Outcomes of epilepsy surgery in adults and children

Impact of Previous Surgery on Success of Magnetic Resonance-guided Laser Interstitial Thermal Therapy (MRgLITT) to Treat Pediatric Epilepsy: An Institutional Experience

BACKGROUND

There is an emerging role for minimally invasive magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) in the treatment of pediatric epilepsy refractory to medication. To date, predictors of MRgLITT success have not been established in a sizeable singular experience. Correspondingly, the aim of this study was to elucidate if previous surgical history predicts MRgLITT success in this setting.

METHODS

A retrospective review was conducted of our MRgLITT procedures for pediatric (patient age <19 years) epilepsy from 2011 to 2020 with documented seizure outcomes at 1 and 2 years after procedure. Categorical and continuous data were compared using χ2 and Student's t test, respectively.

RESULTS

A total of 41 patients satisfied all criteria with 16 (39%) female and 25 (61%) male patients. Following MRgLITT, seizure-freedom at 1-year was achieved in 15 (37%) patients. In the cohort, there were 14 (34%) patients who had undergone previous open surgery for epilepsy at mean age of 9.4 ± 5.5 years. Patients with a previous open surgery history were found to statistically experience longer length of hospitalization after MRgLITT (P = 0.04) with a statistically lower proportion of seizure-freedom at 1-year after MRgLITT (14% vs. 48%, P = 0.03). However, there was no difference in the rate of seizure-freedom at 2 years (29% vs. 41%, P = 0.44), as well as no difference in subsequent surgical interventions for seizure management between groups.

CONCLUSIONS

Based on our institutional experience, patients with previous open surgery history may experience longer length of hospitalization after MRgLITT for pediatric epilepsy and lesser response in seizure-freedom within the first year but with non-inferior seizure freedom by the second year.

Low-grade glioma of the temporal lobe and tumor-related epilepsy in children

PURPOSE

Low-grade glioma is the most common brain tumor among children and adolescents. When these tumors arise in the temporal lobe, patients frequently present with seizures that are poorly controlled with antiepileptic drugs. Here we summarize the clinical features, pathophysiology, preoperative evaluation, surgical treatment, and outcomes of pediatric patients with low-grade gliomas in the temporal lobe.

METHODS

We reviewed the literature on pediatric low-grade gliomas in the temporal lobe, focusing on cohort studies and systematic reviews that described surgical treatment strategies and reported both oncologic and epilepsy outcomes.

RESULTS

The differential diagnoses of pediatric low-grade gliomas in the temporal lobe include ganglioglioma, dysembryoplastic neuroepithelial tumor, desmoplastic infantile ganglioglioma, papillary glioneuronal tumor, pilocytic astrocytoma, pleomorphic xanthoastrocytoma, angiocentric glioma, and polymorphous low-grade neuroepithelial tumor of the young. There is no consensus on the optimal surgical approach for these tumors: lesionectomy alone, or extended lesionectomy with anterior temporal lobectomy, with or without removal of mesial temporal structures. Gross total resection and shorter preoperative duration of epilepsy are strongly associated with favorable seizure outcomes, defined as Engel Class I or Class II, approaching 90% in most series. The risk of surgical complications ranges from 4 to 17%, outweighing the lifetime risks of medically refractory epilepsy.

CONCLUSION

Pediatric patients with temporal low-grade glioma and tumor-related epilepsy are best managed by a multidisciplinary epilepsy surgery team. Early and appropriate surgery leads to prolonged survival and a greater likelihood of seizure freedom, improving their overall quality of life.

Prognostic Value of Complete Resection of the High-Frequency Oscillation Area in Intracranial EEG: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

High-frequency oscillations (HFOs; ripples 80-250 Hz; fast ripples [FRs] 250-500 Hz) recorded with intracranial electrodes generated excitement and debate about their potential to localize epileptogenic foci. We performed a systematic review and meta-analysis on the prognostic value of complete resection of the HFOs-area (crHFOs-area) for epilepsy surgical outcome in intracranial EEG (iEEG) accessing multiple subgroups.

METHODS

We searched PubMed, Embase, and Web of Science for original research from inception to October 27, 2022. We defined favorable surgical outcome (FSO) as Engel class I, International League Against Epilepsy class 1, or seizure-free status. The prognostic value of crHFOs-area for FSO was assessed by (1) the pooled FSO proportion after crHFOs-area; (2) FSO for crHFOs-area vs without crHFOs-area; and (3) the predictive performance. We defined high combined prognostic value as FSO proportion >80% + FSO crHFOs-area >without crHFOs-area + area under the curve (AUC) >0.75 and examined this for the clinical subgroups (study design, age, diagnostic type, HFOs-identification method, HFOs-rate thresholding, and iEEG state). Temporal lobe epilepsy (TLE) was compared with extra-TLE through dichotomous variable analysis. Individual patient analysis was performed for sex, affected hemisphere, MRI findings, surgery location, and pathology.

RESULTS

Of 1,387 studies screened, 31 studies (703 patients) met our eligibility criteria. Twenty-seven studies (602 patients) analyzed FRs and 20 studies (424 patients) ripples. Pooled FSO proportion after crHFOs-area was 81% (95% CI 76%-86%) for FRs and 82% (73%-89%) for ripples. Patients with crHFOs-area achieved more often FSO than those without crHFOs-area (FRs odds ratio [OR] 6.38, 4.03-10.09, p < 0.001; ripples 4.04, 2.32-7.04, p < 0.001). The pooled AUCs were 0.81 (0.77-0.84) for FRs and 0.76 (0.72-0.79) for ripples. Combined prognostic value was high in 10 subgroups: retrospective, children, long-term iEEG, threshold (FRs and ripples) and automated detection and interictal (FRs). FSO after complete resection of FRs-area (crFRs-area) was achieved less often in people with TLE than extra-TLE (OR 0.37, 0.15-0.89, p = 0.006). Individual patient analyses showed that crFRs-area was seen more in patients with FSO with than without MRI lesions (p = 0.02 after multiple correction).

DISCUSSION

Complete resection of the brain area with HFOs is associated with good postsurgical outcome. Its prognostic value holds, especially for FRs, for various subgroups. The use of HFOs for extra-TLE patients requires further evidence.

Surgical outcomes in children with drug-resistant epilepsy and hippocampal sclerosis

BACKGROUND

Hippocampal sclerosis (HS) is a common surgical substrate in adult epilepsy surgery cohorts but variably reported in various pediatric cohorts.

OBJECTIVE

We aimed to study the epilepsy phenotype, radiological and pathological variability, seizure and neurocognitive outcomes in children with drug-resistant epilepsy and hippocampal sclerosis (HS) with or without additional subtle signal changes in anterior temporal lobe who underwent surgery.

METHODS

This retrospective study enrolled children with drug-resistant focal epilepsy and hippocampal sclerosis with or without additional subtle T2-Fluid Attenuated Inversion Recovery (FLAR)/Proton Density (PD) signal changes in anterior temporal lobe who underwent anterior temporal lobectomy with amygdalohippocampectomy. Their clinical, EEG, neuropsychological, radiological and pathological data were reviewed and summarized.

RESULTS

Thirty-six eligible patients were identified. The mean age at seizure onset was 3.7 years; 25% had daily seizures at time of surgery. Isolated HS was noted in 22 (61.1%) cases and additional subtle signal changes in ipsilateral temporal lobe in 14 (38.9%) cases. Compared to the normative population, the group mean performance in intellectual functioning and most auditory and visual memory tasks were significantly lower than the normative sample. The mean age at surgery was 12.3 years; 22 patients (61.1%) had left hemispheric surgeries. ILAE class 1 outcomes was seen in 28 (77.8%) patients after a mean follow up duration of 2.3 years. Hippocampal sclerosis was noted pathologically in 32 (88.9%) cases; type 2 (54.5%) was predominant subtype where further classification was possible. Additional pathological abnormalities were seen in 11 cases (30.6%); these had had similar rates of seizure freedom as compared to children with isolated hippocampal sclerosis/gliosis (63.6% vs 84%, p=0.21). Significant reliable changes were observed across auditory and visual memory tasks at an individual level post surgery.

CONCLUSIONS

Favourable seizure outcomes were seen in most children with isolated radiological hippocampal sclerosis. Patients with additional pathological abnormalities had similar rates of seizure freedom as compared to children with isolated hippocampal sclerosis/gliosis.

Advocacy for Epilepsy Surgery in Africa: Moroccan Experience of 132 Cases

BACKGROUND

In Africa, epilepsy is a real burden. Temporal lobe epilepsy is the most common drug-resistant focal epilepsy disorder, and temporal lobectomy is the most common effective treatment for patients with drug-resistant epilepsy.

OBJECTIVE

We aim to highlight the Moroccan experience in epilepsy surgery and to ascertain its long-term outcome. Through the results of surgical treatment in our series, we hope to raise awareness of the need for epilepsy surgery in Africa and contribute to its development.

METHODS

We present a retrospective study of 132 patients who underwent surgery for epilepsy from January 2005 to December 2021 at our institution. The presurgical evaluation was based on clinical screening, interictal electroencephalography, video-electroencephalography, neuropsychological tests, magnetic resonance imaging, and positron emission tomography in some cases. Data are presented as the median and ranges. For all analyses, P values <0.05 were considered statistically significant.

RESULTS

Our series includes 132 patients (69 males; 52.27%); the median age at surgery was 24 years (range, 1-64). One hundred and fifteen patients (87%) were operated on for temporal lobe epilepsy, of whom 98 (85%) had anterior temporal lobectomy and 17 (15%) had lesionectomy. Seventeen patients (13%) were operated on for extratemporal epilepsy, of whom 4 had lesionectomy, 7 functional hemispherotomy, and 5 Gamma Knife stereotactic radiosurgery. Our postoperative outcomes 3 months after surgery found 113 patients (85.6%) seizure-free (Engel class I), 16 with Engel class II (12.1%), and 3 with Engel class III (2.3%) in temporal lobe epilepsy. In extratemporal lobe epilepsy, 12 patients (70.5%) showed Engel class I, seizure-free, 4 Engel class II (23.5%), and 1 Engel class III (6%).

CONCLUSIONS

These results confirm that most patients with drug-resistant epilepsy may benefit from surgical treatment without submitting to preoperative invasive explorations. This finding should help develop epilepsy surgery widely in Africa.

Reduced long-term mortality after successful resective epilepsy surgery: a population-based study

BACKGROUND

We investigated all-cause and epilepsy-related mortality in patients operated with resective epilepsy surgery and in non-operated patients with drug-resistant epilepsy. Our hypothesis was that patients who proceed to surgery have lower mortality over time compared with non-operated patients.

METHOD

Data from 1329 adults and children from the Swedish National Epilepsy Surgery Register and 666 patients with drug-resistant epilepsy who had undergone presurgical work-up but not been operated were analysed. The operated patients had follow-ups between 2 and 20 years. We used the Swedish Cause of Death Register to identify deaths. Autopsy reports were collected for patients with suspected sudden unexpected death in epilepsy (SUDEP). Kaplan-Meier and Cox regression analyses were performed to identify predictors for mortality and SUDEP.

RESULTS

SUDEP accounted for 30% of all deaths. Surgery was associated with lower all-cause mortality (HR 0.7, 95% CI 0.5 to 0.9), also when adjusted for age, sex and tonic-clonic seizures at inclusion. The benefit of surgery seemed to persist and possibly even increase after 15 years of follow-up. Risk factors of mortality for operated patients were persisting seizures and living alone. Of the operated patients, 37% had seizures, and these had a higher risk of mortality (HR 2.1, 95% CI 1.4 to 3.0) and SUDEP (HR 3.5, 95% CI 1.7 to 7.3) compared with patients with seizure freedom at last follow-up.

CONCLUSIONS

In this large population-based epilepsy surgery cohort, operated patients had a lower all-cause mortality compared with non-operated patients with drug-resistant epilepsy. Seizure freedom was the most important beneficial factor for both all-cause mortality and SUDEP among operated patients.

Investigating the effect of hippocampal sclerosis on parietal memory network

OBJECTIVE

We aimed to investigate differences in episodic memory networks between patients with temporal lobe epilepsy (TLE) due to hippocampal sclerosis and healthy controls, especially with regards to the parietal memory network (PMN), as well as their relation to neuropsychological memory performance after mesial temporal resection.

METHODS

28 healthy subjects as well as 21 patients with TLE (12 left, 9 right) were investigated using a spatial memory fMRI paradigm, which has been shown to activate the PMN. Regions of interest (ROI) were defined based on the results of the second-level analyses and activations within the predefined ROIs were compared across groups and correlated with postoperative verbal and nonverbal memory scores.

RESULTS

Healthy subjects showed activations within regions belonging to the dorsal visual stream and the PMN as well as the bilateral parahippocampal place area, the bilateral frontal eye field, and the bilateral middle frontal gyrus. Comparison between groups revealed that TLE patients activated significantly less in the left middle occipital gyrus and the right precuneus. The activation pattern in left TLE patients showed further reductions, mainly in areas belonging to the dorsal visual stream and the PMN within the left hemisphere. Activations within the left superior parietal lobulus, bilateral inferior parietal lobulus, bilateral middle temporal gyrus, left precuneus, left frontal eye field, and left middle frontal gyrus correlated significantly with postoperative verbal memory scores, and activations within the left superior parietal lobulus, left inferior parietal lobulus, left middle temporal gyrus, and left precuneus correlated significantly with higher performance in postoperative nonverbal memory scores.

SIGNIFICANCE

The PMN is involved in episodic memory encoding. Higher activations in areas belonging to the PMN and the dorsal visual stream, especially within the left hemisphere, before amygdalohippocampectomy may result in higher postoperative memory scores.

PLAIN LANGUAGE SUMMARY

This study aims to investigate the effects of epilepsy due to hippocampal sclerosis, i.e. scarring in the temporal lobe, on memory networks in the brain. We discovered that especially patients with left-sided hippocampal sclerosis show reduced brain activations in visual areas and memory networks within the left hemisphere of the brain during orientation in space. Importantly, higher activations within these areas may result in better memory after epilepsy surgery.

The role of magnetoencephalography in preoperative localization and postoperative outcome prediction in patients with posterior cortical epilepsy

OBJECTIVE

We aimed to explore the value of magnetoencephalography in the presurgical evaluation of patients with posterior cortex epilepsy.

METHODS

A total of 39 patients with posterior cortex epilepsy (PCE) and intact magnetoencephalography (MEG) images were reviewed from August 2019 to July 2022. MEG dipole clusters were classified into single clusters, multiple clusters, and scatter dipoles based on tightness criteria. The association of the surgical outcome with MEG dipole classifications was evaluated using Fisher's exact tests.

RESULTS

Among the 39 cases, there were 24 cases of single clusters (61.5%), nine cases of multiple clusters (23.1%), and six cases of scattered dipoles (15.4%). Patients with single dipole clusters were more likely to become seizure-free. Among single dipole cluster cases (n = 24), complete MEG dipole resection yielded a more favorable surgical outcome than incomplete resection (83.3% vs. 16.7%, p = 0.007). Patients with concordant MRI and MEG findings achieved a significantly more favorable surgical outcome than discordant patients (66.7% vs. 33.3%, p = 0.044), especially in single dipole cluster patients (87.5% vs. 25.0%, p = 0.005).

SIGNIFICANCE

MEG can provide additional valuable information regarding surgical candidate selection, epileptogenic zone localization, electrode implantation schedule, and final surgical planning in patients with posterior cortex epilepsy.

Digital automation of transdermal drug delivery with high spatiotemporal resolution

Transdermal drug delivery is of vital importance for medical treatments. However, user adherence to long-term repetitive drug delivery poses a grand challenge. Furthermore, the dynamic and unpredictable disease progression demands a pharmaceutical treatment that can be actively controlled in real-time to ensure medical precision and personalization. Here, we report a spatiotemporal on-demand patch (SOP) that integrates drug-loaded microneedles with biocompatible metallic membranes to enable electrically triggered active control of drug release. Precise control of drug release to targeted locations (<1 mm2), rapid drug release response to electrical triggers (<30 s), and multi-modal operation involving both drug release and electrical stimulation highlight the novelty. Solution-based fabrication ensures high customizability and scalability to tailor the SOP for various pharmaceutical needs. The wireless-powered and digital-controlled SOP demonstrates great promise in achieving full automation of drug delivery, improving user adherence while ensuring medical precision. Based on these characteristics, we utilized SOPs in sleep studies. We revealed that programmed release of exogenous melatonin from SOPs improve sleep of mice, indicating potential values for basic research and clinical treatments.

Surgical treatment for drug-resistant epilepsy due to early brain injury in children

BACKGROUND

The study aimed to summarize the indications and clinical features of pediatric drug-resistant epilepsy associated with early brain injury, surgical outcomes, and prognostic factors.

METHODS

We retrospectively analyzed children diagnosed with drug-resistant epilepsy due to early brain injury, who had undergone surgery at the Pediatric Epilepsy Center of Peking University First Hospital from May 2014 to May 2021. Clinical data of vasculogenic and non-vasculogenic injuries from early brain damage were compared and analyzed. The surgical outcomes were assessed using the Engel grading system.

RESULTS

The median ages at acquiring injury, seizure onset, and surgery among 65 children were 19.0 (0-120) days, 8.6 (0-136.5) months, and 62.9 (13.5-234) months, respectively. Of the 14 children with non-vasculogenic injuries, 12 had posterior ulegyria. Unilateral or bilateral synchronous interictal epileptiform discharges were located mainly in the posterior quadrant in 10 children (71 %), and unilateral posterior quadrant or non-lateralized ictal region in eight children (57 %). The surgical approach was mainly temporo-parieto-occipital or parieto-occipital disconnection in nine children. Of 49 children with vasculogenic injuries, magnetic resonance imaging revealed hemispheric abnormalities in 38. Unilaterally hemispheric or bilateral interictal epileptiform discharges were observed in 36 children (73 %), whereas 42 (86 %) had unilateral hemispheric or non-lateralized ictal onset. The surgical procedure involved hemispherotomy in 38 children (78 %) and lobectomy or disconnection, multilobectomy or disconnection and hemispherotomy in 5, 20, and 40 children, respectively. Fifty-five patients (84.6 %) achieved remission from seizure during follow-up at 5.4 years. Age at surgery (odds ratio = 1.022, 95 % confidence interval = 1.003-1.042, P = 0.023) and etiology (odds ratio = 17.25, 95 % confidence interval = 2.778-107.108, P = 0.002) affected the seizure outcomes.

CONCLUSION

Children with drug-resistant epilepsy due to early brain injury can successfully be treated with surgery after rigorous preoperative screening. Good surgical outcomes are associated with an early age at surgery and an etiology of vasculogenic injury.

Early antiseizure medication withdrawal and risk of seizure recurrence in children after epilepsy surgery: A retrospective study

OBJECTIVE

The timing of antiseizure medication (ASM) withdrawal in children after epilepsy surgery remains controversial and lacks recognized standards. Given the various negative effects of ASM on development in children, this study aimed to evaluate the safety and feasibility of early ASM withdrawal after epileptic resection surgery.

METHODS

We retrospectively assessed the seizure outcomes and ASM profiles of children who had undergone epileptic resection surgery between August 2015 and August 2020 and attempted ASM reduction in the early postoperative phase. Tapering the dose of ASM was attempted when children were seizure-free with no interictal epileptiform discharges (IEDs) on electroencephalogram (EEG) for at least 6 months postoperatively.

RESULTS

This study included 145 children with a median follow-up duration of 40 months. Early ASM tapering was attempted postoperatively in 99 (68.3 %) children. Postoperative ASM discontinuation was attempted in 87 (60.0 %) children. Nine (9.1 %) children experienced seizure recurrence during the ASM reduction stage, and 10 (11.5 %) experienced recurrence after ASM discontinuation. Incomplete resection (P = 0.003) and postoperative seizures before ASM tapering (P = 0.003) were independent predictors of seizure recurrence during and after early ASM withdrawal.

SIGNIFICANCE

ASM withdrawal is viable and safe to be initiated in children who are seizure-free postoperatively and have no IEDs on the scalp EEG for at least 6 months. Children with incomplete resection and postoperative seizures before ASM withdrawal are at a higher risk of seizure recurrence and may need to continue ASM for a longer period.

[Focal cortical dysplasia: visual assessment of MRI and MR morphometry data]

OBJECTIVE

Assessing the diagnostic significance of MR morphometry in determining the localization of focal cortical dysplasias (FCD).

MATERIAL AND METHODS

The study included 13 children after surgery for drug-resistant epilepsy caused by FCD type II and stable postoperative remission of seizures (Engel class IA, median follow-up 56 months). We analyzed the results of independent expert assessment of native MR data by three radiologists (HARNESS protocol) and MR morphometry data regarding accuracy of FCD localization. We considered 2 indicators, i.e. local cortical thickening and gray-white matter blurring.

RESULTS

FCD detection rate was higher after MR morphometry compared to visual analysis of native MR data using the HARNESS protocol. MR morphometry also makes it possible to more often identify gray-white matter blurring as a sign often missed by radiologists (p<0.05).

CONCLUSION

MR morphometry is an additional non-invasive method for assessing the localization of FCD.

Challenging Cortical Explorations in Difficult-to-Localize Seizures: The Rationale and Usefulness of Perisylvian Paralimbic Explorations With Orthogonal Stereoelectroencephalography Depth Electrodes

BACKGROUND AND OBJECTIVE

Stereoelectroencephalography (SEEG) is an invasive monitoring method designed to define and localize the epileptogenic zone (EZ) and explore the putative network responsible for the electroclinical seizures using anatomo-functional-electroclinical correlations. When indicated by semiology in selected patients, exploration of both limbic and paralimbic (PL) regions is indispensable. However, the PL cortex is located in deep and highly vascularized areas in proximity to the anterior Sylvian fissure and middle cerebral artery branches. Thus, those explorations are considered surgically challenging because of the multilobar location and fear of hemorrhagic events. Here, we discuss and illustrate the rationale and SEEG methodology approach in usefulness of exploring the PL regions using standard orthogonal SEEG depth electrode trajectories with the Talariach reference system.

METHODS

We retrospectively studied PL exploration from a cohort of 71 consecutive SEEG procedures from Nov 2019 to Nov 2022 and identified 31 patients who underwent PL trajectories.

RESULTS

In 31 patients, there were 32 SEEG trajectories, and no major complications were observed. PL electrodes were consistently implanted in the C10/D10 coordinates of the Talariach reference coordinates. The most common confirmed EZ in our cohort was mesio-temporal (45%), followed by temporo-perisylvian regions (16%), ventromedial frontal (13%), and mesio-lateral temporal regions (13%). The PL contacts were involved in the EZ in 10 patients (32%). Of 31 patients, 25 underwent resective surgery, and 19 obtained Engel 1 outcome with a mean follow-up of 25 months (range 12-41 months) after surgery.

CONCLUSION

The orthogonal perisylvian PL trajectories are feasible and useful in sampling multiple PL regions with single-electrode trajectories. In patients with perisylvian seizures, sampling PL structures may contribute to an improved understanding of seizure propagation and the optimal anatomic demarcation of the EZs in this surgically challenging region.

Surgical Treatment of Epilepsy with Bilateral MRI Abnormalities

OBJECTIVE

To investigate the surgical outcomes of patients with drug-resistant epilepsy and bilateral brain magnetic resonance imaging (MRI) abnormalities who had undergone various epilepsy surgeries.

METHODS

Patients with drug-resistant epilepsy and bilateral brain abnormalities on MRI who underwent epilepsy surgery at the Severance Children's Hospital between October 2003 and December 2021 were included. The age of seizure onset was 18 years or younger. Engel's classification was used to assess seizure outcomes at 1, 2, and 5 years after surgery.

RESULTS

A total of 40 patients met the inclusion criteria. The median age at surgery was 10.9 years (interquartile range [IQR] 6.9-15.1); the median interval to surgery was 7.1 years (IQR 2.7-11.5). One year after surgery, a favorable outcome of Engel class I-II was observed in 53% (21/40) of patients. At the 2- and 5-year follow-ups, 56% (20/36) and 63% (17/27) of patients showed good postoperative outcomes, respectively.

CONCLUSIONS

Approximately, half of the patients with bilateral brain MRI abnormalities achieved seizure freedom after epilepsy surgery. The existence of bilateral brain MRI abnormalities should not hinder resective epilepsy surgery.

Role of magnetoencephalography in predicting the epileptogenic zone and post-operative seizure outcome - A retrospective study

PURPOSE

Study assessed the role of MSI in predicting the post-operative seizure outcome.

METHODS

This retrospective study included patients who underwent MEG and epilepsy surgery and had a minimum 6 months of postoperative follow-up. Concordance of MEG cluster with post-surgical resection cavity was classified as follows Class I) Concordant and region-specific, Class II) Concordant and region non-specific, Class III) Concordant lateralization only and Class IV) Discordant lateralization. The relationship between MSI concordance and post-operative seizure outcome was assessed.

RESULTS

A total of 183 patients (M: F = 109:74) were included. The mean age at onset of seizures: 8.0 ± 6.4 years. The dipoles were frequent in 123(67.2 %). The primary cluster orientation was regular in 59 (32.2 %) and mixed in 124 (67.8 %) patients. Concordance between MEG and resection cavity: Class I - 124 (67.8 %), class II- 30 (16.4 %), class III- 23 (12.6 %), and class IV- 6 (3.3 %). The post-surgically mean duration of follow-up was 19.52 ± 11.27 months. At 6-month follow-up period, 144 (78.7 %) patients had complete seizure freedom out of which 106 (73.6 %) had class I concordance. Concordance of MEG with resection cavity was associated with a good outcome at 6 months (p = 0.001), 1 year (p = 0.001), 2 years (p = 0.0005) and 5 years (p = 0.04). MEG cluster characteristics had no association with seizure outcome except the strength of the cluster and outcome at 3 years (p = 0.02) follow-up.

CONCLUSION

The study supports that the complete resection of the MEG cluster had high chance of seizure-freedom and can be used as a complementary noninvasive presurgical evaluation tool.

Neuropsychological assessment in pediatric epilepsy surgery: A French procedure consensus

Neuropsychological assessment is a mandatory part of the pre- and post-operative evaluation in pediatric epilepsy surgery. The neuropsychology task force of the ILAE - French Chapter aims to define a neuropsychological procedure consensus based on literature review and adapted for French practice. They performed a systematic review of the literature published between 1950 and 2023 on cognitive evaluation of individuals undergoing presurgical work-up and post-surgery follow-up and focused on the pediatric population aged 6-16. They classified publications listed in the PubMed database according to their level of scientific evidence. The systematic literature review revealed no study with high statistical power and only four studies using neuropsychological scales in their French version. Afterwards, the experts defined a neuropsychological consensus strategy in pediatric epilepsy surgery according to the psychometric determinants of cognitive tests, specificity of epilepsy, surgery context, French culture and literature reports. A common French neuropsychological procedure dedicated to pediatric epilepsy surgery is now available. This procedure could serve as a guide for the pre- and post-surgical work-up in French centers with pediatric epilepsy surgery programs. The main goal is to anticipate the functional risks of surgery, to support the postoperative outcome beyond the seizure-related one, while taking into consideration the plasticity and vulnerability of the immature brain and allowing the possibility of collaborative studies.

Postoperative seizure and memory outcome of temporal lobe epilepsy with hippocampal sclerosis: A systematic review

We conducted a systematic review and meta-analysis to evaluate postoperative seizure and memory outcomes of temporal lobe epilepsy with different hippocampal sclerosis (HS) subtypes classified by International League Against Epilepsy (ILAE) Consensus Guidelines in 2013. Following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and MOOSE (Meta-Analysis of Observational Studies in Epidemiology) guidelines, we searched PubMed, Embase, Web of Science, and Cochrane Library from January 1, 2013 to August 6, 2023. Observational studies reporting seizure and memory outcomes among different HS subtypes were included. We used the Newcastle-Ottawa scale to assess the risk of bias and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to grade the quality of evidence. Seizure freedom and improved outcome (Engel 1 or ILAE class 1-2) ≥1 year after surgery were defined as the primary and secondary seizure outcome. A random-effects meta-analysis by DerSimonian and Laird method was performed to obtain pooled risk ratio (RRs) with 95% confidence interval (CIs). The memory impairment was narratively reviewed because of various evaluation tools. Fifteen cohort studies with 2485 patients were eligible for the meta-analysis of seizure outcome. Six cohorts with detailed information on postoperative memory outcome were included. The pooled RRs of seizure freedom, with moderate to substantial heterogeneity, were .98 (95% CI = .84-1.15) between HS type 2 and type 1, 1.11 (95% CI = .82-1.52) between type 3 and type 1, and .80 (95% CI = .62-1.03) between the no-HS and HS groups. No significant difference of improved outcome was found between different subtypes (p > .05). The quality of evidence was deemed to be low to very low according to GRADE. The long-term seizure outcome (≥5 years after surgery) and memory impairment remained controversial.

The clinical application of neuro-robot in the resection of epileptic foci: a novel method assisting epilepsy surgery

During surgery for foci-related epilepsy, neurosurgeons face significant difficulties in identifying and resecting MRI-negative or deep-seated epileptic foci. Here, we present a neuro-robotic navigation system that is specifically designed for resection of MRI negative epileptic foci. We recruited 52 epileptic patients, and randomly assigned them to treatment group with either neuro-robotic navigation or conventional neuronavigation system. For each patient, in the neuro-robotic navigation group, we integrated multimodality imaging including MRI and PET-CT into the robotic workstation and marked the boundary of foci from the fused image. During surgery, this boundary was delineated by the robotic laser device with high accuracy, guiding resection for the surgeon. For deeply seated foci, we exploited the neuro-robotic navigation system to localize the deepest point with biopsy needle insertion and methylene dye application to locate the boundary of the foci. Our results show that, compared with the conventional neuronavigation, the neuro-robotic navigation system performs equally well in MRI positive epilepsy patients (ENGEL I ratio: 71.4% vs 100%, p = 0.255) systems and show better performance in patients with MRI-negative focal cortical dysplasia (ENGEL I ratio: 88.2% vs 50%, p = 0.0439). At present, there are no documented neurosurgery robots with similar function and application in the field of epilepsy. Our research highlights the added value of using neuro-robotic navigation systems in resection surgery for epilepsy, particularly in cases that involve MRI-negative or deep-seated epileptic foci.

Seizure-outcome after surgery of low-grade epilepsy associated neuro-epithelial tumors

BACKGROUND

Most patients with glioneuronal tumors present with seizures. Although several studies have shown that greater extent of resection improves overall patient survival, few studies have focused on postoperative seizure outcome after resection of these tumors. The aim of this study was to characterize seizure control rates in patients undergoing glioneuronal tumor resection and evaluate the association between poor seizure outcome and tumor recurrence or progression.

METHODS

The study population included patients who had undergone resection of glioneuronal tumors between 2014 and 2019 at our institution. Seizure outcome was assessed using Engel grading. Preoperative seizure characteristics, tumor characteristics, surgical factors, and postoperative seizure outcomes were reviewed.

RESULTS

Twenty-six patients (N.=16, temporal lobe; N.=6, frontal lobe; N.=4, parietal lobe) with mean seizures duration of 56.9-months, were assessed. Histopathologically, N.=15 dysembryoplastic neurepithelial tumor, N.=7 ganglioglioma and N.=4 Diffuse lepto-meningeal neuroepithelial tumor. There were 2 cases of complex DNET and one case of DLMNT had associated cortical dysplasia. At mean follow-up of 49.7 months, N.=20 Engel 1, N.=4 Engel 2 and N.=2 had Engel 3 outcome. N.=20 underwent gross total excision (N.=18 Engel 1 and N.=2 Engel 2) and N.=6 sub-total excision. Among the 4 patients who needed re-surgery, two were in Engel 2 and another two were in Engel 3.

CONCLUSIONS

Good seizure-outcome is likely associated with extent of resection. Younger age of patient, less than one-year of seizure duration and absence of generalization of seizure are good prognostic indicators. The best seizure-control can be achieved by early surgical intervention.

Evaluating the concordance of functional MRI-based language lateralization and Wada testing in epilepsy patients: A single-center analysis

BACKGROUND

For patients with drug-resistant epilepsy, surgery may be effective in controlling their disease. Surgical evaluation may involve localization of the language areas using functional magnetic resonance imaging (fMRI) or Wada testing. We evaluated the accuracy of task-based fMRI versus Wada-based language lateralization in a cohort of our epilepsy patients.

METHODS

In a single-center, retrospective analysis, we identified patients with medically intractable epilepsy who participated in presurgical language mapping (n = 35) with fMRI and Wada testing. Demographic variables and imaging metrics were obtained. We calculated the laterality index (LI) from task-evoked fMRI activation maps across language areas during auditory and reading tasks to determine lateralization. Possible scores for LI range from -1 (strongly left-hemisphere dominant) to 1 (strongly right-hemisphere dominant). Concordance between fMRI and Wada was estimated using Cohen's Kappa coefficient. Association between the LI scores from the auditory and reading tasks was tested using Spearman's rank correlation coefficient.

RESULTS

The fMRI-based laterality indices were concordant with results from Wada testing in 91.4% of patients during the reading task (κ = .55) and 96.9% of patients during the auditory task (κ = .79). The mean LIs for the reading and auditory tasks were -0.52 ± 0.43 and -0.68 ± 0.42, respectively. The LI scores for the language and reading tasks were strongly correlated, r(30) = 0.57 (p = 0.001).

CONCLUSION

Our findings suggest that fMRI is generally an accurate, low-risk alternative to Wada testing for language lateralization. However, when fMRI indicates atypical language lateralization (e.g., bilateral dominance), patients may benefit from subsequent Wada testing or intraoperative language mapping.

Personalized dynamic network models of the human brain as a future tool for planning and optimizing epilepsy therapy

Epilepsy is a common neurological disorder, with one third of patients not responding to currently available antiepileptic drugs. The proportion of pharmacoresistant epilepsies has remained unchanged for many decades. To cure epilepsy and control seizures requires a paradigm shift in the development of new approaches to epilepsy diagnosis and treatment. Contemporary medicine has benefited from the exponential growth of computational modeling, and the application of network dynamics theory to understanding and treating human brain disorders. In epilepsy, the introduction of these approaches has led to personalized epileptic network modeling that can explore the patient's seizure genesis and predict the functional impact of resection on its individual network's propensity to seize. The application of the dynamic systems approach to neurostimulation therapy of epilepsy allows designing stimulation strategies that consider the patient's seizure dynamics and long-term fluctuations in the stability of their epileptic networks. In this article, we review, in a nontechnical fashion suitable for a broad neuroscientific audience, recent progress in personalized dynamic brain network modeling that is shaping the future approach to the diagnosis and treatment of epilepsy.

SEEG-based reevaluation of epileptogenic networks and the predictive role for reoperation in MTLE patients with surgical failure

OBJECTIVE

Approximately 20%-30% of mesial temporal lobe epilepsy (MTLE) patients got unfavorable seizure control after surgery, and there was a discrepancy about the reasons for the surgical failure. The functional connectivity (FC) patterns obtained from stereo-electroencephalography (SEEG) reveal information about the dynamics of the epileptic brain and the added value of extracting information that was not identifiable in the SEEG data using FC analysis. This study aims to find out the patterns of the potential epileptogenic network of failure patients and the electrophysiological predictors of reoperation.

METHODS

From January 2012 to December 2019, the MTLE patients with surgical failure were reviewed, and all patients underwent SEEG-guided reoperation. The epileptogenic network was quantified by calculating FC indicators, including phase slope index (PSI), mutual information (MI) strength, imaginary coherence (icoh), and Granger causality.

RESULTS

Ten patients with 13 seizures were included in the analysis, and 7 of them achieved a favorable outcome after the SEEG-guided reoperation. The surgical zone (SZ) with a favorable prognosis showed greater outward information flow than the non-SZ, whereas the SZ with an unfavorable prognosis showed greater inward information flow. The recurrent patients with favorable prognosis had strong connectivity between the posterior hippocampus, temporal neocortex, and insula, whereas the patients with unfavorable prognosis showed strong functional connectivity between the insula and temporal-parietal-occipital junction. The power spectrum of patients with favorable prognosis was significantly lower than that of patients with unfavorable prognosis, especially showing a more oscillation power of low frequency.

SIGNIFICANCE

The SEEG-guided reoperation could achieve favorable seizure control outcomes for recurrent patients. The FCs were a potential indicator to help construct the temporal epileptic network and predictor for the reoperative prognosis in the recurrent patients.

Successful stereoelectroencephalography re-evaluation in epilepsy patients after failed initial subdural grid evaluation

OBJECTIVE

Epilepsy surgery success is dependent on accurate localization of the epileptogenic zone. Despite the use of invasive EEG using subdural grids and strips, surgical failures can occur. In this series, we explore the utility of a second evaluation with stereoelectroencephalography in patients whose initial invasive evaluation with subdural grid electrodes was unsuccessful in localizing seizure origin.

METHODS

We conducted a retrospective review of patients who underwent subdural grid evaluation (SDE) at our center and identified patients who underwent a re-evaluation with stereoelectroencephalography (SEEG).

RESULTS

We identified three patients who had both subdural and SEEG electrodes in the region of the identified epileptogenic zone in whom the initial SDE evaluation failed to make the patients seizure-free. Two of these patients underwent a second resection and became seizure-free.

SIGNIFICANCE

Stereoelectroencephalography can be useful in the re-evaluation and re-operation of patients who previously had surgical failure using SDE.

Transuncal Selective Amygdalohippocampectomy by an Inferolateral Preseptal Endoscopic Approach Through Inferior Eyelid Conjunctival Incision: An Anatomic Study

BACKGROUND

Transorbital endoscopic approaches have been described for pathologies of anterior and middle fossae. Standard lateral orbitotomy gives access to mesial temporal lobe, but the axis of work is partially obscured by the temporal pole and working corridor is limited.

OBJECTIVE

To evaluate the usefulness of an inferolateral orbitotomy to provide a more direct corridor to perform a transuncal selective amygdalohippocampectomy.

METHODS

Three adult cadaveric specimens were used for a total of 6 dissections. A step-by-step description and illustration of the transuncal corridor for a selective amygdalohippocampectomy were performed using the inferolateral orbitotomy through an inferior eyelid conjunctival incision. The anatomic landmarks were demonstrated in detail. Orbitotomies and angles of work were measured from computed tomography scans, and the area of resection was illustrated by postdissection MRI.

RESULTS

Inferior eyelid conjunctival incision was made for exposure of the inferior orbital rim. Inferolateral transorbital approach was performed to access the transuncal corridor. Endoscopic selective amygdalohippocampectomy was performed through the entorhinal cortex without damage to the temporal neocortex or Meyer's loop. The mean horizontal diameter of the osteotomy was 14.4 mm, and the vertical one was 13.6 mm. The mean angles of work were 65° and 35.5° in the axial and sagittal planes, respectively. Complete amygdalohippocampectomy was achieved in all 6 dissections.

CONCLUSION

Transuncal selective amygdalohippocampectomy was feasible in cadaveric specimens using the inferolateral transorbital endoscopic approach avoiding damage to the temporal neocortex and Meyer's loop. The inferior eyelid conjunctival incision may result in an excellent cosmetic outcome.

Brain but not serum BDNF levels are associated with structural alterations in the hippocampal regions in patients with drug-resistant mesial temporal lobe epilepsy

Mesial temporal lobe epilepsy is the most common type of focal epilepsy, imposing a significant burden on the health care system worldwide. Approximately one-third of patients with this disease who do not adequately respond to pharmacotherapy are considered drug-resistant subjects. Despite having some clues of how such epileptic activity and resistance to therapy emerge, coming mainly from preclinical models, we still witness a scarcity of human data. To narrow this gap, in this study, we aimed to estimate the relationship between hippocampal and serum levels of brain-derived neurotrophic factor (BDNF), one of the main and most widely studied neurotrophins, and hippocampal subfield volumes in patients with drug-resistant mesial temporal epilepsy undergoing neurosurgical treatment. We found that hippocampal (but not serum) BDNF levels were negatively correlated with the contralateral volumes of the CA1 and CA4 subfields, presubiculum, subiculum, dentate gyrus, and molecular layer of the hippocampus. Taken together, these findings are generally in accordance with existing data, arguing for a proepileptic nature of BDNF effects in the hippocampus and related brain structures.

Deep brain stimulation for patients with refractory epilepsy: nuclei selection and surgical outcome

Objective

By studying the surgical outcome of deep brain stimulation (DBS) of different target nuclei for patients with refractory epilepsy, we aimed to explore a clinically feasible target nucleus selection strategy.

Methods

We selected patients with refractory epilepsy who were not eligible for resective surgery. For each patient, we performed DBS on a thalamic nucleus [anterior nucleus of the thalamus (ANT), subthalamic nucleus (STN), centromedian nucleus (CMN), or pulvinar nucleus (PN)] selected based on the location of the patient's epileptogenic zone (EZ) and the possible epileptic network involved. We monitored the clinical outcomes for at least 12 months and analyzed the clinical characteristics and seizure frequency changes to assess the postoperative efficacy of DBS on the different target nuclei.

Results

Out of the 65 included patients, 46 (70.8%) responded to DBS. Among the 65 patients, 45 underwent ANT-DBS, 29 (64.4%) responded to the treatment, and four (8.9%) of them reported being seizure-free for at least 1 year. Among the patients with temporal lobe epilepsy (TLE, n = 36) and extratemporal lobe epilepsy (ETLE, n = 9), 22 (61.1%) and 7 (77.8%) responded to the treatment, respectively. Among the 45 patients who underwent ANT-DBS, 28 (62%) had focal to bilateral tonic-clonic seizures (FBTCS). Of these 28 patients, 18 (64%) responded to the treatment. Out of the 65 included patients, 16 had EZ related to the sensorimotor cortex and underwent STN-DBS. Among them, 13 (81.3%) responded to the treatment, and two (12.5%) were seizure-free for at least 6 months. Three patients had Lennox-Gastaut syndrome (LGS)-like epilepsy and underwent CMN-DBS; all of them responded to the treatment (seizure frequency reductions: 51.6%, 79.6%, and 79.5%). Finally, one patient with bilateral occipital lobe epilepsy underwent PN-DBS, reducing the seizure frequency by 69.7%.

Significance

ANT-DBS is effective for patients with TLE or ETLE. In addition, ANT-DBS is effective for patients with FBTCS. STN-DBS might be an optimal treatment for patients with motor seizures, especially when the EZ overlaps the sensorimotor cortex. CMN and PN may be considered modulating targets for patients with LGS-like epilepsy or occipital lobe epilepsy, respectively.

Landscape and future directions of machine learning applications in closed-loop brain stimulation

Brain stimulation (BStim) encompasses multiple modalities (e.g., deep brain stimulation, responsive neurostimulation) that utilize electrodes implanted in deep brain structures to treat neurological disorders. Currently, BStim is primarily used to treat movement disorders such as Parkinson's, though indications are expanding to include neuropsychiatric disorders like depression and schizophrenia. Traditional BStim systems are "open-loop" and deliver constant electrical stimulation based on manually-determined parameters. Advancements in BStim have enabled development of "closed-loop" systems that analyze neural biomarkers (e.g., local field potentials in the sub-thalamic nucleus) and adjust electrical modulation in a dynamic, patient-specific, and energy efficient manner. These closed-loop systems enable real-time, context-specific stimulation adjustment to reduce symptom burden. Machine learning (ML) has emerged as a vital component in designing these closed-loop systems as ML models can predict / identify presence of disease symptoms based on neural activity and adaptively learn to modulate stimulation. We queried the US National Library of Medicine PubMed database to understand the role of ML in developing closed-loop BStim systems to treat epilepsy, movement disorders, and neuropsychiatric disorders. Both neural and non-neural network ML algorithms have successfully been leveraged to create closed-loop systems that perform comparably to open-loop systems. For disorders in which the underlying neural pathophysiology is relatively well understood (e.g., Parkinson's, essential tremor), most work has involved refining ML models that can classify neural signals as aberrant or normal. The same is seen for epilepsy, where most current research has focused on identifying optimal ML model design and integrating closed-loop systems into existing devices. For neuropsychiatric disorders, where the underlying pathologic neural circuitry is still being investigated, research is focused on identifying biomarkers (e.g., local field potentials from brain nuclei) that ML models can use to identify onset of symptoms and stratify severity of disease.

Does Adjustment of Antiseizure Medication Regimen after Failed Epilepsy Surgery Improve Outcomes?

Background and Objectives: After failed epilepsy surgery, patients often revert to an antiseizure medication (ASM) ASM regimen, which can be adjusted or optimized in three ways: increasing the dose, alternative therapy, and combination therapy. It is unclear which type of antiseizure medication adjustment method can improve outcomes. Materials and Methods: Children who underwent failed epileptic resection surgery at the Department of Neurosurgery, Children's Hospital of Chongqing Medical University between January 2015 and December 2021 were included in this cohort, who were reviewed for whether they underwent adjustment of ASM with increased dose, alternative therapy, or combination therapy. The seizure outcome and quality of life (QoL) were assessed. Two-tailed Fisher exact test and Mann-Whitney U test were used for statistical analysis. Results: Sixty-three children with failed surgery were included for further analysis, with a median follow-up time of 53 months. The median seizure recurrence time was 4 months. At the last follow-up, 36.5% (n = 23) of patients achieved seizure freedom, 41.3% (n = 26) achieved seizure remission, and 61.9% (n = 39) had a good QoL. None of the three types of ASM adjustment improved children's outcomes, whether considered in terms of seizure-free rate, seizure remission rate, or QoL. Early recurrences were significantly associated with decreased probability of seizure freedom (p = 0.02), seizure remission (p = 0.02), and a good QoL (p = 0.01). Conclusions: Children who underwent failed epilepsy surgery remains some potential for late seizure remission from ASM. Yet adjusting ASM regimen does not increase the probability of seizure remission nor does it improve the QoL. Clinicians should complete evaluations and consider the need for other antiepileptic treatment as soon as possible after surgery failed, especially when dealing with children with an early recurrence.

Cell therapy for neurological disorders: Progress towards an embryonic medial ganglionic eminence progenitor-based treatment

Impairment of development, migration, or function of inhibitory interneurons are key features of numerous circuit-based neurological disorders, such as epilepsy. From a therapeutic perspective, symptomatic treatment of these disorders often relies upon drugs or deep brain stimulation approaches to provide a general enhancement of GABA-mediated inhibition. A more effective strategy to target these pathological circuits and potentially provide true disease-modifying therapy, would be to selectively add new inhibitory interneurons into these circuits. One such strategy, using embryonic medial ganglionic (MGE) progenitor cells as a source of a unique sub-population of interneurons, has already proven effective as a cell transplantation therapy in a variety of preclinical models of neurological disorders, especially in mouse models of acquired epilepsy. Here we will discuss the evolution of this interneuron-based transplantation therapy in acquired epilepsy models, with an emphasis on the recent adaptation of MGE progenitor cells for xenotransplantation into larger mammals.

Periodic cycles of seizure clustering and suppression in children with epilepsy strongly suggest focal cortical dysplasia

AIM

We investigated characteristic seizure patterns in epilepsy caused by focal cortical dysplasia (FCD), which differ from epilepsy by other aetiologies in surgical cases with lesions on magnetic resonance imaging (MRI), then examined if these features were applicable to patients with epilepsy without any lesions on MRI.

METHOD

We retrospectively studied clinicopathological features in 291 (143 females) children with epilepsy who had undergone resective surgery after comprehensive evaluation, including 277 cases with lesions on MRI (136 females, age at resection 0-17 years [mean 6 years 10 months, SD 5 years 7 months]) and 14 cases without any lesions on MRI (seven females, age 0-16 years [mean 7 years 8 months, SD 4 years 8 months]).

RESULTS

Among 277 patients with lesions on MRI, 87 cases exhibited recurrent periodic cycles of seizure clustering (≥5 seizures/day for ≥1 week) and suppression (no seizures for ≥1 week); of these, 80 cases (92%) were pathologically diagnosed with FCD. Other pathologies included glial scar, hippocampal sclerosis, hemimegalencephaly, and cortical tuber in three, two, one, and one case respectively. All 14 patients without any lesions on MRI had significant recurrent periodic seizure cycles and FCD histopathologically.

INTERPRETATION

Periodic seizure cycles characterized by clustering and suppression in patients with epilepsy strongly suggest the presence of FCD regardless of MRI findings, and comprehensive evaluations for epilepsy surgery should be proceeded.

Cost-effectiveness of surgical treatment compared to medical treatment in patients with drug-refractory epilepsy: A systematic review

BACKGROUND AND PURPOSE

Approximately 30% of epilepsy patients develop a drug-refractory epilepsy, that is, seizures cannot be controlled with antiepileptic drugs. Surgery has been evaluated as an effective but costly form of treatment. The aim of this systematic review is to synthesize the available evidence on the cost-effectiveness of surgical treatment compared to medical treatment for these patients.

METHOD

A systematic literature search was performed in MEDLINE, Embase, PsycINFO, Cochrane Library and the National Health Service Economic Evaluation Database until September 2022. Title, abstract and full-text screening were conducted by two researchers. Original studies published in English or German analyzing the cost-effectiveness of surgical compared to medical treatment were included. Study characteristics, effectiveness measures, costs and incremental cost-effectiveness ratios (ICERs) were extracted. The quality of studies was assessed using the Drummond checklist.

RESULTS

Fourteen studies were included. Most studies evaluated surgery as cost-effective. The ICER per patient seizure free ranged from dominant to purchasing power parity US dollars (PPP-USD) 479,275. The ICER per 1% seizure reduction ranged from PPP-USD 227 to PPP-USD 342. The ICER per year without seizures was PPP-USD 4202 and the ICER per quality-adjusted life-year ranged from dominant to PPP-USD 90,874. The studies varied greatly in their methodology and time horizon.

CONCLUSION

Surgical treatment is cost-effective compared to medical treatment, especially when a lifetime horizon is adopted. It is concluded that all disease-specific costs should be considered over a long period when assessing the cost-effectiveness of epilepsy treatment. From an economic perspective, efforts should be made to improve access to surgical treatment for patients with drug-refractory epilepsy.

Neuropathological Insights into Unexpected Cognitive Decline in Epilepsy

OBJECTIVE

Some patients unexpectedly display an unfavorable cognitive course after epilepsy surgery subsequent to any direct cognitive sequelae of the surgical treatment. Therefore, we conducted in-depth neuropathological examinations of resective specimens from corresponding patients to provide insights as to the underlying disease processes.

METHODS

In this study, cases with significant cognitive deterioration following a previous postoperative assessment were extracted from the neuropsychological database of a longstanding epilepsy surgical program. An extensive reanalysis of available specimens was performed using current, state-of-the-art neuropathological examinations. Patients without cognitive deterioration but matched in regard to basic pathologies served as controls.

RESULTS

Among the 355 operated patients who had undergone more than one postoperative neuropsychological examination, 30 (8%) showed significant cognitive decline in the period after surgery. Of the 24 patients with available specimens, 71% displayed further neuropathological changes in addition to the typical spectrum (ie, hippocampal sclerosis, focal cortical dysplasias, vascular lesions, and low-grade tumors), indicating (1) a secondary, putatively epilepsy-independent neurodegenerative disease process; (2) limbic inflammation; or (3) the enigmatic pathology pattern of "hippocampal gliosis" without segmental neurodegeneration. In the controls, the matched individual principal epilepsy-associated pathologies were not found in combination with the secondary pathology patterns of the study group.

INTERPRETATION

Our findings indicate that patients who unexpectedly displayed unfavorable cognitive development beyond any direct surgical effects show rare and very particular pathogenetic causes or parallel, presumably independent, neurodegenerative alterations. A multicenter collection of such cases would be appreciated to discern presurgical biomarkers that help with surgical decision-making. ANN NEUROL 2023;93:536-550.

Epileptic-network-based prediction and control of seizures in humans

Epilepsy is now conceptualized as a network disease. The epileptic brain network comprises structurally and functionally connected cortical and subcortical brain regions - spanning lobes and hemispheres -, whose connections and dynamics evolve in time. With this concept, focal and generalized seizures as well as other related pathophysiological phenomena are thought to emerge from, spread via, and be terminated by network vertices and edges that also generate and sustain normal, physiological brain dynamics. Research over the last years has advanced concepts and techniques to identify and characterize the evolving epileptic brain network and its constituents on various spatial and temporal scales. Network-based approaches further our understanding of how seizures emerge from the evolving epileptic brain network, and they provide both novel insights into pre-seizure dynamics and important clues for success or failure of measures for network-based seizure control and prevention. In this review, we summarize the current state of knowledge and address several important challenges that would need to be addressed to move network-based prediction and control of seizures closer to clinical translation.

Clinical Features, Neuropathology, and Surgical Outcome in Patients With Refractory Epilepsy and Brain Somatic Variants in the SLC35A2 Gene

BACKGROUND AND OBJECTIVES

The SLC35A2 gene, located at chromosome Xp11.23, encodes for a uridine diphosphate-galactose transporter. We describe clinical, genetic, neuroimaging, EEG, and histopathologic findings and assess possible predictors of postoperative seizure and cognitive outcome in 47 patients with refractory epilepsy and brain somatic SLC35A2 gene variants.

METHODS

This is a retrospective multicenter study where we performed a descriptive analysis and classical hypothesis testing. We included the variables of interest significantly associated with the outcomes in the generalized linear models.

RESULTS

Two main phenotypes were associated with brain somatic SLC35A2 variants: (1) early epileptic encephalopathy (EE, 39 patients) with epileptic spasms as the predominant seizure type and moderate to severe intellectual disability and (2) drug-resistant focal epilepsy (DR-FE, 8 patients) associated with normal/borderline cognitive function and specific neuropsychological deficits. Brain MRI was abnormal in all patients with EE and in 50% of those with DR-FE. Histopathology review identified mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy in 44/47 patients and was inconclusive in 3. The 47 patients harbored 42 distinct mosaic SLC35A2 variants, including 14 (33.3%) missense, 13 (30.9%) frameshift, 10 (23.8%) nonsense, 4 (9.5%) in-frame deletions/duplications, and 1 (2.4%) splicing variant. Variant allele frequencies (VAFs) ranged from 1.4% to 52.6% (mean VAF: 17.3 ± 13.5). At last follow-up (35.5 ± 21.5 months), 30 patients (63.8%) were in Engel Class I, of which 26 (55.3%) were in Class IA. Cognitive performances remained unchanged in most patients after surgery. Regression analyses showed that the probability of achieving both Engel Class IA and Class I outcomes, adjusted by age at seizure onset, was lower when the duration of epilepsy increased and higher when postoperative EEG was normal or improved. Lower brain VAF was associated with improved postoperative cognitive outcome in the analysis of associations, but this finding was not confirmed in regression analyses.

DISCUSSION

Brain somatic SLC35A2 gene variants are associated with 2 main clinical phenotypes, EE and DR-FE, and a histopathologic diagnosis of MOGHE. Additional studies will be needed to delineate any possible correlation between specific genetic variants, mutational load in the epileptogenic tissue, and surgical outcomes.

Seizure-free outcome and safety of repeated epilepsy surgery for persistent or recurrent seizures

OBJECTIVE

Reoperation may be an option for select patients with unsatisfactory seizure control after their first epilepsy surgery. The aim of this study was to describe the seizure-free outcome and safety of repeated epilepsy surgery in our tertiary referral center.

METHODS

Thirty-eight patients with focal refractory epilepsy, who underwent repeated epilepsy surgeries and had a minimum follow-up time of 12 months after reoperation, were included. Systematic reevaluation, including comprehensive neuroimaging and noninvasive (n = 38) and invasive (n = 25, 66%) video-electroencephalography monitoring, was performed. Multimodal 3D resection maps were created for individual patients to allow personalized reoperation.

RESULTS

The median time between the first operation and reoperation was 74 months (range 5-324 months). The median age at reoperation was 34 years (range 1-74 years), and the median follow-up was 38 months (range 13-142 months). Repeat MRI after the first epilepsy surgery showed an epileptogenic lesion in 24 patients (63%). The reoperation was temporal in 18 patients (47%), extratemporal in 9 (24%), and multilobar in 11 (29%). The reoperation was left hemispheric in 24 patients (63%), close to eloquent cortex in 19 (50%), and distant from the initial resection in 8 (21%). Following reoperation, 27 patients (71%) became seizure free (Engel class I), while 11 (29%) continued to have seizures. There were trends toward better outcome in temporal lobe epilepsy and for unilobar resections adjacent to the initial surgery, but there was no difference between MRI lesional and nonlesional patients. In all subgroups, Engel class I outcome was at least 50%. Perioperative complications occurred in 4 patients (11%), with no fatalities.

CONCLUSIONS

Reoperation for refractory focal epilepsy is an effective and safe option in patients with persistent or recurrent seizures after initial epilepsy surgery. A thorough presurgical reevaluation is essential for favorable outcome.

Low-intensity focused ultrasound, a novel approach to epilepsy treatment in developing countries

Approximately 80% of patients with epilepsy reside in poor resource settings. Despite the continued advancements and development of new treatment approaches, epilepsy remains a major health problem in developing countries. Consistent findings of epidemiologic studies reflect that both prevalence and treatment gap are higher in the developing world. The objective of this short review was to evaluate current treatment options and low-intensity, pulsed-focused ultrasound (FUS) as a potential new treatment option for epilepsy. Although some of the patients could be candidates for surgery, many factors, including poor health-care infrastructure, socioeconomic status, risks and complications associated with the surgery, and patients' preferences and attitudes toward the surgical procedure, limit the adherence to get surgical therapies. Low-intensity FUS, a novel and noninvasive therapeutic approach, has the potential to be approved by regulatory bodies and added to the list of standard treatment options for epilepsy. Improved understanding of epilepsy's prevalence and incidence in developing worlds, identification of potential new therapeutic options, and their evaluation through continuous studies and clinical trials are needed to reduce the burden of epilepsy and the treatment gap.

Multi-modal characterization and simulation of human epileptic circuitry

Temporal lobe epilepsy is the fourth most common neurological disorder, with about 40% of patients not responding to pharmacological treatment. Increased cellular loss is linked to disease severity and pathological phenotypes such as heightened seizure propensity. While the hippocampus is the target of therapeutic interventions, the impact of the disease at the cellular level remains unclear. Here, we show that hippocampal granule cells change with disease progression as measured in living, resected hippocampal tissue excised from patients with epilepsy. We show that granule cells increase excitability and shorten response latency while also enlarging in cellular volume and spine density. Single-nucleus RNA sequencing combined with simulations ascribes the changes to three conductances: BK, Cav2.2, and Kir2.1. In a network model, we show that these changes related to disease progression bring the circuit into a more excitable state, while reversing them produces a less excitable, "early-disease-like" state.

Complete corpus callosotomy using a frameless navigation probe through a minicraniotomy in children with medically refractory epilepsy: A case series and technical note

Background

Medically refractory epilepsy constitutes up to one-third of the epilepsy pediatric patients. Corpus callosotomy (CC) has been used for the treatment of medically refractory epilepsy in children with atonic seizures and generalized tonic-clonic (GTC) seizures. In this case series study, we are describing a novel technique for CC using the frameless navigation probe through a minicraniotomy.

Methods

Thirteen pediatric patients with the diagnosis of medically refractory epilepsy predominantly GTC with drop attack who underwent extensive Phase I. An L-shape was done, then through a 4 × 3 cm craniotomy, we were able to open the interhemispheric fissure until the corpus callosum is visualized. The Stealth probe is then used to go down to the midline raphe which is followed anteriorly then traced posteriorly to the anterior border of the vein of Galen. Finally, the Stealth probe is used to confirm the completeness of the callosotomy.

Results

The procedure was accomplished successfully with no intraoperative complications; mean surgical time is 3 h:07 m. The mean follow-up was 31.5 months. All patients achieved significant seizure control. No patients experienced worsening of their atonic seizures after surgery compared with their preoperative state; however, six patients achieved Engel Class I, four patients achieved Engel Class II, and three patients achieved Engel Class III.

Conclusion

Complete CC using a frameless navigation probe is a novel and effective technique for the treatment of medically refractory epilepsy with a very good surgical and seizure outcomes, minimal neurological morbidity, minimal blood loss, and short OR time.

Neuroanatomical and psychological considerations in temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy and is associated with a variety of structural and psychological alterations. Recently, there has been renewed interest in using brain tissue resected during epilepsy surgery, in particular 'non-epileptic' brain samples with normal histology that can be found alongside epileptic tissue in the same epileptic patients - with the aim being to study the normal human brain organization using a variety of methods. An important limitation is that different medical characteristics of the patients may modify the brain tissue. Thus, to better determine how 'normal' the resected tissue is, it is fundamental to know certain clinical, anatomical and psychological characteristics of the patients. Unfortunately, this information is frequently not fully available for the patient from which the resected tissue has been obtained - or is not fully appreciated by the neuroscientists analyzing the brain samples, who are not necessarily experts in epilepsy. In order to present the full picture of TLE in a way that would be accessible to multiple communities (e.g., basic researchers in neuroscience, neurologists, neurosurgeons and psychologists), we have reviewed 34 TLE patients, who were selected due to the availability of detailed clinical, anatomical, and psychological information for each of the patients. Our aim was to convey the full complexity of the disorder, its putative anatomical substrates, and the wide range of individual variability, with a view toward: (1) emphasizing the importance of considering critical patient information when using brain samples for basic research and (2) gaining a better understanding of normal and abnormal brain functioning. In agreement with a large number of previous reports, this study (1) reinforces the notion of substantial individual variability among epileptic patients, and (2) highlights the common but overlooked psychopathological alterations that occur even in patients who become "seizure-free" after surgery. The first point is based on pre- and post-surgical comparisons of patients with hippocampal sclerosis and patients with normal-looking hippocampus in neuropsychological evaluations. The second emerges from our extensive battery of personality and projective tests, in a two-way comparison of these two types of patients with regard to pre- and post-surgical performance.

Repeat surgery for pediatric epilepsy: a systematic review and meta-analysis of resection and disconnection approaches

OBJECTIVE

Resection and disconnection surgeries for epilepsy in the pediatric demographic (patients ≤ 18 years of age) are two separate, definitive intervention options in medically refractory cases. Questions remain regarding the role of surgery when seizures persist after an initial incomplete surgery. The aim of this study was to review the contemporary literature and summarize the metadata on the outcomes of repeat surgery in this specific demographic.

METHODS

Searches of seven electronic databases from inception to July 2022 were conducted using PRISMA guidelines. Articles were screened using prespecified criteria. Metadata from the articles were abstracted and pooled by random-effects meta-analysis of proportions.

RESULTS

Eleven studies describing 12 cohorts satisfied all criteria, reporting outcomes of 170 pediatric patients with epilepsy who underwent repeat resection or disconnection surgery. Of these patients, 55% were male, and across all studies, median ages at initial and repeat surgeries were 7.2 and 9.4 years, respectively. The median follow-up duration after repeat surgery was 47.7 months. The most commonly reported etiology for epilepsy was cortical dysplasia. Overall, the estimated incidence of complete seizure freedom (Engel class I) following repeat surgery was 48% (95% CI 40%-56%, p value for heterogeneity = 0.93), and the estimated incidence of postoperative complications following repeat surgery was 25% (95% CI 12%-39%, p = 0.04). There were six cohorts each that described outcomes for repeat resection and repeat disconnection surgeries. There was no statistical difference between these two subgroups with respect to estimated incidence of complete seizure freedom (p value for interaction = 0.92), but postoperative complications were statistically more common following repeat resection (p ≤ 0.01).

CONCLUSIONS

For both resection and disconnection surgeries, repeat epilepsy surgery in children is likely to confer complete seizure freedom in approximately half of the patients who experience unsuccessful initial incomplete epilepsy surgery. More data are needed to elucidate the impact on efficacy based on surgical approach selection. Judicious discussion and planning between the patient, family, and a multidisciplinary team of epilepsy specialists is recommended to optimize expectations and outcomes in this setting.

Seizure onset zone classification based on imbalanced iEEG with data augmentation

Objective. Identifying the seizure onset zone (SOZ) in patients with focal epilepsy is the critical information required for surgery. However, collecting this information is challenging, time-consuming, and subjective. Some machine learning methods reduce the workload of clinical experts in intracranial electroencephalogram (iEEG) visual diagnosis but face significant challenges because interictal iEEG clinical data often suffer from a significant class imbalance. We aim to generate synthetic data for the minority class.Approach. To make the clinically imbalanced data suitable for machine learning, we introduce an EEG augmentation method (EEGAug). The EEGAug method randomly selects several samples from the minority class and transforms them into the frequency domain. Then, different frequency bands from different samples are used to compose new data. Finally, a synthetic sample is generated after converting the new data back to the time domain.Main results. The imbalanced clinical iEEG data can be balanced and applied to machine learning models using the method. A one-dimensional convolutional neural network model is used to classify the SOZ and non-SOZ data. We compare the EEGAug method with other data augmentation methods and another method of class-balanced focal loss function, which is also used for solving the data imbalance problem by adjusting the weights between the minority and majority classes. The results show that the EEGAug method performs best in most data.Significance. Data imbalance is a widespread clinical problem. The EEGAug method can flexibly generate synthetic data for the minority class, yielding synthetic and raw data with a high distribution similarity. By using the EEGAug method, clinical data can be used in machine learning models.

The differential role of magnetic resonance imaging in predicting surgical outcomes between children versus adults with temporal lobe epilepsy

OBJECTIVE

This study aims to investigate the clinical discrepancies and the different predictors of anterior temporal lobectomy (ATL) in children (<18 years at surgery) and adults (>18 years at surgery) with temporal lobe epilepsy (TLE).

MATERIALS AND METHODS

A total of 262 patients (56 children and 206 adults) with TLE who underwent ATL were included in this study. The clinical variables, including patients' characteristics, preoperative evaluations, pathology, surgical prognosis, and surgical predictors were assessed the discrepancies between TLE children versus adults using univariate and multivariate analyses. Kaplan-Meier survival analysis was used to calculate the probability of seizure freedom and AEDs withdrawal after ATL, and the difference between TLE children and adults was analyzed using the Log-Rank test.

RESULTS

There were significant differences including semiology, magnetic resonance imaging (MRI) examinations, numbers of preoperative AEDs, and pathologies between TLE children and adults (P < 0.05, Q < 0.05). The MRI-detected epileptic focus was the only independent predictor of seizure freedom (P = 0.002, Q = 0.036) in TLE children, and the concordance of MRI-detected focus with video-electroencephalography (video-EEG)-detected epileptic zone was the only variable associated with seizure freedom in TLE adults (OR = 2.686, 95% CI = 1.014-7.115, P = 0.047). The TLE children experienced a higher probability of AEDs withdrawal than adults after surgery (P = 0.005).

SIGNIFICANCE

There were remarkable differences in clinical manifestations, MRI examinations, number of preoperative AEDs, and pathologies between TLE children versus adults. TLE children had a higher possibility of AEDs withdrawal than adults after surgery. The favorable seizure outcome of ATL depended on the early complete resection of MRI-detected epileptogenic focus in TLE children, while the concordance of MRI-detected focus with EEG-detected epileptogenic zone was the only predictor of favorable seizure outcomes in TLE adults.

Paediatric epilepsy surgery: Techniques and outcomes

Epilepsy is a neurological condition characterised by recurrent and persistent seizures. For paediatric patients, achieving early seizure freedom can have positive impacts on cognition, development, social integration and mental health, leading to improved quality of life. In general, one third of patients with epilepsy are refractory to medication; for these patients, epilepsy surgery may offer the only chance for improved seizure control. Epilepsy surgery as a therapeutic intervention has become increasingly accepted in the past few decades, with more diverse options available (including neuromodulatory and minimally invasive techniques). In this context, we discuss here the pre-operative workup for paediatric patients with medically refractory epilepsy and provide an updated review on current and emerging surgical therapies for this condition. We also discuss the clinical, neuropsychological, quality of life and economic impacts of epilepsy surgery.

18F-FDG-PET hypometabolism as a predictor of favourable outcome in epilepsy surgery: protocol for a systematic review and meta-analysis

INTRODUCTION

A substantial proportion of patients who undergo surgery for drug resistant focal epilepsy do not become seizure free. While some factors, such as the detection of hippocampal sclerosis or a resectable lesion on MRI and electroencephalogram-MRI concordance, can predict favourable outcomes in epilepsy surgery, the prognostic value of the detection of focal hypometabolism with ¹⁸F-fluorodeoxyglucose positive emission tomography (¹⁸F-FDG-PET) hypometabolism is uncertain. We propose a protocol for a systematic review and meta-analysis to examine whether localisation with ¹⁸F-FDG-PET hypometabolism predicts favourable outcomes in epilepsy surgery.

METHODS AND ANALYSIS

A systematic literature search of Medline, Embase and Web of Science will be undertaken. Publications which include evaluation with ¹⁸F-FDG-PET prior to surgery for drug resistant focal epilepsy, and which report ≥12 months of postoperative surgical outcome data will be included. Non-human, non-English language publications, publications with fewer than 10 participants and unpublished data will be excluded. Screening and full-text review of publications for inclusion will be undertaken by two independent investigators, with discrepancies resolved by consensus or a third investigator. Data will be extracted and pooled using random effects meta-analysis, with heterogeneity quantified using the I² analysis.

ETHICS AND DISSEMINATION

Ethics approval is not required. Once complete, the systematic review will be published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42022324823.

Deep brain stimulation of the subthalamic nucleus for epilepsy

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is a promising palliative option for patients with refractory epilepsy. However, crucial questions remain unanswered: Which patients are the optimal candidates? How, where, and when to stimulate the STN? And what is the mechanism of STN-DBS action on epilepsy? Thus, we reviewed the clinical evidence on the antiepileptic effects of STN-DBS and its possible mechanisms on drug-resistant epilepsy, its safety, and the factors influencing stimulation outcomes. This information may guide clinical decision-making. In addition, based on the current knowledge on the effect of STN-DBS on epilepsy, we suggest research that needs to be carried out in the future.

Precision medicine in pediatric temporal epilepsy surgery: optimization of outcomes through functional MRI memory tasks and tailored surgeries

OBJECTIVE

The goal of epilepsy surgery is both seizure cessation and maximal preservation of function. In temporal lobe (TL) cases, the lack of functional MRI (fMRI) tasks that effectively activate mesial temporal structures hampers preoperative memory risk assessment, especially in children. This study evaluated pediatric TL surgery outcome optimization associated with tailored resection informed by an fMRI memory task.

METHODS

The authors identified focal onset TL epilepsy patients with 1) TL resections; 2) viable fMRI memory scans; and 3) pre- and postoperative neuropsychological (NP) evaluations. They retrospectively evaluated preoperative fMRI memory scans, available Wada tests, pre- and postoperative NP scores, postoperative MRI scans, and postoperative Engel class outcomes. To assess fMRI memory task outcome prediction, the authors 1) overlaid preoperative fMRI activation onto postoperative structural images; 2) classified patients as having "overlap" or "no overlap" of activation and resection cavities; and 3) compared these findings with memory improvement, stability, or decline, based on Reliable Change Index calculations.

RESULTS

Twenty patients met the inclusion criteria. At a median of 2.1 postoperative years, 16 patients had Engel class IA outcomes and 1 each had Engel class IB, ID, IIA, and IID outcomes. Functional MRI activation was linked to NP memory outcome in 19 of 20 cases (95%). Otherwise, heterogeneity characterized the cohort.

CONCLUSIONS

Functional MRI memory task activation effectively predicted individual NP outcomes in the context of tailored TL resections. Patients had excellent seizure and overall good NP outcomes. This small study adds to extant literature indicating that pediatric TL epilepsy does not represent a single clinical syndrome. Findings support individualized surgical intervention using fMRI memory activation to help guide this precision medicine approach.

Seizure Outcome of Temporal Lobe Epilepsy Surgery in Adults and Children: A Systematic Review and Meta-Analysis

BACKGROUND

Temporal lobe epilepsy (TLE) surgery is associated with the best seizure outcome in adults, although its long-term results remain suboptimal. Retrospective pediatric studies suggest better figures whose determinants are poorly understood.

OBJECTIVE

To conduct a systematic review and meta-analysis of studies on the efficacy of TLE surgery in children (age younger than 18 years) and adults.

METHODS

We searched MEDLINE, Embase, and Cochrane Library for TLE surgery original research from January 1, 1990, until May 12, 2020. The outcome measures were seizure freedom since surgery and seizure freedom either at last or longest follow-up. We meta-analyzed the proportion of children and adults achieving either Engel I/International League Against Epilepsy (ILAE) 1 or Engel IA/ILAE 1A outcome by follow-up duration, type of surgery, histopathology, neuroimaging, quality of the studies, and publication period. We used a random effects model with Freeman-Tukey double arcsine transformation of proportions.

RESULTS

From 40 409 records identified, we included 277 studies (30 848 patients). The proportions of patients achieving Engel I/ILAE 1 and Engel IA/ILAE 1A outcomes were 0.74 (95% CI, 0.69-0.78) and 0.61 (0.48-0.74) for children and 0.69 (0.67-0.71) and 0.56 (0.52-0.60) for adults. Histopathology significantly influenced Engel I/ILAE 1 outcome in adults but not in children (P < .0001), while the type of surgery significantly influenced Engel I/ILAE 1 outcome in children but not in adults.

CONCLUSION

The proportion of seizure freedom after TLE surgery was higher in children, although not significantly. Histopathology and the surgical approach can influence seizure outcome, with age-related variability.

The impact of cathodal tDCS on the GABAergic system in the epileptogenic zone: A multimodal imaging study

Objectives

We aimed to investigate the antiepileptic effects of cathodal transcranial direct current stimulation (c-tDCS) and mechanisms of action based on its effects on the neurotransmitters responsible for the abnormal synchrony patterns seen in pharmacoresistant epilepsy. This is the first study to test the impact of neurostimulation on epileptiform interictal discharges (IEDs) and to measure brain metabolites in the epileptogenic zone (EZ) and control regions simultaneously in patients with pharmacoresistant epilepsy.

Methods

This is a hypothesis-driven pilot prospective single-blinded repeated measure design study in patients diagnosed with pharmacoresistant epilepsy of temporal lobe onset. We included seven patients who underwent two sessions of c-tDCS (sham followed by real). The real tDCS session was 20 min in duration and had a current intensity of 1.5 mA delivered via two surface electrodes that had dimensions of 3 × 4 cm. The cathode electrode was placed at FT7 in the center whereas the anode at Oz in the center. After each session, we performed electroencephalographic recording to count epileptiform IEDs over 30 min. We also performed magnetic resonance spectroscopy (MRS) to measure brain metabolite concentrations in the two areas of interest (EZ and occipital region), namely, gamma-aminobutyric acid (GABA), glutamate (Glx), and glutathione. We focused on a homogenous sample where the EZ and antiepileptic medications are shared among patients.

Results

Real tDCS decreased the number of epileptiform IEDs per min (from 9.46 ± 2.68 after sham tDCS to 5.37 ± 3.38 after real tDCS), p = 0.018, as compared to sham tDCS. GABA was decreased in the EZ after real c-tDCS stimulation as compared to sham tDCS (from 0.129 ± 0.019 to 0.096 ± 0.018, p = 0.02). The reduction in EZ GABA correlated with the reduction in the frequency of epileptiform IED per min (rho: 0.9, p = 0.003).

Conclusion

These results provide a window into the antiepileptic mechanisms of action of tDCS, based on local and remote changes in GABA and neural oscillatory patterning responsible for the generation of interictal epileptiform discharges.