Predictors of outcome after temporal lobectomy for the treatment of intractable epilepsy

Surgical: Resection/Destructive Procedures

Surgical resection and ablation are powerful tools in the treatment of medically refractory epilepsy. In this study, we review a broad array of resective and ablative procedures available to the epilepsy surgeon to address surgical epileptic disease. Here, we aim to provide a brief overview of a very broad category of treatments to provide a better understanding of the breadth of treatments available to providers and patients.

Seizure outcomes and associated factors in adults with unilateral mesial temporal lobe epilepsy undergoing surgery

OBJECTIVE

To analyze postoperative seizure outcomes and factors associated with unfavorable seizure control (Engel III-IV) in adults with drug-resistant unilateral mesial temporal epilepsy who underwent temporal lobectomy.

METHODS

This was an observational, longitudinal, and retrospective study. A descriptive analysis of sociodemographic, clinical, and paraclinical characteristics was performed. The incidence rate of inadequate seizure control was calculated, and a Kaplan-Meier curve was reported. Cox regression analysis was conducted to identify factors associated with unfavorable outcomes.

RESULTS

A total of 285 patients were included, 56.4% were women, and 49.12% underwent standard temporal lobectomy. Engel I were achieved in 70.87% of patients, while 6.31% experienced postsurgical complications. The estimated incidence rate of unfavorable outcomes was 3.87 cases per 100 person-years (95% CI: 3.51-4.27). Cox regression analysis indicated that patients with a temporal functional deficit zone, as identified by neuropsychological testing, had a 55.34% lower risk of an unfavorable outcome (adjusted HR: 0.4466, 95% CI: 0.236-0.854) compared to those with non-conclusive or extratemporal deficits. Concordance between video-electroencephalogram and brain magnetic resonance imaging findings in patients with right-sided lesions was also a protective factor (adjusted HR: 0.1868, 95% CI: 0.06-0.578). Discontinuation of anti-seizure treatment significantly increased the risk of an unfavorable outcome (adjusted HR: 6.718, 95% CI: 3.309-13.64).

CONCLUSION

Temporal lobe epilepsy surgery can achieve long-term seizure control in a significant proportion of patients. Neuropsychological assessment and concordance between MRI and video-EEG are essential presurgical factors for favorable outcomes. Additionally, patients should continue with antiepileptic treatment post-surgery to prevent seizure recurrence.

Epilepsy Therapies Symposium | Do We Really "Outgrow" Seizures?

Initiation and maintenance of antiseizure therapy can be relatively straightforward in most patients. Depending on epilepsy type, patients may be more or less likely to enter remission or a resolution of their epilepsy and the International League Against Epilepsy developed clinically guiding definitions in this regard. The mechanisms by which resolution or remission are achieved are poorly understood which complicates clinical decision making and risk estimate for future seizure relapse. The impetus for the maintenance of medical therapy in a seizure-free patient is also age-dependent. In children, one ought to consider the unknown effects of antiseizure medications on the developing brain while family planning, lifestyle, education, or employment are some of the issues that affect the decision making in adults. Patients who enter remission following surgical remediation of their epilepsy represent a distinct category and medication discontinuation is influenced by a number of factors. Another important consideration is comorbidities that often affect medication choices and maintenance. When formulating a management strategy, patient preferences together with careful evaluation and precise and accurate epilepsy diagnosis are key towards guiding medical or surgical management, prognostication for seizure freedom, relapse risk, options for medication discontinuation, and understanding risks and types of comorbidities.

Adding the third dimension: 3D convolutional neural network diagnosis of temporal lobe epilepsy

Convolutional neural networks (CNN) show great promise for translating decades of research on structural abnormalities in temporal lobe epilepsy into clinical practice. Three-dimensional CNNs typically outperform two-dimensional CNNs in medical imaging. Here we explore for the first time whether a three-dimensional CNN outperforms a two-dimensional CNN for identifying temporal lobe epilepsy-specific features on MRI. Using 1178 T1-weighted images (589 temporal lobe epilepsy, 589 healthy controls) from 12 surgical centres, we trained 3D and 2D CNNs for temporal lobe epilepsy versus healthy control classification, using feature visualization to identify important regions. The 3D CNN was compared to the 2D model and to a randomized model (comparison to chance). Further, we explored the effect of sample size with subsampling, examined model performance based on single-subject clinical characteristics, and tested the impact of image harmonization on model performance. Across 50 datapoints (10 runs with 5-folds each) the 3D CNN median accuracy was 86.4% (35.3% above chance) and the median F1-score was 86.1% (33.3% above chance). The 3D model yielded higher accuracy compared to the 2D model on 84% of datapoints (median 2D accuracy, 83.0%), a significant outperformance for the 3D model (binomial test: P < 0.001). This advantage of the 3D model was only apparent at the highest sample size. Saliency maps exhibited the importance of medial-ventral temporal, cerebellar, and midline subcortical regions across both models for classification. However, the 3D model had higher salience in the most important regions, the ventral-medial temporal and midline subcortical regions. Importantly, the model achieved high accuracy (82% accuracy) even in patients without MRI-identifiable hippocampal sclerosis. Finally, applying ComBat for harmonization did not improve performance. These findings highlight the value of 3D CNNs for identifying subtle structural abnormalities on MRI, especially in patients without clinically identified temporal lobe epilepsy lesions. Our findings also reveal that the advantage of 3D CNNs relies on large sample sizes for model training.

Outcomes of stereoelectroencephalography following failed epilepsy surgery in children

INTRODUCTION

Stereoelectroencephalography (SEEG) is valuable for delineating the seizure onset zone (SOZ) in pharmacoresistant epilepsy when non-invasive presurgical techniques are inconclusive. Secondary epilepsy surgery after initial failure is challenging and there is limited research on SEEG following failed epilepsy surgery in children.

OBJECTIVE

The objective of this manuscript is to present the outcomes of children who underwent SEEG after failed epilepsy surgery.

METHODS

In this single-institution retrospective study, demographics, previous surgery data, SEEG characteristics, management, and follow-up were analyzed for pediatric patients who underwent SEEG after unsuccessful epilepsy surgery between August 2016 and February 2023.

RESULTS

Fifty three patients underwent SEEG investigation during this period. Of this, 13 patients were identified who had unsuccessful initial epilepsy surgery (24%). Of these 13 patients, six patients (46%) experienced unsuccessful resective epilepsy surgery that targeted the temporal lobe, six patients (46%) underwent surgery involving the frontal lobe, and one patient (8%) had laser interstitial thermal therapy (LITT) of the right insula. SEEG in two thirds of patients (4/6) with initial failed temporal resections revealed expanded SOZ to include the insula. All 13 patients (100%) had a subsequent surgery after SEEG which was either LITT (54%) or surgical resection (46%). After the subsequent surgery, a favorable outcome (Engel class I/II) was achieved by eight patients (62%), while five patients experienced an unfavorable outcome (Engel class III/IV, 38%). Of the six patients with secondary surgical resection, four patients (67%) had favorable outcomes, while of the seven patients with LITT, two patients (29%) had favorable outcomes (Engel I/II). Average follow-up after the subsequent surgery was 37 months ±23 months.

CONCLUSION

SEEG following initial failed resective epilepsy surgery may help guide next steps at identifying residual epileptogenic cortex and is associated with favorable seizure control outcomes.

Non-lesional epilepsy does not necessarily convey poor outcomes after invasive monitoring followed by resection or thermal ablation

OBJECTIVE

We aimed to compare outcomes including seizure-free status at the last follow-up in adult patients with medically refractory focal epilepsy identified as lesional vs. non-lesional based on their magnetic resonance imaging (MRI) findings who underwent invasive evaluation followed by subsequent resection or thermal ablation (LiTT).

METHODS

We identified 88 adult patients who underwent intracranial monitoring between 2014 and 2021. Of those, 40 received resection or LiTT, and they were dichotomized based on MRI findings, as lesional (N = 28) and non-lesional (N = 12). Patient demographics, seizure characteristics, non-invasive interventions, intracranial monitoring, and surgical variables were compared between the groups. Postsurgical seizure outcome at the last follow-up was rated according to the Engel classification, and postoperative seizure freedom was determined by Kaplan-Meyer survival analysis. Statistical analyses employed Fisher's exact test to compare categorical variables, while a t-test was used for continuous variables.

RESULTS

There were no differences in baseline characteristics between groups except for more often noted PET abnormality in the lesional group (p = 0.0003). 64% of the lesional group and 57% of the non-lesional group received surgical resection or LiTT (p = 0.78). At the last follow-up, 78.5% of the patients with lesional MRI findings achieved Engel I outcomes compared to 66.7% of non-lesional patients (p = 0.45). Kaplan-Meier curves did not show a significant difference in seizure-free duration between both groups after surgical intervention (p = 0.49).

SIGNIFICANCE

In our sample, the absence of lesion on brain MRI was not associated with worse seizure outcomes in adult patients who underwent invasive intracranial monitoring followed by resection or thermal ablation.

PETSurfer-Based Brain Segmentation in Patients with Temporal Lobe Epilepsy and Associated Hippocampal Sclerosis

PURPOSE

In a homogeneous cohort of mesial temporal lobe epilepsy (mTLE) patients with hippocampal sclerosis (HS), this study utilizes the PETSurfer method to quantify and localize areas of cerebral hypometabolism.

METHODS

We selected patients from the University Clinical Center of Serbia who all underwent anterior temporal lobectomy with amygdalohippocampectomy and achieved seizure freedom (Engel class I). Our analysis involved integrating FDG-PET and MRI imaging to compare glucose metabolism between the hemispheres ipsilateral and contralateral to HS.

RESULTS

The quantitative PETSurfer approach identified significant hypometabolism restricted to the ipsilateral temporal lobe structures-the amygdala, hippocampus, temporal pole, superior and middle temporal gyrus-and the ipsilateral thalamus. The lack of significant hypometabolism in extratemporal regions indicates that these 'pure' mTLE cases may not involve the broader network disruptions typically associated with more extensive epileptic pathologies. The effect sizes ranged from small to medium, indicating variable degrees of metabolic reduction across different structures.

CONCLUSION

These findings highlight the localized nature of the epileptogenic focus in HS-related mTLE with good surgical outcome. However, the small sample size and potential cohort bias, necessitate caution in generalizing these results. Future research would benefit from a comparative approach incorporating a control group, providing a broader context for interpreting these hypometabolic patterns.

Stereo-electroencephalographic seizure localization in patients with mesial temporal sclerosis: A single center experience

Objective

Epilepsy patients with mesial temporal sclerosis (MTS) on imaging who are drug-resistant usually undergo epilepsy surgery without previous invasive evaluation. However, up to one-third of patients are not seizure-free after surgery. Prior studies have identified risk factors for surgical failure, but it is unclear if they are associated with bilateral or discordant seizure onset.

Methods

In this retrospective case series, we identified 17 epilepsy patients who had MRI-confirmed MTS but received invasive stereo-EEG (SEEG) evaluation before definitive intervention. We analyzed their presurgical risk factors in relation to SEEG seizure onset localization and MRI/SEEG concordance.

Results

SEEG ictal onset was concordant with MTS localization (i.e. seizures started only from the hippocampus with MTS) in 5 out of 13 patients with unilateral MTS (UMTS) and in 3 out of 4 patients with bilateral MTS.No statistically significant association regarding concordance of SEEG ictal onset and MTS location was found in patients with such risk factors as a history of non-mesial temporal aura, frequent focal to bilateral tonic-clonic seizures, prior viral brain infection, or family history of epilepsy. Nine out of 13 UMTS patients had resective surgery only, 5 out of 9 (56 %) have Engel class I outcome at most recent follow-up (median 46.5 months, range 22-91 months). In Engel class I cohort, the SEEG ictal onset was concordant with MTS location in 3 out of 5 patients, and 2 patients had ipsilateral temporal neocortical ictal onset.

Conclusions

Our findings suggest that patients with MTS might have discordant SEEG ictal onset (in 61.5% patients with UMTS in presented cohort), which may explain poor surgical outcome after destructive surgery in these cases.

Significance

Although no statistically significant association was found in this under-powered study, these findings could be potentially valuable for future meta-analyses.

[18F]FDG PET metabolic patterns in mesial temporal lobe epilepsy with different pathological types

OBJECTIVES

To investigate [18F]FDG PET patterns of mesial temporal lobe epilepsy (MTLE) patients with distinct pathologic types and provide possible guidance for predicting long-term prognoses of patients undergoing epilepsy surgery.

METHODS

This was a retrospective review of MTLE patients who underwent anterior temporal lobectomy between 2016 and 2021. Patients were classified as having chronic inflammation and gliosis (gliosis, n = 44), hippocampal sclerosis (HS, n = 43), or focal cortical dysplasia plus HS (FCD-HS, n = 13) based on the postoperative pathological diagnosis. Metabolic patterns and the severity of metabolic abnormalities were investigated among MTLE patients and healthy controls (HCs). The standardized uptake value (SUV), SUV ratio (SUVr), and asymmetry index (AI) of regions of interest were applied to evaluate the severity of metabolic abnormalities. Imaging processing was performed with statistical parametric mapping (SPM12).

RESULTS

With a mean follow-up of 2.8 years, the seizure freedom (Engel class IA) rates of gliosis, HS, and FCD-HS were 54.55%, 62.79%, and 69.23%, respectively. The patients in the gliosis group presented a metabolic pattern with a larger involvement of extratemporal areas, including the ipsilateral insula. SUV, SUVr, and AI in ROIs were decreased for patients in all three MTLE groups compared with those of HCs, but the differences among all three MTLE groups were not significant.

CONCLUSIONS

MTLE patients with isolated gliosis had the worst prognosis and hypometabolism in the insula, but the degree of metabolic decrease did not differ from the other two groups. Hypometabolic regions should be prioritized for [18F]FDG PET presurgical evaluation rather than [18F]FDG uptake values.

CLINICAL RELEVANCE STATEMENT

This study proposes guidance for optimizing the operation scheme in patients with refractory MTLE and emphasizes the potential of molecular neuroimaging with PET using selected tracers to predict the postsurgical histology of patients with refractory MTLE epilepsy.

KEY POINTS

• MTLE patients with gliosis had poor surgical outcomes and showed a distinct pattern of decreased metabolism in the ipsilateral insula. • In the preoperative assessment of MTLE, it is recommended to prioritize the evaluation of glucose hypometabolism areas over [18F]FDG uptake values. • The degree of glucose hypometabolism in the epileptogenic focus was not associated with the surgical outcomes of MTLE.

Clinical Correlation of Altered Molecular Signatures in Epileptic Human Hippocampus and Amygdala

Widespread alterations in the expression of various genes could contribute to the pathogenesis of epilepsy. The expression levels of various genes, including major inhibitory and excitatory receptors, ion channels, cell type-specific markers, and excitatory amino acid transporters, were assessed and compared between the human epileptic hippocampus and amygdala, and findings from autopsy controls. Moreover, the potential correlation between molecular alterations in epileptic brain tissues and the clinical characteristics of patients undergoing epilepsy surgery was evaluated. Our findings revealed significant and complex changes in the expression of several key regulatory genes in both the hippocampus and amygdala of patients with intractable epilepsy. The expression changes in various genes differed considerably between the epileptic hippocampus and amygdala. Different correlation patterns were observed between changes in gene expression and clinical characteristics, depending on whether the patients were considered as a whole or were subdivided. Altered molecular signatures in different groups of epileptic patients, defined within a given category, could be viewed as diagnostic biomarkers. Distinct patterns of molecular changes that distinguish these groups from each other appear to be associated with epilepsy-specific functional consequences.

Current state of the art of traditional and minimal invasive epilepsy surgery approaches

Introduction

Open resective surgery remains the main treatment modality for refractory epilepsy, but is often considered a last resort option due to its invasiveness.

Research question

This manuscript aims to provide an overview on traditional as well as minimally invasive surgical approaches in modern state of the art epilepsy surgery.

Materials and methods

This narrative review addresses both historical and contemporary as well as minimal invasive surgical approaches in epilepsy surgery. Peer-reviewed published articles were retrieved from PubMed and Scopus. Only articles written in English were considered for this work. A range of traditional and minimally invasive surgical approaches in epilepsy surgery were examined, and their respective advantages and disadvantages have been summarized.

Results

The following approaches and techniques are discussed: minimally invasive diagnostics in epilepsy surgery, anterior temporal lobectomy, functional temporal lobectomy, selective amygdalohippocampectomy through a transsylvian, transcortical, or subtemporal approach, insulo-opercular corticectomies compared to laser interstitial thermal therapy, radiofrequency thermocoagulation, stereotactic radiosurgery, neuromodulation, high intensity focused ultrasound, and disconnection surgery including callosotomy, hemispherotomy, and subpial transections.

Discussion and conclusion

Understanding the benefits and disadvantages of different surgical approaches and strategies in traditional and minimal invasive epilepsy surgery might improve the surgical decision tree, as not all procedures are appropriate for all patients.

Ectopic expression of neuronal adenosine kinase, a biomarker in mesial temporal lobe epilepsy without hippocampal sclerosis

AIMS

Mesial temporal lobe epilepsy without hippocampal sclerosis (no-HS MTLE) refers to those MTLE patients who have neither magnetic resonance imaging (MRI) lesions nor definite pathological evidence of hippocampal sclerosis. They usually have resistance to antiepileptic drugs, difficulties in precise seizure location and poor surgical outcomes. Adenosine is a neuroprotective neuromodulator that acts as a seizure terminator in the brain. The role of adenosine in no-HS MTLE is still unclear. Further research to explore the aetiology and pathogenesis of no-HS MTLE may help to find new therapeutic targets.

METHODS

In surgically resected hippocampal specimens, we examined the maladaptive changes of the adenosine system of patients with no-HS MTLE. In order to better understand the dysregulation of the adenosine pathway in no-HS MTLE, we developed a rat model based on the induction of focal cortical lesions through a prenatal freeze injury.

RESULTS

We first examined the adenosine system in no-HS MTLE patients who lack hippocampal neuronal loss and found ectopic expression of the astrocytic adenosine metabolising enzyme adenosine kinase (ADK) in hippocampal pyramidal neurons, as well as downregulation of neuronal A1 receptors (A1 Rs) in the hippocampus. In the no-HS MTLE model rats, the transition of ADK from neuronal expression to an adult pattern of glial expression in the hippocampus was significantly delayed.

CONCLUSIONS

Ectopic expression of neuronal ADK might be a pathological hallmark of no-HS MTLE. Maladaptive changes in adenosine metabolism might be a novel target for therapeutic intervention in no-HS MTLE.

Convolutional Neural Network Algorithm to Determine Lateralization of Seizure Onset in Patients With Epilepsy: A Proof-of-Principle Study

BACKGROUND AND OBJECTIVES

A new frontier in diagnostic radiology is the inclusion of machine-assisted support tools that facilitate the identification of subtle lesions often not visible to the human eye. Structural neuroimaging plays an essential role in the identification of lesions in patients with epilepsy, which often coincide with the seizure focus. In this study, we explored the potential for a convolutional neural network (CNN) to determine lateralization of seizure onset in patients with epilepsy using T1-weighted structural MRI scans as input.

METHODS

Using a dataset of 359 patients with temporal lobe epilepsy (TLE) from 7 surgical centers, we tested whether a CNN based on T1-weighted images could classify seizure laterality concordant with clinical team consensus. This CNN was compared with a randomized model (comparison with chance) and a hippocampal volume logistic regression (comparison with current clinically available measures). Furthermore, we leveraged a CNN feature visualization technique to identify regions used to classify patients.

RESULTS

Across 100 runs, the CNN model was concordant with clinician lateralization on average 78% (SD = 5.1%) of runs with the best-performing model achieving 89% concordance. The CNN outperformed the randomized model (average concordance of 51.7%) on 100% of runs with an average improvement of 26.2% and outperformed the hippocampal volume model (average concordance of 71.7%) on 85% of runs with an average improvement of 6.25%. Feature visualization maps revealed that in addition to the medial temporal lobe, regions in the lateral temporal lobe, cingulate, and precentral gyrus aided in classification.

DISCUSSION

These extratemporal lobe features underscore the importance of whole-brain models to highlight areas worthy of clinician scrutiny during temporal lobe epilepsy lateralization. This proof-of-concept study illustrates that a CNN applied to structural MRI data can visually aid clinician-led localization of epileptogenic zone and identify extrahippocampal regions that may require additional radiologic attention.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in patients with drug-resistant unilateral temporal lobe epilepsy, a convolutional neural network algorithm derived from T1-weighted MRI can correctly classify seizure laterality.

Multivariate analysis of seizure outcomes after resective surgery for focal epilepsy: a single-center study on 833 patients

The predictors of seizure outcomes after resective surgery for focal epilepsy, for an update on the features of good and poor outcomes, are investigated. A retrospective study of patients with focal epilepsy undergoing resective surgery from March 2011 to April 2019 was performed. There were 3 groups according to the seizure outcomes: seizure freedom, seizure improvement, and no improvement. Predictors of seizure outcomes were identified by multivariate logistic regression analysis. Of all 833 patients, 561 (67.3%) patients remained seizure-free at the last follow-up, 203 (24.4%) patients had seizure improvement, and 69 (8.3%) had no improvement. The mean follow-up duration was 5.2 years (range: 2.7 to 9.6). Predictors of better outcomes included epilepsy duration < 5 years, localized discharge, no. of antiepileptic drugs at surgery < 3, and temporal lobe resection. However, predictors of worse outcomes included intracranial hemorrhage in infancy, interictal abnormal discharge, intracranial electrode monitoring, and acute postoperative seizure. Our study suggests that resective surgery for focal epilepsy has satisfactory outcomes. Short epilepsy duration, localized discharge, and temporal lobe resection are positive predictors of seizure freedom. Patients with these predictors are intensively recommended for surgery.

MicroRNAs as Biomarkers of Surgical Outcome in Mesial Temporal Lobe Epilepsy: A Systematic Review

Mesial temporal lobe epilepsy is the most common type of epilepsy. For most patients suffering from TLE, the only treatment option is surgery. However, there is a high possibility of relapse. Invasive EEG as a method for predicting the outcome of surgical treatment is a very complex and invasive manipulation, so the search for outcome biomarkers is an urgent task. MicroRNAs as potential biomarkers of surgical outcome are the subject of this study. For this study, a systematic search for publications in databases such as PubMed, Springer, Web of Science, Scopus, ScienceDirect, and MDPI was carried out. The following keywords were used: temporal lobe epilepsy, microRNA, biomarkers, surgery, and outcome. Three microRNAs were studied as prognostic biomarkers of surgical outcome: miR-27a-3p, miR-328-3p, and miR-654-3p. According to the results of the study, only miR-654-3p showed a good ability to discriminate between patients with poor and good surgical outcomes. MiR-654-3p is involved in the following biological pathways: ATP-binding cassette drug transporters, glutamate transporter SLC7A11, and TP53. A specific target for miR-654-3p is GLRA2, the glycine receptor subunit. MicroRNAs, which are diagnostic biomarkers of TLE, and epileptogenesis, miR-134-5p, MiR-30a, miRs-143, etc., can be considered as potential biomarkers of surgical outcome, as they can be indicators of early and late relapses. These microRNAs are involved in the processes characteristic of epilepsy: oxidative stress and apoptosis. The study of miRNAs as potential predictive biomarkers of surgical outcome is an urgent task and should be continued. However, when studying miRNA expression profiles, it is important to take into account and note a number of factors, such as the type of sample under study, the time of sampling for the study, the type and duration of the disease, and the type of antiepileptic treatment. Without taking into account all these factors, it is impossible to assess the influence and involvement of miRNAs in epileptic processes.

The endoscopic anterior transmaxillary temporal pole approach for mesial temporal lobe epilepsies: a feasibility study

OBJECTIVE

In mesial temporal lobe epilepsy (MTLE), the ideal surgical approach to achieve seizure freedom and minimize morbidity is an unsolved question. Selective approaches to mesial temporal structures often result in suboptimal seizure outcomes. The authors report the results of a pilot study intended to evaluate the clinical feasibility of using an endoscopic anterior transmaxillary (eATM) approach for minimally invasive management of MTLEs.

METHODS

The study is a prospectively collected case series of four consecutive patients who underwent the eATM approach for the treatment of MTLE and were followed for a minimum of 12 months. All participants underwent an epilepsy workup and surgical care at a tertiary referral comprehensive epilepsy center and had medically refractory epilepsy. The noninvasive evaluations and intracranial recordings of these patients confirmed the presence of anatomically restricted epileptogenic zones located in the mesial temporal structures. Data on seizure freedom at 1 year, neuropsychological outcomes, diffusion tractography, and adverse events were collected and analyzed.

RESULTS

By applying the eATM technique and approaching the far anterior temporal lobe regions, mesial-basal resections of the temporal polar areas and mesial temporal structures were successfully achieved in all patients (2 with left-sided approaches, 2 with right-sided approaches). No neurological complications or neuropsychological declines were observed. All 4 patients achieved Engel class Ia outcome up to the end of the follow-up period (19, 15, 14, and 12 months). One patient developed hypoesthesia in the left V2 distribution but there were no other adverse events. The low degree of white matter injury from the eATM approach was analyzed using high-definition fiber tractography in 1 patient as a putative mechanism for preserving neuropsychological function.

CONCLUSIONS

The described series demonstrates the feasibility and potential safety profile of a novel approach for medically refractory MTLE. The study affirms the feasibility of performing efficacious mesial temporal lobe resections through an eATM approach.

Multidimensional Early Prediction Score for Drug-Resistant Epilepsy

Background and Purpose

Achieving favorable postoperative outcomes in patients with drug-resistant epilepsy (DRE) requires early referrals for preoperative examinations. The purpose of this study was to investigate the possibility of a user-friendly early DRE prediction model that is easy for nonexperts to utilize.

Methods

A two-step genotype analysis was performed, by applying 1) whole-exome sequencing (WES) to the initial test set (n=243) and 2) target sequencing to the validation set (n=311). Based on a multicenter case–control study design using the WES data set, 11 genetic and 2 clinical predictors were selected to develop the DRE risk prediction model. The early prediction scores for DRE (EPS-DRE) was calculated for each group of the selected genetic predictors (EPS-DRE_gen), clinical predictors (EPS-DRE_cln), and two types of predictor mix (EPS-DRE_mix) in both the initial test set and the validation set.

Results

The multidimensional EPS-DRE_mix of the predictor mix group provided a better match to the outcome data than did the unidimensional EPS-DRE_gen or EPS-DRE_cln. Unlike previous studies, the EPS-DRE_mix model was developed using only 11 genetic and 2 clinical predictors, but it exhibited good discrimination ability in distinguishing DRE from drug-responsive epilepsy. These results were verified using an unrelated validation set.

Conclusions

Our results suggest that EPS-DRE_mix has good performance in early DRE prediction and is a user-friendly tool that is easy to apply in real clinical trials, especially by nonexperts who do not have detailed knowledge or equipment for assessing DRE. Further studies are needed to improve the performance of the EPS-DRE_mix model.

Quantitative Analysis of Visually Reviewed Normal Scalp EEG Predicts Seizure Freedom Following Anterior Temporal Lobectomy

Objective

Anterior temporal lobectomy (ATL) is a widely performed and successful intervention for drug‐resistant temporal lobe epilepsy (TLE). However, up to one third of patients experience seizure recurrence within 1 year after ATL. Despite the extensive literature on presurgical electroencephalography (EEG) and magnetic resonance imaging (MRI) abnormalities to prognosticate seizure freedom following ATL, the value of quantitative analysis of visually reviewed normal interictal EEG in such prognostication remains unclear. In this retrospective multicenter study, we investigate whether machine learning analysis of normal interictal scalp EEG studies can inform the prediction of postoperative seizure freedom outcomes in patients who have undergone ATL.

Methods

We analyzed normal presurgical scalp EEG recordings from 41 Mayo Clinic (MC) and 23 Cleveland Clinic (CC) patients. We used an unbiased automated algorithm to extract eyes closed awake epochs from scalp EEG studies that were free of any epileptiform activity and then extracted spectral EEG features representing (a) spectral power and (b) interhemispheric spectral coherence in frequencies between 1 and 25 Hz across several brain regions. We analyzed the differences between the seizure‐free and non–seizure‐free patients and employed a Naïve Bayes classifier using multiple spectral features to predict surgery outcomes. We trained the classifier using a leave‐one‐patient‐out cross‐validation scheme within the MC data set and then tested using the out‐of‐sample CC data set. Finally, we compared the predictive performance of normal scalp EEG‐derived features against MRI abnormalities.

Results

We found that several spectral power and coherence features showed significant differences correlated with surgical outcomes and that they were most pronounced in the 10–25 Hz range. The Naïve Bayes classification based on those features predicted 1‐year seizure freedom following ATL with area under the curve (AUC) values of 0.78 and 0.76 for the MC and CC data sets, respectively. Subsequent analyses revealed that (a) interhemispheric spectral coherence features in the 10–25 Hz range provided better predictability than other combinations and (b) normal scalp EEG‐derived features provided superior and potentially distinct predictive value when compared with MRI abnormalities (>10% higher F1 score).

Significance

These results support that quantitative analysis of even a normal presurgical scalp EEG may help prognosticate seizure freedom following ATL in patients with drug‐resistant TLE. Although the mechanism for this result is not known, the scalp EEG spectral and coherence properties predicting seizure freedom may represent activity arising from the neocortex or the networks responsible for temporal lobe seizure generation within vs outside the margins of an ATL.

Surgical outcome of temporal plus epilepsy is improved by multilobar resection

OBJECTIVE

Temporal plus epilepsy (TPE) represents a rare type of epilepsy characterized by a complex epileptogenic zone including the temporal lobe and the close neighboring structures. We investigated whether the complete resection of temporal plus epileptogenic zone as defined through stereoelectroencephalography (SEEG) might improve seizure outcome in 38 patients with TPE.

METHODS

Inclusion criteria were as follows: epilepsy surgery performed between January 1990 and December 2001, SEEG defining a temporal plus epileptogenic zone, unilobar temporal operations ("temporal lobe epilepsy [TLE] surgery") or multilobar interventions including the temporal lobe ("TPE surgery"), magnetic resonance imaging either normal or showing signs of hippocampal sclerosis, and postoperative follow-up of at least 12 months. For each assessment of postoperative seizure outcome, at 1, 2, 5, and 10 years, we carried out descriptive analysis and classical tests of hypothesis, namely, Pearson χ² test or Fisher exact test of independence on tables of frequency for each categorical variable of interest and Student t-test for each continuous variable of interest, when appropriate.

RESULTS

Twenty-one patients underwent TPE surgery and 17 underwent TLE surgery with a follow-up of 12.4 ± 8.16 years. In the multivariate models, there was a significant effect of the time from surgery on Engel Class IA versus IB-IV outcome, with a steadily worsening trend from 5-year follow-up onward. TPE surgery was associated with better results than TLE surgery.

SIGNIFICANCE

This study suggests that surgical outcome in patients with TPE can be improved by a tailored, multilobar resection and confirms that SEEG is mandatory when a TPE is suspected.

Long-term seizure and psychiatric outcomes following laser ablation of mesial temporal structures

OBJECTIVE

Postsurgical seizure outcome following laser interstitial thermal therapy (LiTT) for the management of drug-resistant mesial temporal lobe epilepsy (MTLE) has been limited to 2 years. Furthermore, its impact on presurgical mood and anxiety disorders has not been investigated. The objectives of this study were (1) to identify seizure outcome changes over a period ranging from 18 to 81 months; (2) to investigate the seizure-free rate in the last follow-up year; (3) to identify the variables associated with seizure freedom; and (4) to identify the impact of LiTT on presurgical mood and anxiety disorders.

METHODS

Medical records of all patients who underwent LiTT for MTLE from 2013 to 2019 at the University of Miami Comprehensive Epilepsy Center were retrospectively reviewed. Demographic, epilepsy-related, cognitive, psychiatric, and LiTT-related data were compared between seizure-free (Engel Class I) and non-seizure-free (Engel Class II + III + IV) patients. Statistical analyses included univariate and multivariate stepwise logistic regression analyses.

RESULTS

Forty-eight patients (mean age = 43 ± 14.2 years, range = 21-78) were followed for a mean period of 50 ± 20.7 months (range = 18-81); 29 (60.4%) achieved an Engel Class I outcome, whereas 11 (22.9%) had one to three seizures/year. Seizure-freedom rate decreased from 77.8% to 50% among patients with 24- and >61-month follow-up periods, respectively. In the last follow-up year, 83% of all patients were seizure-free. Seizure freedom was associated with having mesial temporal sclerosis (MTS), no presurgical focal to bilateral tonic-clonic seizures, and no psychopathology in the last follow-up year. Presurgical mood and/or anxiety disorder were identified in 30 patients (62.5%) and remitted after LiTT in 19 (62%).

SIGNIFICANCE

LiTT appears to be a safe and effective surgical option for treatment-resistant MTLE, particularly among patients with MTS. Remission of presurgical mood and anxiety disorders can also result from LiTT.

Comparative Effectiveness of Stereotactic Electroencephalography Versus Subdural Grids in Epilepsy Surgery

OBJECTIVE

The aim was to compare the outcomes of subdural electrode (SDE) implantations versus stereotactic electroencephalography (SEEG), the 2 predominant methods of intracranial electroencephalography (iEEG) performed in difficult-to-localize drug-resistant focal epilepsy.

METHODS

The Surgical Therapies Commission of the International League Against Epilepsy created an international registry of iEEG patients implanted between 2005 and 2019 with ≥1 year of follow-up. We used propensity score matching to control exposure selection bias and generate comparable cohorts. Study endpoints were: (1) likelihood of resection after iEEG; (2) seizure freedom at last follow-up; and (3) complications (composite of postoperative infection, symptomatic intracranial hemorrhage, or permanent neurological deficit).

RESULTS

Ten study sites from 7 countries and 3 continents contributed 2,012 patients, including 1,468 (73%) eligible for analysis (526 SDE and 942 SEEG), of whom 988 (67%) underwent subsequent resection. Propensity score matching improved covariate balance between exposure groups for all analyses. Propensity-matched patients who underwent SDE had higher odds of subsequent resective surgery (odds ratio [OR] = 1.4, 95% confidence interval [CI] 1.05, 1.84) and higher odds of complications (OR = 2.24, 95% CI 1.34, 3.74; unadjusted: 9.6% after SDE vs 3.3% after SEEG). Odds of seizure freedom in propensity-matched resected patients were 1.66 times higher (95% CI 1.21, 2.26) for SEEG compared with SDE (unadjusted: 55% seizure free after SEEG-guided resections vs 41% after SDE).

INTERPRETATION

In comparison to SEEG, SDE evaluations are more likely to lead to brain surgery in patients with drug-resistant epilepsy but have more surgical complications and lower probability of seizure freedom. This comparative-effectiveness study provides the highest feasible evidence level to guide decisions on iEEG. ANN NEUROL 2021;90:927-939.

Focal to bilateral motor seizures in temporal lobe epilepsy during video-EEG monitoring: effects on surgical outcome

The aim of this study was to determine whether the occurrence of focal to bilateral motor seizures in the course of partial drug withdrawal during video-EEG monitoring (FTBMS-M) had a predictive value for seizure recurrence in surgically treated patients with mesial temporal lobe epilepsy (MTLE). We analyzed the outcomes of 59 patients who underwent temporal lobe resection at 12 month postoperative follow up. In total, 48 out of 59 patients were rendered seizure free (81.4%). We analyzed seizure recurrence after surgery with reference to: (i) occurrence of seizures after partial drug withdrawal during video-EEG monitoring (FTBMS-M); (ii) history of secondarily generalized seizures during antiepileptic drug treatment prior to presurgical evaluation (FTBMS-H) and (iii) other possible confounding factors (sex, age, epilepsy duration, side of surgery, presence of hippocampal sclerosis, and history of febrile seizures). We found no differences in the frequency of seizure recurrences between patients with FTBMS-M and patients without FTBMS-M (4/20 vs. 7/39; p = 0.848). Conversely, the frequency of seizure recurrence was significantly higher among the patients with FTBMS-H than among the patients without FTBMS-H (7/20 vs. 4/39; p = 0.021). The predictive value of FTBMS-H for postoperative seizure recurrence was confirmed in logistic regression analysis. We found a statistically significant influence of FTBMS-H on poor outcome after surgery, but not of FTBMS-M or other confounding variables, which suggests that withdrawal seizures do not affect postsurgical seizure control.

Dynamical Analysis of Seizure in Epileptic Brain: a Dynamic Phase-Amplitude Coupling Estimation Approach

Cross-frequency coupling in general and phase-amplitude coupling (PAC) as a particular form of it, provides an opportunity to investigate the complex interactions between neural oscillations in the human brain and neurological disorders such as epilepsy. Using PAC detection methods on temporal sliding windows, we developed a map of dynamic PAC evolution to investigate the spatiotemporal changes occurring during ictal transitions in a patient with intractable mesial temporal lobe epilepsy. The map is built by computing the modulation index between the amplitude of high frequency oscillations and the phase of lower frequency rhythms from the intracranial stereoelectroencephalography recordings during seizure. Our preliminary results show early abnormal PAC changes occurring in the preictal state prior to the occurrence of clinical or visible electrographic seizure onset, and suggest that dynamic PAC measures may serve as a potential clinical technique for analyzing seizure dynamics.Clinical Relevance-Application of a dynamic temporal PAC map as a new tool may provide novel insights into the neurophysiology of epileptic seizure activity and its spatio-temporal dynamics.

Improving the prediction of epilepsy surgery outcomes using basic scalp EEG findings

OBJECTIVE

This study aims to evaluate the role of scalp electroencephalography (EEG; ictal and interictal patterns) in predicting resective epilepsy surgery outcomes. We use the data to further develop a nomogram to predict seizure freedom.

METHODS

We retrospectively reviewed the scalp EEG findings and clinical data of patients who underwent surgical resection at three epilepsy centers. Using both EEG and clinical variables categorized into 13 isolated candidate predictors and 6 interaction terms, we built a multivariable Cox proportional hazards model to predict seizure freedom 2 years after surgery. Harrell's step-down procedure was used to sequentially eliminate the least-informative variables from the model until the change in the concordance index (c-index) with variable removal was less than 0.01. We created a separate model using only clinical variables. Discrimination of the two models was compared to evaluate the role of scalp EEG in seizure-freedom prediction.

RESULTS

Four hundred seventy patient records were analyzed. Following internal validation, the full Clinical + EEG model achieved an optimism-corrected c-index of 0.65, whereas the c-index of the model without EEG data was 0.59. The presence of focal to bilateral tonic-clonic seizures (FBTCS), high preoperative seizure frequency, absence of hippocampal sclerosis, and presence of nonlocalizable seizures predicted worse outcome. The presence of FBTCS had the largest impact for predicting outcome. The analysis of the models' interactions showed that in patients with unilateral interictal epileptiform discharges (IEDs), temporal lobe surgery cases had a better outcome. In cases with bilateral IEDs, abnormal magnetic resonance imaging (MRI) predicted worse outcomes, and in cases without IEDs, patients with extratemporal epilepsy and abnormal MRI had better outcomes.

SIGNIFICANCE

This study highlights the value of scalp EEG, particularly the significance of IEDs, in predicting surgical outcome. The nomogram delivers an individualized prediction of postoperative outcome, and provides a unique assessment of the relationship between the outcome and preoperative findings.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

SIGNIFICANCE

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

Resective temporal lobe surgery in refractory temporal lobe epilepsy: prognostic factors of postoperative seizure outcome

OBJECTIVE

Temporal lobe epilepsy (TLE) is one of the most common forms of epilepsy. In approximately 30% of patients, seizures are refractory to drug treatment. Despite the achievements of modern presurgical evaluation in recent years, the presurgical prediction of seizure outcome remains difficult. The aim of this study was to evaluate the seizure outcome in patients with drug-refractory TLE who underwent resective temporal lobe surgery (rTLS) and to determine features associated with unfavorable postsurgical seizure outcome.

METHODS

Patients with medically refractory TLE who underwent rTLS between 2012 and 2017 were reviewed from the prospectively collected epilepsy surgery database. A retrospective analysis of clinical, radiological, neuropsychological, histopathological, and perioperative findings of 161 patients was performed. The patients were divided into two groups according to seizure outcome (group I, International League Against Epilepsy [ILAE] class 1; group II, ILAE class ≥ 2). For identification of independent risk factors for unfavorable postoperative seizure outcome (ILAE class ≥ 2), a multivariate logistic regression analysis was performed.

RESULTS

Seizure freedom (ILAE class 1) was achieved in 121 patients (75.2%). The neuropsychological evaluation demonstrated that losses in cognitive performance were more pronounced in verbal memory after resections in the left temporal lobe and in nonverbal memory after right-sided resections, whereas attention improved after surgery. Overall, postoperative visual field deficits (VFDs) were common and occurred in 51% of patients. There was no statistically significant difference in the incidence of VFD in patients with selective surgical procedures compared to the patients with nonselective procedures. The lack of MRI lesions and placement of depth electrodes were preoperatively identified as predictors for unfavorable seizure outcome.

CONCLUSIONS

rTLS is an effective treatment method in patients with refractory TLE. However, patients with a lack of MRI lesions and placement of depth electrodes prior to rTLS are at higher risk for an unfavorable postsurgical seizure outcome.

Subtraction ictal SPECT co-registered to MRI (SISCOM) patterns in children with temporal lobe epilepsy

OBJECTIVE

We evaluated SISCOM patterns and their relationship with surgical outcome in children with temporal lobe epilepsy (TLE) who had undergone a temporal lobe surgery.

METHODS

This was an observational study evaluating SISCOM patterns in 40 children with TLE. We classified SISCOM patterns into 4 categories; (i) unilateral anteromesial and/or anterolateral temporal pattern; (ii) unilateral anteromesial and/or anterolateral temporal plus posterior extension pattern; (iii) bilateral anteromesial and/or anterolateral temporal pattern; and (iv) atypical pattern. Determinants of SISCOM pattern and correlation between postoperative outcomes and SISCOM patterns were evaluated.

RESULTS

Pattern (i), (ii), (iii), and (iv) were identified in 10 (25%), 14 (35%), 0 (0%), and 16 (40%) patients, respectively. There was no significant correlation between patterns and postoperative outcomes. SISCOM patterns significantly associated with the presence of hippocampal sclerosis and type of focal cortical dysplasia (p-value = 0.048 and 0.036, respectively). Patients with HS had 5 times the odds of having unilateral temporal pattern, compared to patients with other neuropathology (OR = 5, 95% CI 0.92 to 27.08). Patients with FCD type 2 had 9.71 times the odds of having atypical pattern, compared to patients with other types of FCD (OR = 9.71, 95% CI 0.92 to 103.04). Lobar concordance of SISCOM and ictal and interictal scalp EEG significantly correlated with postoperative outcomes (p-value = 0.018 and 0.013, respectively).

CONCLUSION

Three SISCOM patterns were seen. Patients with HS had increased odds of having unilateral temporal pattern while patients with FCD type 2 had increased odds of having atypical pattern. However, there was no significant correlation between SISCOM patterns and postoperative outcomes. Lobar concordance of SISCOM and ictal and interictal scalp EEG significantly correlated with postoperative outcome.

SIGNIFICANCE

This study shows that the distribution of SISCOM patterns and their relationship with postoperative outcomes in children with TLE are different from adult population. Besides, SISCOM may add only limited diagnostic and prognostic information in children with drug-resistant TLE undergoing epilepsy surgery. Further evaluation to identify patient populations that may benefit from SISCOM is desirable.

Patient specific prediction of temporal lobe epilepsy surgical outcomes

OBJECTIVE

Drug-resistant temporal lobe epilepsy (TLE) is the most common type of epilepsy for which patients undergo surgery. Despite the best clinical judgment and currently available prediction algorithms, surgical outcomes remain variable. We aimed to build and to evaluate the performance of multidimensional Bayesian network classifiers (MBCs), a type of probabilistic graphical model, at predicting probability of seizure freedom after TLE surgery.

METHODS

Clinical, neurophysiological, and imaging variables were collected from 231 TLE patients who underwent surgery at the University of California, San Francisco (UCSF) or the Montreal Neurological Institute (MNI) over a 15-year period. Postsurgical Engel outcomes at year 1 (Y1), Y2, and Y5 were analyzed as primary end points. We trained an MBC model on combined data sets from both institutions. Bootstrap bias corrected cross-validation (BBC-CV) was used to evaluate the performance of the models.

RESULTS

The MBC was compared with logistic regression and Cox proportional hazards according to the area under the receiver-operating characteristic curve (AUC). The MBC achieved an AUC of 0.67 at Y1, 0.72 at Y2, and 0.67 at Y5, which indicates modest performance yet superior to what has been reported in the state-of-the-art studies to date.

SIGNIFICANCE

The MBC can more precisely encode probabilistic relationships between predictors and class variables (Engel outcomes), achieving promising experimental results compared to other well-known statistical methods. Multisite application of the MBC could further optimize its classification accuracy with prospective data sets. Online access to the MBC is provided, paving the way for its use as an adjunct clinical tool in aiding pre-operative TLE surgical counseling.

Does etiology really matter for epilepsy surgery outcome?

Multiple factors influence the outcomes of epilepsy surgery. Prognostic indicators varying from clinical characteristics, imaging findings, ictal, and interictal electrophysiological activity have been linked to surgical outcomes. In this review, we focus on the relatively under‐studied role of the underlying epilepsy histopathology in driving post‐surgical outcomes, specifically focusing on the broad categories of seizure outcomes and cognitive outcomes. For each of these two outcomes of interest, we answer two questions: 1)‐ does etiology matter? and 2)‐ how could it matter? The goal is to review the existing literature on the relationship between etiology and surgical outcomes to provide the best possible judgment as to whether a causal relationship exists between histopathology and the ultimate surgical outcome as an initial step. Then, we delve into the possible mechanisms via which such relationships can be explained. We conclude with a call to action to the epilepsy surgery and histopathology research community to push the mechanistic understanding of the pathology‐outcome interaction and identify actionable knowledge and biomarkers that could inform patient care in a timely fashion.

In this review, we focus on the relatively under‐studied role of the underlying epilepsy histopathology in driving post‐surgical outcomes, specifically focusing on the broad categories of seizure outcomes and cognitive outcomes. For each of these two outcomes of interest, we answer two questions: (1) does etiology matter? and (2) how could it matter? We then delve into the mechanisms of these answers.

Intracranial recordings for non-lesional mesiotemporal epilepsy? Almost always, but not quite always

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The majority of patients with non-lesional mesial TLE needs intracranial recordings.

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This rule should not be rigid and there are some exceptions. Decisions should be individualized.

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For bilateral mesial temporal lobe epilepsy, chronic ECoG with RNS may be preferable over “traditional” short-term intracranial recording.

Granule cell dispersion is associated with hippocampal neuronal cell loss, initial precipitating injury, and other clinical features in mesial temporal lobe epilepsy and hippocampal sclerosis

PURPOSE

To characterize a 10-year series of patients with mesial temporal lobe epilepsy (MTLE) and unilateral hippocampal sclerosis (HS) and determine the histopathological characteristic of the association between granule cell dispersion (GCD) and hippocampal neuronal loss.

METHODS

The study included 108 MTLE/HS patients. Histopathological analyses were performed in NeuN-stained hippocampal sections for HS pattern, neuronal density, dentate gyrus (DG) pathology, and granule cell layer width. Statistical tests investigated the association between DG pathologies and HS patterns, as well as the correlation of DG width with total hippocampal and subfield-specific neuronal densities.

RESULTS

Fifty-six patients (51.9%) presented right HS. All the four ILAE HS patterns were represented (90 Type 1, 11 Type 2, 2 Type 3, and 5 no-HS). Sixty-seven patients (62.0%) presented GCD, 39 (36.1%) normal DG, and 2 (1.9%) narrow DG. GCD was associated with initial precipitating injury, higher numbers of monthly focal seizures and lifetime bilateral tonic-clonic seizures, longer epilepsy duration, and older age at surgery. GCD was prevalent in all HS patterns, except for Type 2 (81.8% normal versus 18.2% GCD, p = 0.005). GCD was associated with total hippocampal and subfield-specific neuronal loss, except for CA1. DG width correlated with total hippocampal (r = -0.201, p = 0.037) and CA4 neuronal densities (r = -0.299, p = 0.002). Patients with HS Type 1 had better surgical outcomes, with 51 (61.4%) seizure-free in the first year post-surgery.

CONCLUSIONS

This study confirmed that seizure control in MTLE/HS patients submitted to surgical treatment is comparable worldwide. Moreover, histopathological analyses showed an association between GCD and hippocampal neuronal loss, especially in the CA4 subfield.

Resective epilepsy surgery in patients aged 50years and older - a retrospective study regarding seizure outcome, memory performance, and psychopathology

PURPOSE

To assess clinical and demographic characteristics in two cohorts of elderly patients with drug-resistant focal epilepsy, undergoing resective epilepsy surgery (RES). Further, to determine seizure, neuropsychological, and mental health outcomes after RES and evaluate possible influencing factors.

METHODS

Consecutive patients aged ≥50 years with temporal lobe epilepsy (TLE) who underwent curative RES in the Hamburg epilepsy surgery program (2004-2017) were identified. Data were retrospectively analyzed. Seizure outcome was classified according to ILAE and Engel outcome scales in patients with first-time surgeries and with reoperations. Previously reported predictors of the seizure outcome were evaluated using regression analyses. Changes in verbal memory were assessed for patients with complete pre- and postoperative datasets (n=30) using repeated-measures analysis of variance. For evaluation of possible predictors of psychopathologic changes after RES a regression analysis was conducted.

RESULTS

Fifty-one elderly patients underwent RES of the temporal lobe, including twelve aged ≥60 years, and five with reoperations. After one year, 65% of the patients with first-time surgeries were seizure free and 91% had a favorable outcome. At last follow-up, 49% were seizure free since surgery. Three reoperated patients had an Engel I outcome. Seizure outcome was not dependent on age at surgery, duration of epilepsy, or other evaluated variables. There was no significant decline in the memory performance after surgery. Significant improvements in mental health were found.

CONCLUSION

RES for drug-resistant TLE is safe, effective, and improves mental health also in patients aged ≥ 50 years. Thus, it should be evaluated as the treatment of choice also in this age group.

Consanguinity in patients with mesial temporal lobe epilepsy due to hippocampal sclerosis in a Saudi population

Objectives:

To investigate if there is an association between consanguinity and hippocampal sclerosis (HS) in the Saudi population.

Methods:

A retrospective case-control study was conducted by assessing the prevalence of consanguinity in patients with pathologically proven HS, who underwent epilepsy surgery at King Faisal Specialist Hospital and Research Center, Jeddah, Saudi Arabia, between January 2004 and December 2015. We reviewed the medical records to extract data, which included; age, gender, duration of epilepsy, history of febrile seizure, family history of epilepsy in a first or second-degree relative, and pathology reports.

Results:

A total of 120 patients, out of which 40 patients (65% male) having mesial temporal lobe epilepsy due to HS, and 80 controls (56% male) with cryptogenic epilepsy, were identified. Twenty-two patients (53.5%) in the HS group had a history of consanguinity. In the control group, 30 patients (37.5%) had a history of consanguinity. The odds ratio was 2.04 (95% confidence interval = 0.94 - 4.4, p = 0.052). A family history of epilepsy was found in 28% of the patients with HS and 32.5% cryptogenic epilepsy. Only 8 patients (19.5%) with HS reported a history of febrile seizure.

Conclusion:

Our retrospective case-control study suggests that consanguinity might increase the likelihood of developing HS.

Non-lesional mesial temporal lobe epilepsy requires bilateral invasive evaluation

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

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

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

Purpose

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

Methods

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

Results

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

Conclusion

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

Consequences of mesial temporal sparing temporal lobe surgery in medically refractory epilepsy

OBJECTIVE

We compared long-term seizure outcome, neuropsychological outcome, and occupational outcome of anterior temporal lobectomy (ATL) with and without sparing of mesial structures to determine whether mesial sparing temporal lobectomy prevents memory decline and thus disability, with acceptable seizure outcome.

METHODS

We studied patients (n = 21) and controls (n = 21) with no evidence of mesial temporal sclerosis (MTS) on MRI who had surgery to treat drug-resistant epilepsy. Demographic and pre- and postsurgical clinical characteristics were compared. Patients had neuropsychological assessment before and after surgery. Neuropsychological analyses were limited to patients with left-sided surgery and available data (n = 14 in each group) as they were at risk of verbal memory impairment. The California Verbal Learning Test II (CVLT-II) (sum of trials 1-5, delayed free recall) and the Logical Memory subtest of the Wechsler Memory Scale III or IV (WMS-III or WMS-IV) (learning and delayed recall of prose passages) were used to assess verbal episodic learning and memory. Seizure and occupational outcomes were assessed.

RESULTS

The chance of attaining seizure freedom was similar in the two groups, so sparing mesial temporal structures did not lessen the chance of stopping seizures. Sparing mesial temporal structures mitigated the extent of postoperative verbal memory impairment, though some of these individuals suffered decline as a consequence of surgery. Occupational outcome was similar in both groups.

SIGNIFICANCE

Mesial temporal sparing resections provide a similar seizure outcome as ATL, while producing a better memory outcome. Anterior temporal lobectomy including mesial structure resection did not increase the risk of postoperative disability.

Temporal lobe epilepsy surgery in children and adults: A multicenter study

OBJECTIVE

To assess seizure and cognitive outcomes and their predictors in children (<16 years at surgery) and adults undergoing temporal lobe epilepsy (TLE) surgery in eight Italian centers.

METHODS

This is a retrospective multicenter study. We performed a descriptive analysis and subsequently carried out multivariable mixed-effect models corrected for multiple comparisons.

RESULTS

We analyzed data from 511 patients (114 children) and observed significant differences in several clinical features between adults and children. The possibility of achieving Engel class IA outcome and discontinuing antiepileptic drugs (AEDs) at last follow-up (FU) was significantly higher in children (P = .006 and < .0001). However, percentages of children and adults in Engel class I at last FU (mean ± SD, 45.9 ± 17 months in children; 45.9 ± 20.6 months in adults) did not differ significantly. We identified different predictors of seizure outcome in children vs adults and at short- vs long-term FU. The only variables consistently associated with class I outcome over time were postoperative electroencephalography (EEG) in adults (abnormal, improved,odds ratio [OR] = 0.414, P = .023, Q = 0.046 vs normal, at 2-year FU and abnormal, improved, OR = 0.301, P = .001, Q = 0.002 vs normal, at last FU) and the completeness of resection of temporal magnetic resonance (MR) abnormalities other than hippocampal sclerosis in children (OR = 7.93, P = .001, Q = 0.003, at 2-year FU and OR = 45.03, P < .0001, Q < 0.0001, at last FU). Cognitive outcome was best predicted by preoperative performances in either age group.

SIGNIFICANCE

Clinical differences between adult and pediatric patients undergoing TLE surgery are reflected in differences in long-term outcomes and predictors of failures. Children are more likely to achieve sustained seizure freedom and withdraw AEDs after TLE surgery. Earlier referral should be encouraged as it can improve surgical outcome.

Ictal Onset Signatures Predict Favorable Outcomes of Laser Thermal Ablation for Mesial Temporal Lobe Epilepsy

Background: Laser interstitial thermal therapy (LiTT) has emerged as a minimally invasive option for surgical treatment of refractory epilepsy. However, LiTT of the mesial temporal (MT) structures is still inferior to anterior temporal lobectomy (ATL) in terms of postoperative outcome. In this pilot study, we identify intracranial EEG (iEEG) biomarkers that distinguish patients with favorable outcome from those with poor outcome after MT LiTT.

Methods: We performed a retrospective review of 9 adult refractory epilepsy patients who underwent stereotactic electroencephalography (sEEG) followed by LiTT of MT structures. Their iEEG was retrospectively reviewed in both time and frequency domains.

Results: In the time-domain, the presence of sustained 14–30 Hz in MT electrodes coupled with its absence from extra-MT electrodes at ictal onset was highly correlated with favorable outcomes, whereas the appearance of sustained 14–30 Hz or >30 Hz activity in extra-MT sites was negatively correlated to favorable outcomes. In the frequency domain, a declining spectral phase, beginning at the high frequency range (>14 Hz) at ictal onset and following a smooth progressive decline toward lower frequencies as the seizure further evolved, was positively correlated with improved outcomes. On the contrary, low frequency (<14 Hz) patterns and “crescendo-decrescendo” patterns with an early increasing frequency component at ictal onset that reaches the high-beta and low gamma bands before decreasing smoothly, were both correlated with poor surgical outcomes.

Conclusions: This pilot study demonstrates the first evidence that iEEG analysis can provide neurophysiological markers for successful MT LiTT and therefore we strongly advocate for systematic sEEG investigations before offering MT LiTT to TLE and MTLE patients.

Resective epilepsy surgery: assessment of randomized controlled trials

Epilepsy is the most common form of chronic neurologic disease. Here, we review the available randomized controlled trials (RCTs) that examined the efficacy of resective epilepsy surgery in select patients suffering from medically intractable epilepsy (defined as persistent epilepsy despite two or more antiepileptic drugs [AEDs]). Three RCTs (two adult RCTs and one pediatric RCT) consistently supported the efficacy of resective surgery as treatment for epilepsy with semiology localized to the mesial temporal lobe. In these studies, 58-100% of the patients who underwent resective surgery achieved seizure freedom, in comparison to 0-13% of medically treated patients. In another RCT, the likelihood of seizure freedom after resective surgery was independent of the surgical approach (transSylvian [64%] versus subtemporal [62%]). Two other RCTs demonstrated that hippocampal resection is essential to optimize seizure control. But, no significant gain in seizure control was achieved beyond removing 2.5 cm of the hippocampus. Across RCTs, minor complications (deficit lasting < 3 months) and major complications (deficit > 3 months) ranged 2-5% and 5-11% respectively. However, nonincapacitating superior subquadrantic visual-field defects (not typically considered a minor or major complication) were noted in up to 55% of the surgical cohort. The available RCTs provide compelling support for resective surgery as a treatment for mesial temporal lobe epilepsy and offer insights toward optimal surgical strategy.

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

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

Subtemporal selective amygdalohippocampectomy in patients with mesial temporal lobe epilepsy: Systematic review of seizure and neuropsychological outcomes

In addition to standard anterior temporal lobectomy (ATL), subtemporal selective amygdalohippocampectomy (sSAH) is also a common technique for the treatment of medically intractable mesial temporal lobe epilepsy (MTLE). We conducted a systematic literature review to determine the seizure and neuropsychological outcomes in patients with MTLE who underwent sSAH. We searched PubMed and Embase using Medical Subject Headings and keywords related to sSAH, seizure outcome, and neuropsychological outcome. Titles, abstracts, and full-texts were screened in light of inclusion and exclusion criteria that were established a priori. Potential papers were reviewed by 3 reviewers, who reached a consensus on the final papers to be included. Literature review identified 208 abstracts from which a total of 29 full-text articles were reviewed. Six studies containing data from 4 countries (3 continents) met our inclusion criteria. The seizure-free rates at 12 months after sSAH ranged from 59.1% to 61.5% in 4 studies. Four studies showed that seizure-free rates ranged from 56% to 82.6% at 24 months after surgery. Six studies evaluated the neuropsychological changes of patients with MTLE after sSAH, including intelligence, verbal memory, nonverbal memory, language function, and so on. In terms of neuropsychological outcomes, there are some differences among the 6 studies. Taken together, sSAH can provide a considerable rate of seizure freedom. In addition, the neuropsychological outcomes of patients who underwent sSAH were slightly different among 6 studies. Therefore, large-scale case series or randomized controlled trials (RCTs) are needed to clarify the advantages and disadvantages of the sSAH.

Trends in lobectomy/amygdalohippocampectomy over time and the impact of hospital surgical volume on hospitalization outcomes: A population-based study

OBJECTIVE

Despite national guidelines supporting surgical referral in drug-resistant epilepsy, it is hypothesized that surgery is underutilized. We investigated the volumes of lobectomy/amygdalohippocampectomy surgeries over time and examined differences in outcomes between (1) high-volume (HV), middle-volume (MV), and low-volume (LV) hospitals and (2) Level 4 Centers versus non-Level 4 Centers.

METHODS

The 2003-2014 National Inpatient Sample (the largest all-payer hospitalization database, representative of the US population) was utilized. Epilepsy was identified using a previously validated International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) case definition and surgeries using ICD-9-CM procedure codes. A hospital was considered a Level 4 Center if it performed intracranial electroencephalographic (EEG) monitoring. Tumor surgeries were excluded. Linear regression was used to perform trend tests. Weighted multivariate logistic regression was used to summarize association of surgery with outcomes.

RESULTS

A total of 4,487 lobectomy/amygdalohippocampectomy surgeries were performed in children and adults with epilepsy. Lobectomy/amygdalohippocampectomy surgeries significantly decreased over time (slope: -0.24, P < .001). This declining surgical trend was greater for all resective/disconnective surgery (slope: -0.45, P < .001), and greatest when compared to all types of epilepsy surgery, for example, resection/disconnection/radiosurgery/laser interstitial thermal therapy/vagus nerve stimulation/deep brain stimulation/responsive neurostimulation/intracranial EEG (slope: -0.95, P < .001). LV compared to HV hospitals had higher odds of transfer to other facilities (13.60% vs 4.24%, odds ratio [OR] = 2.76, 95% confidence interval [CI] = 1.11-6.82). LV hospitals had higher odds of surgical complications versus MV (12.69% vs 6.80%, OR = 2.20, 95% CI = 1.01-5.09). HV hospitals incurred the least total charges. There were no differences in discharge status, adverse events, length of stay, or cost between Level 4 Centers versus non-Level 4 Centers.

SIGNIFICANCE

Lobectomies/amygdalohippocampectomies are decreasing over time, suggesting ongoing underutilization. LV centers are associated with greater complication and transfer rates. Future studies are required to understand the reason for worse outcomes in LV centers and to determine whether a minimum number of surgeries must be performed to meet necessary standards.

Intrinsic brain activity changes in temporal lobe epilepsy patients revealed by regional homogeneity analysis

PURPOSE

Temporal lobe epilepsy is increasingly being recognized as a disorder associated with brain networks extending outside the seizure onset zone. In the current study, we aim to clarify regional functional changes using a regional homogeneity method.

METHODS

We retrospectively included resting-state fMRI data from 14 left and 18 right temporal lobe epilepsy patients. Data from the control group were acquired from an open dataset. Regional homogeneity was calculated, and a two-sample t-test was performed to compare the left and right temporal lobe epilepsy groups with the control group.

RESULTS

Compared with the healthy control group, the left temporal lobe epilepsy group showed increased regional homogeneity in the left anterior and middle cingulate cortex, and putamen; right inferior frontal gyrus; bilateral temporal lobe and precentral gyrus and decreased regional homogeneity in the left superior parietal gyrus, cuneus and inferior occipital gyrus; right inferior parietal lobule and bilateral rectus. The right temporal lobe epilepsy group showed increased regional homogeneity in the left middle cingulate cortex, precuneus, precentral and postcentral gyrus; right insula and bilateral temporal lobe and decreased regional homogeneity in the left cuneus and superior occipital gyrus; right supramarginal gyrus, fusiform gyrus, lingual gyrus, inferior occipital gyrus and putamen; and the bilateral rectus.

CONCLUSION

Regional homogeneity measurements provide evidence supporting that temporal lobe epilepsy is a complex network disease. Functional disruption of temporal lobe epilepsy at the brain region level was revealed, which may provide novel insights for any potential diagnostic and therapeutic approaches.

Focal-to-bilateral motor seizures in temporal lobe epilepsy during video-EEG monitoring: effects on surgical outcome

The aim of this study was to determine whether the occurrence of focal-to-bilateral motor seizures in the course of partial drug withdrawal during video-EEG monitoring (FTBMS-M) had a predictive value for seizure recurrence in surgically treated patients with mesial temporal lobe epilepsy (MTLE). We analyzed the outcomes of 59 patients who underwent temporal lobe resection and had postoperative follow-up from 6 to 58 months. In total, 48 out of 59 patients were rendered seizure free (81.4%). We analyzed seizure recurrence after surgery with reference to: (i) occurrence of seizures after partial drug withdrawal during video-EEG monitoring (FTBMS-M); (ii) history of secondarily generalized seizures during antiepileptic drug treatment prior to presurgical evaluation (FTBMS-H) and (iii) other possible confounding factors (sex, age, epilepsy duration, side of surgery, presence of hippocampal sclerosis, and history of febrile seizures). We found no differences in the frequency of seizure recurrences between patients with FTBMS-M and patients without FTBMS-M (4/20 vs. 7/39; p = 0.848). Conversely, the frequency of seizure recurrence was significantly higher among the patients with FTBMS-H than among the patients without FTBMS-H (7/20 vs. 4/39; p = 0.021). The predictive value of FTBMS-H for postoperative seizure recurrence was confirmed in logistic regression analysis. We found a statistically significant influence of FTBMS-H on poor outcome after surgery, but not of FTBMS-M or other confounding variables, which suggests that withdrawal seizures do not affect post-surgical seizure control.

Surgical treatment in children with intractable epilepsy after viral encephalitis

PURPOSE

To investigate the surgical outcome in children with epilepsy after viral encephalitis (VE), we studied the prognostic factors for surgery and summarized the surgical strategies of children with epilepsy secondary to VE.

METHODS

We retrospectively analyzed 23 surgically treated children with VE. The subjects were divided into two groups according to their surgical outcome. All presurgical evaluation data were collected and analyzed.

RESULTS

Among the 23 operated children, the mean age at surgery was 6.1 years. Surgeries were hemispherotomy (n = 12), temporal-parietal-occipital disconnection (n = 4), whole corpus callosotomy (n = 3), lobectomy (n = 3), and vagus nerve stimulation (n = 1). The mean patient follow-up time was 37.2 months, and 13 children had a good outcome (ILAE classification 1-3). Univariate analyses revealed that the latency from infection to the first unprovoked seizure, MRI laterality, concordance of PET and MRI abnormalities, and acute postoperative seizure (APOS) were prognostic factors of seizure outcomes (P < 0.05). No correlation was found between generalized seizures and poor outcome (P = 0.229).

CONCLUSIONS

We concluded that the children who achieve favorable surgical outcomes are those with longer latency, unilateral abnormalities on MRI, consistency of PET and MRI abnormalities, and no APOS. Without invasive studies, epilepsy surgery may be successful for selected children with epilepsy after VE, despite diffuse interictal epileptiform discharges on scalp EEG. In addition, children with generalized seizures were not an absolute contraindication for surgery.

Cost-effectiveness of surgery for drug-resistant temporal lobe epilepsy in the US

OBJECTIVE

Surgery is an effective but costly treatment for many patients with drug-resistant temporal lobe epilepsy (DR-TLE). We aim to evaluate whether, in the United States, surgery is cost-effective compared to medical management for patients deemed surgical candidates and whether surgical evaluation is cost-effective for patients with DR-TLE in general.

METHODS

We use a semi-Markov model to assess the cost-effectiveness of surgery and surgical evaluation over a lifetime horizon. We use second-order Monte Carlo simulations to conduct probabilistic sensitivity analyses to estimate variation in model output. We adopt both health care and societal perspectives, including direct health care costs (e.g., surgery, antiepileptic drugs) and indirect costs (e.g., lost earnings by patients and care providers.) We compare the incremental cost-effectiveness ratio to societal willingness to pay (∼$100,000 per quality-adjusted life-year [QALY]) to determine whether surgery is cost-effective.

RESULTS

Epilepsy surgery is cost-effective compared to medical management in surgically eligible patients by virtue of being cost-saving ($328,000 vs $423,000) and more effective (16.6 vs 13.6 QALY) than medical management in the long run. Surgical evaluation is cost-effective in patients with DR-TLE even if the probability of being deemed a surgical candidate is only 5%. From a societal perspective, surgery becomes cost-effective within 3 years, and 89% of simulations favor surgery over the lifetime horizon.

CONCLUSION

For surgically eligible patients with DR-TLE, surgery is cost-effective. For patients with DR-TLE in general, referral for surgical evaluation (and possible subsequent surgery) is cost-effective. Patients with DR-TLE should be referred for surgical evaluation without hesitation on cost-effectiveness grounds.