodes per patient was 18 ± 3. The average mean registration error was 0.77 ± 0.11 mm. All patients were implanted with Ad-Tech depth electrodes. No clinically relevant complications were reported. Analysis of trajectory error was performed on 446 electrodes. The median entry point error was 1.03 mm (IQR 0.69-1.54). The median TP error was 2.26 mm (IQR 1.63-2.93). The mean angular error was 0.03 radians (IQR 0.02-0.05). There was no significant correlation between root mean square error and lead error. Root mean square error did not appreciably change over time, nor were there any significant changes in average angular, entry point, or TP error metrics. CONCLUSION: A novel, noninvasive, Leksell G frame-based fiducial attachment was developed, tested, and validated, facilitating O-arm-based stereotactic registration for sEEG. This simple innovation maintained an excellent accuracy and safety profile for sEEG procedures in epilepsy patients, with the added advantages of providing additional reference points for stereotactic registration, without requiring additional scalp incisions.

Effective connectivity relates seizure outcome to electrode placement in responsive neurostimulation.

Responsive neurostimulation is a closed-loop neuromodulation therapy for drug resistant focal epilepsy. Responsive neurostimulation electrodes are placed near ictal onset zones so as to enable detection of epileptiform activity and deliver electrical stimulation. There is no standard approach for determining the optimal placement of responsive neurostimulation electrodes. Clinicians make this determination based on presurgical tests, such as MRI, EEG, magnetoencephalography, ictal single-photon emission computed tomography and intracranial EEG. Currently functional connectivity measures are not being used in determining the placement of responsive neurostimulation electrodes. Cortico-cortical evoked potentials are a measure of effective functional connectivity. Cortico-cortical evoked potentials are generated by direct single-pulse electrical stimulation and can be used to investigate cortico-cortical connections in vivo. We hypothesized that the presence of high amplitude cortico-cortical evoked potentials, recorded during intracranial EEG monitoring, near the eventual responsive neurostimulation contact sites is predictive of better outcomes from its therapy. We retrospectively reviewed 12 patients in whom cortico-cortical evoked potentials were obtained during stereoelectroencephalography evaluation and subsequently underwent responsive neurostimulation therapy. We studied the relationship between cortico-cortical evoked potentials, the eventual responsive neurostimulation electrode locations and seizure reduction. Directional connectivity indicated by cortico-cortical evoked potentials can categorize stereoelectroencephalography electrodes as either receiver nodes/in-degree (an area of greater inward connectivity) or projection nodes/out-degree (greater outward connectivity). The follow-up period for seizure reduction ranged from 1.3-4.8 years (median 2.7) after responsive neurostimulation therapy started. Stereoelectroencephalography electrodes closest to the eventual responsive neurostimulation contact site tended to show larger in-degree cortico-cortical evoked potentials, especially for the early latency cortico-cortical evoked potentials period (10-60 ms period) in six out of 12 patients. Stereoelectroencephalography electrodes closest to the responsive neurostimulation contacts (≤5 mm) also had greater significant out-degree in the early cortico-cortical evoked potentials latency period than those further away (≥10 mm) (P < 0.05). Additionally, significant correlation was noted between in-degree cortico-cortical evoked potentials and greater seizure reduction with responsive neurostimulation therapy at its most effective period (P < 0.05). These findings suggest that functional connectivity determined by cortico-cortical evoked potentials may provide additional information that could help guide the optimal placement of responsive neurostimulation electrodes.

Postoperative shunt failure following hemispherectomy in pediatric patients with pre-existing hydrocephalus.

OBJECTIVE: The risk of hydrocephalus following hemispherectomy for drug resistant epilepsy (DRE) remains high. Patients with pre-existing hydrocephalus pose a postoperative challenge, as maintaining existing shunt patency is necessary but lacks a clearly defined strategy. This study examines the incidence and predictors of shunt failure in pediatric hemispherectomy patients with pre-existing ventricular shunts. METHODS: We performed a retrospective chart review at our center to identify pediatric patients diagnosed with DRE who were treated with ventricular shunt prior to their first hemispherectomy surgery. Demographic and perioperative data were obtained including shunt history, hydrocephalus etiology, epilepsy duration, surgical technique, and postoperative outcomes. Univariate analysis was performed using Fisher's exact test and Pearson correlation, with Bonferroni correction to a = 0.00625 and a = 0.01, respectively. RESULTS: Five of nineteen (26.3%) patients identified with ventriculoperitoneal shunting prior to hemispherectomy experienced postoperative shunt malfunction. All 5 of these patients underwent at least 1 shunt revision prior to hemispherectomy, with a significant association between pre- and post-hemispherectomy shunt revisions. There was no significant association between post-hemispherectomy shunt failure and valve type, intraoperative shunt alteration, postoperative external ventricular drain placement, hemispherectomy revision, lateralization of shunt relative to resection, postoperative complications, or postoperative aseptic meningitis. There was no significant correlation between number of post-hemispherectomy shunt revisions and age at shunt placement, age at hemispherectomy, epilepsy duration, or shunt duration prior to hemispherectomy. CONCLUSIONS: Earlier shunt revision surgery may portend a subsequent need for shunt revision following hemispherectomy. These findings may guide neurosurgeons in counseling patients with pre-existing ventricular shunts prior to hemispherectomy surgery.

Predictors of therapeutic response following thalamic neuromodulation for drug-resistant pediatric epilepsy: A systematic review and individual patient data meta-analysis.

We sought to perform a systematic review and individual participant data meta-analysis to identify predictors of treatment response following thalamic neuromodulation in pediatric patients with medically refractory epilepsy. Electronic databases (MEDLINE, Ovid, Embase, and Cochrane) were searched, with no language or data restriction, to identify studies reporting seizure outcomes in pediatric populations following deep brain stimulation (DBS) or responsive neurostimulation (RNS) implantation in thalamic nuclei. Studies featuring individual participant data of patients with primary or secondary generalized drug-resistant epilepsy were included. Response to therapy was defined as >50% reduction in seizure frequency from baseline. Of 417 citations, 21 articles reporting on 88 participants were eligible. Mean age at implantation was 13.07 ± 3.49 years. Fifty (57%) patients underwent DBS, and 38 (43%) RNS. Sixty (68%) patients were implanted in centromedian nucleus and 23 (26%) in anterior thalamic nucleus, and five (6%) had both targets implanted. Seventy-four (84%) patients were implanted bilaterally. The median time to last follow-up was 12 months (interquartile range = 6.75-26.25). Sixty-nine percent of patients achieved response to treatment. Age, target, modality, and laterality had no significant association with response in univariate logistic regression. Until thalamic neuromodulation gains widespread approval for use in pediatric patients, data on efficacy will continue to be limited to small retrospective cohorts and case series. The inherent bias of these studies can be overcome by using individual participant data. Thalamic neuromodulation appears to be a safe and effective treatment for epilepsy. Larger, prolonged prospective, multicenter studies are warranted to further evaluate the efficacy of DBS over RNS in this patient population where resection for curative intent is not a safe option.

Predictive factors of hydrocephalus development in pediatric patients undergoing hemispherectomy for intractable epilepsy.

OBJECTIVE: Hemispherectomy surgery is an effective procedure for pediatric patients with intractable hemispheric epilepsy. Hydrocephalus is a well-documented complication of hemispherectomy contributing substantially to patient morbidity. Despite some clinical and operative factors demonstrating an association with hydrocephalus development, the true mechanism of disease is incompletely understood. The aim of this study was to investigate a range of clinical and surgical factors that may contribute to hydrocephalus to enhance understanding of the development of this complication and to aid the clinician in optimizing peri- and postoperative surgical management. METHODS: A retrospective chart review was conducted on all pediatric patients younger than 21 years who underwent hemispherectomy surgery at the Cleveland Clinic between 2002 and 2016. Data collected for each patient included general demographic information, neurological and surgical history, surgical technique, pathological analysis, presence and duration of perioperative CSF diversion, CSF laboratory values obtained while an external ventricular drain (EVD) was in place, length of hospital stay, postoperative aseptic meningitis, and in-hospital surgical complications (including perioperative stroke, hematoma formation, wound breakdown, and/or infection). Outcomes data included hemispherectomy revision and Engel grade at last follow-up (based on the Engel Epilepsy Surgery Outcome Scale). RESULTS: Data were collected for 204 pediatric patients who underwent hemispherectomy at the authors' institution. Twenty-eight patients (14%) developed hydrocephalus requiring CSF diversion. Of these 28 patients, 13 patients (46%) presented with hydrocephalus during the postoperative period (within 90 days), while the remaining 15 patients (54%) presented later (beyond 90 days after surgery). Multivariate analysis revealed postoperative aseptic meningitis (OR 7.0, p = 0.001), anatomical hemispherectomy surgical technique (OR 16.3 for functional/disconnective hemispherectomy and OR 7.6 for modified anatomical, p = 0.004), male sex (OR 4.2, p = 0.012), and surgical complications (OR 3.8, p = 0.031) were associated with an increased risk of hydrocephalus development, while seizure freedom (OR 0.3, p = 0.038) was associated with a decreased risk of hydrocephalus. CONCLUSIONS: Hydrocephalus remains a prominent complication following hemispherectomy, presenting both in the postoperative period and months to years after surgery. Aseptic meningitis, anatomical hemispherectomy surgical technique, male sex, and surgical complications show an association with an increased rate of hydrocephalus development while seizure freedom postsurgery is associated with a decreased risk of subsequent hydrocephalus. These findings speak to the multifactorial nature of hydrocephalus development and should be considered in the management of pediatric patients undergoing hemispherectomy for medically intractable epilepsy.

Radiofrequency ablation during stereoelectroencephalography: from diagnostic tool to therapeutic intervention. Illustrative case.

BACKGROUND: Radiofrequency thermocoagulation (RFTC) during intracranial stereoelectroencephalography (sEEG) was first described as a safe technique for creating lesions of epileptic foci in 2004. Since that time, the method has been applied as a diagnostic and/or palliative intervention. Although widely practiced in European epilepsy surgical programs, the technique has not been popularized in the United States given the lack of Food and Drug Administration (FDA)-approved technologies permitting safe usage of in situ sEEG electrodes for this purpose. OBSERVATIONS: The authors present a case report of a young female patient with refractory left neocortical temporal lobe epilepsy undergoing sEEG electrode implantation, who underwent sEEG-guided RFTC via a stereotactic temperature-sensing pallidotomy probe. Although used as a diagnostic step in her workup, the patient has remained seizure-free for nearly 18 months. LESSONS: The use of in situ sEEG electrodes for RFTC remains limited in the United States. In this context, this case highlights a safe alternative and temporizing approach to performing diagnostic sEEG-guided RFTC, using a temperature-sensing pallidotomy probe to create small, precise stereotactic lesions. The authors caution careful consideration of this technique as a temporary work-around solution while also highlighting the rising need for new FDA-approved technologies for safe RFTC through in situ temperature-sensing sEEG electrodes.

The impact of skull thickness on pediatric stereoencephalography electrode implantation and technical considerations.

OBJECTIVE: One consideration in pediatric stereoencephalography (SEEG) is decreased skull thicknesses compared with adults, which may limit traditional bolt-based anchoring of electrodes. The authors aimed to investigate the safety profile, complication rates, and technical adaptations of placing SEEG electrodes in pediatric patients. METHODS: The authors retrospectively reviewed all patients aged 12 years or younger at the time of SEEG implantation at their institution. Postimplantation CT scans were used to measure skull thickness at the entry point of each SEEG lead. Postimplantation lead accuracy was also assessed. RESULTS: Fifty-three patients were reviewed. The median skull thickness was 4.1 (interquartile range [IQR] 3.15-5.2) mm. There were 5 total complications: 1 retained bolt fragment, 3 asymptomatic subdural hematomas, and 1 asymptomatic intracranial hemorrhage. Median radial error from the lead target was 3.5 (IQR 2.24-5.25) mm. Linear regression analysis revealed that increasing skull thickness decreased the deviation from the intended target, implying an improved accuracy to target at thicker skull entry points; this trended towards improved accuracy, but did not achieve statistical significance (p = 0.54). CONCLUSIONS: This study found a 1.9% hardware complication rate and a 9.4% asymptomatic hemorrhage rate. Suturing electrodes to the scalp may represent a reasonable option if there are concerns of young age or a thin skull. These data indicate that invasive SEEG evaluation is safe among patients 12 years old or younger.

Determinants of epileptogenic zone identification and seizure outcome in children with refractory epilepsy undergoing stereoelectroencephalography.

OBJECTIVE: The objective of this paper was to investigate the factors associated with successful epileptogenic zone (EZ) identification and postsurgical seizure freedom in pediatric patients with drug-resistant epilepsy who underwent first-time stereoelectroencephalography (SEEG). METHODS: The authors conducted a retrospective cohort study of all consecutive patients younger than 18 years of age at the time of recommendation for invasive evaluation with SEEG who were treated from July 2009 to June 2020. The authors excluded patients who had undergone failed prior resective epilepsy surgery or prior intracranial electrode evaluation for seizure localization. For their primary outcome, the authors evaluated the relationship between clinical and radiographic factors and successful identification of a putative EZ. For their secondary outcome, the authors investigated whether these factors had a significant relationship with seizure freedom (according to the Engel classification) at last follow-up. RESULTS: The authors included 101 patients in this study. SEEG was safe, with no major morbidity or mortality experienced. The population was complex, with an MRI lesion present in less than 40% of patients and patients as young as 2.9 years included. A proposed EZ was identified in 88 (87%) patients. Patients with an older onset of epilepsy (OR 1.20/year, p = 0.04) or epilepsy etiology suspected to be due to a developmental lesion (OR 8.38, p = 0.02) were more likely to have proposed EZ identification. Patients with a preimplantation bilateral seizure-onset hypothesis (OR 0.29, p = 0.047) and those who underwent longer periods of monitoring (OR 0.86/day, p = 0.006) were somewhat less likely to have proposed EZ identification. The presence of an MRI lesion was a positive factor on secondary analyses (OR 4.18, p = 0.049; 1-tailed test). Fifty percent of patients who underwent surgical treatment with resection or laser ablation achieved Engel class I outcomes, in contrast to 0% of patients who underwent neuromodulation. Patients with a preimplantation hypothesis in the frontal/parietal lobes had increased odds of seizure freedom compared with patients with a hypothesis in other locations (OR 3.64, p = 0.01). CONCLUSIONS: Pediatric SEEG is safe and often identifies a proposed resectable EZ. These results suggest that SEEG is effective in patients with frontal/parietal preimplantation hypothesis, with or without identified lesions on MRI.

Characterization and Prediction of Short-term Outcomes in Memory After Temporal Lobe Resection in Children With Epilepsy.

BACKGROUND AND OBJECTIVES: The aim of this study was to characterize short-term outcomes in episodic memory, as assessed by the Children's Memory Scale (CMS), after temporal lobe resection in children with epilepsy using empirical methods for assessing cognitive change (i.e., reliable change indices [RCI] and standardized regression-based change scores [SRB]) and develop and internally validate clinically applicable models to predict postoperative memory decline. METHODS: This retrospective cohort study included children aged 6-16 years who underwent resective epilepsy surgery that included the temporal lobe (temporal only: "temporal" and multilobar: "temporal plus") and who completed preoperative and postoperative neuropsychological assessments including the CMS. Change scores on the CMS delayed memory subtests (Faces, Stories, and Word Pairs) were classified as decline, no change, or improvement using epilepsy-specific RCI and SRB. Logistic regression models for predicting postoperative memory decline were developed and internally validated with bootstrapping. RESULTS: Of the 126 children included, most of them demonstrated either no significant change (54%-69%) or improvement (8%-14%) in memory performance using RCI on individual measures at a median of 7 months after surgery. A subset of children (23%-33%) showed postoperative declines. Change distributions obtained using RCI and SRB were not statistically significantly different from each other. Preoperative memory test score, surgery side, surgery extent, and preoperative full-scale IQ were predictors of memory decline. Prediction models for memory decline included subsets of these variables with bias-corrected concordance statistics ranging from 0.70 to 0.75. The models were well calibrated although slightly overestimated the probability of verbal memory decline in high-risk patients. DISCUSSION: This study used empiric methodology to characterize memory outcome in children after temporal lobe resection. Provided online calculator and nomograms may be used by clinicians to estimate the risk of postoperative memory decline for individual patients before surgery.

Clinical significance of ictal magnetoencephalography in patients undergoing epilepsy surgery.

OBJECTIVE: The significance of ictal magnetoencephalography (MEG) is not well appreciated. We evaluated the relationships between ictal MEG, MRI, intracranial electroencephalography (ICEEG), surgery and postoperative seizure outcome. METHODS: A total of 45 patients (46 cases) with ictal MEG who underwent epilepsy surgery was included. We examined the localization of each modality, surgical resection area and seizure freedom after surgery. RESULTS: Twenty-one (45.7%) out of 46 cases were seizure-free at more than 6 months follow-up. Median duration of postoperative follow-up was 16.5 months. The patients in whom ictal, interictal single equivalent current dipole (SECD) and MRI lesion localization were completely included in the resection had a higher chance of being seizure-free significantly (p < 0.05). Concordance between ictal and interictal SECD localizations was significantly associated with seizure-freedom. Concordance between MRI lesion and ictal SECD, concordance between ictal ICEEG and ictal and interictal SECD, as well as concordance between ictal ICEEG and MRI lesion were significantly associated with seizure freedom. CONCLUSIONS: Ictal MEG can contribute useful information for delineating the resection area in epilepsy surgery. SIGNIFICANCE: Resection should include ictal, interictal SECDs and MRI lesion localization, when feasible. Concordant ictal and interictal SECDs on MEG can be a favorable predictor of seizure freedom.

Beyond seizure freedom: Dissecting long-term seizure control after surgical resection for drug-resistant epilepsy.

OBJECTIVE: This study was undertaken to better understand the long-term palliative and disease-modifying effects of surgical resection beyond seizure freedom, including frequency reduction and both late recurrence and remission, in patients with drug-resistant epilepsy. METHODS: This retrospective database-driven cohort study included all patients with >9 years of follow-up at a single high-volume epilepsy center. We included patients who underwent lobectomy, multilobar resection, or lesionectomies for drug-resistant epilepsy; we excluded patients who underwent hemispherectomies. Our main outcomes were (1) reduction in frequency of disabling seizures (at 6 months, each year up to 9 years postoperatively, and at last follow-up), (2) achievement of seizure remission (>6 months, >1 year, and longest duration), and (3) seizure freedom at last follow-up. RESULTS: We included 251 patients; 234 (93.2%) achieved 6 months and 232 (92.4%) experienced 1 year of seizure freedom. Of these, the average period of seizure freedom was 10.3 years. A total of 182 (72.5%) patients were seizure-free at last follow-up (defined as >1 year without seizures), with a median 11.9 years since remission. For patients not completely seizure-free, the mean seizure frequency reduction at each time point was 76.2%, and ranged from 66.6% to 85.0%. Patients decreased their number of antiseizure medications on average by .58, and 53 (21.2%) patients were on no antiseizure medication at last follow-up. Nearly half (47.1%) of those seizure-free at last follow-up were not seizure-free immediately postoperatively. SIGNIFICANCE: Patients who continue to have seizures after resection often have considerable reductions in seizure frequency, and many are able to achieve seizure freedom in a delayed manner.

Cytochrome P450-mediated antiseizure medication interactions influence apoptosis, modulate the brain BAX/Bcl-XL ratio and aggravate mitochondrial stressors in human pharmacoresistant epilepsy.

Polytherapy with antiseizure medications (ASMs) is often used to control seizures in patients suffering from epilepsy, where about 30% of patients are pharmacoresistant. While drug combinations are intended to be beneficial, the consequence of CYP-dependent drug interactions on apoptotic protein levels and mitochondrial function in the epileptic brain remains unclear. We examined the interactions of ASMs given prior to surgery in surgically resected brain tissues and of three ASMs (lacosamide, LCM; oxcarbazepine, OXC; levetiracetam LEV) in isolated brain cells from patients with drug-resistant epilepsy (n = 23). We divided the patients into groups-those who took combinations of NON-CYP + CYP substrate ASMs, NON-CYP + CYP inducer ASMs, CYP substrate + CYP substrate or CYP substrate + CYP inducer ASMs-to study the 1) pro- and anti-apoptotic protein levels and other apoptotic signaling proteins and levels of reactive oxygen species (reduced glutathione and lipid peroxidation) in brain tissues; 2) cytotoxicity at blood-brain barrier epileptic endothelial cells (EPI-ECs) and subsequent changes in mitochondrial membrane potential in normal neuronal cells, following treatment with LCM + OXC (CYP substrate + CYP inducer) or LCM + LEV (CYP substrate + NON-CYP-substrate) after blood-brain barrier penetration, and 3) apoptotic and mitochondrial protein targets in the cells, pre-and post-CYP3A4 inhibition by ketoconazole and drug treatments. We found an increased BAX (pro-apoptotic)/Bcl-XL (anti-apoptotic) protein ratio in epileptic brain tissue after treatment with CYP substrate + CYP substrate or inducer compared to NON-CYP + CYP substrate or inducer, and subsequently decreased glutathione and elevated lipid peroxidation levels. Further, increased cytotoxicity and Mito-ID levels, indicative of compromised mitochondrial membrane potential, were observed after treatment of LCM + OXC in combination compared to LCM + LEV or these ASMs alone in EPI-ECs, which was attenuated by pre-treatment of CYP inhibitor, ketoconazole. A combination of two CYP-mediated ASMs on EPI-ECs resulted in elevated caspase-3 and cytochrome c with decreased SIRT3 levels and activity, which was rescued by CYP inhibition. Together, the study highlights for the first time that pro- and anti-apoptotic proteins levels are dependent on ASM combinations in epilepsy, modulated via a CYP-mediated mechanism that controls free radicals, cytotoxicity and mitochondrial activity. These findings lead to a better understanding of future drug selection choices offsetting pharmacodynamic CYP-mediated interactions.

Quality of life after epilepsy surgery: How domain-specific cognitive changes impact QOL within the context of seizure outcome.

PURPOSE: Neurosurgery is an effective treatment option for pharmacoresistant epilepsy. Although post-surgical seizure freedom is considered the primary goal of epilepsy surgery, other factors that impact Quality of Life (QOL) are also important to consider, including post-surgical cognitive changes. This study aimed to examine the impact of post-surgical cognitive changes on QOL in the context of seizure outcomes. METHODS: Participants were 196 adults with focal epilepsy who underwent either frontal (n = 27) or temporal (n = 169) lobe resection. Each participant completed pre- and post-surgical neuropsychological evaluations, and cognitive composites were constructed for the following domains: language, attention/processing speed, memory, executive function, and visuospatial skill. The Quality of Life in Epilepsy (QOLIE-10) questionnaire was used to assess QOL. Seizure outcome was determined by seizure status six months post-surgery. RESULTS: Eighty-one percent of patients were seizure-free post-surgery and generally reported improved QOL. While a significant portion of patient's demonstrated declines in language and verbal memory following surgery, only a decline in verbal memory was associated with worse QOL; however, this relationship was no longer significant after controlling for seizure outcome. Instead, reduced post-surgical QOL was primarily observed in those who experienced both seizure recurrence and a decline in executive function. Notably, depression was a significant covariate in all of the models. CONCLUSIONS: The findings from this study improve our ability to counsel patients about the trade-off between cognitive decline and seizure remittance in the greater context of overall QOL. Reassuringly, it appears that QOL is improved regardless of cognitive changes when patients have good seizure outcomes. However, for those that experience a "double hit" (i.e., cognitive decline without seizure remission), post-surgical QOL may be reduced. Changes in depression also appear to play a crucial role in QOL outcomes.

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.

Epileptiform abnormalities in the disconnected hemisphere are common in seizure-free patients after hemispherectomy

Objective: The spectrum of EEG abnormalities in the disconnected hemisphere in seizure-free patients after hemispherectomy has not been well characterized. Methods: Fifty consecutive patients who were seizure-free following hemispheric disconnection were identified. Data on preoperative clinical, EEG and neuroimaging findings and postoperative EEG findings and antiseizure medication status were collected. Results: Forty-seven patients (94%) had functional hemispherectomy, and three (6%) had more extensive tissue resection of the posterior quadrant or frontal region along with hemispheric disconnection. Etiologies included: residual effects from vascular lesions including perinatal stroke in 35 patients, Rasmussen encephalitis in six, malformation of cortical development in seven, and Sturge-Weber syndrome in two. Pre-operative EEG showed focal epileptiform discharges in the affected hemisphere in 26 patients and in both hemispheres in 19. Eleven patients had diffuse bisynchronous epileptiform discharges. Postoperative EEGs at six to 12 months after surgery showed slowing and attenuation of physiological rhythms on the operated side in all patients. Thirty-four patients (68%) had epileptiform discharges exclusively from the operated hemisphere, six (12%) had bilateral independent epileptiform discharges, nine (18%) had no epileptiform discharges on either side, and one (2%) had epileptiform discharges from the contralateral hemisphere only. Lateralized periodic discharges from the operated hemisphere were noted in three patients (6%). EEG seizures from the operated hemisphere without clinical signs were noted in four patients (8%). After a median follow-up of three years, 30 patients (60%) were off all antiseizure medications, including 8/9 (89%) patients with no epileptiform discharges, 20/34 (59%) patients with postoperative epileptiform discharges from the operated hemisphere, and 2/7 (28%) patients with contralateral discharges. Significance: The majority of patients who are seizure-free after disconnective hemispherectomy will continue to show epileptiform discharges in the operated hemisphere. The presence of such discharges should not preclude tapering, nor prompt restarting of antiseizure medication in seizure-free patients.

Seizure Outcomes and Reoperation in Surgical Rasmussen Encephalitis Patients.

BACKGROUND: Rasmussen encephalitis (RE) is a rare inflammatory disease affecting one hemisphere, causing progressive neurological deficits and intractable seizures. OBJECTIVE: To report long-term seizure outcomes, reoperations, and functional outcomes in patients with RE who underwent hemispherectomy at our institution. METHODS: Retrospective review was performed for all patients with RE who had surgery between 1998 and 2020. We collected seizure history, postoperative outcomes, and functional data. Imaging was independently reviewed in a blinded fashion by 2 neurosurgeons and a neuroradiologist. RESULTS: We analyzed 30 patients with RE who underwent 35 hemispherectomies (5 reoperations). Using Kaplan-Meier analysis, seizure-freedom rate was 81.5%, 63.6%, and 55.6% at 1, 5, and 10 years after surgery, respectively. Patients with shorter duration of hemiparesis preoperatively were less likely to be seizure-free at follow-up (P = .011) and more likely to undergo reoperation (P = .004). Shorter duration of epilepsy (P = .026) and preoperative bilateral MRI abnormalities (P = .011) were associated with increased risk of reoperation. Complete disconnection of diseased hemisphere on postoperative MRI after the first operation improved seizure-freedom (P = .021) and resulted in fewer reoperations (P = .034), and reoperation resulted in seizure freedom in every case. CONCLUSION: Obtaining complete disconnection is critical for favorable seizure outcomes from hemispherectomy, and neurosurgeons should have a low threshold to reoperate in patients with RE with recurrent seizures. Rapid progression of motor deficits and bilateral MRI abnormalities may indicate a subpopulation of patients with RE with increased risk of needing reoperation. Overall, we believe that hemispherectomy is a curative surgery for the majority of patients with RE, with excellent long-term seizure outcome.

Glucocorticoid Receptor ß Isoform Predominates in the Human Dysplastic Brain Region and Is Modulated by Age, Sex, and Antiseizure Medication.

The glucocorticoid receptor (GR) at the blood−brain barrier (BBB) is involved in the pathogenesis of drug-resistant epilepsy with focal cortical dysplasia (FCD); however, the roles of GR isoforms GRα and GRß in the dysplastic brain have not been revealed. We utilized dysplastic/epileptic and non-dysplastic brain tissue from patients who underwent resective epilepsy surgery to identify the GRα and GRß levels, subcellular localization, and cellular specificity. BBB endothelial cells isolated from the dysplastic brain tissue (EPI-ECs) were used to decipher the key BBB proteins related to drug regulation and BBB integrity compared to control and transfected GRß-overexpressed BBB endothelial cells. GRß was upregulated in dysplastic compared to non-dysplastic tissues, and an imbalance of the GRα/GRß ratio was significant in females vs. males and in patients > 45 years old. In EPI-ECs, the subcellular localization and expression patterns of GRß, Hsp90, CYP3A4, and CYP2C9 were consistent with GRß+ brain endothelial cells. Active matrix metalloproteinase levels and activity increased, whereas claudin-5 levels decreased in both EPI-ECs and GRß+ endothelial cells. In conclusion, the GRß has a major effect on dysplastic BBB functional proteins and is age and gender-dependent, suggesting a critical role of brain GRß in dysplasia as a potential biomarker and therapeutic target in epilepsy.

Cognitive phenotypes in frontal lobe epilepsy.

OBJECTIVE: Neuropsychological profiles are heterogeneous both across and within epilepsy syndromes, but especially in frontal lobe epilepsy (FLE), which has complex semiology and epileptogenicity. This study aimed to characterize the cognitive heterogeneity within FLE by identifying cognitive phenotypes and determining their demographic and clinical characteristics. METHOD: One hundred and six patients (age 16-66; 44% female) with FLE completed comprehensive neuropsychological testing, including measures within five cognitive domains: language, attention, executive function, processing speed, and verbal/visual learning. Patients were categorized into one of four phenotypes based on the number of impaired domains. Patterns of domain impairment and clinical and demographic characteristics were examined across phenotypes. RESULTS: Twenty-five percent of patients met criteria for the Generalized Phenotype (impairment in at least four domains), 20% met criteria for the Tri-Domain Phenotype (impairment in three domains), 36% met criteria for the Domain-Specific Phenotype (impairment in one or two domains), and 19% met criteria for the Intact Phenotype (no impairment). Language was the most common domain-specific impairment, followed by attention, executive function, and processing speed. In contrast, learning was the least impacted cognitive domain. The Generalized Phenotype had fewer years of education compared to the Intact Phenotype, but otherwise, there was no differentiation between phenotypes in demographic and clinical variables. However, qualitative analysis suggested that the Generalized and Tri-Domain Phenotypes had a more widespread area of epileptogenicity, whereas the Intact Phenotype most frequently had seizures limited to the lateral frontal region. SIGNIFICANCE: This study identified four cognitive phenotypes in FLE that were largely indistinguishable in clinical and demographic features, aside from education and extent of epileptogenic zone. These findings enhance our appreciation of the cognitive heterogeneity within FLE and provide additional support for the development and use of cognitive taxonomies in epilepsy.

The Clinical Utility of Surgical Histopathology in Predicting Seizure Outcomes in Patients with Rasmussen Encephalitis Undergoing Hemispherectomy.

OBJECTIVE: The objectives of this study were to determine the relationship between the severity of pathology and seizure outcomes in patients who underwent hemispherectomy for Rasmussen encephalitis (RE) and to investigate which clinical factors correlated with severity of pathology. METHODS: In this retrospective cohort study, we collected and reviewed pathology and clinical variables. We ascertained seizure outcomes using Engel's classification, and Pardo stages were used to grade pathology. RESULTS: We included 29 unique patients who underwent 34 hemispherectomy procedures for analysis. There was no statistically significant correlation between Pardo stage and seizure outcome (P = 1). Increasing duration of epilepsy (ß = 0.011, P = 0.02) and duration of hemiparesis (ß = 0.024, P = 0.01) were significantly associated with a more severe Pardo stage. In contrast, the presence of epilepsia partialis continua had a negative relationship with Pardo stage (ß = -0.49, P = 0.04). Twenty-six (89.75%) patients were Engel class I at the last follow-up, including all 5 patients who underwent redo hemispherectomy in our cohort. CONCLUSIONS: Consistent with the progressive nature of RE, more severe pathology was associated with a longer duration of epilepsy and longer duration of hemiparesis, while the presence of epilepsia partialis continua was associated with less severe pathology. Results from this series suggest the degree of cortical involvement with RE as assessed on surgical histopathology does not correlate with seizure outcome after hemispherectomy, which appears to be more dependent on surgical technique/complete disconnection.

Mother knows best or does she? Perceptions of the memory abilities of pediatric patients with epilepsy as reported by patients and their parents across time.

PURPOSE: This study compared the self-reported and parent-reported memory of children with epilepsy across time and explored the relationships between these measures of subjective memory and the children's actual performance on objective neuropsychological tests. METHOD: One-hundred and nineteen children with epilepsy who were surgical candidates underwent comprehensive neuropsychological testing that included the Everyday Verbal Memory Questionnaire (EVMQ). Each child's parent and 82 of the children themselves completed the appropriate version of this subjective memory measure. After 9 months, the children returned for a second neuropsychological evaluation with 71 parents and 39 children completing the same questionnaire. Approximately one-third of the children in the study underwent surgery between the two evaluations. Standardized regression-based norms were used to quantify change in cognitive abilities across assessments. RESULTS: Results revealed significant relationships between parent reports and child reports of the children's memory abilities. Parent reports, but not child reports, correlated with the children's objective test scores at baseline. In contrast, children were more attuned to changes in their memory across time. CONCLUSIONS: These findings demonstrate the importance of considering both parent and child perceptions of everyday cognitive functioning when evaluating cognition and cognitive changes over time in pediatric patients with epilepsy.