Predicting long-term seizure outcome after resective epilepsy surgery: The Multicenter Study

The effect of epilepsy surgery on tonic-clonic seizures

OBJECTIVE

Epilepsy surgery outcomes tend to be judged by the percentage in seizure reduction without considering the effect on specific seizure types, particularly tonic-clonic seizures, which produce the greatest morbidity and mortality. We assess how often focal to bilateral tonic-clonic seizures (BTCS) stop and how often they appear de novo after epilepsy surgery.

METHODS

Analysis of a prospectively maintained epilepsy surgery database between 1986 and 2022 that characterizes the burden of BTCS after resective epilepsy surgery. Patients were stratified according to presence or absence of preoperative BTCS and whether these were active (defined as ≥1 BTCS/year prior to surgery) or remote.

RESULTS

A total of 804 patients were followed for a median of 7 years (interquartile range [IQR] = 3-13 years) after epilepsy surgery, most being temporal lobe resections (91%, 95% confidence interval [CI] = 89-93%). At last visit, 72% of patients (95% CI = 69-75%) were seizure-free for 1 year or more. Of 521 patients with preoperative BTCS, 300 (58%, 95% CI = 53%-61%) no longer had them after surgery. BTCS recurred in 221 patients, but 128 of them (58%, 95% CI = 51%-64%) had no BTCS in the last year of follow-up. Those patients who continued to experience BTCS after surgery had a median reduction of 92% in yearly BTCS frequency (IQR = 65%-98%, p < .001). Of 283 patients with no preoperative BTCS, 17 developed de novo BTCS (6%, 95% CI = 4%-9%), with a median of 2 BTCS during the entire follow-up period. Forty-seven percent (95% CI = 42%-53%) of patients without preoperative BTCS became seizure-free after surgery, compared with 33% (95% CI = 29-37, p < .001) of patients with preoperative BTCS.

SIGNIFICANCE

Epilepsy surgery markedly reduces or eliminates BTCS, which should have a potential positive impact on morbidity and mortality. This favors offering surgery even if the chance of seizure freedom is not high and calls for a new surgical outcome scale to factor in seizure severity reduction.

Accuracy of SEEG Source Localization: A Pilot Study Using Corticocortical Evoked Potentials

INTRODUCTION

EEG source localization is an established technique for localizing scalp EEG in medically refractory epilepsy but has not been adequately studied with intracranial EEG (iEEG). Differences in sensor location and spatial sampling may affect the accuracy of EEG source localization with iEEG. Corticocortical evoked potentials can be used to evaluate EEG source localization algorithms for iEEG given the known source location.

METHODS

We recorded 205 sets of corticocortical evoked potentials using low-frequency single-pulse electrical stimulation in four patients with iEEG. Averaged corticocortical evoked potentials were analyzed using 11 distributed source algorithms and compared using the Wilcoxon signed-rank test ( P < 0.05). We measured the localization error from stimulated electrodes and the spatial dispersion of each solution.

RESULTS

Minimum norm, standard low-resolution electromagnetic tomography (sLORETA), LP Norm, sLORETA-weighted accurate minimum norm (SWARM), exact LORETA (eLORETA), standardized weighted LORETA (swLORETA), and standardized shrinking LORETA-FOCUSS (ssLOFO) had the least localization error (13.3-15.7 mm) and were superior to focal underdetermined system solver (FOCUSS), logistic autoregressive average (LAURA, and LORETA, 17.9-21.7, P < 0.001). The FOCUSS solution had the smallest spatial dispersion (7.4 mm), followed by minimum norm, L1 norm, LP norm, and SWARM (20.8-28.3 mm). Gray matter stimulations had less localization error than white matter (median differences 3.1-6.1 mm) across all algorithms except SWARM, LORETA, and logistic autoregressive average. A multivariate linear regression showed that distance from the source to sensors and gray/white matter stimulation had a significant effect on localization error for some algorithms but not SWARM, minimum norm, focal underdetermined system solver, logistic autoregressive average, and LORETA.

CONCLUSIONS

Our study demonstrated that minimum norm, L1 norm, LP norm, and SWARM localize iEEG corticocortical evoked potentials well with lower localization error and spatial dispersion. Larger studies are needed to confirm these findings.

Lateralization of memory function in temporal lobe epilepsy using scene memory fMRI

Functional magnetic resonance imaging (fMRI) offers an alternative to the traditional Wada test for presurgical language and memory lateralization that carries almost no risk. However, fMRI lateralization of episodic memory remains challenging because the hippocampus, which is fundamental to episodic memory, is smaller, more prone to susceptibility artifact, and harder to functionally modulate than language regions. We previously showed that a complex scene memory task can lateralize memory function in the mesial temporal lobe. Using data acquired from N = 45 patients with temporal lobe epilepsy acquired with an improved stimulus paradigm and high-resolution fMRI, we now demonstrate that memory activation can be successfully lateralized within hippocampus proper. PLAIN LANGUAGE SUMMARY: Epilepsy surgery can improve seizure control in patients with temporal lobe epilepsy (TLE) that cannot be controlled with medications also, but ablation or removal of temporal lobe brain tissue can also cause cognitive deficits. Functional MRI (fMRI) can noninvasively map brain activation and perform well in lateralizing and localizing language function, but localizing and lateralizing memory function is more challenging. Building upon prior work using complex scene encoding to map memory function, we demonstrate that the use of high-resolution fMRI along with an optimized task paradigm allows memory activation to be detected within the hippocampus. Because the hippocampus is both a common site of TLE and a key region underlying memory, this approach is expected to contribute to presurgical evaluation of TLE.

Epilepsy-surgery for fronto-basal lesions: Management, outcome, and review of literature

BACKGROUND

In this study, we isolated a cohort of patients who have refractory epilepsy who underwent surgery with frontobasal focus. This work aimed to develop prognostic factors associated with a better seizure outcome and identify risk factors determining postoperative morbidity.

METHODS

We identified all patients with frontobasal epilepsy who underwent surgery due to refractory epilepsy at the University Hospital Bonn over 22 years. Although this is a retrospective study, all data sets were collected prospectively. We evaluated both surgical and functional outcomes.

RESULTS

In total, 32 patients were identified for inclusion in this study. With a long and stable postoperative seizure outcome averaging 109 months, we were able to show that patients with frontobasal epilepsy can achieve a better outcome (53 % seizure-free, ILAE1) than patients with frontal epilepsy. In contrast to other brain regions, the resection size (isolated or extended) did not influence the outcome. Low-grade tumors, on the other hand, were associated with a better seizure outcome, and gliosis or non-specific histological findings with a worse seizure outcome. Stereo-EEG with depth electrodes is more suitable for invasive diagnostics at the frontal base than strip or grid electrodes. Patients who did not become seizure-free after surgery and underwent a second surgery did not profit significantly concerning seizure outcome.

CONCLUSION

Patients with frontobasal epilepsy who are operated on early in the course of the disease, are MRI-positive, and have a tumor as an epileptogenic pathology have the best chance of seizure freedom.

Is lateralization concordance between preoperative video-EEG, ictal SPECT, and MRI to be associated with positive psychiatric outcomes after cortico-amygdalohippocampectomy in patients with pharmacoresistant temporal lobe epilepsy associated to mesial temporal sclerosis? A retrospective cohort study

OBJECTIVE

The occurrence of comorbid psychiatric disorders (PD) in patients with pharmacoresistant temporal lobe epilepsy (TLE) associated to mesial temporal sclerosis (MTS) can be considered as a result of the complex interaction between biological and psychosocial factors, as well as the effects of antiseizure medications (ASM). Regarding biological aspects, despite the growing amount of knowledge, there is still a scarcity of data in literature clarifying whether a more precise definition of the seizure onset zone (SOZ) could be associated with a more favorable post-surgical psychiatric outcome. In the present study, the clinical and sociodemographic pre-surgical variables, including the results of neurophysiological and neuroimaging exams, were evaluated in patients with pharmacoresistant TLE-MTS aiming to investigate possible risk factors for the presence of PD after cortico-amygdalohippocampectomy (CAH).

METHODS

A retrospective cohort analysis of medical records from initially 106 pre-surgical patients with pharmacoresistant TLE-MTS with PD (n = 51; 48.1 %) and without PD (n = 55; 51.9 %) proceeded. Pre-surgical clinical and sociodemographic data were compared between both groups and the predictors for the presence of post-surgical PD were characterized up to one and two years after CAH.

RESULTS

Seventeen patients (16 %) had lost their follow-up in the first year after surgery, and 89 (84 %) had completed the study. No clinical and sociodemographic differences were observed between both groups of patients (p > 0.05), except for a history of previous psychiatric treatment (p = 0.001). Eighteen patients (35.29 %) with pre-surgical history of PD had remission of PD after CAH, while eight (14.5 %) developed de novo PD. The previous history of PD was directly associated with the development of post-surgical PD one year after CAH (p < 0.0001). Previous psychiatric treatment (p < 0.01), previous history of mood (p = 0.002) and anxiety (p = 0.03) disorder, as well as discordance in lateralization between MRI, SPECT, and EEG (p = 0.02), were predictors for the development of PD two years after CAH. Post-surgical psychiatric outcomes were associated to seizure outcome based on the Engel classification (p < 0,0001).

CONCLUSION

The present data observed an association between lateralization concordance of results of pre-surgical investigative exams and positive postoperative psychiatric outcomes in patients with pharmacoresistant TLE-MTS. These results could suggest that a more precise definition of the SOZ could be associated with a more favorable post-surgical psychiatric outcome after CAH.

Do we have to continue antiseizure medications post surgery in long-term epilepsy associated tumors (LEATs)?

OBJECTIVE

To identify the rate of successful antiseizure medication (ASM) withdrawal after resective surgery in patients with long-term epilepsy-associated tumors (LEATs).

METHODS

A retrospective analysis (from our prospectively archived data) on the post-operative ASM profile of 123 consecutive patients who completed a minimum of 2 years after resection of LEATs for ASM-resistant epilepsy. A comparison between recurred and non-recurred groups in terms of seizure recurrence was used to identify the potential predictors of seizure recurrence whose attributes were further analyzed using univariate and multiple logistic regression analysis. Kaplan-Meier survival curves were used to study the probability of ASM freedom following surgery.

RESULTS

We attempted ASM withdrawal in 102 (82.9 %) patients. Forty-eight (47.1 %) had seizure recurrence while reducing ASM, of which 22 (21.6 %) continued to have seizures even after ASM optimisation. On univariate analysis, presence of pre-operative secondary generalized seizure(s) was the only factor associated with seizure recurrence. At a mean follow-up of 6.1 years, 72 (58.5 %) patients were seizure-free and aura-free at terminal follow-up (53 patients were off any ASM). The cumulative probability of achieving complete ASM-free status was 29 % at fourth year, 42 % at sixth year, 55 % at eighth year, and 59 % at 10th year after surgery.

CONCLUSIONS

Following resective surgery for LEATs, ASM(s) could be successfully discontinued in half of the patients. About one-third of the patients may have recurrent seizures on follow-up. Presence of secondary generalized seizure(s) prior to surgery predicts seizure recurrence, whereas MRI defined completeness of resection will not. This information will help in rationalising decisions on ASM management post-resection.

Mesial temporal lobe spiking reveals distinct patterns of blood oxygen level-dependent functional magnetic resonance imaging activation using simultaneous intracranial electroencephalography-functional magnetic resonance imaging

OBJECTIVE

Temporal lobe epilepsy (TLE) has a high probability of becoming drug resistant and is frequently considered for surgical intervention. However, 30% of TLE cases have nonlesional magnetic resonance imaging (MRI) scans, which is associated with worse surgical outcomes. Characterizing interactions between temporal and extratemporal structures in these patients may help understand these poor outcomes. Simultaneous intracranial electroencephalography-functional MRI (iEEG-fMRI) can measure the hemodynamic changes associated with interictal epileptiform discharges (IEDs) recorded directly from the brain. This study was designed to characterize the whole brain patterns of IED-associated fMRI activation recorded exclusively from the mesial temporal lobes of patients with nonlesional TLE.

METHODS

Eighteen patients with nonlesional TLE undergoing iEEG monitoring with mesial temporal IEDs underwent simultaneous iEEG-fMRI at 3 T. IEDs were marked, and statistically significant clusters of fMRI activation were identified. The locations of IED-associated fMRI activation for each patient were determined, and patients were grouped based on the location and pattern of fMRI activation.

RESULTS

Two patterns of IED-associated fMRI activation emerged: primarily localized (n = 7), where activation was primarily located within the ipsilateral temporal lobe, and primarily diffuse (n = 11), where widespread bilateral extratemporal activation was detected. The primarily diffuse group reported significantly fewer focal to bilateral tonic-clonic seizures and had better postsurgical outcomes.

SIGNIFICANCE

Simultaneous iEEG-fMRI can measure the hemodynamic changes associated with focal IEDs not visible on scalp EEG, such as those arising from the mesial temporal lobe. Significant fMRI activation associated with these IEDs was observed in all patients. Two distinct patterns of IED-associated activation were seen: primarily localized to the ipsilateral temporal lobe and more widespread, bilateral activation. Patients with widespread IED associated-activation had fewer focal to bilateral tonic-clonic seizures and better postsurgical outcome, which may suggest a neuroprotective mechanism limiting the spread of ictal events.

Defining benchmark outcomes for mesial temporal lobe epilepsy surgery: A global multicenter analysis of 1119 cases

OBJECTIVE

Benchmarking has been proposed to reflect surgical quality and represents the highest standard reference values for desirable results. We sought to determine benchmark outcomes in patients after surgery for drug-resistant mesial temporal lobe epilepsy (MTLE).

METHODS

This retrospective multicenter study included patients who underwent MTLE surgery at 19 expert centers on five continents. Benchmarks were defined for 15 endpoints covering surgery and epilepsy outcome at discharge, 1 year after surgery, and the last available follow-up. Patients were risk-stratified by applying outcome-relevant comorbidities, and benchmarks were calculated for low-risk ("benchmark") cases. Respective measures were derived from the median value at each center, and the 75th percentile was considered the benchmark cutoff.

RESULTS

A total of 1119 patients with a mean age (range) of 36.7 (1-74) years and a male-to-female ratio of 1:1.1 were included. Most patients (59.2%) underwent anterior temporal lobe resection with amygdalohippocampectomy. The overall rate of complications or neurological deficits was 14.4%, with no in-hospital death. After risk stratification, 377 (33.7%) benchmark cases of 1119 patients were identified, representing 13.6%-72.9% of cases per center and leaving 742 patients in the high-risk cohort. Benchmark cutoffs for any complication, clinically apparent stroke, and reoperation rate at discharge were ≤24.6%, ≤.5%, and ≤3.9%, respectively. A favorable seizure outcome (defined as International League Against Epilepsy class I and II) was reached in 83.6% at 1 year and 79.0% at the last follow-up in benchmark cases, leading to benchmark cutoffs of ≥75.2% (1-year follow-up) and ≥69.5% (mean follow-up of 39.0 months).

SIGNIFICANCE

This study presents internationally applicable benchmark outcomes for the efficacy and safety of MTLE surgery. It may allow for comparison between centers, patient registries, and novel surgical and interventional techniques.

The impact of a history of status epilepticus for epilepsy surgery outcome

OBJECTIVE

Patients with focal drug resistant epilepsy are excellent candidates for epilepsy surgery. Status epilepticus (SE) and seizure clusters (SC), described in a subset of patients, have both been associated with extended epileptogenic cerebral networks within one or both hemispheres. In this retrospective study, we were interested to determine if a history of SE or SC is associated with a worse surgical outcome.

METHODS

Data of 244 patients operated between 2000 to 2018 were reviewed, with a follow-up of at least 2 years. Patients with a previous history of SE or SC were compared to operated patients without these conditions (control group, CG).

RESULTS

We identified 27 (11%) and 38 (15.5%) patients with history of SE or SC, respectively. No difference in post-operative outcome was found for SE and SC patients. Compared to the control group, patients with a history of SE were diagnosed and operated significantly at earlier age(p = 0.01), and after a shorter duration of the disease (p = 0.027), but with a similar age of onset.

SIGNIFICANCE

A history of SE or SC was not associated with a worse post-operative prognosis. Earlier referral of SE patients for surgery suggests a heightened awareness regarding serious complications of recurrent SE by the referring neurologist or neuropediatrician. While the danger of SE is evident, policies to underline the impact for SC or very frequent seizures might be an efficient approach to accelerate patient referral also for this patient group.

Who are the Better Candidates for Epilepsy Surgery?

The resective epilepsy surgery can be the effective procedure to get seizure-free outcome in these drug resistant epilepsy (DRE) patients. Class I evidence firmly establishes the superiority of epilepsy surgery over medical treatments in both seizure control and quality of life for DRE patients. For the effective identification of optimal surgical candidates, it's essential to understand the prognostic factors of epilepsy surgery based on the surgical methods employed. Established positive prognostic indicators for temporal resection include the presence of hippocampal sclerosis on magnetic resonance imaging (MRI), focal lesions on MRI, unilateral temporal spikes, concordant ictal electroencephalography (EEG), and a history of prolonged febrile convulsion. Potential negative predictors encompass preoperative secondary generalized tonic-clonic seizures, a normal MRI, postoperative EEG spikes, and age at the time of surgery. For neocortical epilepsy, the prognostic factors identified through multivariate analysis were the presence of a discrete lesion, localized hypometabolism on Fluorodeoxyglucose positron emission tomography (FDG-PET), and localized ictal EEG. A significant correlation was found between achieving a seizure-free outcome in no visible lesion on MRI (MR-negative) epilepsy patients and having concordance in two or more presurgical evaluations, specifically in interictal EEG, ictal EEG, FDG-PET, and ictal single-photon emission computed tomography. There was a marked improvement in the seizure-free outcome in MR-negative temporal lobe epilepsy (TLE) by the application of this strategy. The better surgical candidates for epilepsy surgery are the followings: patients displaying a discrete lesion on MRI with concordant video-EEG monitoring (VEM) results, patients diagnosed with unilateral hippocampal sclerosis who have concordant VEM results, patients with unilateral hippocampal sclerosis but discordant VEM results, patients with focal cortical dysplasia and concordant VEM results, and patients diagnosed with MR-negative TLE who exhibit two or more consistent results from presurgical evaluations.

Postsurgical outcomes in a cohort of patients with hippocampal sclerosis: Initial experience in a referral epilepsy center in Peru

Mesial temporal lobe epilepsy, one of the most common forms of epilepsy, is often linked with drug resistance. Surgical intervention is a reliable and safe treatment option, though research into postsurgical outcomes in our locality remains limited. We performed a retrospective observational study included 91 patients with mesial temporal lobe epilepsy and hippocampal sclerosis who had undergone anterior temporal lobectomy between 2012 and 2020 at a surgical epilepsy center located in Lima, Peru. Postoperative outcomes were analyzed using bivariate and multivariate analysis based on the Engel classification. We found that after 12 months of follow-up, 78.65% of the 91 patients achieved an Engel IA classification, while 9.09% attained Engel IB classification and 11.24% were designated as Engel II, with only 1.12% classified as Engel IVA. The median QOLIE31 score was 84 (IQR: 75-90), with 74.16% of the participants successfully reintegrating into academic or employment activities. After 24 months, only 68 patients completed the follow-up, with 69.12% achieving an Engel IA classification. Individuals with a secondary education or higher were more likely to achieve an Engel IA classification at 12 months (OR: 5.11; P = 0.005; CI: 1.63-16.01), after adjusting for sex and age. We concluded that most patients exhibited favorable outcomes after 1 year of follow-up. However, lower educational attainment was linked to worse postsurgical outcomes.

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.

Modern intracranial electroencephalography for epilepsy localization with combined subdural grid and depth electrodes with low and improved hemorrhagic complication rates

OBJECTIVE

Recent trends have moved from subdural grid electrocorticography (ECoG) recordings toward stereo-electroencephalography (SEEG) depth electrodes for intracranial localization of seizures, in part because of perceived morbidity from subdural grid and strip electrodes. For invasive epilepsy monitoring, the authors describe the outcomes of a hybrid approach, whereby patients receive a combination of subdural grids, strips, and frameless stereotactic depth electrode implantations through a craniotomy. Evolution of surgical techniques was employed to reduce complications. In this study, the authors review the surgical hemorrhage and functional outcomes of this hybrid approach.

METHODS

A retrospective review was performed of consecutive patients who underwent hybrid implantation from July 2012 to May 2022 at an academic epilepsy center by a single surgeon. Outcomes included hemorrhagic and nonhemorrhagic complications, neurological deficits, length of monitoring, and number of electrodes.

RESULTS

A total of 137 consecutive procedures were performed; 113 procedures included both subdural and depth electrodes. The number of depth electrodes and electrode contacts did not increase the risk of hemorrhage. A mean of 1.9 ± 0.8 grid, 4.9 ± 2.1 strip, and 3.0 ± 1.9 depth electrodes were implanted, for a mean of 125.1 ± 32 electrode contacts per patient. The overall incidence of hematomas over the study period was 5.1% (7 patients) and decreased significantly with experience and the introduction of new surgical techniques. The incidence of hematomas in the last 4 years of the study period was 0% (55 patients). Symptomatic hematomas were all delayed and extra-axial. These patients required surgical evacuation, and there were no cases of hematoma recurrence. All neurological deficits related to hematomas were temporary and were resolved at hospital discharge. There were 2 nonhemorrhagic complications. The mean duration of monitoring was 7.3 ± 3.2 days. Seizures were localized in 95% of patients, with 77% of patients eventually undergoing resection and 17% undergoing responsive neurostimulation device implantation.

CONCLUSIONS

In the authors' institutional experience, craniotomy-based subdural and depth electrode implantation was associated with low hemorrhage rates and no permanent morbidity. The rate of hemorrhage can be nearly eliminated with surgical experience and specific techniques. The decision to use subdural electrodes or SEEG should be tailored to the patient's unique pathology and surgeon experience.

Hippocampal resection in temporal lobe epilepsy: Do we need to resect the tail?

INTRODUCTION

Anteromesial temporal lobe resection is the most common surgical technique used to treat drug-resistant mesial temporal lobe epilepsy, particularly when secondary to hippocampal sclerosis. Structural and functional imaging data suggest the importance of sparing the posterior hippocampus for minimising language and memory deficits. Recent work has challenged the view that maximal posterior hippocampal resection improves seizure outcome. This study was designed to assess whether resection of posterior hippocampal atrophy was associated with improved seizure outcome.

METHODS

Retrospective analysis of a prospective database of all anteromesial temporal lobe resections performed in individuals with hippocampal sclerosis at our epilepsy surgery centre, 2013-2021. Pre- and post-operative MRI were reviewed by 2 neurosurgical fellows to assess whether the atrophic segment, displayed by automated hippocampal morphometry, was resected, and ILAE seizure outcomes were collected at 1 year and last clinical follow-up. Data analysis used univariate and binary logistic regression.

RESULTS

Sixty consecutive eligible patients were identified of whom 70% were seizure free (ILAE Class 1 & 2) at one year. There was no statistically significant difference in seizure freedom outcomes in patients who had complete resection of atrophic posterior hippocampus or not (Fisher's Exact test statistic 0.69, not significant at p < .05) both at one year, and at last clinical follow-up. In the multivariate analysis only a history of status epilepticus (OR=0.2, 95%CI:0.042-0.955, p = .04) at one year, and pre-operative psychiatric disorder (OR=0.145, 95%CI:0.036-0.588, p = .007) at last clinical follow-up, were associated with a reduced chance of seizure freedom.

SIGNIFICANCE

Our data suggest that seizure freedom is not associated with whether or not posterior hippocampal atrophy is resected. This challenges the traditional surgical dogma of maximal posterior hippocampal resection in anteromesial temporal lobe resections and is a step further optimising this surgical procedure to maximise seizure freedom and minimise associated language and memory deficits.

Clinical adult outcome 11-30 years after pediatric epilepsy surgery: Complications and other surgical adverse events, seizure control, and cure of epilepsy

OBJECTIVE

Pediatric epilepsy surgery promises seizure freedom or even cure of epilepsy. We evaluated the long-term (≥10 years) adult clinical outcome including surgery-related adverse events and complications, which are generally underreported.

METHODS

A monocentric, single-arm, questionnaire study in now adult patients who underwent epilepsy surgery during childhood. A novel ad hoc parental/patient questionnaire, which addressed diverse outcome domains was applied.

RESULTS

From a total of 353 eligible patients, 203 could be contacted (3 patients died of causes unknown) and 101 (50%) returned appropriately filled-in surveys. No evidence for a survey-response bias was found. The rate of surgical complications according to the patient records was 9%. As regards the survey, half of the parents/patients reported surgical adverse events (expected and unexpected issues) and one-third reported permanent aversive sequels. Two-thirds of the patients were seizure-free during the last year before follow-up; 63% were Engel class 1A; favorable seizure outcomes (including auras only) were obtained in 73%; and 54% were seizure-free and off antiseizure medicine (ASM), that is, cured of epilepsy. In non-seizure-free patients, seizure relapse occurred at any time during the follow-up interval but 87% of those with a seizure-free first postoperative year were seizure-free at follow-up. One patient experienced a seizure relapse during the ASM withdrawal trial but became seizure-free again with ASMs. Eleven patients reported an increased number of ASMs as compared to the time before surgery. Earlier focal surgery did not affect the long-term clinical outcome.

SIGNIFICANCE

Pediatric epilepsy surgery was capable of curing epilepsy in about one-half of the children and to significantly control seizures in about three-fourths. Long-term success of focal surgery did not depend on age at surgery or duration of epilepsy. Surgical adverse events including complications may be underreported and must be assessed more thoroughly.

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

OBJECTIVE

This study was undertaken to better understand the long-term palliative and disease-modifying effects of surgical resection beyond seizure freedom, including frequency reduction and both late recurrence and remission, in patients with drug-resistant epilepsy.

METHODS

This retrospective database-driven cohort study included all patients with >9 years of follow-up at a single high-volume epilepsy center. We included patients who underwent lobectomy, multilobar resection, or lesionectomies for drug-resistant epilepsy; we excluded patients who underwent hemispherectomies. Our main outcomes were (1) reduction in frequency of disabling seizures (at 6 months, each year up to 9 years postoperatively, and at last follow-up), (2) achievement of seizure remission (>6 months, >1 year, and longest duration), and (3) seizure freedom at last follow-up.

RESULTS

We included 251 patients; 234 (93.2%) achieved 6 months and 232 (92.4%) experienced 1 year of seizure freedom. Of these, the average period of seizure freedom was 10.3 years. A total of 182 (72.5%) patients were seizure-free at last follow-up (defined as >1 year without seizures), with a median 11.9 years since remission. For patients not completely seizure-free, the mean seizure frequency reduction at each time point was 76.2%, and ranged from 66.6% to 85.0%. Patients decreased their number of antiseizure medications on average by .58, and 53 (21.2%) patients were on no antiseizure medication at last follow-up. Nearly half (47.1%) of those seizure-free at last follow-up were not seizure-free immediately postoperatively.

SIGNIFICANCE

Patients who continue to have seizures after resection often have considerable reductions in seizure frequency, and many are able to achieve seizure freedom in a delayed manner.

Clinical factors associated with late seizure remission after failed epilepsy surgery

BACKGROUND

Some patients who initially fail epilepsy surgery later become seizure-free, but it is not clear how the clinical characteristics of the patients or post-operative modifications of anti-seizure medication (ASM) regimens contribute to late seizure remission.

METHODS

We performed a retrospective chart review of patients undergoing epilepsy surgery at the University of Washington Regional Epilepsy Center between 2007 and 2017, including patients receiving neocortical resection, temporal lobectomy, and hippocampal laser interstitial therapy (LITT) ablation. We assessed seizure freedom, ASM changes, seizure frequency at the first and last follow-up, and type of lesion. Two-tailed Fisher's exact test and Mann-Whitney U test were used for statistical analyses.

RESULTS

Two hundred and fifteen patients undergoing epilepsy surgery between 2007 and 2017 had both first and last follow-ups. Ninety-eight (46%) were not seizure-free at the first follow-up (mean 1.1 years post-operative). By the last follow-up (mean 4.7 years post-operative), 20% of those not initially seizure-free had become so. Those who were seizure-free at the last visit had lower median seizures per month in the first post-operative year (0.21 versus 0.95 per month in those not seizure-free, p < 0.001). There was also a significantly higher proportion of patients with cavernomas who were seizure-free at the last visit (25% vs. 1% of those not seizure-free at the last visit; p = 0.001), but no other differences in clinical characteristics. Of the 98 patients who had seizures at the first follow-up, 63% underwent post-operative modification of their ASM regimens. The rate of late seizure freedom was similar for patients with or without ASM changes: 21% were seizure-free at the last visit with ASM changes and 19% without ASM changes. There were no significant differences in which ASMs were changed between those who became seizure-free and those who did not, but patients who were subjected to further medical management were less likely to have had mesial temporal sclerosis (MTS) than those who were not. A number of patients not initially seizure-free who underwent ASM changes achieved seizure freedom as long as 10 years post-surgery.

CONCLUSION

A substantial proportion of patients who initially fail epilepsy surgery will have late seizure remission. Those with cavernous hemangiomas were more likely to achieve late remission from seizures as were those with lower rates of seizures in the first year after surgery. The chances of achieving remission were similar in those with or without modification of their ASM regimens, but those with pre-operative MTS were more likely to achieve late seizure freedom without medication changes. At the individual level, patients may still achieve seizure freedom with ASM changes as long as ten years after the initial surgery.

Mapping hippocampal glutamate in mesial temporal lobe epilepsy with glutamate weighted CEST (GluCEST) imaging

Temporal lobe epilepsy (TLE) is one of the most common subtypes of focal epilepsy, with mesial temporal sclerosis (MTS) being a common radiological and histopathological finding. Accurate identification of MTS during presurgical evaluation confers an increased chance of good surgical outcome. Here we propose the use of glutamate-weighted chemical exchange saturation transfer (GluCEST) magnetic resonance imaging (MRI) at 7 Tesla for mapping hippocampal glutamate distribution in epilepsy, allowing to differentiate lesional from non-lesional mesial TLE. We demonstrate that a directional asymmetry index, which quantifies the relative difference between GluCEST contrast in hippocampi ipsilateral and contralateral to the seizure onset zone, can differentiate between sclerotic and non-sclerotic hippocampi, even in instances where traditional presurgical MRI assessments did not provide evidence of sclerosis. Overall, our results suggest that hippocampal glutamate mapping through GluCEST imaging is a valuable addition to the presurgical epilepsy evaluation toolbox.

Multiple hippocampal transection for mesial temporal lobe epilepsy: A systematic review

PURPOSE

Multiple hippocampal transection (MHT) is a surgical technique that offers adequate seizure control with minimal perioperative morbidity. However, there is little evidence available to guide neurosurgeons in selecting this technique for use in appropriate patients. This systematic review analyzes patient-level data associated with MHT for intractable epilepsy, focusing on postoperative seizure control and memory outcomes.

METHODS

The systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Relevant articles were identified from 3 databases (PubMed, Medline, Embase) up to August 1, 2021. Inclusion criteria were that the majority of patients had received a diagnosis of intractable epilepsy, the article was written in English, MHT was the primary procedure, and patient-level metadata were included.

RESULTS

Fifty-nine unique patients who underwent MHT were identified across 11 studies. Ten (17%) of 59 patients underwent MHT alone. Forty-three (75%) of 57 patients who had a follow-up 12 months or longer were seizure free at last follow-up. With respect to postoperative verbal memory retention, 9 of 38 (24%) patient test scores did not change, 14 (37%) decreased, and 16 (42%) increased. With respect to postoperative nonverbal memory retention, 12 of 38 (34%) patient test scores did not change, 13 (34%) decreased, and 13 (33%) increased.

CONCLUSION

There are few reported patients analyzed after MHT. Although the neurocognitive benefits of MHT are unproven, this relatively novel technique has shown promise in the management of seizures in patients with intractable epilepsy. However, structured trials assessing MHT in isolation are warranted.

Validation of the Taiwanese version of the Epilepsy Surgery Satisfaction Questionnaire (Tw-ESSQ-19)

OBJECTIVE

Satisfaction with epilepsy surgery in Mandarin-speaking countries remains unknown. We aimed to validate in our Taiwanese patients an existing instrument to measure patient satisfaction with epilepsy surgery, the 19-item Epilepsy Surgery Satisfaction Questionnaire (ESSQ-19).

METHODS

Consecutive patients with epilepsy who received epilepsy surgery one year earlier in Taipei Veterans General Hospital were recruited and provided clinical and demographic data. The Mandarin version of the ESSQ-19 for the Taiwanese population and eight other questionnaires were completed to assess construct validity. To evaluate the validity and reliability of the tool, the data were analyzed by confirmatory factor analysis, Spearman's rank correlation, and internal consistency analysis.

RESULTS

The study involved 120 patients (70 F/50 M, median age 35 years [IQR = 28-41]). The mean summary score (±SD) of the Tw-ESSQ-19 was 82.5 ± 14.5. The mean scores of the four domains were 90.3 ± 15.4 (surgical complications), 83.2 ± 16.7 (seizure control), 80.1 ± 17.3 (recovery from surgery), and 76.6 ± 18.3 (psychosocial functioning). The questionnaire was shown to have good construct validity with satisfactory goodness-of-fit of the data (standardized root mean square residual = 0.0492; comparative fit index = 0.946). It also demonstrated good discriminant validity (being seizure free [AUC 0.78; 95% CI 0.68-0.89], endorsing depression [AUC 0.84; 95% CI 0.76-0.91], self-rating epilepsy as disabling [AUC 0.71; 95% CI 0.58-0.84], and self-rating epilepsy as severe [AUC 0.78; 95% CI 0.64-0.93]), high internal consistency in four domains (Cronbach's alpha = 0.83-0.96), and no significant floor/ceiling effects of the summary score.

SIGNIFICANCE

The Mandarin version of the ESSQ-19 adapted for the Taiwanese population is a reliable and valid self-reported questionnaire for assessing patient satisfaction with epilepsy surgery.

Factors Predicting Outcome After Intracranial EEG Evaluation in Patients With Medically Refractory Epilepsy

BACKGROUND AND OBJECTIVES

The aim of this study was to identify predictors of a resective surgery and subsequent seizure freedom following intracranial EEG (ICEEG) for seizure-onset localization.

METHODS

This is a retrospective chart review of 178 consecutive patients with medically refractory epilepsy who underwent ICEEG monitoring from 2002 to 2015. Univariable and multivariable regression analysis identified independent predictors of resection vs other options. Stepwise Akaike information criteria with the aid of clinical consideration were used to select the best multivariable model for predicting resection and outcome. Discrete time survival analysis was used to analyze the factors predicting seizure-free outcome. Cumulative probability of seizure freedom was analyzed using Kaplan-Meier curves and compared between resection and nonresection groups. Additional univariate analysis was performed on 8 select clinical scenarios commonly encountered during epilepsy surgical evaluations.

RESULTS

Multivariable analysis identified the presence of a lesional MRI, presurgical hypothesis suggesting temporal lobe onset, and a nondominant hemisphere implant as independent predictors of resection (p < 0.0001, area under the receiver operating characteristic curve 0.80, 95% CI 0.73-0.87). Focal ICEEG onset and undergoing a resective surgery predicted absolute seizure freedom at the 5-year follow-up. Patients who underwent resective surgery were more likely to be seizure-free at 5 years compared with continued medical treatment or neuromodulation (60% vs 7%; p < 0.0001, hazard ratio 0.16, 95% CI 0.09-0.28). Even patients thought to have unfavorable predictors (nonlesional MRI or extratemporal lobe hypothesis or dominant hemisphere implant) had ≥50% chance of seizure freedom at 5 years if they underwent resection.

DISCUSSION

Unfavorable predictors, including having nonlesional extratemporal epilepsy, should not deter a thorough presurgical evaluation, including with invasive recordings in many cases. Resective surgery without functional impairment offers the best chance for sustained seizure freedom and should always be considered first.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that the presence of a lesional MRI, presurgical hypothesis suggesting temporal lobe onset, and a nondominant hemisphere implant are independent predictors of resection. Focal ICEEG onset and undergoing resection are independent predictors of 5-year seizure freedom.

Interictal SEEG Resting-State Connectivity Localizes the Seizure Onset Zone and Predicts Seizure Outcome

Localization of epileptogenic zone currently requires prolonged intracranial recordings to capture seizure, which may take days to weeks. The authors developed a novel method to identify the seizure onset zone (SOZ) and predict seizure outcome using short-time resting-state stereotacticelectroencephalography (SEEG) data. In a cohort of 27 drug-resistant epilepsy patients, the authors estimated the information flow via directional connectivity and inferred the excitation-inhibition ratio from the 1/f power slope. They hypothesized that the antagonism of information flow at multiple frequencies between SOZ and non-SOZ underlying the relatively stable epilepsy resting state could be related to the disrupted excitation-inhibition balance. They found flatter 1/f power slope in non-SOZ regions compared to the SOZ, with dominant information flow from non-SOZ to SOZ regions. Greater differences in resting-state information flow between SOZ and non-SOZ regions are associated with favorable seizure outcome. By integrating a balanced random forest model with resting-state connectivity, their method localized the SOZ with an accuracy of 88% and predicted the seizure outcome with an accuracy of 92% using clinically determined SOZ. Overall, this study suggests that brief resting-state SEEG data can significantly facilitate the identification of SOZ and may eventually predict seizure outcomes without requiring long-term ictal recordings.

Multimodal prognostic features of seizure freedom in epilepsy surgery

OBJECTIVE

Accurate preoperative predictions of seizure freedom following surgery for focal drug resistant epilepsy remain elusive. Our objective was to systematically evaluate all meta-analyses of epilepsy surgery with seizure freedom as the primary outcome, to identify clinical features that are consistently prognostic and should be included in the future models.

METHODS

We searched PubMed and Cochrane using free-text and Medical Subject Heading (MeSH) terms according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses. This study was registered on PROSPERO. We classified features as prognostic, non-prognostic and uncertain and into seven subcategories: 'clinical', 'imaging', 'neurophysiology', 'multimodal concordance', 'genetic', 'surgical technique' and 'pathology'. We propose a structural causal model based on these features.

RESULTS

We found 46 features from 38 meta-analyses over 22 years. The following were consistently prognostic across meta-analyses: febrile convulsions, hippocampal sclerosis, focal abnormal MRI, Single-Photon Emission Computed Tomography (SPECT) coregistered to MRI, focal ictal/interictal EEG, EEG-MRI concordance, temporal lobe resections, complete excision, histopathological lesions, tumours and focal cortical dysplasia type IIb. Severe learning disability was predictive of poor prognosis. Others, including sex and side of resection, were non-prognostic. There were limited meta-analyses investigating genetic contributions, structural connectivity or multimodal concordance and few adjusted for known confounders or performed corrections for multiple comparisons.

SIGNIFICANCE

Seizure-free outcomes have not improved over decades of epilepsy surgery and despite a multitude of models, none prognosticate accurately. Our list of multimodal population-invariant prognostic features and proposed structural causal model may serve as an objective foundation for statistical adjustments of plausible confounders for use in high-dimensional models.

PROSPERO REGISTRATION NUMBER

CRD42021185232.

Epilepsy Surgery in Extratemporal vs Temporal Lobe Epilepsy: Changes in Surgical Volumes and Seizure Outcome Between 1990 and 2017

Objective:

Seizure outcome after extratemporal lobe epilepsy (exTLE) surgery has often been poorer than after temporal lobe epilepsy (TLE) surgery, but recent improvements in diagnostics and surgery may have changed this. Our aim was to analyze the changes in presurgical and surgical volumes and seizure outcome two years after surgery for patients with exTLE compared to those with TLE.

Methods:

We performed a retrospective, single-center cohort study including patients from the Bethel presurgical-surgical-postsurgical database from 1990 to 2017. We used logistic regression to analyze factors influencing the odds for surgery and the odds for seizure freedom after surgery.

Results:

We included 3822 patients with presurgical evaluation, 2404 of whom had subsequently undergone surgery. The proportion of exTLE patients in presurgical evaluation increased from 41% between 1990-1993 to 64% in 2014-2017. The odds for surgery decreased over time (2003-2011: OR=0.50 [95%CI 0.36-0.70]; 2012-2017: OR=0.24 [CI 0.17-0.35]; reference: 1990-2002), and patients with exTLE had lower odds for surgery than TLE patients, but this difference diminished over time (exTLE vs. TLE 1990-2002: OR=0.14 [CI 0.09-0.20]; 2003-2011: OR=0.32 [CI 0.24-0.44]; 2012-2017: OR=0.46 [CI 0.34-0.63]). Etiology, the side of the epileptogenic lesion and invasive recordings additionally influenced the odds for surgery. The most frequent reasons for not undergoing surgery were the missing identification of a circumscribed epileptogenic zone or an unacceptable risk of postsurgical deficits in exTLE patients and the patient’s decision in TLE patients. Compared to TLE patients, the odds for seizure freedom after surgery started lower for patients with exTLE in earlier years, but increased (≤2 lobes 1990-2002: OR=0.47 [CI 0.33-0.68]; 2003-2011: OR=0.62 [CI 0.44-0.87]; 2012-2017: OR=0.78 [CI 0.53-1.15]; ≥3 lobes 1990-2002: OR=0.37 [CI 0.22-0.62]; 2003-2011: OR=0.73 [CI 0.43-1.23]; 2012-2017: OR=1.46 [CI 0.91-2.42]). Etiology, age at surgery and invasive recordings were further predictors for the odds for seizure freedom.

Conclusion:

Over the past 28 years, the success of resective surgery for patients with exTLE has improved. At the same time, the number of exTLE patients being evaluated for surgery increased as well as their odds for undergoing surgery.

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.

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.

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.

Comparison of the real-world effectiveness of vertical versus lateral functional hemispherotomy techniques for pediatric drug-resistant epilepsy: A post hoc analysis of the HOPS study

Objective

This study was undertaken to determine whether the vertical parasagittal approach or the lateral peri‐insular/peri‐Sylvian approach to hemispheric surgery is the superior technique in achieving long‐term seizure freedom.

Methods

We conducted a post hoc subgroup analysis of the HOPS (Hemispheric Surgery Outcome Prediction Scale) study, an international, multicenter, retrospective cohort study that identified predictors of seizure freedom through logistic regression modeling. Only patients undergoing vertical parasagittal, lateral peri‐insular/peri‐Sylvian, or lateral trans‐Sylvian hemispherotomy were included in this post hoc analysis. Differences in seizure freedom rates were assessed using a time‐to‐event method and calculated using the Kaplan–Meier survival method.

Results

Data for 672 participants across 23 centers were collected on the specific hemispherotomy approach. Of these, 72 (10.7%) underwent vertical parasagittal hemispherotomy and 600 (89.3%) underwent lateral peri‐insular/peri‐Sylvian or trans‐Sylvian hemispherotomy. Seizure freedom was obtained in 62.4% (95% confidence interval [CI] = 53.5%–70.2%) of the entire cohort at 10‐year follow‐up. Seizure freedom was 88.8% (95% CI = 78.9%–94.3%) at 1‐year follow‐up and persisted at 85.5% (95% CI = 74.7%–92.0%) across 5‐ and 10‐year follow‐up in the vertical subgroup. In contrast, seizure freedom decreased from 89.2% (95% CI = 86.3%–91.5%) at 1‐year to 72.1% (95% CI = 66.9%–76.7%) at 5‐year to 57.2% (95% CI = 46.6%–66.4%) at 10‐year follow‐up for the lateral subgroup. Log‐rank test found that vertical hemispherotomy was associated with durable seizure‐free progression compared to the lateral approach (p = .01). Patients undergoing the lateral hemispherotomy technique had a shorter time‐to‐seizure recurrence (hazard ratio = 2.56, 95% CI = 1.08–6.04, p = .03) and increased seizure recurrence odds (odds ratio = 3.67, 95% CI = 1.05–12.86, p = .04) compared to those undergoing the vertical hemispherotomy technique.

Significance

This pilot study demonstrated more durable seizure freedom of the vertical technique compared to lateral hemispherotomy techniques. Further studies, such as prospective expertise‐based observational studies or a randomized clinical trial, are required to determine whether a vertical approach to hemispheric surgery provides superior long‐term seizure outcomes.

Outcome of epilepsy surgery in lesional epilepsy: Experiences from a developing country

BACKGROUND

Our aim was to report the postoperative seizure outcome and associated factors in patients with lesional epilepsy, in a low-income setting.

METHODS

This longitudinal prospective study included patients who underwent epilepsy surgery at Kashani Comprehensive Epilepsy Center between 2014 and 2019. Post-surgical outcomes were reported according to the Engel score, and patients were classified into two groups of seizure free (SF) and not-seizure free (NSF).

RESULTS

A total of 148 adult patients, with a mean age of 30.45 ± 9.23 years were included. The SF outcome was reported in 86.5% of patients and antiepileptic drugs (AEDs) were reduced or discontinued in 45.9%. The mean follow-up duration was 26.7 ± 14.9 months. Temporal lobe lesions (76.3%) and mesial temporal sclerosis (MTS) (56.7%) were the most frequent etiologies. Temporal lesion (Incidence relative risk (IRR): 1.76, 95% CI [1.08-2.87], p = 0.023), prior history of CNS infection (IRR:1.18, 95% CI [1.03-1.35], p = 0.019), use of intra-operative ECoG (IRR:1.73, 95% CI [1.06-2.81], p = 0.028), and absence of IEDs in postoperative EEG (IRR: 1.41, 95% CI [1.18-1.70], p < 0.001) were positive predictors for a favorable outcome.

CONCLUSION

Many patients with drug-resistant lesional epilepsy showed a favorable response to surgery. We believe that resective epilepsy surgery in low-income settings is a major treatment option. The high frequency of patients with drug-resistant epilepsy in developing countries is associated with high rates of morbidity and mortality. Hence, strategies to increase access to epilepsy surgery in these settings are urgently needed.

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.

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.

Localization of interictal discharge origin: A simultaneous intracranial electroencephalographic-functional magnetic resonance imaging study

OBJECTIVE

Scalp electroencephalographic (EEG)-functional magnetic resonance imaging (fMRI) studies suggest that the maximum blood oxygen level-dependent (BOLD) response to an interictal epileptiform discharge (IED) identifies the area of IED generation. However, the maximum BOLD response has also been reported in distant, seemingly irrelevant areas. Given the poor postoperative outcomes associated with extra-temporal lobe epilepsy, we hypothesized this finding is more common when analyzing extratemporal IEDs as compared to temporal IEDs. We further hypothesized that a subjective, holistic assessment of other significant BOLD clusters to identify the most clinically relevant cluster could be used to overcome this limitation and therefore better identify the likely origin of an IED. Specifically, we also considered the second maximum cluster and the cluster closest to the electrode contacts where the IED was observed.

METHODS

Maps of significant IED-related BOLD activation were generated for 48 different IEDs recorded from 33 patients who underwent intracranial EEG-fMRI. The locations of the maximum, second maximum, and closest clusters were identified for each IED. An epileptologist, blinded to these cluster assignments, selected the most clinically relevant BOLD cluster, taking into account all available clinical information. The distances between these BOLD clusters and their corresponding IEDs were then measured.

RESULTS

The most clinically relevant cluster was the maximum cluster for 56% (27/48) of IEDs, the second maximum cluster for 13% (6/48) of IEDs, and the closest cluster for 31% (15/48) of IEDs. The maximum clusters were closer to IED contacts for temporal than for extratemporal IEDs (p = .022), whereas the most clinically relevant clusters were not significantly different (p = .056).

SIGNIFICANCE

The maximum BOLD response to IEDs may not always be the most indicative of IED origin. We propose that available clinical information should be used in conjunction with EEG-fMRI data to identify a BOLD cluster representative of the IED origin.

Surgical revision after Vagus Nerve Stimulation. A case series

With increasing use of vagus nerve stimulation (VNS) as an adjunct treatment for drug-resistant epilepsy, revision surgery of VNS grows in importance. Indications for revision surgery are diverse and extend of surgery varies. We report a retrospective review on indications and complications of VNS revision surgery at our center. Of 90 VNS procedures 54.4% were revision surgeries. Among those the vast majority was due to depletion of the battery. The entire system was explanted in 15 patients, due to no beneficial effect detected (n = 4), due to irritating side effects (n = 4), and so further diagnostics could cbe carried out (n = 7). Interestingly in three of the patients who underwent further diagnostics, resective epilepsy surgery was performed. Surgical complications occurred in 8.2%. In our experience, revision surgery of VNS was a frequent and safe procedure. There is a need to carefully reviewthe initial indication for VNS implantation prior to revision surgery.

Magnetic resonance-guided laser interstitial thermal therapy: Correlations with seizure outcome

OBJECTIVE

This study was undertaken to identify clinical factors associated with seizure freedom after magnetic resonance-guided laser interstitial thermal therapy (MRgLiTT) in temporal lobe epilepsy patients with unilateral mesial temporal sclerosis (MTS).

METHODS

We identified 56 patients with magnetic resonance imaging-defined MTS who underwent MRgLiTT with at least 1 year of follow-up. Primary outcome was seizure freedom at 1 year. We examined the association of seizure freedom and the following clinical factors: age at surgery, gender, history of febrile seizures, history of focal to bilateral tonic-clonic seizures, duration of epilepsy at the time of surgery, frequency of interictal epileptiform discharges (IEDs), seizure frequency, and presence of bilateral IEDs.

RESULTS

Thirty-five (62.5%) patients were seizure-free at 1 year. The presence of bilateral IEDs and age at surgery were associated with 1-year seizure freedom after MRgLiTT. The presence of bilateral IEDS was associated with lower odds of seizure freedom (odds ratio [OR] = .05, 95% confidence interval [CI] = .01-.46, p = .008), whereas increasing age at surgery was associated with increased odds of seizure freedom (OR = 1.10, 95% CI = 1.03-1.19, p = .009).

SIGNIFICANCE

This study demonstrates associations between presence of bilateral IEDs and age at surgery and seizure freedom at 1 year after MRgLiTT.

Relative contribution of individual versus combined functional imaging studies in predicting seizure freedom in pediatric epilepsy surgery: an area under the curve analysis

OBJECTIVE

The goal of this study was to evaluate the predictive value and relative contribution of noninvasive presurgical functional imaging modalities based on the authors' institutional experience in pursuing seizure-free surgical outcomes in children with medically refractory epilepsy.

METHODS

This was a retrospective, single-institution, observational cohort study of pediatric patients who underwent evaluation and surgical treatment for medically refractory partial epilepsy between December 2003 and June 2016. During this interval, 108 children with medically refractory partial epilepsy underwent evaluation for localization and resective epilepsy surgery. Different noninvasive functional imaging modalities, including ictal SPECT, FDG-PET, and magnetoencephalography-magnetic source imaging, were utilized to augment a standardized paradigm (electroencephalography/semiology, MRI, and neuropsychology findings) for localization. Outcomes were evaluated at a minimum of 2 years (mean 7.5 years) utilizing area under the receiver operating characteristic curve analysis. Localizing modalities and other clinical covariates were examined in relation to long-term surgical outcomes.

RESULTS

There was variation in the contribution of each test, and no single presurgical workup modality could singularly and reliably predict a seizure-free outcome. However, concordance of presurgical modalities yielded a high predictive value. No difference in long-term outcomes between inconclusive (normal or diffusely abnormal) and abnormal focal MRI results were found. Long-term survival analyses revealed a statistically significant association between seizure freedom and patients with focal ictal EEG, early surgical intervention, and no history of generalized convulsions.

CONCLUSIONS

Comprehensive preoperative evaluation utilizing multiple noninvasive functional imaging modalities is not redundant and can improve pediatric epilepsy surgical outcomes.

Imaging slow brain activity during neocortical and hippocampal epileptiform events with electrical impedance tomography

OBJECTIVE

Electrical impedance tomography (EIT) is an imaging technique that produces tomographic images of internal impedance changes within an object using surface electrodes. It can be used to image the slow increase in cerebral tissue impedance that occurs over seconds during epileptic seizures, which is attributed to cell swelling due to disturbances in ion homeostasis following hypersynchronous neuronal firing and its associated metabolic demands. In this study, we characterised and imaged this slow impedance response during neocortical and hippocampal epileptiform events in the rat brain and evaluated its relationship to the underlying neural activity.

APPROACH

Neocortical or hippocampal seizures, comprising repeatable series of high-amplitude ictal spikes, were induced by electrically stimulating the sensorimotor cortex or perforant path of rats anaesthetised with fentanyl-isoflurane. Transfer impedances were measured during ≥30 consecutive seizures, by applying a sinusoidal current through independent electrode pairs on an epicortical array, and combined to generate an EIT image of slow activity.

MAIN RESULTS

The slow impedance responses were consistently time-matched to the end of seizures and EIT images of this activity were reconstructed reproducibly in all animals (p < 0.03125, N = 5). These displayed foci of activity that were spatially confined to the facial somatosensory cortex and dentate gyrus for neocortical and hippocampal seizures, respectively, and encompassed a larger volume as the seizure progressed. Centre-of-mass analysis of reconstructions revealed that this activity corresponded to the true location of the epileptogenic zone, as determined by EEG recordings and fast neural EIT measurements which were obtained simultaneously.

SIGNIFICANCE

These findings suggest that the slow impedance response presents a reliable marker of hypersynchronous neuronal activity during epileptic seizures and can thus be utilised for investigating the mechanisms of epileptogenesis in vivo and for aiding localisation of the epileptogenic zone during presurgical evaluation of patients with refractory epilepsies.

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.

Seizure Freedom After Epilepsy Surgery and Higher Baseline Cognition May Be Associated With a Negatively Correlated Epilepsy Network in Temporal Lobe Epilepsy

Background: Brain regions positively correlated with the epileptogenic zone in patients with temporal lobe epilepsy vary in spread across the brain and in the degree of correlation to the temporal lobes, thalamus, and limbic structures, and these parameters have been associated with pre-operative cognitive impairment and seizure freedom after epilepsy surgery, but negatively correlated regions have not been as well studied. We hypothesize that connectivity within a negatively correlated epilepsy network may predict which patients with temporal lobe epilepsy will respond best to surgery. Methods: Scalp EEG and resting state functional MRI (rsfMRI) were collected from 19 patients with temporal lobe epilepsy and used to estimate the irritative zone. Using patients' rsfMRI, the negatively correlated epilepsy network was mapped by determining all the brain voxels that were negatively correlated with the voxels in the epileptogenic zone and the spread and average connectivity within the network was determined. Results: Pre-operatively, connectivity within the negatively correlated network was inversely related to the spread (diffuseness) of that network and positively associated with higher baseline verbal and logical memory. Pre-operative connectivity within the negatively correlated network was also significantly higher in patients who would go on to be seizure free. Conclusion: Patients with higher connectivity within brain regions negatively correlated with the epilepsy network had higher baseline memory function, narrower network spread, and were more likely to be seizure free after surgery.

Assessment of the response to antiepileptic drugs in epileptic patients with structural lesion(s) on neuroimaging

Background

Focal epilepsy is the most common form of epilepsy in adults. Advances in brain imaging allowed better identification of different structural lesions underlying focal epilepsy. However, the response to antiepileptic drugs in lesional epilepsy is heterogeneous and difficult to anticipate. This study aimed to evaluate the response to antiepileptic drugs (AED) in patients with lesional epilepsy and to identify the predictors for poor seizure control.

Methods

One hundred and sixty-five patients with lesional epilepsy were included; the clinical diagnosis of epilepsy and seizure classification was based on the revised criteria of the International League Against Epilepsy (ILAE). Patients were subjected to full clinical assessment, MRI brain imaging epilepsy protocol, and EEG monitoring. All subjects were followed in the epilepsy clinic for at least 6 months.

Results

75.8% of patients with lesional epilepsy showed poor response to antiepileptic medications. Cerebromalatic lesions related to brain trauma was the most frequently encountered (21.8%). Malformations of cortical development were significantly associated with poor response to AED (p = 0.040). Polytherapy and the combined use of 1st- and 2nd-generation AED were higher in the poor response group. Logistic regression analysis revealed that younger age at seizure onset and abnormal EEG findings was 0.965 times and 2.5 times more associated with poor seizure control, respectively.

Conclusion

This study revealed that patients with lesional epilepsy who develop seizures in their early life, who suffer from malformations of cortical development, or who show abnormal EEG findings are more suspected to show poor response to AED.

Treatment of Multi-Focal Epilepsy With Resective Surgery Plus Responsive Neurostimulation (RNS): One Institution's Experience

Objective: Patients with medically refractory focal epilepsy can be difficult to treat surgically, especially if invasive monitoring reveals multiple ictal onset zones. Possible therapeutic options may include resection, neurostimulation, laser ablation, or a combination of these surgical modalities. To date, no study has examined outcomes associated with resection plus responsive neurostimulation (RNS, Neuropace, Inc., Mountain View, CA) implantation and we describe our initial experience in patients with multifocal epilepsy undergoing this combination therapy.

Methods: A total of 43 responsive neurostimulation (RNS) devices were implanted at UCI from 2015 to 2019. We retrospectively reviewed charts of patients from the same time period who underwent both resection and RNS implantation. Patients were required to have independent or multifocal onset, undergo resection and RNS implantation, and have a minimum of six-months for follow-up to be included in the study. Demographics, location of ictal onset, location of surgery, complications, and seizure outcome were collected.

Results: Ten patients met inclusion criteria for the study, and seven underwent both procedures in the same setting. The average age was 36. All patients had multifocal ictal onset on video electroencephalogram or invasive EEG with four patients undergoing subdural grid placement and four patients undergoing bilateral sEEG prior to the definitive surgery. Five patients underwent resection plus ipsilateral RNS placement and the remainder underwent resection with contralateral RNS placement. Two minor complications were encountered in this group. At six months follow up, there was an average of 81% ± 9 reduction in seizures, while four patients experienced complete seizure freedom at 1 year.

Conclusion: Patients with multifocal epilepsy can be treated with partial resection plus RNS. The complication rates are low with potential for worthwhile seizure reduction.

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.

Long-Term Epilepsy-Associated Tumors (LEATs): A Single-Center, Retrospective Series and Review of Literature on Factors Affecting the Seizure Outcome

BACKGROUND

Tumors presenting with drug-resistant seizures are termed as long-term epilepsy-associated tumors (LEATs). LEATs are more common in the temporal lobe, occur predominantly in pediatric age, and focal neurological deficits are rare. In this article, we aim to highlight our surgical experience in terms of seizure outcome among LEATs and discuss the factors affecting outcome.

METHODOLOGY

We have retrospectively analyzed all the operated cases of intra-axial brain tumors with seizures (2015-2019). The clinical and radiographic data were collected from the hospital record system. For comparison, 2 groups were made (group 1 with good seizure control, i.e., Engel 1; and group 2 poor seizure outcome, i.e., Engel 2 and 3).

RESULTS

A total of 51 cases were included; the temporal lobe was the most common location (n = 27); 23 patients had seizure frequency of "more than 1 seizure per week." Focal unaware seizures/complex partial seizures were the most common type of seizures encountered (n = 28). At a mean follow-up of 39.60 months, 38 patients had Engel 1 (78.5%) outcome (35 cases [71.05%] had the seizure duration of ≤2 years). The median duration of symptoms (group 1, 25 months vs. group 2, 65 months) was significantly different (P = 0.002). On comparing patients with seizure duration, we found a statistically significant difference (P < 0.00001).

CONCLUSION

A shorter duration of symptoms, younger age of the patient, partial/focal seizures, and gross total excision were predictors of a good seizure outcome. Histopathology of the tumor does not affect the outcome when one compares glioneuronal tumors with non-glioneuronal tumors.

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.

Factors affecting seizure outcome in Long-term epilepsy associated tumors (LEATs) in children and young adolescents

OBJECTIVE

Tumors with seizures as primary mode of presentation are collectively called Long-term epilepsy associated tumors (LEATs or Epileptomas). The overall survival is good so 'seizure outcome' becomes the primary goal rather than neuro-oncological outcome.

METHODS

A retrospective analysis of our surgical database (2015-19) was done to find operated patients of intra-axial brain tumors with age less than 25-years and who had presented with seizures.

RESULTS

The mean age at presentation was 16.44 years (SD + 6.82 years). Complex partial seizures/focal unaware seizures were the most common type of seizures encountered (n = 22) with mean duration of seizures was 49.50 months (SD + 31.04 months). The most common pathology was glioneuronal tumors (GNTs) (n = 17). Gross total resection (GTR) group had a significantly better seizure outcome as compared with the Subtotal resection (STR) group (p = 0.006). Presence of focal or partial seizure was a significant factor pointing towards a better seizure control (p = 0.005).

CONCLUSION

The shorter duration of symptoms, partial/focal seizures and gross total excision were predictors of a good seizure-outcome. Age of the patient and the histopathology of the tumor does not affect seizure-outcome on comparing GNTs with non GNTs.

A historical cohort of temporal lobe surgery for medically refractory epilepsy: a systematic review and meta-analysis to guide future nonrandomized controlled trial studies

OBJECTIVE

Recent trials for temporal lobe epilepsy (TLE) highlight the challenges of investigating surgical outcomes using randomized controlled trials (RCTs). Although several reviews have examined seizure-freedom outcomes from existing data, there is a need for an overall seizure-freedom rate estimated from level I data as investigators consider other methods besides RCTs to study outcomes related to new surgical interventions.

METHODS

The authors performed a systematic review and meta-analysis of the 3 RCTs of TLE in adults and report an overall surgical seizure-freedom rate (Engel class I) composed of level I data. An overall seizure-freedom rate was also collected from level II data (prospective cohort studies) for validation. Eligible studies were identified by filtering a published Cochrane meta-analysis of epilepsy surgery for RCTs and prospective studies, and supplemented by searching indexed terms in MEDLINE (January 1, 2012-April 1, 2018). Retrospective studies were excluded to minimize heterogeneity in patient selection and reporting bias. Data extraction was independently reverified and pooled using a fixed-effects model. The primary outcome was overall seizure freedom following surgery. The historical benchmark was applied in a noninferiority study design to compare its power to a single-study cohort.

RESULTS

The overall rate of seizure freedom from level I data was 72.4% (55/76 patients, 3 RCTs), which was nearly identical to the overall seizure-freedom rate of 71.7% (1325/1849 patients, 18 studies) from prospective cohorts (z = 0.134, p = 0.89; z-test). Seizure-freedom rates from level I and II studies were consistent over the years of publication (R2 < 0.01, p = 0.73). Surgery resulted in markedly improved seizure-free outcomes compared to medical management (RR 10.82, 95% CI 3.93-29.84, p < 0.01; 2 RCTs). Noninferiority study designs in which the historical benchmark was used had significantly higher power at all difference margins compared to using a single cohort alone (p < 0.001, Bonferroni's multiple comparison test).

CONCLUSIONS

The overall rate of seizure freedom for temporal lobe surgery is approximately 70% for medically refractory epilepsy. The small sample size of the RCT cohort underscores the need to move beyond standard RCTs for epilepsy surgery. This historical seizure-freedom rate may serve as a useful benchmark to guide future study designs for new surgical treatments for refractory TLE.

Magnetoencephalography resting state connectivity patterns as indicatives of surgical outcome in epilepsy patients

OBJECTIVE

Focal epilepsy is a disorder affecting several brain networks; however, epilepsy surgery usually targets a restricted region, the so-called epileptic focus. There is a growing interest in embedding resting state (RS) connectivity analysis into pre-surgical workup.

APPROACH

In this retrospective study, we analyzed Magnetoencephalography (MEG) long-range RS functional connectivity patterns in patients with drug-resistant focal epilepsy. MEG recorded prior to surgery from seven seizure-free (Engel Ia) and five non seizure-free (Engel III or IV) patients were analyzed (minimum 2-years post-surgical follow-up). MEG segments without any detectable epileptic activity were source localized using wavelet-based Maximum Entropy on the Mean method. Amplitude envelope correlation in the theta (4-8 Hz), alpha (8-13 Hz), and beta (13-26 Hz) bands were used for assessing connectivity.

MAIN RESULTS

For seizure-free patients, we found an isolated epileptic network characterized by weaker connections between the brain region where interictal epileptic discharges (IED) are generated and the rest of the cortex, when compared to connectivity between the corresponding contralateral homologous region and the rest of the cortex. Contrarily, non seizure-free patients exhibited a widespread RS epileptic network characterized by stronger connectivity between the IED generator and the rest of the cortex, in comparison to the contralateral region and the cortex. Differences between the two seizure outcome groups concerned mainly distant long-range connections and were found in the alpha-band.

SIGNIFICANCE

Importantly, these connectivity patterns suggest specific mechanisms describing the underlying organization of the epileptic network and were detectable at the individual patient level, supporting the prospect use of MEG connectivity patterns in epilepsy to predict post-surgical seizure outcome.

Prediction of Memory Impairment in Epilepsy Surgery by White Matter Diffusion

OBJECTIVE

To analyze the relationship between cognitive performance and white matter integrity in patients with temporal lobe epilepsy (TLE) to establish radiologic criteria to help with patient selection for surgery.

METHODS

The study included 19 adults with temporal lobe epilepsy. A tractography analysis of fractional anisotropy and mean diffusivity (MD) of the following fascicles was performed: arcuate fascicle, cingulum, fornix, inferior fronto-occipital fascicle, inferior longitudinal fascicle, parahippocampal fibers of the cingulum, and uncinate fascicle. The Wechsler Memory Scale-Third Edition neuropsychological test was performed to evaluate short- and long-term verbal (Logical Memory I and II subtests) and nonverbal (Visual Reproduction I and II subtests) memory. Relationships between memory scores and diffusion were calculated.

RESULTS

Lower Logical Memory I subtest scores were correlated with lower MD of the right inferior fronto-occipital fascicle, while lower Logical Memory II subtest scores were related to higher values of fractional anisotropy in bilateral cingulum, right uncinate, and right parahippocampal fibers of the cingulum and lower MD in left cingulum fascicle. Finally, lower values in Visual Reproduction I subtest scores were associated with lower values in MD in right cingulum and inferior fronto-occipital fascicles.

CONCLUSIONS

Structural changes of some white matter tracts were associated with deterioration of both short- and long-term memory. These alterations were more associated with verbal memory than with nonverbal memory. These changes mainly consist of an increase in fractional anisotropy and a decrease in MD, which could be interpreted as reorganization phenomena. Diffusion tensor imaging could be a useful tool for cognitive assessment in surgical candidates with temporal lobe epilepsy who are not suitable for neuropsychological testing or in whom their results do not lead to definitive conclusions.

Temporal lobe structural evaluation after transsylvian selective amygdalohippocampectomy

OBJECTIVE

Mesial temporal lobe epilepsy (MTLE) is the most common type of focal epilepsy in adolescents and adults, and in 65% of cases, it is related to hippocampal sclerosis (HS). Selective surgical approaches to the treatment of MTLE have as their main goal resection of the amygdala and hippocampus with minimal damage to the neocortex, temporal stem, and optic radiations (ORs). The object of this study was to evaluate late postoperative imaging findings on the temporal lobe from a structural point of view.

METHODS

The authors conducted a retrospective evaluation of all patients with refractory MTLE who had undergone transsylvian selective amygdalohippocampectomy (SAH) in the period from 2002 to 2015. A surgical group was compared to a control group (i.e., adults with refractory MTLE with an indication for surgical treatment of epilepsy but who did not undergo the surgical procedure). The inferior frontooccipital fasciculus (IFOF), uncinate fasciculus (UF), and ORs were evaluated on diffusion tensor imaging analysis. The temporal pole neocortex was evaluated using T2 relaxometry.

RESULTS

For the IFOF and UF, there was a decrease in anisotropy, voxels, and fibers in the surgical group compared with those in the control group (p < 0.001). An increase in relaxometry time in the surgical group compared to that in the control group (p < 0.001) was documented, suggesting gliosis and neuronal loss in the temporal pole.

CONCLUSIONS

SAH techniques do not seem to totally preserve the temporal stem or even spare the neocortex of the temporal pole. Therefore, although the transsylvian approaches have been considered to be anatomically selective, there is evidence that the temporal pole neocortex suffers structural damage and potentially functional damage with these approaches.