Repeat surgery for focal cortical dysplasias in children: indications and outcomes

Identification and treatment of surgically-remediable causes of infantile epileptic spasms syndrome

INTRODUCTION

Infantile epileptic spasms syndrome (IESS) is a common developmental and epileptic encephalopathy with poor long-term outcomes. A substantial proportion of patients with IESS have a potentially surgically remediable etiology. Despite this, epilepsy surgery is underutilized in this patient group. Some surgically remediable etiologies, such as focal cortical dysplasia and malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE), are under-diagnosed in infants and young children. Even when a surgically remediable etiology is recognised, for example, tuberous sclerosis or focal encephalomalacia, epilepsy surgery may be delayed or not considered due to diffuse EEG changes, unclear surgical boundaries, or concerns about operating in this age group.

AREAS COVERED

In this review, the authors discuss the common surgically remediable etiologies of IESS, their clinical and EEG features, and the imaging techniques that can aid in their diagnosis. They then describe the surgical approaches used in this patient group, and the beneficial impact that early epilepsy surgery can have on developing brain networks.

EXPERT OPINION

Epilepsy surgery remains underutilized even when a potentially surgically remediable cause is recognized. Overcoming the barriers that result in under-recognition of surgical candidates and underutilization of epilepsy surgery in IESS will improve long-term seizure and developmental outcomes.

Clinical and Surgical Approach for Cerebral Cortical Dysplasia

The present article describes pathophysiological and clinical aspects of congenital malformations of the cerebral tissue (cortex and white matter) that cause epilepsy and very frequently require surgical treatment. A particular emphasis is given to focal cortical dysplasias, the most common pathology among these epilepsy-related malformations. Specific radiological and surgical features are also highlighted, so a thorough overview of cortical dysplasias is provided.

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.

Extended resection for seizure control of pure motor strip focal cortical dysplasia during awake craniotomy: illustrative case

BACKGROUND

Focal cortical dysplasias (FCD) represent highly intrinsically epileptogenic lesions that require complete resection for seizure control. Resection of pure motor strip FCD can be challenging. Effective control of postoperative seizures is crucial and extending the boundaries of resection in an eloquent zone remains controversial.

OBSERVATIONS

The authors report a 52-year-old right-handed male with refractory epilepsy. The seizure phenotype was a focal crisis with preserved awareness and a clonic motor onset of right-hemibody. Epilepsy surgery protocol demonstrated a left pure motor strip FCD and a full-awake resective procedure with motor brain mapping was performed. Further resection of surgical boundaries monitoring function along intraoperative motor tasks with no direct electrical stimulation corroborated by intraoperative-neuromonitorization was completed as the final part of the surgery. In the follow-up period of 3-years, the patient has an Engel-IB seizure-control with mild distal lower limb palsy and no gate compromise.

LESSONS

This report represents one of the few cases with pure motor strip FCD resection. In a scenario similar to this case, the authors consider that this variation can be useful to improve seizure control and the quality of life of these patients by extending the resection of a more extensive epileptogenic zone minimizing functional damage.

Predictors of Seizure Outcome after Repeat Pediatric Epilepsy Surgery: Reasons for Failure, Sex, Electrophysiology, and Temporal Lobe Surgery

Considering that seizure freedom is one of the most important goals in the treatment of epilepsy, repeat epilepsy surgery could be considered for patients who continue to experience drug-resistant seizures after epilepsy surgery. However, the chance of seizure freedom is reported to be below 50% after reoperation for failed epilepsy surgery. This study aimed to elucidate the predictive factors for seizure outcomes after repeat pediatric epilepsy surgery. In all, 39 pediatric patients who underwent repeat curative epilepsy surgery between 2008 and 2020 at our institution were retrospectively studied. The relationship between preoperative clinical factors and postoperative seizure freedom at the last follow-up was statistically evaluated. The mean age at the first surgery was 5.5 years (0-16). The etiology of epilepsy was malformation of cortical development in 33 patients. The average time to seizure recurrence after the first surgery was 6.4 months (range, 0-26 months). In all, 16 patients (41.0%) achieved seizure freedom after the second surgery. Seven patients underwent a third surgery, and three (42.9%) achieved seizure freedom. Overall, 19 patients achieved seizure freedom after repeat epilepsy surgery (48.7%). Female sex, surgical failure due to technical limitations, congruent electroencephalography (EEG) findings, lesional magnetic resonance imaging (MRI) and Rt-sided surgery were predictive of seizure freedom, and surgery limited to the temporal lobe was predictive of residual seizures, as determined in the multivariate analysis. The reoperation of failed epilepsy surgery is challenging. Consideration of the above predictive factors can be helpful in deciding whether to reoperate on pediatric patients whose initial surgical intervention failed.

Palliative Epilepsy Surgery Procedures in Children

Surgical treatment of epilepsy typically focuses on identification of a seizure focus with subsequent resection and/or disconnection to "cure" the patient's epilepsy and achieve seizure freedom. Palliative epilepsy surgery modalities are efficacious in improving seizure frequency, severity, and quality of life. In this paper, we review palliative epilepsy surgical options for children: vagus nerve stimulation, responsive neurostimulation, deep brain stimulation, hemispherotomy, corpus callosotomy, lobectomy and/or lesionectomy and multiple subpial transection. Reoperation after surgical resection should also be considered. If curative resection is not a viable option for seizure freedom, these methods should be considered with equal emphasis and urgency in the treatment of drug-resistant epilepsy.

Convolutional neural networks to identify malformations of cortical development: A feasibility study

OBJECTIVE

To develop and test a deep learning model to automatically detect malformations of cortical development (MCD).

METHODS

We trained a deep learning model to distinguish between diffuse cortical malformation (CM), periventricular nodular heterotopia (PVNH), and normal magnetic resonance imaging (MRI). We trained 4 different convolutional neural network (CNN) architectures. We used batch normalization, global average pooling, dropout layers, transfer learning, and data augmentation to minimize overfitting.

RESULTS

There were 45 subjects (866 images) with a normal MRI, 52 subjects (790 images) with CM, and 32 subjects (750 images) with PVNH. There was no subject overlap between the training, validation, and test sets. The InceptionResNetV2 architecture performed best in the validation set in all models and was evaluated in the test set with the following results: 1) the model distinguishing between CM and normal MRI yielded an area under the curve (AUC) of 0.89 and accuracy of 0.81; 2) the model distinguishing between PVNH and normal MRI yielded an AUC of 0.90 and accuracy of 0.84; 3) the model distinguishing between the three classes (CM, PVNH, and normal MRI) yielded an AUC of 0.88 and accuracy of 0.74. Visualization with gradient-weighted class activation maps and saliency maps showed that the deep learning models classified images based on relevant areas within each image.

SIGNIFICANCE

This study showed that CNNs can detect MCD at a clinically useful performance level with a fully automated workflow without image feature selection.

One-Stage, Limited-Resection Epilepsy Surgery for Bottom-of-Sulcus Dysplasia

OBJECTIVE

To determine whether 1-stage, limited corticectomy controls seizures in patients with MRI-positive, bottom-of-sulcus dysplasia (BOSD).

METHODS

We reviewed clinical, neuroimaging, electrocorticography (ECoG), operative, and histopathology findings in consecutively operated patients with drug-resistant focal epilepsy and MRI-positive BOSD, all of whom underwent corticectomy guided by MRI and ECoG.

RESULTS

Thirty-eight patients with a median age at surgery of 10.2 (interquartile range [IQR] 6.0-14.1) years were included. BOSDs involved eloquent cortex in 15 patients. Eighty-seven percent of patients had rhythmic spiking on preresection ECoG. Rhythmic spiking was present in 22 of 24 patients studied with combined depth and surface electrodes, being limited to the dysplastic sulcus in 7 and involving the dysplastic sulcus and gyral crown in 15. Sixty-eight percent of resections were limited to the dysplastic sulcus, leaving the gyral crown. Histopathology was focal cortical dysplasia (FCD) type IIb in 29 patients and FCDIIa in 9. Dysmorphic neurons were present in the bottom of the sulcus but not the top or the gyral crown in 17 of 22 patients. Six (16%) patients required reoperation for postoperative seizures and residual dysplasia; reoperation was not correlated with ECoG, neuroimaging, or histologic abnormalities in the gyral crown. At a median 6.3 (IQR 4.8-9.9) years of follow-up, 33 (87%) patients are seizure-free, 31 off antiseizure medication.

CONCLUSION

BOSD can be safely and effectively resected with MRI and ECoG guidance, corticectomy potentially being limited to the dysplastic sulcus, without need for intracranial EEG monitoring and functional mapping.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that 1-stage, limited corticectomy for BOSD is safe and effective for control of seizures.

Focal cortical dysplasia: an update on diagnosis and treatment

INTRODUCTION

Focal cortical dysplasias (FCDs) represent the most common etiology in pediatric drug-resistant focal epilepsies undergoing surgical treatment. The localization, extent and histopathological features of FCDs are considerably variable. Somatic mosaic mutations of genes that encode proteins in the PI3K-AKTmTOR pathway, which also includes the tuberous sclerosis associated genes TSC1 and TSC2, have been implicated in FCD type II in a substantial subset of patients. Surgery is the principal therapeutic option for FCD-related epilepsy. Advanced neurophysiological and neuroimaging techniques have improved surgical outcome and reduced the risk of postsurgical deficits. Pharmacological MTOR inhibitors are being tested in clinical trials and might represent an example of personalized treatment of epilepsy based on the known mechanisms of disease, used alone or in combination with surgery.

AREAS COVERED

This review will critically analyze the advances in the diagnosis and treatment of FCDs, with a special focus on the novel therapeutic options prompted by a better understanding of their pathophysiology.

EXPERT OPINION

Focal cortical dysplasia is a main cause of drug-resistant epilepsy, especially in children. Novel, personalized approaches are needed to more effectively treat FCD-related epilepsy and its cognitive consequences.

Advantages of magnetoencephalography, neuronavigation and intraoperative MRI in epilepsy surgery re-operations

Objective: Management of patients after failed epilepsy surgery is still challenging. Advanced diagnostic and intraoperative tools including magneto-encephalography (MEG) as well as neuronavigation and intraoperative magnetic resonance imaging (iopMRI) may contribute to a better postoperative seizure outcome in this patient group.Methods: We retrospectively analyzed consecutive patients after reoperation of failed epilepsy surgery for medically refractory epilepsy at the University of Erlangen between 1988 and 2017. Inclusion criteria for patients were available MEG, neuronavigation and iopMRI data. The Engel scale was used to categorize seizure outcome.Results: We report on 27 consecutive patients (13 female/14 male mean age at first surgery 29.4 years) who had operative revision of the first resection after failed epilepsy surgery. An improved seizure outcome postoperatively was observed in 78% of patients (p < 0.001) with 55% seizure free (Engel I) patients after a mean follow-up time of 4.9 years. In detail, 80% of lesional cases were seizure free compared to 59% of MRI negative patients. Localizing MEG spike activity in the vicinity of the first resection cavity was present in 12 of 27 patients (44%) corresponding to 83% (10/12) of MEG localizing spike patients having advanced seizure outcome after operative revision.Conclusion: Re-operation after failed surgery in refractory epilepsy may lead to a better seizure outcome in the majority of patients. Preoperative MEG may support the decision for surgery and may facilitate targeting epileptogenic tissue for re-resection by employing navigation and iopMR imaging.

5-Aminolevulinic Acid-Induced Fluorescence in Focal Cortical Dysplasia: Report of 3 Cases

BACKGROUND

Three patients enrolled in a clinical trial of 5-aminolevulinic-acid (5-ALA)-induced fluorescence-guidance, which has been demonstrated to facilitate intracranial tumor resection, were found on neuropathological examination to have focal cortical dysplasia (FCD).

OBJECTIVE

To evaluate in this case series visible fluorescence and quantitative levels of protoporphyrin IX (PpIX) during surgery and correlate these findings with preoperative magnetic resonance imaging (MRI) and histopathology.

METHODS

Patients were administered 5-ALA (20 mg/kg) approximately 3 h prior to surgery and underwent image-guided, microsurgical resection of their MRI- and electrophysiologically identified lesions. Intraoperative visible fluorescence was evaluated using an operating microscope adapted with a commercially available blue light module. Quantitative PpIX levels were assessed using a handheld fiber-optic probe and a wide-field imaging spectrometer. Sites of fluorescence measurements were co-registered with both preoperative MRI and histopathological analysis.

RESULTS

Three patients with a pathologically confirmed diagnosis of FCD (Types 1b, 2a, and 2b) underwent surgery. All patients demonstrated some degree of visible fluorescence (faint or moderate), and all patients had quantitatively elevated concentrations of PpIX. No evidence of neoplasia was identified on histopathology, and in 1 patient, the highest concentrations of PpIX were found at a tissue site with marked gliosis but no typical histological features of FCD.

CONCLUSION

FCD has been found to be associated with intraoperative 5-ALA-induced visible fluorescence and quantitatively confirmed elevated concentrations of the fluorophore PpIX in 3 patients. This finding suggests that there may be a role for fluorescence-guidance during surgical intervention for epilepsy-associated FCD.

Long-term outcomes of reoperations in epilepsy surgery

OBJECTIVE

To analyze longitudinal seizure outcomes following epilepsy surgery, including reoperations, in patients with intractable focal epilepsy.

METHODS

Clinicoradiological characteristics of patients who underwent epilepsy surgery from 1995 to 2016 with follow-up of ≥1 year were reviewed. In patients undergoing reoperations, the latest resection was considered the index surgery. The primary outcome was complete seizure freedom (Engel I) at last follow-up. Potentially significant outcome variables were first identified using univariate analyses and then fit in multivariate Cox proportional hazards models.

RESULTS

Of 898 patients fulfilling study criteria, 110 had reoperations; 92 had one resection prior to the index surgery and 18 patients had two or more prior resective surgeries. Two years after the index surgery, 69% of patients with no prior surgeries had an Engel score of I, as opposed to only 42% of those with one prior surgery, and 33% of those with two or more prior resections (P < .001). Among surgical outcome predictors, the number of prior epilepsy surgeries, female sex, lesional initial magnetic resonance imaging, no prior history of generalization, and pathology correlated with better seizure outcomes on univariate analysis. However, only sex (P = .011), history of generalization (P = .016), and number of prior surgeries (P = .002) remained statistically significant in the multivariate model.

SIGNIFICANCE

Although long-term seizure control is possible in patients with failed prior epilepsy surgery, the chances of success diminish with every subsequent resection. Outcome is additionally determined by inherent biological markers (sex and secondary generalization tendency), rather than traditional outcome predictors, supporting a hypothesis of "surgical refractoriness."

Measure thrice, cut twice: On the benefit of reoperation for failed pediatric epilepsy surgery

OBJECTIVE

To determine whether clinical outcomes are improved after repeat surgery for medically refractory epilepsy in children.

METHODS

This is a single-center retrospective cohort analysis of all patients who received repeat resective surgery for ongoing seizures from 2000-2017. From a total of 251 consecutive individual epilepsy surgical patients for focal resection, 53 patients met study inclusion criteria and had adequate follow-up documented.

RESULTS

Median age of seizure-onset was 2.0-years-old (IQR 0.3-5.5 years). The median age at first epilepsy surgery was 6.3-years-old (IQR 2.9-9.2 years) and at second epilepsy surgery was 8.4-years-old (IQR 4.7-12.6 years). Overall, 53 % (n = 28) of this series achieved Engel Class I (seizure freedom); with improved seizure control (Engel Class I-II) in 83 % (n = 44) of the cohort. 64 % (n = 34) had one reoperation; 26 % (n = 14) had two; and 9% (n = 5) had three. Pathology: 58 % (n = 31) had focal cortical dysplasia; 13 % (n = 10) tumor; 9% (n = 5) encephalitis; 6% (n = 3) gliosis; 4% (n = 2) mesial temporal sclerosis; and 2% (n = 1) hemimegalencephaly. Tumor pathology was associated with increased chance (p = 0.01) for seizure freedom (90 % of tumor patients had Engel Class I outcome). MTS had worse outcome with both patients having ongoing seizures (Engel II-IV). There were 6 patients who developed post-operative hemiparesis; one was unplanned but resolved.

SIGNIFICANCE

Reoperation for pediatric epilepsy surgery can lead to seizure freedom in many cases and improved seizure control in most cases. Reoperation for brain tumor pathology is associated with a high rate of seizure freedom.

Predictors of seizure recurrence in patients with surgery for focal cortical dysplasia: pairwise and network meta-analysis and trial sequential analysis

OBJECT

The aim of this study was to determine the predictors of seizure recurrence in surgery for focal cortical dysplasia (FCD) by conducting a meta-analysis.

METHODS

Publications that met the pre-stated inclusion criteria were selected from PubMed and CNKI databases. Two authors extracted data independently about prognostic factors, surgical outcome, and clinical characteristics of participants. A fixed-effects model was used to calculate the summary of odds ratio (OR) with 95% confidence interval (CI).

RESULTS

Forty-eight studies were included in our meta-analysis. Three predictors of seizure recurrence (Engel class III/IV)-histological FCD type I, incomplete resection, and extratemporal location were determined; combined OR with 95% CI were 1.94 (95%CI 1.53-2.46), 12.06 (95%CI 7.32-19.88), and 1.91 (95%CI 1.06-3.44), respectively. Trial sequential analysis revealed that the outcomes had a sufficient sample size to reach firm conclusions. Furthermore, seizure location was not substantially modified by geographic region, while histological FCD type I and incomplete resection showed a significant association with seizure recurrence in different continents except Asia for incomplete resection. Sensitivity analyses restricted to studies for each variable yielded robust results. Little evidence of publication bias was observed. Meanwhile, the difference in the standard for outcome failed to influence the results for prognosis. Network meta-analysis including 13 trials comparing subtypes of FCD found the FCD IIb had the lowest seizure recurrence rate.

CONCLUSIONS

This meta-analysis suggests that histological FCD type I, incomplete resection, and extratemporal location are recurrence factors in patients with epilepsy surgery for FCD. In addition, FCD IIb is associated with the highest rates of postoperative seizure control among the subtypes of FCD, type I and type II.

Voxel-based morphometric magnetic resonance imaging postprocessing in non-lesional pediatric epilepsy patients using pediatric normal databases

BACKGROUND AND PURPOSE

Pre-surgical evaluation of pediatric patients with drug-resistant focal epilepsy and negative (non-lesional) magnetic resonance imaging (MRI) is particularly challenging. Focal cortical dysplasia (FCD), a frequent pathological substrate in such setting, may be subtle on MRI and evade detection. The aim of this study was to use voxel-based MRI postprocessing to improve the detection of subtle FCD in pediatric surgical candidates.

METHODS

A consecutive cohort of pediatric patients undergoing pre-surgical evaluation with a negative MRI by visual analysis was included. MRI postprocessing was performed using a voxel-based morphometric analysis program (MAP) on T1-weighted volumetric MRI, with comparison to an age-specific normal pediatric database. The pertinence of MAP-positive areas was confirmed by surgical outcome and pathology.

RESULTS

A total of 78 patients were included. Forty-four patients (56%) had positive MAP regions. Complete resection of the MAP-positive regions was positively associated with seizure-free outcome compared with the no/partial resection group (P < 0.001). Patients with no/partial resection of the MAP-positive regions had worse seizure outcomes than the MAP-negative group (P = 0.002). The MAP-positive rate was 100%, 77%, 63% and 40% in the 3-5, 5-10, 10-15 and 15-21 year age groups, respectively. MAP-positive rates were 45% in patients with temporal resection and 63% in patients with extratemporal resection. Complete resection of the MAP-positive regions was positively associated with seizure-free outcome in the extratemporal group (P = 0.001) but not in the temporal group (P = 0.070).

CONCLUSION

Our data suggest the importance of using MRI postprocessing in the pre-surgical evaluation process of pediatric epilepsy patients with apparently normal MRI.

Presurgical intracranial investigations in epilepsy surgery

Identification and localization of the "epileptogenic process" in the brain of patients with drug-resistant epilepsy for surgical cure is the goal of presurgical investigations. Intracranial recordings are required when conflicting data between seizure clinical semiology and EEG prevent precise localization within one hemisphere or lateralization, when a visible lesion on MRI seems unrelated to the electroclinical data, or in MRI-negative cases. Two methods are currently used. The objective of the subdural grid electrocorticography with or without depth electrodes (SDG/DE) is the best possible identification of the area of onset of spontaneous seizures and localization of the eloquent cortex. The objective of stereoelectroencephalography (SEEG) is to define the epileptogenic zone (configured as a network) and its relation to an unmasked lesion. Two-dimensional (SDG) and three-dimensional (SEEG) brain sampling dictate different strategies for noninvasive presurgical phase I goals as well as for data analysis. SEEG must resolve several potential localization hypotheses in a manner that cannot be achieved with SDG. SDG operates through brain surface coverage, unlike SEEG, which samples networks. SDG estimates the extent of cortical resection through a lobar or sublobar localization of ictal onset and constraints from functional mapping. SEEG defines a tailored resection according to the results of anatomo-electro-clinical correlations in stereotaxic space that will guide the ablation of the epileptogenic zone. SEEG is currently expanding faster than SDG. The prerequisites (especially in the preimplantation hypothetical strategy) and technical tools (especially stimulation and functional mapping) in the two methods are very different. This chapter presents a comparative review of the rationale, indications, electrode implantation strategies, interpretation, and surgical decision making of these two approaches of presurgical evaluation for epilepsy surgery.

Rates and predictors of success and failure in repeat epilepsy surgery: A meta-analysis and systematic review

OBJECTIVE

Medically refractory epilepsy is a debilitating disorder that is particularly challenging to treat in patients who have already failed a surgical resection. Evidence regarding outcomes of further epilepsy surgery is limited to small case series and reviews. Therefore, our group performed the first quantitative meta-analysis of the literature from the past 30 years to assess for rates and predictors of successful reoperations.

METHODS

A PubMed search was conducted for studies reporting outcomes of repeat epilepsy surgery. Studies were excluded if they reported fewer than five eligible patients or had average follow-ups < 1 year, and patients were excluded from analysis if they received a nonresective intervention. Outcomes were stratified by each variable of interest, and quantitative meta-analysis was performed to generate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Seven hundred eighty-two patients who received repeat resective epilepsy surgery from 36 studies were included. Engel I outcome was observed in 47% (n = 369) of patients. Significant predictors of seizure freedom included congruent over noncongruent electrophysiology data (OR = 3.6, 95% CI = 1.6-8.2), lesional over nonlesional epilepsy (OR = 3.2, 95% CI = 1.9-5.3), and surgical limitations over disease-related factors associated with failure of the first surgery (OR = 2.6, 95% CI = 1.3-5.3). Among patients with at least one of these predictors, seizure freedom was achieved in 58%. Conversely, the use of invasive monitoring was associated with worse outcome (OR = 0.4, 95% CI = 0.2-0.9). Temporal lobe over extratemporal/multilobe resection (OR = 1.5, 95% CI = 0.8-3.0) and abnormal over normal preoperative magnetic resonance imaging (OR = 1.9, 95% CI = 0.6-5.4) showed nonsignificant trends toward seizure freedom.

SIGNIFICANCE

This analysis supports considering further resection in patients with intractable epilepsy who continue to have debilitating seizures after an initial surgery, especially in the context of factors predictive of a favorable outcome.