Challenges in the surgical treatment of epilepsy patients with cortical dysplasia

New interinstitutional, multimodal presurgical evaluation protocol associated with improved seizure freedom for poorly defined cases of focal epilepsy in children

OBJECTIVE

In an attempt to improve postsurgical seizure outcomes for poorly defined cases (PDCs) of pediatric focal epilepsy (i.e., those that are not visible or well defined on 3T MRI), the authors modified their presurgical evaluation strategy. Instead of relying on concordance between video-electroencephalography and 3T MRI and using functional imaging and intracranial recording in select cases, the authors systematically used a multimodal, 3-tiered investigation protocol that also involved new collaborations between their hospital, the Montreal Children's Hospital, and the Montreal Neurological Institute. In this study, the authors examined how their new strategy has impacted postsurgical outcomes. They hypothesized that it would improve postsurgical seizure outcomes, with the added benefit of identifying a subset of tests contributing the most.

METHODS

Chart review was performed for children with PDCs who underwent resection following the new strategy (i.e., new protocol [NP]), and for the same number who underwent treatment previously (i.e., preprotocol [PP]); ≥ 1-year follow-up was required for inclusion. Well-defined, multifocal, and diffuse hemispheric cases were excluded. Preoperative demographics and clinical characteristics, resection volumes, and pathology, as well as seizure outcomes (Engel class Ia vs > Ia) at 1 year postsurgery and last follow-up were reviewed.

RESULTS

Twenty-two consecutive NP patients were compared with 22 PP patients. There was no difference between the two groups for resection volumes, pathology, or preoperative characteristics, except that the NP group underwent more presurgical evaluation tests (p < 0.001). At 1 year postsurgery, 20 of 22 NP patients and 10 of 22 PP patients were seizure free (OR 11.81, 95% CI 2.00-69.68; p = 0.006). Magnetoencephalography and PET/MRI were associated with improved postsurgical seizure outcomes, but both were highly correlated with the protocol group (i.e., independent test effects could not be demonstrated).

CONCLUSIONS

A new presurgical evaluation strategy for children with PDCs of focal epilepsy led to improved postsurgical seizure freedom. No individual presurgical evaluation test was independently associated with improved outcome, suggesting that it may be the combined systematic protocol and new interinstitutional collaborations that makes the difference rather than any individual test.

Sociodemographic Factors in Pediatric Epilepsy Surgery

BACKGROUND

Despite documented efficacy of surgical treatment in carefully selected patients, surgery is delayed and/or underutilized in both adult and children with focal onset epilepsy. The reasons for surgical delay are often assumed or theorized, and studies have predominantly targeted the adult population. To focus on a more targeted pediatric population and to determine identifiable reasons for intervention, this study aimed to investigate time to epilepsy surgery among pediatric patients with medically intractable epilepsy associated with focal cortical dysplasia and to identify sociodemographic and clinical associations in time to epilepsy surgery.

METHODS

We reviewed 96 consecutive pediatric patients who underwent surgery for medically intractable epilepsy with a diagnosis of focal cortical dysplasia. Descriptive statistics, univariate and multivariate analyses were conducted to study the association of sociodemographic variables of patients with focal cortical dysplasia and time to epilepsy surgery and postoperative seizure control.

RESULTS

We identified that non-white patients on average had a longer duration of epilepsy before surgery and traveled shorter distances for care. Non-white patients were more likely to have government-funded insurance. Patients who traveled the shortest distance to the surgical center underwent epilepsy surgery at an older age.

CONCLUSIONS

Sociodemographic factors of travel distance, insurance, and race influenced time to epilepsy surgery for children with focal cortical dysplasia. Further research is warranted to target barriers in access to subspecialty care and develop ways to identify earlier the patients who may benefit from evaluation and deployment of surgical intervention.

Comparison of clinical features and surgical outcome in focal cortical dysplasia type 1 and type 2

INTRODUCTION

Recent ILAE classification defined focal cortical dysplasia (FCD) patients with accompanying epileptic lesions as a separate group. We investigated data of patients with sole FCD lesions regarding long-term seizure outcome and different characteristics of FCD type 1 and type 2 patients.

METHODS

Eighty children and adult patients underwent surgery for FCD were included to the analysis of factors differentiating FCD type 1 and type 2 groups and their effect on long-term outcome.

RESULTS

FCD type 2 patients had earlier epilepsy onset (8.1 vs. 6.1 years. p=0.019) and underwent surgery younger than type 1 (18.2 vs. 23.7 years. p=0.034). FCD type 2 patients were more prominently MR positive (77.8% vs. 53.8%. p=0.029), which increased within FCD type 2 group as patients become younger (p=0.028). FCD Type 1 lesions showed mostly multilobar extension and FCD type 2 mostly located in frontal lobe. Seizure freedom was achieved in 65.4% of FCD type 1 patients and 70.4% of FCD type 2 patients. Seven patients had permanent de novo neurological deficits. Mean follow-up time was 5.5 years (Range: 1-11 years).

CONCLUSION

Surgical intervention in carefully selected patients may facilitate favorable seizure outcome leading to better quality of life. FCD type 1 and type 2 groups present with evident differences, which may promote medical and surgical management of these pathologies.

MicroRNA hsa-miR-134 is a circulating biomarker for mesial temporal lobe epilepsy

Epilepsy is misdiagnosed in up to 25% of patients, leading to serious and long-lasting consequences. Recently, circulating microRNAs have emerged as potential biomarkers in a number of clinical scenarios. The purpose of this study was to identify and to validate circulating microRNAs that could be used as biomarkers in the diagnosis of epilepsy. Quantitative real-time PCR was used to measure plasma levels of three candidate microRNAs in two phases of study: an initial discovery phase with 14 patients with mesial temporal lobe epilepsy (MTLE), 13 with focal cortical dysplasia (FCD) and 16 controls; and a validation cohort constituted of an independent cohort of 65 patients with MTLE and 83 controls. We found hsa-miR-134 downregulated in patients with MTLE (p = 0.018) but not in patients with FCD, when compared to controls. Furthermore, hsa-miR-134 expression could be used to discriminate MTLE patients with an area under the curve (AUC) of 0.75. To further assess the robustness of hsa-miR-134 as a biomarker for MTLE, we studied an independent cohort of 65 patients with MTLE, 27 of whom MTLE patients were responsive to pharmacotherapy, and 38 patients were pharmacoresistant and 83 controls. We confirmed that hsa-miR-134 was significantly downregulated in the plasma of patients with MTLE when compared with controls (p < 0.001). In addition, hsa-miR-134 identified patients with MTLE regardless of their response to pharmacotherapy or the presence of MRI signs of hippocampal sclerosis. We revealed that decreased expression of hsa-miR-134 could be a potential non-invasive biomarker to support the diagnosis of patients with MTLE.

Pediatric Epilepsy: Neurology, Functional Imaging, and Neurosurgery

In this chapter we provide a comprehensive review of the current role that functional imaging can have in the care of the pediatric epilepsy patient from the perspective of the epilepsy neurologist and the epilepsy neurosurgeon. In the neurology section, the diagnosis and classification of epilepsy adapted by the International League Against Epilepsy as well as the etiology and incidence of the disease is presented. The neuroimaging section describes how advanced nuclear medicine imaging methods can be synergized to provide a maximum opportunity to localize an epileptogenic focus. This section described the value of FDG-PET and regional cerebral blood flow SPECT in the identification of an epileptogenic focus. The imaging section also emphasizes the importance on developing a dedicated epilepsy management team, comprised of an epilepsy imaging specialist, epilepsy neurologist and epilepsy neurosurgeon, to provide the maximum benefit to each child with epilepsy. An emphasis is placed on preparation for ictal SPECT injection procedures, including the critical role of an automated injector well as the use of state-of-the-art dedicated nuclear medicine imaging and analysis protocols to correctly localize the epileptogenic focus location. In the final section, surgical options, approaches and expected outcomes for the different classes of epilepsy is presented.

Optogenetic Approaches for Controlling Seizure Activity

Optogenetics, a technique that utilizes light-sensitive ion channels or pumps to activate or inhibit neurons, has allowed scientists unprecedented precision and control for manipulating neuronal activity. With the clinical need to develop more precise and effective therapies for patients with drug-resistant epilepsy, these tools have recently been explored as a novel treatment for halting seizure activity in various animal models. In this review, we provide a detailed and current summary of these optogenetic approaches and provide a perspective on their future clinical application as a potential neuromodulatory therapy.

Epilepsy surgery in pediatric epileptic encephalopathy: when interictal EEG counts the most

PURPOSE

Traditionally, seizure onset localization in ictal electro-encephalography (EEG) is the main factor guiding resective epilepsy surgery. The situation is often different in infantile epileptic encephalopathy. We demonstrate the importance of the underrated interictal (rather than ictal) surface EEG in informing decision-making in epilepsy surgery for children with epileptic encephalopathy caused by subtle focal cortical dysplasia (FCD).

METHODS

We present a small case series of three children who had an epileptic encephalopathy with either epileptic spasms or tonic seizures. All three were thought initially to have normal neuroimaging.

RESULTS

Ictal EEG localizing features were seen in none and lateralizing features were seen only clinically in one of the three. However, the interictal EEG showed persistent and consistent focal irregular slowing in all, particularly after medically resolving the diffuse encephalopathy. Subtle FCDs were uncovered in all. Surgery was performed in all with excellent outcome.

CONCLUSION

In infantile epileptic encephalopathy caused by subtle FCD, the often underrated interictal surface EEG (particularly persistent foal irregular slowing) informs the most; not only to the target area for surgical resection but also to its extent. This may negate the need for unnecessary and sometimes non-informative invasive monitoring in these cases. A matter of "zooming out" to define the extent of a resectable abnormality rather than "zooming in" to define a seemingly localized epileptic focus that may change with time.

Hyperactive mTOR signals in the proopiomelanocortin-expressing hippocampal neurons cause age-dependent epilepsy and premature death in mice

Epilepsy is a frequent comorbidity in patients with focal cortical dysplasia (FCD). Recent studies utilizing massive sequencing data identified subsets of genes that are associated with epilepsy and FCD. AKT and mTOR-related signals have been recently implicated in the pathogenic processes of epilepsy and FCD. To clarify the functional roles of the AKT-mTOR pathway in the hippocampal neurons, we generated conditional knockout mice harboring the deletion of Pten (Pten-cKO) in Proopiomelanocortin-expressing neurons. The Pten-cKO mice developed normally until 8 weeks of age, then presented generalized seizures at 8–10 weeks of age. Video-monitored electroencephalograms detected paroxysmal discharges emerging from the cerebral cortex and hippocampus. These mice showed progressive hypertrophy of the dentate gyrus (DG) with increased expressions of excitatory synaptic markers (Psd95, Shank3 and Homer). In contrast, the expression of inhibitory neurons (Gad67) was decreased at 6–8 weeks of age. Immunofluorescence studies revealed the abnormal sprouting of mossy fibers in the DG of the Pten-cKO mice prior to the onset of seizures. The treatment of these mice with an mTOR inhibitor rapamycin successfully prevented the development of seizures and reversed these molecular phenotypes. These data indicate that the mTOR pathway regulates hippocampal excitability in the postnatal brain.

Activation of extracellular regulated kinase and mechanistic target of rapamycin pathway in focal cortical dysplasia

Neuropathology of resected brain tissue has revealed an association of focal cortical dysplasia (FCD) with drug-resistant epilepsy (DRE). Recent studies have shown that the mechanistic target of rapamycin (mTOR) pathway is hyperactivated in FCD as evidenced by increased phosphorylation of the ribosomal protein S6 (S6) at serine 240/244 (S(240/244) ), a downstream target of mTOR. Moreover, extracellular regulated kinase (ERK) has been shown to phosphorylate S6 at serine 235/236 (S(235/236) ) and tuberous sclerosis complex 2 (TSC2) at serine 664 (S(664) ) leading to hyperactive mTOR signaling. We evaluated ERK phosphorylation of S6 and TSC2 in two types of FCD (FCD I and FCD II) as a candidate mechanism contributing to mTOR pathway dysregulation. Tissue samples from patients with tuberous sclerosis (TS) served as a positive control. Immunostaining for phospho-S6 (pS6(240/244) and pS6(235/236) ), phospho-ERK (pERK), and phospho-TSC2 (pTSC2) was performed on resected brain tissue with FCD and TS. We found increased pS6(240/244) and pS6(235/236) staining in FCD I, FCD II and TS compared to normal-appearing tissue, while pERK and pTSC2 staining was increased only in FCD IIb and TS tissue. Our results suggest that both the ERK and mTOR pathways are dysregulated in FCD and TS; however, the signaling alterations are different for FCD I as compared to FCD II and TS.

Functional MRI of neuronal activation in epilepsy patients with malformations of cortical development

Malformations of cortical development are disturbances in brain formation that arise from abnormalities affecting the processes of cortical development. Surgical treatment of intractable epilepsy in patients with malformations of cortical development requires localization of both epileptogenic and eloquent cortices. Functional magnetic resonance imaging has been shown to detect the reorganization of activation patterns in such patients. The purpose of this study was to determine whether functional reorganization of the primary sensory and motor cortices occurs in patients with epileptogenic malformations of cortical development. Functional MRI data were obtained for 11 patients (four male, seven female) with a mean age of 36 years (range 18-55 years). The mean age at epilepsy onset was 23 years (range 3-55 years). Twelve healthy controls (six male, six female) with mean age of 33 years (range 28-51 years) were also recruited for comparison. High resolution anatomical MRI was used to confirm the presence and the location of the malformation. All imaging experiments were performed using a 3.0T Siemens Tim Trio whole body MRI. Each subject performed four block-paradigm fMRI experiments to study motor and sensory activation for each hand. A total of 132 image sets were collected for each paradigm over 5.5min (2.5s per image). Each paradigm consisted of seven stimulus periods lasting 30s (12 images) and stimulus onset of 30, 90, 150, 210 and 270s. Functional data were obtained from all eligible patients and compared to those of controls. Reorganization and reduction in function in the motor and sensory areas were observed in patients with cortical dysplasia. Patients with polymicrogyria did not present with significant functional reorganization and patients with heterotopias and coexisting polymicrogyria and/or cortical dysplasia had variable patterns of activation. In summary, this study showed evidence of functional reorganization of sensory and motor cortices in patients with cortical dysplasia development. Such information should be carefully considered in surgical planning and treatment.

Surgical management of cortical dysplasia in infancy and early childhood

PURPOSE

To describe operative procedures, seizure control and complications of surgery for cortical dysplasia (CD) causing intractable epilepsy in infancy and early childhood.

METHODS

Fifty-six consecutive children (less than 6years old) underwent resective epilepsy surgery for CD from December 2000 to August 2011. Age at surgery ranged from 2 to 69months (mean 23months) and the follow-up was from 1 to 11years (mean 4years 4months).

RESULTS

Half of the children underwent surgery during infancy at an age less than 10months, and the majority (80%) of these infants needed extensive surgical procedures, such as hemispherotomy and multi-lobar disconnection. Seizure free (ILAE class 1) outcome was obtained in 66% of the cases (class 1a; 55%): 85% with focal resection (n=13), 50% with lobar resection (n=18), 71% with multilobar disconnection (n=7) and 67% with hemispherotomy (n=18). Peri-ventricular and insular structures were resected in 23% of focal and 61% of lobar resections. Repeated surgery was performed in 9 children and 5 (56%) became seizure free. Histological subtypes included hemimegalencephaly (16 patients), polymicrogyria (5 patients), and FCD type I (6 patients), type IIA (19 patients), type IIB (10 patients). Polymicrogyria had the worst seizure outcome compared to other pathologies. Surgical complications included 1 post-operative hydrocephalus, 1 chronic subdural hematoma, 2 intracranial cysts, and 1 case of meningitis. No mortality or severe morbidities occurred.

CONCLUSIONS

Early surgical intervention in children with CD and intractable seizures in infancy and early childhood can yield favorable seizure outcome without mortality or severe morbidities although younger children often need extensive surgical procedures.

Surgical and postmortem pathology studies: contribution for the investigation of temporal lobe epilepsy

Pathology studies in epilepsy patients bring useful information for comprehending the physiopathology of various forms of epilepsy, as well as aspects related to response to treatment and long-term prognosis. These studies are usually restricted to surgical specimens obtained from patients with refractory focal epilepsies. Therefore, most of them pertain to temporal lobe epilepsy (TLE) with mesial temporal sclerosis (MTS) and malformations of cortical development (MCD), thus providing information of a selected group of patients and restricted regions of the brain. Postmortem whole brain studies are rarely performed in epilepsy patients, however they may provide extensive information on brain pathology, allowing the analysis of areas beyond the putative epileptogenic zone. In this article, we reviewed pathology studies performed in epilepsy patients with emphasis on neuropathological findings in TLE with MTS and MCD. Furthermore, we reviewed data from postmortem studies and discussed the importance of performing these studies in epilepsy populations.

Local epileptic activity, histological and neuroimaging findings in symptomatic epilepsy

OBJECTIVE

This study is aimed at revealing the relationship between local interictal epileptic activity, cytoarchitectural disturbances and magnetic resonance imaging (MRI) findings.

MATERIAL AND METHODS

We prospectively investigated a series of 25 patients with symptomatic epilepsy due to isolated forms of focal cortical dysplasia (FCD) or hippocampal sclerosis and low-grade tumours associated with FCD, all of whom underwent tailored surgical procedures under intraoperative electrocorticography; we conducted neuropathological examinations of 92 biopsies taken from different places. We examined the relationship between dysplastic changes in the cortex and the absence or presence of seizure patterns (SPs), including regular spikes/sharp waves, recruiting discharges, paroxysmal fast activity and rhythmic delta-theta activity. Comparisons with MRI findings were also performed.

RESULTS

Complete removal of the SPs zone was associated with better results of surgical treatment. Areas with isolated architectural abnormalities were associated with SPs significantly more often than those where the cortex contains immature or giant neurons; these areas were associated with SPs more than areas containing dysmorphic neurons. The extent of MRI signs appearance in the neocortex correlated neither with the presence of SPs nor with the types of histological changes.

CONCLUSIONS

We suppose an inverse relationship between the morphological changes in neurons and their ability to generate epileptic activity. Electrocorticography may be used for the identification of the MRI-negative epileptogenic lesions.

The impact of positron emission tomography imaging on the clinical management of patients with epilepsy

Clinical positron emission tomography (PET) imaging of human epilepsy has a 30-year history, but it is still searching for its exact role among rapidly advancing neuroimaging techniques. The vast majority of epilepsy PET studies used this technique to improve detection of epileptic foci for surgical resection. Here, we review the main trends emerging from three decades of PET research in epilepsy, with a particular emphasis on how PET imaging has impacted on the clinical management of patients with intractable epilepsy. While reviewing the latest studies, we also present an argument for a changing role of PET and molecular imaging in the future, with an increasing focus on epileptogenesis and newly discovered molecular mechanisms of epilepsy. These new applications will be facilitated by technological advances, such as the use of integrated PET/MRI systems and utilization of novel radiotracers, which may also enhance phenotype-genotype correlations and assist rational, individualized treatment strategies.

Implantable stimulator for epileptic seizure suppression with loading impedance adaptability

The implantable stimulator for epileptic seizure suppression with loading impedance adaptability was proposed in this work. The stimulator consisted of the high voltage generator, output driver, adaptor, and switches, can constantly provide the required 40-μA stimulus currents, as the loading impedance varied within 10 kΩ -300 kΩ. The performances of this design have been successfully verified in silicon chip fabricated by a 0.35- μm 3.3-V/24-V CMOS process. The power consumption of this work was only 1.1 mW-1.4 mW. The animal test results with the fabricated chip of proposed design have successfully verified in the Long-Evans rats with epileptic seizures.

Advances in the diagnosis and treatment of epilepsy

Epilepsy is the most common serious brain disorder in children, occurring in all parts of the world and within every stratum of the population. Through its effects, it exerts a significant physical, psychological, economic, and social toll on children and their caregivers. Historically, the surgical treatment of epilepsy has been viewed with skepticism with regard to its indications, safety, and therapeutic benefit. However, continued refinements in diagnostic and operative techniques are helping to put to rest the antiquated notion that surgery is a last-resort procedure in the management of pediatric epilepsy. Surgery can be performed safely, even in infants and young children, with excellent patient outcomes in properly selected patients. This review focuses on the surgical treatment of pediatric epilepsy. A brief background discussion of seizures and epilepsy is followed by a substantive discussion regarding the intricacies of selecting patients for epilepsy surgery, emphasizing the important role of advanced imaging techniques in the decision-making process. The indications and outcomes of the most common epilepsy surgical procedures are then reviewed. The article ends with a discussion of the future of epilepsy surgery.

Ictal MEG onset source localization compared to intracranial EEG and outcome: improved epilepsy presurgical evaluation in pediatrics

PURPOSE

Magnetoencephalography (MEG) has been shown a useful diagnostic tool for presurgical evaluation of pediatric medically intractable partial epilepsy as MEG source localization has been shown to improve the likelihood of seizure onset zone (SOZ) sampling during subsequent evaluation with intracranial EEG (ICEEG). We investigated whether ictal MEG onset source localization further improves results of interictal MEG in defining the SOZ.

METHODS

We identified 20 pediatric patients with one habitual seizure during MEG recordings between October 2007 and April 2011. MEG was recorded with sampling rates of 600Hz and 4000Hz for 10 and 2min respectively. Continuous head localization (CHL) was applied. Source localization analyses were applied using multiple algorithms, both at the beginning of ictal onset and for interictal MEG discharges. Ictal MEG onsets were identified by visual inspection and power spectrum using short-time Fourier transform (STFT). Source localizations were compared with ICEEG, surgical procedure and outcome.

KEY FINDINGS

Eight patients met all inclusion criteria. Five of the 8 patients (63%) had concordant ictal MEG onset source localization and interictal MEG discharge source localizations in the same lobe, but the source of ictal MEG onset was closer to the SOZ defined by ICEEG.

SIGNIFICANCE

Although the capture of seizures during MEG recording is challenging, the source localization for ictal MEG onset proved to be a useful tool for presurgical evaluation in our pediatric population with medically intractable epilepsy.

Extent of EEG epileptiform pattern distribution in "focal" cortical dysplasia

To assess the pathophysiological complexity of cortical dysplasia-related intractable focal epilepsy among surgical candidates, using our data-based EEG classification system, we reviewed preresection scalp awake and sleep EEGs (median, 8) in 46 consecutive patients whose resected pathology disclosed cortical dysplasia. Epileptiform phenomena occurred on at least one EEG in 42 (91%) patients. Twenty-three (50%) of the 46 patients displayed at least one type of independently occurring abnormality (spikes, excess delta, or theta) in each hemisphere. Nineteen of these 23 (83%), thus 41% of all 46 patients, showed independently occurring epileptiform abnormalities (spikes) in each hemisphere, i.e., the multiple independent spike foci phenomenon. In an additional 13 of the 46 (28%) patients, spike foci involving more than one lobe appeared within a single hemisphere. Thus, spike foci involving more than one lobe appeared in 32 of the 46 (70%) patients. Generalized bilaterally synchronous epileptiform features (spike waves, slow spike waves, or fast rhythmic waves) appeared in 10 (22%) of the 46 patients. Two findings suggest more widespread dysfunction among extratemporal patients than temporal patients: (1) a significantly higher number of lobes containing focal interictal epileptiform activity in extra temporal patients (mean = 3.14) than among temporal patients (mean = 2.14) (P = 0.02), (2) a higher percentage of bisynchronous epileptiform abnormalities: 8 of 23 (35%) versus 2 of 23 (9%). Among 34 patients with a Principal Spike Lobe (more active spiking over more EEGs), those of 32 (94%) arose from the ultimately resected lobe. Of the 30 patients with scalp-recorded seizures, relationship between seizure origin and ultimately resected lobe were same lobe (16 patients), same and adjacent lobes (12), adjacent lobe only (1), and distant lobe (1). Thus, despite the multifocality of several EEG features, Principal Spike Lobe and scalp-recorded seizure origin correlate well with epileptogenesis.

Improved outcomes in pediatric epilepsy surgery: the UCLA experience, 1986-2008

OBJECTIVE

Epilepsy neurosurgery is a treatment option for children with refractory epilepsy. Our aim was to determine if outcomes improved over time.

METHODS

Pediatric epilepsy surgery patients operated in the first 11 years (1986-1997; pre-1997) were compared with the second 11 years (1998-2008; post-1997) for differences in presurgical and postsurgical variables.

RESULTS

Despite similarities in seizure frequency, age at seizure onset, and age at surgery, the post-1997 series had more lobar/focal and fewer multilobar resections, and more patients with tuberous sclerosis complex and fewer cases of nonspecific gliosis compared with the pre-1997 group. Fewer cases had intracranial EEG studies in the post-1997 (0.8%) compared with the pre-1997 group (9%). Compared with the pre-1997 group, the post-1997 series had more seizure-free patients at 0.5 (83%, +16%), 1 (81%, +18%), 2 (77%, +19%), and 5 (74%, +29%) years, and more seizure-free patients were on medications at 0.5 (97%, +6%), 1 (88%, +9%), and 2 (76%, +29%), but not 5 (64%, +8%) years after surgery. There were fewer complications and reoperations in the post-1997 series compared with the pre-1997 group. Logistic regression identified post-1997 series and less aggressive medication withdrawal as the main predictors of becoming seizure-free 2 years after surgery.

CONCLUSIONS

Improved technology and surgical procedures along with changes in clinical practice were likely factors linked with enhanced and sustained seizure-free outcomes in the post-1997 series. These findings support the general concept that clearer identification of lesions and complete resection are linked with better outcomes in pediatric epilepsy surgery patients.

Neuropathological findings in intractable epilepsy: 435 Chinese cases

The number of patients with intractable epilepsy undergoing surgical management in China is increasing rapidly. We retrospectively reviewed 435 consecutive cases of intractable epilepsy receiving surgical resection from 2005 to 2008 in our hospital, looking specifically at the neuropathological findings. The three most common causes of intractable epilepsy were focal cortical dysplasia (FCD; 52.9%), scar lesions (22.8%) and brain tumors (11.7%). Hippocampal sclerosis was identified in 74 cases (17.0%), although most of these were accompanied by dual pathology with FCD (especially Palmini type IB), scar lesions or tumors. Among FCD cases, Palmini type I lesions are the most frequently observed abnormality, with a preferred location in the temporal lobe (60.1%) and often accompanied by dual pathology. In contrast, Palmini type II FCD lesions occurred predominantly in the frontal regions and with a lower age of onset. Most tumors were mixed neuronal-glial tumors, mainly ganglioglioma (19 cases) and dysembryoplastic neuroepithelial tumor (10 cases), with a trend toward a temporal location and usually accompanied by cortical dysplasia in the peritumor area. Our data on the neuropathology of intractable epilepsy in China show that glioneuronal lesions are the most prominent cause of intractable epilepsy, and this is consistent with reports from other countries.