Surgery for extratemporal nonlesional epilepsy in children: a meta-analysis

Neurological morbidity of surgery for suprasylvian operculoinsular epilepsy

OBJECTIVE

The objective of this study was to identify risk factors associated with surgery-related neurological morbidity in patients with drug-resistant epilepsy undergoing suprasylvian operculoinsular resections. As secondary outcomes, we also analyzed the risk factors for ischemic lesion (IL) of corona radiata and seizure recurrence.

METHODS

A retrospective analysis was conducted on a cohort of patients who underwent suprasylvian operculoinsular resections for drug-resistant epilepsy. The association of several presurgical, surgical, and postsurgical factors with both primary (persistent neurological deficits) and secondary (structural abnormalities on postoperative magnetic resonance imaging [MRI] and seizure recurrence) postoperative outcomes was investigated with univariate and multivariate statistical analysis.

RESULTS

The study included a total of 65 patients; 46.2% of patients exhibited postoperative neurological deficits, but only 12.3% experienced persistent deficits. On postoperative MRI, IL in the corona radiata and corticospinal tract Wallerian degeneration (CSTWd) were seen in 68% and 29% of cases, respectively. Only CSTWd was significantly associated with persistent neurological deficits (relative risk [RR] = 2.6). Combined operculoinsular resection (RR = 3.62) and surgery performed on the left hemisphere (RR = .37) were independently associated with IL in the corona radiata. Variables independently associated with CSTWd were the presence of malacic components in the IL (RR = 1.96), right central operculum resection (RR = 1.79), and increasing age at surgery (RR = 1.03). Sixty-two patients had a postoperative follow-up > 12 months (median = 56, interquartile range = 30.75-73.5), and 62.9% were in Engel class I at last outpatient control. The risk of seizure recurrence was reduced by selective opercular resection (RR = .25) and increased by the histological diagnosis of aspecific gliosis (RR = 1.39).

SIGNIFICANCE

This study provides insights into the risk factors associated with surgery-related neurological morbidity, as well as further evidence on the postoperative occurrence of subcortical injury and seizure recurrence in epileptic patients undergoing suprasylvian operculoinsular resections. The findings highlighted in this study may be useful to better understand the processes supporting the increased surgical risk in the operculoinsular region.

Predictors of outcomes after surgery for medically intractable insular epilepsy: A systematic review and individual participant data meta-analysis

Insular epilepsy (IE) is an increasingly recognized cause of drug-resistant epilepsy amenable to surgery. However, concerns of suboptimal seizure control and permanent neurological morbidity hamper widespread adoption of surgery for IE. We performed a systematic review and individual participant data meta-analysis to determine the efficacy and safety profile of surgery for IE and identify predictors of outcomes. Of 2483 unique citations, 24 retrospective studies reporting on 312 participants were eligible for inclusion. The median follow-up duration was 2.58 years (range, 0-17 years), and 206 (66.7%) patients were seizure-free at last follow-up. Younger age at surgery (≤18 years; HR = 1.70, 95% CI = 1.09-2.66, P = .022) and invasive EEG monitoring (HR = 1.97, 95% CI = 1.04-3.74, P = .039) were significantly associated with shorter time to seizure recurrence. Performing MR-guided laser ablation or radiofrequency ablation instead of open resection (OR = 2.05, 95% CI = 1.08-3.89, P = .028) was independently associated with suboptimal or poor seizure outcome (Engel II-IV) at last follow-up. Postoperative neurological complications occurred in 42.5% of patients, most commonly motor deficits (29.9%). Permanent neurological complications occurred in 7.8% of surgeries, including 5% and 1.4% rate of permanent motor deficits and dysphasia, respectively. Resection of the frontal operculum was independently associated with greater odds of motor deficits (OR = 2.75, 95% CI = 1.46-5.15, P = .002). Dominant-hemisphere resections were independently associated with dysphasia (OR = 13.09, 95% CI = 2.22-77.14, P = .005) albeit none of the observed language deficits were permanent. Surgery for IE is associated with a good efficacy/safety profile. Most patients experience seizure freedom, and neurological deficits are predominantly transient. Pediatric patients and those requiring invasive monitoring or undergoing stereotactic ablation procedures experience lower rates of seizure freedom. Transgression of the frontal operculum should be avoided if it is not deemed part of the epileptogenic zone. Well-selected candidates undergoing dominant-hemisphere resection are more likely to exhibit transient language deficits; however, the risk of permanent deficit is very low.

Responsive neurostimulation for pediatric patients with drug-resistant epilepsy: a case series and review of the literature

OBJECTIVE

Responsive neurostimulation (RNS) is a promising treatment for pediatric patients with drug-resistant epilepsy for whom resective surgery is not an option. The relative indications and risk for pediatric patients undergoing RNS therapy require further investigation. Here, the authors report their experience with RNS implantation and therapy in pediatric patients.

METHODS

The authors performed a retrospective chart review to identify patients implanted with RNS depth or strip electrodes for the treatment of drug-resistant epilepsy at their institution between 2020 and 2022. Patient demographics, surgical variables, and patient seizure outcomes (Engel class and International League Against Epilepsy [ILAE] reporting) were evaluated.

RESULTS

The authors identified 20 pediatric patients ranging in age from 8 to 21 years (mean 15 [SD 4] years), who underwent RNS implantation, including depth electrodes (n = 15), strip electrodes (n = 2), or both (n = 3). Patient seizure semiology, onset, and implantation strategy were heterogeneous, including bilateral centromedian nucleus (n = 5), mesial temporal lobe (n = 4), motor cortex or supplementary motor area (n = 7), or within an extratemporal epileptogenic zone (n = 4). There were no acute complications of RNS implantation (hemorrhage or stroke) or device malfunctions. One patient required rehospitalization for postoperative infection. At the longest follow-up (mean 10 [SD 7] months), 13% patients had Engel class IIB, 38% had Engel class IIIA, 6% had Engel class IIIB, 19% had Engel class IVA, 19% had Engel class IVB, and 6% had Engel class IVC outcomes. Using ILAE metrics, 6% were ILAE class 3, 25% were ILAE class 4, and 69% were ILAE class 5.

CONCLUSIONS

This case series supports current literature suggesting that RNS is a safe and potentially effective surgical intervention for pediatric patients with drug-resistant epilepsy. The authors report comparable rates of serious adverse events to current RNS literature in pediatric and adult populations. Seizure outcomes may continue to improve with follow-up as stimulation strategy is refined and the chronic neuromodulatory effect evolves, as previously described in patients with RNS. Further large-scale, multicenter case series of RNS in pediatric patients with drug-resistant epilepsy are required to determine long-term pediatric safety and effectiveness.

Brain Surgery for Medically Intractable Epilepsy

This review covers the broad topic of brain surgery in the treatment of pediatric intractable epilepsy. The authors review the latest advancements in the presurgical workup as well as the mandatory tests needed to explore the epilepsy workup in these children. They describe the different types of epilepsy from a surgical standpoint (temporal, extratemporal, multifocal, and hemispheric epilepsies) and various surgical procedures that can be proposed depending on the clinical scenario: lesionectomies, lobectomies, hemispherectomies, neuromodulation, and palliative surgeries. They also describe the key differences of the pediatric patient as compared with the adult patient in such pathologic conditions.

Imaging in medically refractory epilepsy at 3 Tesla: a 13-year tertiary adult epilepsy center experience

Objectives

MRI negative epilepsy has evolved through increased usage of 3 T and insights from surgically correlated studies. The goal of this study is to describe dedicated 3 T epilepsy MRI findings in medically refractory epilepsy (MRE) patients at a tertiary epilepsy center to familiarize radiologists with an updated spectrum and frequency of potential imaging findings in the adult MRE population.

Methods

Included were all patients with MRE admitted to the epilepsy monitoring unit who were discussed at weekly interdisciplinary imaging conferences at Toronto Western Hospital with MRI studies (3 T with dedicated epilepsy protocol) performed between January 2008 and January 2021. Lesion characterization was performed by two readers based on most likely imaging diagnosis in consensus. Lobes involved per case were recorded.

Results

A total of 738 patients (386 female; mean age 35 years, range 15–77) were included. A total of 262 patients (35.5%) were MRI negative. The most common imaging finding was mesial temporal sclerosis, seen in 132 patients (17.9%), followed by encephalomalacia and gliosis, either posttraumatic, postoperative, postischemic, or postinfectious in nature, in 79 patients (10.7%). The most common lobar involvement (either partially or uniquely) was temporal (341 cases, 58.6%). MRE patients not candidates for surgical resection were included in the study, as were newly described pathologies from surgically correlated studies revealing findings seen retrospectively on reported MRI negative exams (isolated enlargement of the amygdala, temporal pole white matter abnormality, temporal encephalocele).

Conclusion

This study provides an updated description of the spectrum of 3 T MRI findings in adult MRE patients from a tertiary epilepsy center.

Robot-assisted stereoelectroencephalography in young children: technical challenges and considerations

Robot-assisted stereoelectroencephalography (sEEG) is frequently employed to localize epileptogenic zones in patients with medically refractory epilepsy (MRE). Its methodology is well described in adults, but less so in children. Given the limited information available on pediatric applications, the objective is to describe the unique technical challenges and considerations of sEEG in the pediatric population. In this report, we describe our institutional experience with the technical aspects of robot-assisted sEEG in an exclusively pediatric epilepsy surgery unit, focusing on pre-, intra-, and post-operative nuances that are particular to the pediatric population. The pediatric population presents several unique challenges in sEEG, including reduced skull thickness relative to adults, incomplete neurologic development, and often special behavioral considerations. Pre-operative selection of putative epileptogenic zones requires careful multidisciplinary decision-making. Intraoperative attention to nuances in positioning, clamp selection, registration, and electrode placement are necessary. Activity considerations and electrode migration and removal are key post-operative considerations. Robot-assisted sEEG is a valuable tool in the armamentarium of techniques to characterize MRE. However, special considerations must be given to the pediatric population to optimize safety and efficacy.

Seizure control after epilepsy surgery in early childhood: A systematic review and meta-analysis

OBJECTIVE

This meta-analysis aimed to determine the main factors influencing surgical outcomes in children <3 years old with refractory epilepsy.

METHODS

The PubMed and Cochrane database were systematically searched for epilepsy surgery outcomes from December 1, 1991, to March 30, 2021, using the following search terms: "Epilepsy surgery OR Seizure operation" AND "under three years" OR "first three years" OR "early childhood" OR "infancy OR infants." Seizure onset, duration of epilepsy, magnetic resonance imaging findings, age at the time of surgery, surgical methods, resection extent, and pathological findings were considered potential moderators of differences in seizure outcomes. The fixed-effects models, combined effect sizes, and 95% confidence intervals (CI) were used to calculate the influence of potential factors on seizure outcomes.

RESULTS

Thirty two studies (559 cases) were included in the meta-analysis. The significant factors that correlated with a lower seizure control rate were frontal lobectomy (odds ratio [OR]: 0.33, 95% CI: 0.12-0.91; p = 0.03) and malformation of cortical development (MCD) (OR, 0.38; 95% CI: 0.24-0.62; p < 0.01). A higher seizure control rate was observed in children with tumors (92.86%) and Sturge-Weber syndrome (SWS, 91.43%). Frontal lobe epilepsy induced by MCD was related to the worst postoperative efficacy (OR, 0.26; 95% CI: 0.13-0.53; p < 0.01).

SIGNIFICANCE

The results of our meta-analyses revealed that pathology and surgical location play critical roles in the outcome of epilepsy surgery in children <3 years old. Clarification of the etiology of epilepsy before surgery is critical for better postoperative outcomes.

The Missed Value of Underutilizing Pediatric Epilepsy Surgery: A Systematic Review

Pediatric epilepsy surgery is underutilized. Only 1%-11% of children with drug resistant epilepsy (DRE) undergo surgical treatment, or less than half of those estimated to benefit. We conducted a systematic review of articles published in PubMed, EMBASE, and Web of Science in order to study the factors related to surgery underutilization as well as the impact on both the individual and the healthcare system. Our review demonstrates multiple factors leading to underutilization, including family misconceptions about epilepsy surgery, lack of provider knowledge, as well as systemic health disparities. While the upfront cost of epilepsy surgery is significant, the long-term financial benefits and reduced health resource utilization tilt the economic advantage in favor of surgery in children with DRE. Additionally, timely interventions improve seizure and cognitive outcomes with low risk of complications. Further interventions are needed at the levels of family, provider, and the healthcare system to increase access to pediatric epilepsy surgery.

Epilepsy Surgery in Children

Epilepsy in children continues to present a major medical and economic burden on society. Left untreated, seizures can present the risk of sudden death and severe cognitive impairment. It is understood that primary care providers having concerns about abnormal movements or behaviors in children will make a prompt referral to a trusted pediatric neurologist. The authors present a brief introduction to seizure types, classification, and management with particular focus on what surgery for epilepsy can offer. Improved seizure control and its attendant improvements in quality of life can be achieved with timely referral and intervention.

Perampanel treatment in highly drug-resistant epilepsies including nonsurgical candidates and failed surgery

OBJECTIVE

To evaluate the effectiveness and tolerability of perampanel (PER) treatment for patients with highly drug-resistant epilepsies (HDRE) including nonsurgical candidates and failed surgery in real-world setting.

METHODS

All patients who were treated with PER during June 2015 to August 2019 were selected. Primary outcomes were percentage of seizure reduction, responder rate, and seizure freedom rate. Seizure frequency after taking PER at 3 and 12 months were compared with baseline seizure frequency within the same time period prior to starting PER. Secondary outcomes were retention rate, side effects, and predictors for a response to PER. Descriptive statistics and the Kernel regression model were employed.

RESULTS

Forty-one patients received PER treatment during the study period. Six patients who had no baseline seizure frequency recordings were excluded, for a total of 35 patients included for analysis. Mean age was 40.06 years (SD 12.34). All were highly resistant to several antiseizure drugs (ASDs) with a median number of previously failed ASDs of 8 items. Eleven, 16, 5, and 3 patients were lesional, nonlesional focal epilepsy, nonsurgical candidate, and failed surgery, respectively. At 3 months after PER treatment, the median percentage of seizure reduction was 20 % (-35.71, 100), the responder rate was 22.86 % (8/35), and the seizure freedom rate was 17.14% (6/35). At 12 months after PER treatment, the corresponding outcomes were 25% (-20.57, 91.60), 22.58% (7/31), and 9.68% (3/31), respectively. Retention rates at 3 and 12 months were 100% and 91.43% (32/35), respectively. Nineteen patients (54.29%) experienced side effects from PER. Side effects were somnolence (6/35), dizziness (3/35), irritability (2/35), and ataxia (2/35), and one each for weight loss, nausea, headache, insomnia, verbal aggressivity, and depression. Median duration for 2-mg dose increment was 2.2 months.

CONCLUSIONS

In real-world practice, slow-titration PER regimen is well-tolerable and shows benefit in helping control seizures in patients with very difficult-to-treat HDRE.

Surgical Outcome in Extratemporal Epilepsies Based on Multimodal Pre-Surgical Evaluation and Sequential Intraoperative Electrocorticography

Objective: to present the postsurgical outcome of extratemporal epilepsy (ExTLE) patients submitted to preoperative multimodal evaluation and intraoperative sequential electrocorticography (ECoG). Subjects and methods: thirty-four pharmaco-resistant patients with lesional and non-lesional ExTLE underwent comprehensive pre-surgical evaluation including multimodal neuroimaging such as ictal and interictal perfusion single photon emission computed tomography (SPECT) scans, subtraction of ictal and interictal SPECT co-registered with magnetic resonance imaging (SISCOM) and electroencephalography (EEG) source imaging (ESI) of ictal epileptic activity. Surgical procedures were tailored by sequential intraoperative ECoG, and absolute spike frequency (ASF) was calculated in the pre- and post-resection ECoG. Postoperative clinical outcome assessment for each patient was carried out one year after surgery using Engel scores. Results: frontal and occipital resection were the most common surgical techniques applied. In addition, surgical resection encroaching upon eloquent cortex was accomplished in 41% of the ExTLE patients. Pre-surgical magnetic resonance imaging (MRI) did not indicate a distinct lesion in 47% of the cases. In the latter number of subjects, SISCOM and ESI of ictal epileptic activity made it possible to estimate the epileptogenic zone. After one- year follow up, 55.8% of the patients was categorized as Engel class I–II. In this study, there was no difference in the clinical outcome between lesional and non lesional ExTLE patients. About 43.7% of patients without lesion were also seizure- free, p = 0.15 (Fischer exact test). Patients with satisfactory seizure outcome showed lower absolute spike frequency in the pre-resection intraoperative ECoG than those with unsatisfactory seizure outcome, (Mann– Whitney U test, p = 0.005). Conclusions: this study has shown that multimodal pre-surgical evaluation based, particularly, on data from SISCOM and ESI alongside sequential intraoperative ECoG, allow seizure control to be achieved in patients with pharmacoresistant ExTLE epilepsy.

Safety of responsive neurostimulation in pediatric patients with medically refractory epilepsy

OBJECTIVE

Approximately 75% of pediatric patients who suffer from epilepsy are successfully treated with antiepileptic drugs, while the disease is drug resistant in the remaining patients, who continue to have seizures. Patients with drug-resistant epilepsy (DRE) may have options to undergo invasive treatment such as resection, laser ablation of the epileptogenic focus, or vagus nerve stimulation. To date, treatment with responsive neurostimulation (RNS) has not been sufficiently studied in the pediatric population because the FDA has not approved the RNS device for patients younger than 18 years of age. Here, the authors sought to investigate the safety of RNS in pediatric patients.

METHODS

The authors performed a retrospective single-center study of consecutive patients with DRE who had undergone RNS system implantation from September 2015 to December 2019. Patients were followed up postoperatively to evaluate seizure freedom and complications.

RESULTS

Of the 27 patients studied, 3 developed infections and were treated with antibiotics. Of these 3 patients, one required partial removal and salvaging of a functioning system, and one required complete removal of the RNS device. No other complications, such as intracranial hemorrhage, stroke, or device malfunction, were seen. The average follow-up period was 22 months. All patients showed improvement in seizure frequency.

CONCLUSIONS

The authors demonstrated the safety and efficacy of RNS in pediatric patients, with infections being the main complication.

ABBREVIATIONS

DBS = deep brain stimulation; DRE = drug-resistant epilepsy; MDC = multidisciplinary conference; MER = microelectrode recording; MSHS = Mount Sinai Health System; RNS = responsive neurostimulation; SEEG = stereo-EEG; VNS = vagus nerve stimulation.

MRI-negative PET-negative epilepsy long-term surgical outcomes: A single-institution retrospective review

PURPOSE

Surgical planning for people with drug resistant non-lesional focal epilepsy can be challenging. Prior studies focus on cases that are only MRI-negative or MRI-negative with PET-positive imaging, but little is known about outcomes in patients with non-lesional findings on both MRI and PET imaging. In this study, we investigate 5-year surgical outcomes in patients who underwent epilepsy surgery for drug resistant MRI/PET-negative focal epilepsy.

METHODS

We collected clinical and testing data on 131 consecutive patients with drug resistant non-lesional epilepsy who were presented at a multidisciplinary epilepsy surgery conference at the New York University Comprehensive Epilepsy Center between 2010 and 2014, and identified those who underwent epilepsy surgery in order to review 5-year surgical outcomes.

RESULTS

There were 103 with non-lesional MRI studies, and of these, 22 had corresponding non-lesional PET imaging. 14 MRI/PET-negative patients pursued a surgical treatment option and 9 underwent resections after intracranial EEG. At 5 years, 77.8 % of patients had favorable (ILAE class 1 and 2) outcomes. Most (77.8 %) had focal cortical dysplasia type Ia (FCDIa) on pathology.

CONCLUSION

These findings suggest that with careful planning and patient selection, surgery for patients with drug resistant MRI/PET-negative focal epilepsy can be successful.

Frontal disconnection surgery for drug-resistant epilepsy: Outcome in a series of 16 patients

OBJECTIVE

To evaluate the effectiveness of frontal disconnection surgery in seizure control and related consequences in a consecutive patient series.

METHODS

We conducted a retrospective analysis of patients who underwent frontal disconnection surgery for drug-resistant epilepsy (DRE). Baseline epilepsy characteristics, detailed presurgical evaluation including epileptogenic zone (EZ) localization, magnetic resonance imaging (MRI) detection of epileptogenic lesion, and pathological findings were reviewed. Patients were followed postoperatively for seizure outcome at 1 year.

RESULTS

A total of 16 patients were identified (six children and 10 adults). Most patients had a childhood onset of DRE with a median duration of epilepsy of 6.5 years (interquartile range 3.5-17.5 years) before surgery. In 10 (62.5%) patients, the EZ was localized to the frontal lobe, while in six patients, the EZ involved also adjacent lobes or consisted of multiple foci. In 10 (62.5%) patients, an epileptogenic lesion was detected on presurgical MRI, four of which (40%) had all MRI abnormalities confined to the frontal lobe. Two-thirds of the patients (11/16; 68.8%) underwent isolated frontal disconnection procedure, while remaining patients had frontal disconnection combined with resection of an adjacent lobe. Of the 12 patients in whom biopsy was taken from the disconnected frontal lobe, six (50%) had pathology-proven focal cortical dysplasia. We observed surgical-related complications in three (18.8%) cases, neurological deficits in other three (18.8%) patients, and worsening cognitive abilities in one (6.3%) patient. Overall, eight (50%) patients became completely seizure-free (ILAE 1) at one-year follow-up.

SIGNIFICANCE

Frontal disconnection surgery for DRE can result in seizure freedom in certain patients, especially when the EZ is strictly limited to the ipsilateral frontal region, and the MRI shows an epileptogenic lesion that is purely frontal in location. Frontal lobe disconnection procedure is safe and has a limited complication rate. However, further studies with larger patient population will yield more significance.

Recent Aspects of Pediatric Epilepsy Surgery

Surgery has been and is now a well-established treatment indicated for adults and children with drug-resistant epilepsy (DRE). The surgical landscape for children with DRE appears to be expanding, and surgical cases of pediatric epilepsy have increased significantly in the past decade, contrary to adult epilepsy. Several fundamental changes have led to the widespread surgical treatment for DRE in children, based on a risk-benefit analysis of pediatric epilepsy surgery, and a change in our overall approach to evaluation. There are unique and age-related differences associated with pediatric epilepsy surgery, characterized by different types of etiologies, concerns for developmental progress, and safety issues. Indications for “pediatric epilepsy surgery” have been broadened to include a wide spectrum of etiologies without excluding children with “generalized” seizures, “generalized or multifocal eletroencephlography”, or patients with contra-lateral epileptiform activity or magnetic resonance imaging abnormalities. Furthermore, epilepsy surgery is increasingly considered in infancy and early childhood, which has similar surgical outcomes as the case of late childhood, in an effort to improve the eventual development outcome. Seizure freedom, or at least seizure reduction, is an excellent result with resolution of the associated epileptic encephalopathy, normalization of the EEG, and decrease in the total epileptic burden in the pediatric field.

Seizure outcome of pediatric epilepsy surgery

Objective

This systematic review and meta-analyses assessed seizure outcome following pediatric epilepsy surgery.

Methods

MEDLINE, EMBASE, and Cochrane were searched for pediatric epilepsy surgery original research from 1990 to 2017. The outcome was seizure freedom at 12 months or longer follow-up. Using random-effects models, the effect sizes for controlled studies, uncontrolled studies on surgery locations (temporal lobe [TL], extratemporal lobe [ETL], or hemispheric surgery), pathologies, nonlesional epilepsy, and incomplete resection were estimated. Meta-regression assessed the relationship between age at surgery, age at seizure onset, and seizure outcome. Random-effects network meta-analysis was conducted for surgery locations.

Results

Two hundred fifty-eight studies were included. Surgery achieved higher seizure freedom than medical therapy (odds ratio [OR] = 6.49 [95% confidence interval [CI]: 2.87–14.70], p < 0.001). Seizure freedom declined over time after surgery, from 64.8% (95% CI: 51.2%–76.4%; p = 0.034) at 1 year, to 60.3% (95% CI: 52.9%–67.4%; p = 0.007) at 5 years, and to 39.7% (95% CI: 28.4%–52.2%, p = 0.106) at 10 years. Seizure freedom was (1) highest for hemispheric surgery, followed by TL and ETL surgery, and (2) highest for tumor and lower for malformations of cortical development. Seizure freedom was lower for nonlesional than lesional epilepsy (OR = 0.54 [95% CI: 0.34, 0.88], p = 0.013) and incomplete than complete resection (OR = 0.13 [95% CI: 0.08, 0.21], p < 0.001). Age at surgery and age at seizure onset were associated with seizure freedom for mixed pathologies and surgery locations and TL surgery.

Conclusion

Epilepsy surgery was more effective than medical therapy to control seizures. Understanding seizure outcomes of different surgery locations, pathologies, nonlesional epilepsy, and incomplete resection will assist with presurgical counseling.

Operculoinsular cortectomy for refractory epilepsy. Part 1: Is it effective?

OBJECTIVE

Patients with refractory epilepsy of operculoinsular origin are often denied potentially effective surgical treatment with operculoinsular cortectomy (also termed operculoinsulectomy) because of feared complications and the paucity of surgical series with a significant number of cases documenting seizure control outcome. The goal of this study was to document seizure control outcome after operculoinsular cortectomy in a group of patients investigated and treated by an epilepsy team with 20 years of experience with this specific technique.

METHODS

Clinical, imaging, surgical, and seizure control outcome data of all patients who underwent surgery for refractory epilepsy requiring an operculoinsular cortectomy were retrospectively reviewed. Tumors and progressive encephalitis cases were excluded. Descriptive and uni- and multivariate analyses were done to determine seizure control outcome and predictors.

RESULTS

Forty-three patients with 44 operculoinsular cortectomies were studied. Kaplan-Meier estimates of complete seizure freedom (first seizure recurrence excluding auras) for years 0.5, 1, 2, and 5 were 70.2%, 70.2%, 65.0%, and 65.0%, respectively. With patients with more than 1 year of follow-up, seizure control outcome Engel class I was achieved in 76.9% (mean follow-up duration 5.8 years; range 1.25-20 years). With multivariate analysis, unfavorable seizure outcome predictors were frontal lobe-like seizure semiology, shorter duration of epilepsy, and the use of intracranial electrodes for invasive monitoring. Suspected causes of recurrent seizures were sparing of the language cortex part of the focus, subtotal resection of cortical dysplasia/polymicrogyria, bilateral epilepsy, and residual epileptic cortex with normal preoperative MRI studies (insula, frontal lobe, posterior parieto-temporal, orbitofrontal).

CONCLUSIONS

The surgical treatment of operculoinsular refractory epilepsy is as effective as epilepsy surgeries in other brain areas. These patients should be referred to centers with appropriate experience. A frontal lobe-like seizure semiology should command more sampling with invasive monitoring. Recordings with intracranial electrodes are not always required if the noninvasive investigation is conclusive. The complete resection of the epileptic zone is crucial to achieve good seizure control outcome.

Robot-assisted stereoelectroencephalography in children

OBJECTIVEThe goal in the study was to describe the clinical outcomes associated with robot-assisted stereoelectroencephalography (SEEG) in children.METHODSThe authors performed a retrospective, single-center study in consecutive children with medically refractory epilepsy who were undergoing robot-assisted SEEG. Kaplan-Meier survival analysis was used to calculate the probability of seizure freedom. Both univariate and multivariate methods were used to analyze the preoperative and operative factors associated with seizure freedom.RESULTSFifty-seven children underwent a total of 64 robot-assisted procedures. The patients' mean age was 12 years, an average of 6.4 antiepileptic drugs (AEDs) per patient had failed prior to implantation, and in 56% of the patients the disease was considered nonlesional. On average, children had 12.4 electrodes placed per implantation, with an implantation time of 9.6 minutes per electrode and a 10-day postoperative stay. SEEG analysis yielded a definable epileptogenic zone in 51 (89%) patients; 42 (74%) patients underwent surgery, half of whom were seizure free at last follow-up, 19.6 months from resection. In a multivariate generalized linear model, resective surgery, older age, and shorter SEEG-related hospital length of stay were associated with seizure freedom. In a Cox proportional hazards model including only the children who underwent resective surgery, older age was the only significant factor associated with seizure freedom. Complications related to bleeding were the major contributors to morbidity. One patient (1.5%) had a symptomatic hemorrhage resulting in a permanent neurological deficit.CONCLUSIONSThe authors report one of the largest pediatric-specific SEEG series demonstrating that the modern surgical management of medically refractory epilepsy in children can lead to seizure freedom in many patients, while also highlighting the challenges posed by this difficult patient population.

Quality of Life After Epilepsy Surgery in Children: A Systematic Review and Meta-Analysis

BACKGROUND

Pediatric epilepsy surgery is a treatment modality appropriate for select patients with debilitating medication-resistant seizures. Previous publications have studied seizure freedom as the main outcome of epilepsy surgery. However, there has been no systematic assessment of the postoperative life quality for these children.

OBJECTIVE

To estimate the quality of life (QOL) long-term outcomes after surgery for intractable epilepsy in pediatric patients.

METHODS

A systematic search of the PubMed and Cochrane databases was performed. Studies reporting questionnaire-assessed QOL at least 12 months postoperatively were included. QOL means and standard deviations were compared between surgically and medically managed patients, between the preoperative and postoperative state of each patient, and were further stratified into patients achieving seizure freedom, and those who did not. Meta-analysis was performed using fixed effects models for weighted mean differences (WMD), 95% confidence intervals (CI) and sensitivity analyses. Funnel plots and Begg's tests were utilized to detect publication bias.

RESULTS

The search yielded 18 retrospective studies, reporting 890 surgical patients. Following epilepsy surgery, children had significant QOL improvement compared to their preoperative state (WMD: 16.71, 95% CI: 12.19-21.22, P < .001) and better QOL than matched medically treated controls (WMD: 12.42, 95% CI: 6.25-18.58, P < .001). Patients achieving total seizure freedom after surgery had significant postoperative QOL improvement (WMD: 16.12, 95% CI: 7.98-24.25, P < .001), but patients not achieving seizure freedom did not achieve statistical significance (P = .79).

CONCLUSION

Epilepsy surgery can effectively improve QOL in children with medication-resistant seizures, through seizure freedom, which was associated with the greatest improvement in life quality.

Treatment of medically refractory seizures with responsive neurostimulation: 2 pediatric cases

The responsive neurostimulation (RNS) system, an adjunctive treatment for pharmacoresistant partial-onset seizures with 1 or 2 foci, has been available to patients aged 18 years or older since the device's FDA approval in 2013. Herein, the authors describe their off-label application of this technology in 2 pediatric patients and the consequent therapeutic benefit without surgical complications or treatment side effects. A 14-year-old nonambulatory, nonverbal male with severe developmental delay was considered for RNS therapy for medically and surgically refractory epilepsy with bilateral seizure onsets in the setting of a normal radiological examination and a known neuropathological diagnosis of type I cortical dysplasia. The RNS system was implanted with strip electrodes placed on the left lateral frontal and right lateral temporal neocortex. At 19 months' follow-up, cortical stimulation resulted in sustained reduction in both seizure frequency-3 seizures per day down from 15 to 30 per day-and seizure severity. The patient subsequently underwent a trial of corticothalamic stimulation with a right temporal cortical strip and a left thalamic depth electrode, which resulted in a further 50% reduction in seizure frequency. In a second case, a 9-year-old right-handed female with radiological evidence of a small watershed infarct on the left and medically refractory seizures was referred for presurgical evaluation. Invasive monitoring revealed an unresectable seizure focus in the eloquent cortex of the left posterior frontal and parietal lobes. The RNS device was implanted with cortical leads placed at the putative seizure focus. At 21 months after surgery, the patient had been seizure free for 4 months, following a 17-month period in which the seizure frequency had decreased from 12 per month to 2 per month, with associated functional and behavioral improvement. The authors' results suggest that RNS may be a palliative option for children with intractable seizures whose condition warrants off-label use of the surgical device. The improved therapeutic effect noted with time and sustained RNS treatment points to a possible neuromodulatory effect.

Seizure Outcome of Patients with Magnetic Resonance Imaging-Negative Epilepsies: Still An Ongoing Debate

BACKGROUND

Surgical results regarding MRI-negative epilepsy were presented and related clinical and histopathological parameters were discussed.

METHODS

Thirty-six MRI-negative epilepsy patients were retrospectively analyzed. Histopathological specimens were re-reviewed by 2 blind neuropathologists and re-classified based on the current classifications.

RESULTS

The mean age at surgery and seizure onset was 24.5 years and 9.3 years, respectively. Eight patients were younger than 18 years. Mean duration of seizures was 15.3 years. All but 2 underwent invasive monitorization. Eighteen patients had hypometabolism on FDG-PET with temporal lobe involvement in majority (66.7%). Hypometabolism was found in all patients with hippocampal sclerosis (HS), which was present in 50% and 66.7% of focal cortical dysplasia (FCD) type I and II patients, respectively. The frontal lobe resection was the most frequent type of operation followed by resections in temporal, parietal and occipital lobes. In 7 patients, multilobar resection was performed. Histopathological diagnosis was FCD type I, II, III, HS, and gliosis in 14, 12, 2, 3 and 2 patients, respectively. The mean follow-up was 5.8 years. Seventeen patients were seizure free and favorable outcome (Engel's I and II) was found in 69.7%. FCD type I tend to have more favorable seizure outcome. Duration of epilepsy and hypometabolism on FDG-PET was significantly related to outcome, whereas involved lobe was not.

CONCLUSIONS

Our results suggest it is worth pursuing resective surgery in adults as well as in children with drug-resistant epilepsy with normal MRI.

Seizure Outcomes in Children Following Electrocorticography-Guided Single-Stage Surgical Resection

BACKGROUND

In children with abnormal imaging, single-stage epilepsy surgery is an attractive alternative to the two-stage approach that relies on invasive recording of seizures. Implanted electrodes carry risks of their own and extend hospitalization, but the efficacy of one-stage resections in a variety of pathologies and cerebral locations is not well established. We report our center's experience with single-stage epilepsy surgery guided by intraoperative electrocorticography (ECoG).

METHODS

We retrospectively analyzed 130 consecutive patients who underwent single-stage epilepsy surgery before age 19 years and had at least a two-year follow-up. Intraoperative ECoG was available for review in 113. Patients were considered seizure-free if they were continuously Engel Class I up to the two-year postoperative mark. ECoG findings were classified according to the presence of interictal attenuation, spikes, both, or neither. Complications and hospital length of stay were evaluated.

RESULTS

Eighty percent of 130 patients were seizure-free at two years. All but one had an abnormal MRI. Patients with tumor had a better seizure outcome than patients with cortical malformation. Frontal resections had worse outcome, especially among tumors. Intraoperative ECoG revealed both attenuation and spikes in 48%, attenuation only in 23%, spikes only in 20%, and neither in 9%. The complication rate was 6.9%, with no major neurological complications. The average length of stay was 5.7 nights.

CONCLUSIONS

With ECoG-guided single-stage surgery, we achieved results comparable with other pediatric surgical series and with a low complication rate. An extensive two-stage approach may not be required when there is a lesion on imaging and other information is concordant, even when the MRI abnormality is subtle and unclearly delineated. Frontal foci may present a challenge because of their proximity to "eloquent" nonresectable cortex or critical structures.

Pediatric epilepsy surgery: could age be a predictor of outcomes?

OBJECTIVE Like adults, many children suffering from intractable seizures benefit from surgical therapy. Although various reports indicate that early intervention may avoid severe developmental consequences often associated with intractable epilepsy, surgery is still considered a last option for many children. In this retrospective study, the authors aimed to determine whether pediatric epilepsy surgery, in particular during the first years of life, relates to measurable benefits. METHODS Data from 78 patients (age range 5 months to 17 years) who underwent epilepsy surgery at the Geneva and Lausanne University Hospitals between 1997 and 2012 were reviewed retrospectively. Patients were dichotomized into 2 groups: infants (≤ 3 years of age, n = 19), and children/adolescents (4-17 years of age, n = 59). Compared with children/adolescents, infants more often had a diagnosis of dysplasia (37% vs 10%, respectively; p < 0.05, chi-square test). RESULTS The overall seizure-free rate was 76.9%, with 89.5% in infants and 72.9% in the children/adolescents group. Infants were 2.76 times as likely to achieve seizure-free status as children/adolescents. Postoperative antiepileptic medication was reduced in 67.9% of patients. Only 11.4% of the patients were taking more than 2 antiepileptic drugs after surgery, compared with 43% before surgery (p < 0.0001). The overall complication rate was 15.1% (6.4% transient hemiparesis), and no major complications or deaths occurred. CONCLUSIONS The data show a high seizure-free rate in children ≤ 3 years of age, despite a higher occurrence of dysplastic, potentially ill-defined lesions. Pediatric patients undergoing epilepsy surgery can expect a significant reduction in their need for medication. Given the excellent results in the infant group, prospective studies are warranted to determine whether age ≤ 3 years is a predictor for excellent surgical outcome.

Source localization of the seizure onset zone from ictal EEG/MEG data

INTRODUCTION

Surgical treatment of drug-resistant epilepsy relies on the identification of the seizure onset zone (SOZ) and often requires intracranial EEG (iEEG). We have developed a new approach for non-invasive magnetic and electric source imaging of the SOZ (MSI-SOZ and ESI-SOZ) from ictal magnetoencephalography (MEG) and EEG recordings, using wavelet-based Maximum Entropy on the Mean (wMEM) method. We compared the performance of MSI-SOZ and ESI-SOZ with interictal spike source localization (MSI-spikes and ESI-spikes) and clinical localization of the SOZ (i.e., based on iEEG or lesion topography, denoted as clinical-SOZ).

METHODS

A total of 46 MEG or EEG seizures from 13 patients were analyzed. wMEM was applied around seizure onset, centered on the frequency band showing the strongest power change. Principal component analysis applied to spatiotemporal reconstructed wMEM sources (0.4-1 s around seizure onset) identified the main spatial pattern of ictal oscillations. Qualitative sublobar concordance and quantitative measures of distance and spatial overlaps were estimated to compare MSI/ESI-SOZ with MSI/ESI-Spikes and clinical-SOZ.

RESULTS

MSI/ESI-SOZ were concordant with clinical-SOZ in 81% of seizures (MSI 90%, ESI 64%). MSI-SOZ was more accurate and identified sources closer to the clinical-SOZ (P = 0.012) and to MSI-Spikes (P = 0.040) as compared with ESI-SOZ. MSI/ESI-SOZ and MSI/ESI-Spikes did not differ in terms of concordance and distance from the clinical-SOZ.

CONCLUSIONS

wMEM allows non-invasive localization of the SOZ from ictal MEG and EEG. MSI-SOZ performs better than ESI-SOZ. MSI/ESI-SOZ can provide important additional information to MSI/ESI-Spikes during presurgical evaluation. Hum Brain Mapp 37:2528-2546, 2016. © 2016 Wiley Periodicals, Inc.

Optimising EEG-fMRI for Localisation of Focal Epilepsy in Children

BACKGROUND

Early surgical intervention in children with drug resistant epilepsy has benefits but requires using tolerable and minimally invasive tests. EEG-fMRI studies have demonstrated good sensitivity for the localization of epileptic focus but a poor yield although the reasons for this have not been systematically addressed. While adults EEG-fMRI studies are performed in the "resting state"; children are commonly sedated however, this has associated risks and potential confounds. In this study, we assessed the impact of the following factors on the tolerability and results of EEG-fMRI in children: viewing a movie inside the scanner; movement; occurrence of interictal epileptiform discharges (IED); scan duration and design efficiency. This work's motivation is to optimize EEG-fMRI parameters to make this test widely available to paediatric population.

METHODS

Forty-six children with focal epilepsy and 20 controls (6-18) underwent EEG-fMRI. For two 10 minutes sessions subjects were told to lie still with eyes closed, as it is classically performed in adult studies ("rest sessions"), for another two sessions, subjects watched a child friendly stimulation i.e. movie ("movie sessions"). IED were mapped with EEG-fMRI for each session and across sessions. The resulting maps were classified as concordant/discordant with the presumed epileptogenic focus for each subject.

FINDINGS

Movement increased with scan duration, but the movie reduced movement by ~40% when played within the first 20 minutes. There was no effect of movie on the occurrence of IED, nor in the concordance of the test. Ability of EEG-fMRI to map the epileptogenic region was similar for the 20 and 40 minute scan durations. Design efficiency was predictive of concordance.

CONCLUSIONS

A child friendly natural stimulus improves the tolerability of EEG-fMRI and reduces in-scanner movement without having an effect on IED occurrence and quality of EEG-fMRI maps. This allowed us to scan children as young as 6 and obtain localising information without sedation. Our data suggest that ~20 minutes is the optimal length of scanning for EEG-fMRI studies in children with frequent IED. The efficiency of the fMRI design derived from spontaneous IED generation is an important factor for producing concordant results.

EEG resting state analysis of cortical sources in patients with benign epilepsy with centrotemporal spikes

Benign epilepsy with centrotemporal spikes (BECTS) is the most common idiopathic childhood epilepsy, which is often associated with developmental disorders in children. In the present study, we analyzed resting state EEG spectral changes in the sensor and source spaces in eight BECTS patients compared with nine age-matched controls. Using high-resolution scalp EEG data, we assessed statistical differences in spatial distributions of EEG power spectra and cortical sources of resting state EEG rhythms in five frequency bands: δ (0.5–3.5 Hz), θ (4–8 Hz), α (8.5–13 Hz), β₁ (13.5–20 Hz) and β₂ (20.5–30 Hz) under the eyes-closed resting state condition. To further investigate the impact of centrotemporal spikes on EEG spectra, we split the EEG data of the patient group into EEG portions with and without spikes. Source localization demonstrated the homogeneity of our population of BECTS patients with a common epileptic zone over the right centrotemporal region. Significant differences in terms of both spectral power and cortical source densities were observed between controls and patients. Patients were characterized by significantly increased relative power in θ, α, β₁ and β₂ bands in the right centrotemporal areas over the spike zone and in the right temporo-parieto-occipital junction. Furthermore, the relative power in all bands significantly decreased in the bilateral frontal and parieto-occipital areas of patients regardless of the presence or absence of spikes in EEG segments. However, the spectral differences between patients and controls were more pronounced in the presence of spikes. This observation emphasized the impact of benign epilepsy on cortical source power, especially in the right centrotemporal regions. Spectral changes in bilateral frontal and parieto-occipital areas may also suggest alterations in the default mode network in BECTS patients.

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BECTS patients exhibited enhanced θ activity over all cortical regions.

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BECTS patients displayed reduced α activity at the occipital regions.

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Patients showed increased power in θ, α, β in right temporo-parieto-occipital pole.

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EEG spectral changes in BECTS patients indicate dysfunction at the epileptic zone.

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EEG spectral changes in BECTS patients may show alteration in default mode network.

The evolution of epilepsy surgery between 1991 and 2011 in nine major epilepsy centers across the United States, Germany, and Australia

OBJECTIVE

Epilepsy surgery is the most effective treatment for select patients with drug-resistant epilepsy. In this article, we aim to provide an accurate understanding of the current epidemiologic characteristics of this intervention, as this knowledge is critical for guiding educational, academic, and resource priorities.

METHODS

We profile the practice of epilepsy surgery between 1991 and 2011 in nine major epilepsy surgery centers in the United States, Germany, and Australia. Clinical, imaging, surgical, and histopathologic data were derived from the surgical databases at various centers.

RESULTS

Although five of the centers performed their highest number of surgeries for mesial temporal sclerosis (MTS) in 1991, and three had their highest number of MTS surgeries in 2001, only one center achieved its peak number of MTS surgeries in 2011. The most productive year for MTS surgeries varied then by center; overall, the nine centers surveyed performed 48% (95% confidence interval [CI] -27.3% to -67.4%) fewer such surgeries in 2011 compared to either 1991 or 2001, whichever was higher. There was a parallel increase in the performance of surgery for nonlesional epilepsy. Further analysis of 5/9 centers showed a yearly increase of 0.6 ± 0.07% in the performance of invasive electroencephalography (EEG) without subsequent resections. Overall, although MTS was the main surgical substrate in 1991 and 2001 (proportion of total surgeries in study centers ranging from 33.3% to 70.2%); it occupied only 33.6% of all resections in 2011 in the context of an overall stable total surgical volume.

SIGNIFICANCE

These findings highlight the major aspects of the evolution of epilepsy surgery across the past two decades in a sample of well-established epilepsy surgery centers, and the critical current challenges of this treatment option in addressing complex epilepsy cases requiring detailed evaluations. Possible causes and implications of these findings are discussed.

Look back to leap forward: The emerging new role of magnetoencephalography (MEG) in nonlesional epilepsy

This review considers accumulating evidence for a new role of MEG/MSI in increasing the diagnostic yield of supposedly negative MRIs, and suggests changes in the use of MEG/MSI in presurgical epilepsy evaluations. Specific alterations in practice protocols for both the MEG practitioner (i.e. physician magnetoencephalographer) and MEG user (i.e. referring physician) are proposed that should further enhance the overall value of MEG/MSI. Although advances in MEG analysis methods will likely become increasingly assisted by computers, interpretive competency and prudent clinical judgment remain irreplaceable.

Epilepsy surgery: current status and ongoing challenges

This article reviews the current status of surgical treatment of epilepsy and introduces the ongoing challenges. Seizure outcome of resective surgery for focal seizures associated with focal lesions is satisfactory. Particularly for mesial temporal lobe epilepsy, surgical treatment should be considered from the earlier stage of the disease. Meanwhile, surgical outcome in nonlesional extratemporal lobe epilepsy is still to be improved using various approaches. Disconnective surgeries reduce surgical complications of extensive resections while achieving equivalent or better seizure outcomes. Multiple subpial transection is still being modified expecting a better outcome by transection to the vertical cortices along the sulci- and multi-directional transection from a single entry point. Hippocampal transection is expected to preserve memory function while interrupting the abnormal epileptic synchronization. Proper selection or combination of subdural and depth electrodes and a wide-band analysis of electroencephalography may improve the accurate localization of epileptogenic region. Patients for whom curative resective surgery is not indicated because of generalized or bilateral multiple nature of their epilepsies, neuromodulation therapies are options of treatment which palliate their seizures.

Seizure control after subtotal lesional resection

Reports on seizure outcomes following surgery for lesional epilepsy consistently cite extent of resection as a significant predictor of outcome. Unfortunately, gross-total resection is not technically feasible in all cases of medically refractory tumor-associated epilepsy. Here, the authors present the case of a 4-year-old girl whose epilepsy was medically controlled after 1-stage electrocorticography-guided subtotal resection (STR) of a large diffuse protoplasmic astrocytoma. They also review the modern literature on epilepsy associated with brain tumors. Outcomes are compared with those following surgical treatment of focal cortical dysplasia and vascular lesions. Gross-total lesional resection shows significant superiority across pathologies and anatomical regions. Despite a considerable number of STRs yielding seizure freedom, other favorable treatment factors have not been defined. Although gross-total lesional resection, if possible, is clearly superior, tailored surgery may still offer patients a significant opportunity for a good outcome. Treatment factors yielding successful seizure control following STR remain to be fully elucidated.

Patients with refractory epilepsy treated using a modified multiple subpial transection technique

BACKGROUND

: Multiple subpial transection (MST) is a potential surgical treatment for patients with epileptogenic foci located in cortical areas with higher functions. As neurosurgical teams have become more experienced with MST, the original technique has adapted.

OBJECTIVE

: To report our 6-year experience with a modified MST technique.

METHODS

: The population included 62 consecutive patients with medically refractory epilepsy treated by MST, with a follow-up period ranging from 2 to 9 years. MST was performed on gyri under neuronavigation and guided by intraoperative electrocorticography. We performed radiating MST from a single cortical entry point. The MST technique was described according to the number of transections performed and the Brodmann areas (BAs) involved. Any MST-related complications were registered and followed up. Clinical outcome was described in terms of seizure suppression or reduction according to the Engel modified classification.

RESULTS

: Twelve patients underwent MST alone (MSTa), and 50 had MST with another procedure. The main MST sites were BA 4 (61%) and 3, 1, 2 (58%); in 22% of cases, MST was performed in BA 44, 22, 39, and 40. Permanent neurological deficits were observed in 4 (6.4%) patients; 2 minor deficits were MST related (3.2%). A reduction in the seizure rate of at least 50% was seen in 79% of patients (MSTa group, 75%), and 42% became seizure free (MSTa group, 33%).

CONCLUSION

: This study demonstrates the efficacy and low morbidity of radiating MST performed under neuronavigation and intraoperative electrocorticography.

ABBREVIATIONS

: BA, Brodmann areaEEG, electroencephalogramFDG, 18-fluorodeoxyglucoseioECoG, intraoperative electrocorticographyMRE, medically refractory epilepsyMST, multiple subpial transectionMSTa, multiple subpial transection aloneMST+, multiple subpial transection with other procedures.

Identification of common predictors of surgical outcomes for epilepsy surgery

Although epilepsy surgery is an effective treatment for patients with drug-resistant epilepsy, surgical outcomes vary across patient groups and studies. Identification of reliable prognostic factors for surgical outcome is important for outcome research. In this study, recent systematic reviews and meta-analyses on prediction of seizure outcome have been analyzed, and common predictors of seizure outcome or unrelated factors for temporal lobe epilepsy (TLE), lesional extratemporal lobe epilepsy (ETLE), and tuberous sclerosis complex have been identified. Clinical factors such as lesional epilepsy, abnormal magnetic resonance imaging, partial seizures, and complete resection were found to be common positive predictors, and factors such as nonlesional epilepsy, poorly defined and localized epileptic focus, generalized seizures, and incomplete resection are common negative predictors, while factors such as age at surgery and side of surgery are unrelated to seizure outcome for TLE and lesional ETLE. In addition, diagnostic neuroimaging and resection are among the most important predictors of seizure outcome. However, common predictors of seizure outcome could not be identified in nonlesional ETLE because no predictors were found to be significant in adult patients (by meta-analysis), and outcome prediction is difficult in this case. Meta-analysis of other outcomes, such as neuropsychologic outcomes, is rare due to lack of evaluation standards. Further studies on identification of reliable predictors of surgical outcomes are needed.

Acceptance of epilepsy surgery in the pediatric age - what the parents think and what the doctors can do

Epilepsy surgery (ES) in pediatrics is safe and effective but can be underutilized. Possible barriers could be parental resistance and doctor inertia. We surveyed 138 parents of pediatric patients with epilepsy and found that 25.2% were opposed to this treatment. However, upon completing the questionnaire that contained factual information about ES, 50.4% of the responders stated that they had become more favorable vs. 3.3% more contrary and 46.3% unchanged. Parents of prepubescent patients were most receptive (p=0.0343) and more likely to shift to a more favorable attitude. Thus, pediatric neurologists should not hesitate to discuss ES as soon as indicated, providing all necessary information to increase acceptance. However, among 60 child neurologists surveyed, 60% did not fully comply with guidelines or follow accepted standards of practice, indicating that they may not be apt to provide proper parental guidance. We conclude that education of both practicing neurologists and parents is needed to facilitate the process.

Effects of dual pathology on cognitive outcome following left anterior temporal lobectomy for treatment of epilepsy

The objective of this retrospective study was to determine if dual pathology [DUAL - focal cortical dysplasia (FCD) and mesial temporal sclerosis (MTS)] in patients with left temporal lobe epilepsy is associated with greater risk for cognitive decline following temporal lobectomy than single pathology (MTS only). Sixty-three adults (Mage=36.5years, female: 52.4%) who underwent left anterior temporal lobectomy for treatment of epilepsy (MTS=28; DUAL=35) completed preoperative and postoperative neuropsychological evaluations. The base rate of dual pathology was 55.5%. Repeated measures ANOVAs yielded significant 2-way interactions (group×time) on most measures of language and memory with generally moderate effect sizes. Specifically, patients with MTS only demonstrated postoperative declines, while those with dual pathology remained unchanged or improved. Results suggest that dual pathology may be associated with better cognitive outcome following epilepsy surgery than MTS alone, possibly reflecting limited functionality of the resected tissue or intrahemispheric reorganization of function in the context of a developmental lesion.

The pathology of magnetic-resonance-imaging-negative epilepsy

Patients with magnetic-resonance-imaging (MRI)-negative (or 'nonlesional') pharmacoresistant focal epilepsy are the most challenging group undergoing presurgical evaluation. Few large-scale studies have systematically reviewed the pathological substrates underlying MRI-negative epilepsies. In the current study, histopathological specimens were retrospectively reviewed from MRI-negative epilepsy patients (n=95, mean age=30 years, 50% female subjects). Focal cortical dysplasia cases were classified according to the International League Against Epilepsy (ILAE) and Palmini et al classifications. The most common pathologies found in this MRI-negative cohort included: focal cortical dysplasia (n=43, 45%), gliosis (n=21, 22%), hamartia+gliosis (n=12, 13%), and hippocampal sclerosis (n=9, 9%). The majority of focal cortical dysplasia were ILAE type I (n=37) or Palmini type I (n=39). Seven patients had no identifiable pathological abnormalities. The existence of positive pathology was not significantly associated with age or temporal/extratemporal resection. Follow-up data post surgery was available in 90 patients; 63 (70%) and 57 (63%) attained seizure freedom at 6 and 12 months, respectively. The finding of positive pathology was significantly associated with seizure-free outcome at 6 months (P=0.035), but not at 12 months. In subgroup analysis, the focal cortical dysplasia group was not significantly correlated with seizure-free outcome, as compared with the negative-pathology groups at either 6 or 12 months. Of note, the finding of hippocampal sclerosis had a significant positive correlation with seizure-free outcome when compared with the negative-pathology group (P=0.009 and 0.004 for 6- and 12-month outcome, respectively). Absence of a significant histopathology in the resected surgical specimen did not preclude seizure freedom. In conclusion, our study highlights the heterogeneity of epileptic pathologies in MRI-negative epilepsies, with focal cortical dysplasia being the most common finding. The existence of positive pathology in surgical specimen may be a good indication for short-term good seizure outcome. There is a small subset of cases in which no pathological abnormalities are identified.

Identifying the cortical substrates of interictal epileptiform activity in patients with extratemporal epilepsy: An EEG-fMRI sequential analysis and FDG-PET study

PURPOSE

The aim of this study was to apply sequential analysis of electroencephalography-functional magnetic resonance imaging (EEG-fMRI) data to study the cortical substrates related to the generation of the interictal epileptiform activity (IEA) in patients with pharmacoresistant extratemporal epilepsy.

METHODS

We analyzed fMRI data from 21 children, adolescents, and young adults patients who showed frequent bursts or runs of spikes on EEG, by using the sequential analysis method. We contrasted consecutive fixed-width blocks of 10 s to obtain the relative variations in cerebral activity along the entire fMRI runs. Significant responses (p < 0.05, family-wise error (FWE) corrected), time-related to the IEA recorded on scalp EEG, were considered potential IEA cortical sources. These results were compared with those from the fluorodeoxyglucose-positron emission tomography (FDG-PET), intracranial EEG (two patients), and surgery outcome (eight patients).

KEY FINDINGS

The typical IEA was recorded in all patients. After the sequential analysis, at least one significant blood oxygen level-dependent (BOLD) response spatially consistent with the presumed epileptogenic zone was found. These IEA-related activation areas coincided when superimposed with the hypometabolism depicted by the FDG-PET. These data were also consistent with the invasive EEG findings. Epileptic seizures were recorded in eight patients. A subset of IEA-associated fMRI activations was consistent the activations at seizure-onset determined by sequential analysis. The inclusion of the IEA-related areas in the resection rendered the patients seizure-free (five of eight operated patients).

SIGNIFICANCE

The EEG-fMRI data sequential analysis could noninvasively identify cortical areas involved in the IEA generation. The spatial relationship of these areas with the cortical metabolic abnormalities depicted by the FDG-PET and their intrinsic relationship regarding the ictal-onset zone could be useful in epilepsy surgery planning.

Seizure outcome after extratemporal epilepsy surgery in childhood

AIM

The aim of the study was to describe seizure outcome following surgery for focal extratemporal epilepsy and identify factors associated with prolonged postsurgical freedom from seizures.

METHOD

In this retrospective cohort study, children with drug-resistant focal extratemporal epilepsy were treated surgically and followed up in a single tertiary care centre between 1997 and 2008.

RESULTS

Eighty children were identified for inclusion in the study (42 males, 38 females; median age 9y 1mo, range 3mo-18y 7mo). The aetiology was identified as focal cortical dysplasia (n=37), low-grade tumour (n=22), tuberous sclerosis (n=9), or non-specific (n=12). Children were followed for a median of 3 years 1 month (range 8mo-10y 7mo) after surgery. Overall, at last follow-up, 50% of the children had been completely seizure free since surgery (Engel class Ia); of these 40 individuals, 15 had discontinued all antiepileptic drugs. Several presurgical factors were associated with a favourable outcome. However, after controlling for confounding factors, aetiology appeared to be the only determinant of long-term seizure outcome as non-specific lesion pathology was associated with seizure recurrence (hazard ratio 10.43; 95% confidence interval 3.26-33.39).

INTERPRETATION

In 50% of cases, children with surgically treated drug-resistant extratemporal epilepsies have an excellent long-term outcome. The aetiology of the epileptogenic lesion appears to be the only significant determinant of surgical outcome in this population of children. It is difficult to correctly identify non-specific pathology on presurgical magnetic resonance imaging.

Individually tailored extratemporal epilepsy surgery in children: anatomo-electro-clinical features and outcome predictors in a population of 53 cases

Surgery for refractory extratemporal lobe epilepsy (ETLE) in the pediatric age group has been reported to be associated with a high percentage of failure and relapse. We performed a retrospective study of 53 consecutive patients with epilepsy onset before 12 years of age, who underwent, mostly at a pediatric age, an individually tailored ETLE surgery (32 in frontal and 21 in posterior cerebral areas) for pharmacoresistant seizures; these patients were selected and followed by a single national tertiary care pediatric center. Mean age at seizure onset was 3.14 years, and mean age at surgery was 11.23 years. Complete seizure freedom was achieved in 75% of the subjects. Short duration of illness before surgery, MRI features, no invasive pre-surgical evaluation, a localized interictal and ictal pattern as well as the presence of ictal fast activity on scalp EEG, localized interictal fast rhythms and absence of a diffuse initial ictal modification during SEEG, a complete resection of the epileptogenic zone, a type II FCD, and the absence of acute postoperative seizures correlated in a statistically significant way with a seizure-free outcome. We conclude that the seizure outcome of ETLE surgery in a carefully selected pediatric population can be excellent.

Neurosurgical management of frontal lobe epilepsy in children

OBJECT

Pediatric frontal lobe epilepsy (FLE) remains a challenging condition for neurosurgeons and epileptologists to manage. Postoperative seizure outcomes remain far inferior to those observed in temporal lobe epilepsies, possibly due to inherent difficulties in delineating and subsequently completely resecting responsible epileptogenic regions. In this study, the authors review their institutional experience with the surgical management of FLE and attempt to find predictors that may help to improve seizure outcome in this population.

METHODS

All surgically treated cases of intractable FLE from 1990 to 2008 were reviewed. Demographic information, preoperative and intraoperative imaging and electrophysiological investigations, and follow-up seizure outcome were assessed. Inferential statistics were performed to look for potential predictors of seizure outcome.

RESULTS

Forty patients (20 male, 20 female) underwent surgical management of FLE during the study period. Patients were an average of 5.6 years old at the time of FLE onset and 11.7 years at the time of surgery; patients were followed for a mean of 40.25 months. Most patients displayed typical FLE semiology. Twenty-eight patients had discrete lesions identified on MRI. Eight patients underwent 2 operations. Cortical dysplasia was the most common pathological diagnosis. Engel Class I outcome was obtained in 25 patients (62.5%), while Engel Class II outcome was observed in 5 patients (12.5%). No statistically significant predictors of outcome were found.

CONCLUSIONS

Control of FLE remains a challenging problem. Favorable seizure outcome, obtained in 62% of patients in this series, is still not as easily obtained in FLE as it is in temporal lobe epilepsy. While no statistically significant predictors of seizure outcome were revealed in this study, patients with FLE continue to require extensive workup and investigation to arrive at a logical and comprehensive neurosurgical treatment plan. Future studies with improved neuroimaging and advanced invasive monitoring strategies may well help define factors for success in this form of epilepsy that is difficult to control.

A retrospective study comparing preoperative evaluations and postoperative outcomes in paediatric and adult patients undergoing surgical resection for refractory epilepsy

PURPOSE

To review and compare the preoperative characteristics and postsurgical outcomes in paediatric and adult patients who underwent surgical resections from 2001 to 2009.

METHODS

Combined data from noninvasive measures such as ictal semiology, interictal/ictal scalp EEGs, MRI and SPECT were utilised to identify the epileptogenic zones (EZ). When noninvasive investigations produced inconclusive or inconsistent findings, patients underwent intracranial EEG monitoring. Resective micro-surgical procedures were conducted according to the results of the anatomo-electro-clinical investigations and were carried out to remove the EZ. We then followed up 222 paediatric (≤18 years old) and 100 adult patients (≥19 years old) for 1-9 years postoperatively.

RESULTS

The mean age of seizure onset in paediatric group was significantly lower than that in adult group. 95 (43%) of the paediatric and 42 (42%) of the adult patients required long-term intracranial EEG recording. 54 (24.3%) of the paediatric and 62 (62%) of the adult patients were found to have temporal lobe epilepsy (TLE), while 149 (67.1%) of the paediatric and 37 (37.0%) of the adult patients had extra-temporal lobe epilepsy (ETLE) (p=0.000). 19 (8.6%) of the paediatric patients and 1 (1%) adult patient had hemispheric lesions (p=0.009). 148 (66.7%) of the paediatric and 61 (61.0%) of the adult patients were seizure-free during the follow-up period. 17 of 19 (89.5%) children who underwent hemispherectomy were seizure-free. In both paediatric and adult groups, the surgical outcome for patients with TLE was significantly better than that of patients with ETLE (p=0.018 in children, p=0.029 in adults). Both the location of EZs and seizure-free ratio were significantly different (p<0.001) between the preadolescent (≤12 years old) and adolescent (13-18 years old) group. Hippocampal sclerosis was the most common pathologic finding in patients with TLE in both groups, and was followed by focal cortical dysplasia. In patients with TLE, the proportion of tumour was significantly higher in the paediatric than the adult group (25.9% vs. 10%, p=0.021).

CONCLUSION

Paediatric patients with refractory seizures had more extratemporal or hemispheric resectable epileptogenic foci and fewer temporal foci than adults. Our study demonstrates that resective surgery is an effective and safe early intervention in strictly selected paediatric patients with refractory epilepsy.

[Epilepsy surgery]

Epilepsy surgery is an important therapeutic option for patients with epilepsy since one third of all epilepsy patients will still not be become seizure free despite newly developed antiepileptic drugs. Anterior temporal lobe resection is the most common procedure. Extratemporal resections require more complex diagnostics and often invasive evaluation which is not the case in most temporal epilepsy patients due to improved imaging (MRI, PET, SPECT). Electrical stimulation of the anterior thalamus has been available as a treatment option since last year.