Changes in gamma-aminobutyric acid and somatostatin in epileptic cortex associated with low-grade gliomas

Study of the relationship among biomarkers, cell and tissue of glioma through Raman spectroscopy

Glioma is the most common brain tumors with high mortality and recurrence rates. Currently, the diagnosis methods for glioma are mainly based on tissue level, cellular level and biomarker level. In this paper, the characteristics of biomarkers (γ-aminobutyric acid and matrix mtalloproteinses-2), U87MG glioma cell and tissue were studied based on Raman spectroscopy, respectively. The results showed that the γ-aminobutyric acid concentration exhibited a linear relation with the intensity of characteristic peaks in 800-1600 cm-1 region, whereas the spectral baseline increased with the increasing of sample concentration in 200-700 cm-1 region. The Raman characteristics of matrix mtalloproteinses-2 in 20-1800 cm-1 region was investigated. Especially, it is demonstrated that the matrix mtalloproteinses-2 showed sixteen low-wavenumber Raman peaks in the range of 20-300 cm-1. Moreover, the U87MG glioma cell showed seven different Raman characteristic peaks in 600-1800 cm-1 region. Compared with the normal tissue, the Raman intensity of tumor tissue showed apparent intensity differences in 300-1800 cm-1, where the intensity changes of these Raman peaks were related to the reducing of the lipid metabolic pathways, and increase of the RNA in tumor tissue region. Furthermore, it is found that the Raman spectra of U87MG glioma cell and tumor tissue had corresponding peaks in the Raman spectra of the liquid γ-aminobutyric acid and matrix mtalloproteinses-2. It is suggested that the γ-aminobutyric acid and matrix mtalloproteinses-2 contributed to the formation and growth of glioma cell and tissue. Thus, Raman spectroscopy not only can diagnose glioma at the biomarkers, cellular and tissue level, but also analyze the relationship among the three. Furthermore, the results provided a physical marker for the detection of glioma in clinically.

Reciprocal interactions between glioma and tissue-resident cells fueling tumor progression

Gliomas are the most frequent primary brain tumor and are essentially incurable. While nondiffuse gliomas are circumscribed, diffuse gliomas display an aggressive behavior characterized by tumor cell migration over large distances into the brain parenchyma, thereby precluding curative surgical resection. Almost all diffuse gliomas progress and recur as higher grades and become resistant to standard-of-care treatments. It is being increasingly recognized that glioma cells establish functional interactions with cells residing in the tumor microenvironment. Of these, tumor-associated microglia and macrophages (TAMs) play critical roles in immunosuppression through modulation of the extracellular matrix, and the secretion of molecules such as cytokines, neurotrophic factors, and micro-RNAs (miRNAs). Conversely, glioma cell signals influence cell states and drive the metabolic reprogramming of TAMs. Similarly, emergent evidence indicates that neuronal activity influences glioma by released factors and by establishing functional synapses with glioma cells to promote tumor growth and invasion. Glioma cells also affect local neuronal activities and maintain connections through microtube gap junctions to amplify local effects. Here, we discuss the molecular mechanisms underlying bidirectional interactions between glioma cells and TAMs, as well as between glioma cells and neurons. A better understanding of these cellular cross talks is crucial for the development of novel therapeutic strategies for diffuse gliomas.

Meningioma: International Consortium on Meningiomas consensus review on scientific advances and treatment paradigms for clinicians, researchers, and patients

Meningiomas are the most common primary intracranial tumors in adults and are increasing in incidence due to the aging population and increased access to neuroimaging. While most exhibit nonmalignant behavior, a subset of meningiomas are biologically aggressive and are associated with treatment resistance, resulting in significant neurologic morbidity and even mortality. In recent years, meaningful advances in our understanding of the biology of these tumors have led to the incorporation of molecular biomarkers into their grading and prognostication. However, unlike other central nervous system (CNS) tumors, a unified molecular taxonomy for meningiomas has not yet been established and remains an overarching goal of the Consortium to Inform Molecular and Practical Approaches to CNS Tumor Taxonomy-Not Official World Health Organization (cIMPACT-NOW) working group. Additionally, clinical equipoise still remains on how specific meningioma cases and patient populations should be optimally managed. To address these existing gaps, members of the International Consortium on Meningiomas including field-leading experts, have prepared this comprehensive consensus narrative review directed toward clinicians, researchers, and patients. Included in this manuscript are detailed overviews of proposed molecular classifications, novel biomarkers, contemporary treatment strategies, trials on systemic therapies, health-related quality-of-life studies, and management strategies for unique meningioma patient populations. In each section, we discuss the current state of knowledge as well as ongoing clinical and research challenges to road map future directions for further investigation.

Multi-omics technologies and molecular biomarkers in brain tumor-related epilepsy

BACKGROUND

Brain tumors are one of the leading causes of epilepsy, and brain tumor-related epilepsy (BTRE) is recognized as the major cause of intractable epilepsy, resulting in huge treatment cost and burden to patients, their families, and society. Although optimal treatment regimens are available, the majority of patients with BTRE show poor resolution of symptoms. BTRE has a very complex and multifactorial etiology, which includes several influencing factors such as genetic and molecular biomarkers. Advances in multi-omics technologies have enabled to elucidate the pathophysiological mechanisms and related biomarkers of BTRE. Here, we reviewed multi-omics technology-based research studies on BTRE published in the last few decades and discussed the present status, development, opportunities, challenges, and prospects in treating BTRE.

METHODS

First, we provided a general review of epilepsy, BTRE, and multi-omics techniques. Next, we described the specific multi-omics (including genomics, transcriptomics, epigenomics, proteomics, and metabolomics) techniques and related molecular biomarkers for BTRE. We then presented the associated pathogenetic mechanisms of BTRE. Finally, we discussed the development and application of novel omics techniques for diagnosing and treating BTRE.

RESULTS

Genomics studies have shown that the BRAF gene plays a role in BTRE development. Furthermore, the BRAF V600E variant was found to induce epileptogenesis in the neuronal cell lineage and tumorigenesis in the glial cell lineage. Several genomics studies have linked IDH variants with glioma-related epilepsy, and the overproduction of D2HG is considered to play a role in neuronal excitation that leads to seizure occurrence. The high expression level of Forkhead Box O4 (FOXO4) was associated with a reduced risk of epilepsy occurrence. In transcriptomics studies, VLGR1 was noted as a biomarker of epileptic onset in patients. Several miRNAs such as miR-128 and miRNA-196b participate in BTRE development. miR-128 might be negatively associated with the possibility of tumor-related epilepsy development. The lncRNA UBE2R2-AS1 inhibits the growth and invasion of glioma cells and promotes apoptosis. Quantitative proteomics has been used to determine dynamic changes of protein acetylation in epileptic and non-epileptic gliomas. In another proteomics study, a high expression of AQP-4 was detected in the brain of GBM patients with seizures. By using quantitative RT-PCR and immunohistochemistry assay, a study revealed that patients with astrocytomas and oligoastrocytomas showed high BCL2A1 expression and poor seizure control. By performing immunohistochemistry, several studies have reported the relationship between D2HG overproduction and seizure occurrence. Ki-67 overexpression in WHO grade II gliomas was found to be associated with poor postoperative seizure control. According to metabolomics research, the PI3K/AKT/mTOR pathway is associated with the development of glioma-related epileptogenesis. Another metabolomics study found that SV2A, P-gb, and CAD65/67 have the potential to function as biomarkers for BTRE.

CONCLUSIONS

Based on the synthesized information, this review provided new research perspectives and insights into the early diagnosis, etiological factors, and personalized treatment of BTRE.

Unexplained Causes of Glioma-Associated Epilepsies: A Review of Theories and an Area for Research

Approximately 30% of glioma patients are able to survive beyond one year postdiagnosis. And this short time is often overshadowed by glioma-associated epilepsy. This condition severely impairs the patient's quality of life and causes great suffering. The genetic, molecular and cellular mechanisms underlying tumour development and epileptogenesis remain incompletely understood, leading to numerous unanswered questions. The various types of gliomas, namely glioblastoma, astrocytoma and oligodendroglioma, demonstrate distinct seizure susceptibility and disease progression patterns. Patterns have been identified in the presence of IDH mutations and epilepsy, with tumour location in cortical regions, particularly the frontal lobe, showing a more frequent association with seizures. Altered expression of TP53, MGMT and VIM is frequently detected in tumour cells from individuals with epilepsy associated with glioma. However, understanding the pathogenesis of these modifications poses a challenge. Moreover, hypoxic effects induced by glioma and associated with the HIF-1a factor may have a significant impact on epileptogenesis, potentially resulting in epileptiform activity within neuronal networks. We additionally hypothesise about how the tumour may affect the functioning of neuronal ion channels and contribute to disruptions in the blood-brain barrier resulting in spontaneous depolarisations.

The clinical and genomic features of seizures in meningiomas

Meningiomas are the most common central nervous system tumors. Although these tumors are extra-axial, a relatively high proportion (10%-50%) of meningioma patients have seizures that can substantially impact the quality of life. Meningiomas are believed to cause seizures by inducing cortical hyperexcitability that results from mass effect and cortical irritation, brain invasion, or peritumoral brain edema. In general, meningiomas that are associated with seizures have aggressive features, with risk factors including atypical histology, brain invasion, and higher tumor grade. Somatic NF2 mutated meningiomas are associated with preoperative seizures, but the effect of the driver mutation is mediated through atypical features. While surgical resection is effective in controlling seizures in most patients with meningioma-related epilepsy, a history of seizures and uncontrolled seizures prior to surgery is the most significant predisposing factor for persistent postoperative seizures. Subtotal resection (STR) and relatively larger residual tumor volume are positive predictors of postoperative seizures. Other factors, including higher WHO grade, peritumoral brain edema, and brain invasion, are inconsistently associated with postoperative seizures, suggesting they might be crucial in the development of an epileptogenic focus, but do not appear to play a substantial role after seizure activity has been established. Herein, we review and summarize the current literature surrounding meningioma-related epilepsy and underscore the interaction of multiple factors that relate to seizures in patients with meningioma.

The Concept of «Peritumoral Zone» in Diffuse Low-Grade Gliomas: Oncological and Functional Implications for a Connectome-Guided Therapeutic Attitude

Diffuse low-grade gliomas (DLGGs) are heterogeneous and poorly circumscribed neoplasms with isolated tumor cells that extend beyond the margins of the lesion depicted on MRI. Efforts to demarcate the glioma core from the surrounding healthy brain led us to define an intermediate region, the so-called peritumoral zone (PTZ). Although most studies about PTZ have been conducted on high-grade gliomas, the purpose here is to review the cellular, metabolic, and radiological characteristics of PTZ in the specific context of DLGG. A better delineation of PTZ, in which glioma cells and neural tissue strongly interact, may open new therapeutic avenues to optimize both functional and oncological results. First, a connectome-based “supratotal” surgical resection (i.e., with the removal of PTZ in addition to the tumor core) resulted in prolonged survival by limiting the risk of malignant transformation, while improving the quality of life, thanks to a better control of seizures. Second, the timing and order of (neo)adjuvant medical treatments can be modulated according to the pattern of peritumoral infiltration. Third, the development of new drugs specifically targeting the PTZ could be considered from an oncological (such as immunotherapy) and epileptological perspective. Further multimodal investigations of PTZ are needed to maximize long-term outcomes in DLGG patients.

Altered Spontaneous Glutamatergic and GABAergic Activity in the Peritumoral Cortex of Low-Grade Gliomas Presenting With History of Seizures

The peritumoral regions of WHO grade II gliomas, like astrocytoma and oligodendroglioma, have been reported to show epileptiform activities. An imbalance of glutamatergic and GABAergic mechanisms is primarily responsible for the generation of epileptiform activities. Here we have compared the electrophysiological properties of pyramidal neurons in intraoperative peritumoral specimens obtained from glioma patients with (GS) and without (GN) a history of seizures at presentation. Histology and immunohistochemistry were performed to assess the infiltration of proliferating cells at the peritumoral tissues. Whole-cell patch clamp technique was performed to measure the spontaneous glutamatergic and GABAergic activity onto pyramidal neurons in the peritumoral samples of GS (n = 11) and GN (n = 15) patients. The cytoarchitecture of the peritumoral tissues was devoid of Ki67 immuno-positive cells. We observed a higher frequency of spontaneous glutamatergic and GABAergic activities onto pyramidal neurons of the peritumoral samples of GS patients. Our findings suggest that, in spite of similar histopathological features, the pyramidal neurons in the peritumoral samples of GS and GN patients showed differences in spontaneous excitatory and inhibitory synaptic neurotransmission. An alteration in postsynaptic currents may contribute to the spontaneous epileptiform activity in GS patients.

Association of preoperative seizures with tumor metabolites quantified by magnetic resonance spectroscopy in gliomas

Seizures are common in patients with gliomas; however, the mechanisms of epileptogenesis in gliomas have not been fully understood. This study hypothesized that analyzing quantified metabolites using magnetic resonance spectroscopy (MRS) might provide novel insights to better understand the epileptogenesis in gliomas, and specific metabolites might be indicators of preoperative seizures in gliomas. We retrospectively investigated patient information (gender, age at diagnosis of tumor, their survival time) and tumor information (location, histology, genetic features, and metabolites according to MRS) in patients with gliomas. The data were correlated with the incidence of seizure and analyzed statistically. Of 146 adult supratentorial gliomas, isocitrate dehydrogenase (IDH) mutant tumors significantly indicated higher incidence of preoperative seizures than IDH wild-type gliomas. However, MRS study indicated that glutamate concentration in IDH wild-type gliomas was higher than that in IDH mutant gliomas. Glutamate was not associated with high frequency of preoperative seizures in patients with gliomas. Instead, increased total N-acetyl-L-aspartate (tNAA) was significantly associated with them. Moreover, multivariable analysis indicated that increased level of tNAA was an independent predictor of preoperative seizures. According to MRS analysis, tNAA, rather than glutamate, might be a useful to detect preoperative seizures in patient with supratentorial gliomas.

Seizures in meningioma

More than one-third of patients with meningiomas will experience seizures at some point in their disease. Despite this, meningioma-associated epilepsy remains significantly understudied, as most investigations focus on tumor progression, extent of resection, and survival. Due to the impact of epilepsy on the patient's quality of life, identifying predictors of preoperative seizures and postoperative seizure freedom is critical. In this chapter, we review previously reported rates and predictors of seizures in meningioma and discuss surgical and medical treatment options. Preoperative epilepsy occurs in approximately 30% of meningioma patients with peritumoral edema on neuroimaging being one of the most significant predictor of seizures. Other associated factors include age <18, male gender, the absence of headache, and non-skull base tumor location. Following tumor resection, approximately 70% of individuals with preoperative epilepsy achieve seizure freedom. Variables associated with persistent seizures include a history of preoperative epilepsy, peritumoral edema, skull base tumor location, tumor progression, and epileptiform discharges on postoperative electroencephalogram. In addition, after surgery, approximately 10% of meningioma patients without preoperative epilepsy experience new seizures. Variables associated with new postoperative seizures include tumor progression, prior radiation exposure, and gross total tumor resection. Both pre- and postoperative meningioma-related seizures are often responsive to antiepileptic drugs (AEDs), although AED prophylaxis in the absence of seizures is not recommended. AED selection is based on current guidelines for treating focal seizures with additional considerations including efficacy in tumor-related epilepsy, toxicities, and potential drug-drug interactions. Continued investigation into medical and surgical strategies for preventing and alleviating epilepsy in meningioma is warranted.

Tumor-related epilepsy: epidemiology, pathogenesis and management

INTRODUCTION

Seizure is a common comorbidity in patients with brain tumor. It may be the presenting symptom or develop after the tumor diagnosis. The underlying pathophysiology of brain tumor-related epilepsy remains poorly understood.

METHODS

A comprehensive literature review of Pubmed English articles from 1980-2017 was performed to summarize current knowledge and treatment options of brain tumor-related epilepsy.

RESULTS

Multiple factors have been found to contribute to tumor-related epilepsy, including tumor type, speed of tumor growth, location, and tumor burden. The underlying pathogenesis of epilepsy is not clear but perturbations in the peri-tumoral regions, both structural and cellular communications, have been implicated.

CONCLUSIONS

Surgical and medical treatments of tumor-related epilepsy remain challenging as additional factors such as the extent of surgical resection, interactions with tumor-related oncological treatments and anti-epileptic medication related side effects need to be considered.

Long-range and short-range tumor-stroma networks synergistically contribute to tumor-associated epilepsy

Epileptic seizures are frequently caused by brain tumors. Traditional anti-epileptic treatments do not acquire satisfactory responses. Preoperative and postoperative seizures seriously influence the quality of life of patients. Thus, tumor-associated epilepsy (TAE) is an important subject of the current research. The delineation of the etiology of epileptogenesis in patients with primary brain tumor may help to find the novel and effective drug targets for treating this disease. In this review, we describe the current status of treatment of TAE. More importantly, we focus on the factors that are involved in the functional connectivity between tumors and stromal cells. We propose that there exist two modes, namely, long-range and short-range modes, which likely trigger neuronal hyperexcitation and subsequent epileptic seizures. The long-range mode is referred to as factors released by tumors including glutamate and GABA, binding to the corresponding receptor on the cellular membrane and causing neuronal hyperactivity, while the short-range mode is considered to involve direct intracellular communication between tumor cells and stromas. Gap junctions and tunneling nanotube network are involved in cellular interconnections. Future investigations focused on those two modes may find a potential novel therapeutic target for treating TAE.

Efficacy and safety of Levetiracetam vs. other antiepileptic drugs in Hispanic patients with glioblastoma

Epilepsy is a common symptom in patients with glioblastoma (GB). 213 patients with GB from RedLANO follow-up registry were included. All patients underwent surgery, if feasible, followed by chemoradiation based on temozolomide (Stupp platform). Information was recorded regarding demographics, seizure timing, anti-epileptic drugs (AEDs), dosage, time to next seizure, total seizures in 6 months, and main side effects of AEDs. The relationship between epilepsy treatment and overall survival (OS) was evaluated. Mean age was 53 years old and 56.8% were male. Seventy-eight patients (37%) were treated with levetiracetam (LEV), 27% were given another AED and 36% did not require any AED. Choice of AED was not associated with age (p = 0.67), performance status (p = 0.24) or anatomic tumor site (p = 0.34). Seizures and AED requirement were greater in those having primary GB (p = 0.04). After starting an AED, the mean time until next crisis was 9.9 days (SD ± 6.3), which was shorter in those receiving LEV (p = 0.03); mean number of seizures during the first 3 and 6 months were 2.9 and 4, respectively. Most patients treated with LEV (n = 46) required less than two medication adjustments compared to those treated with other AEDs (p = 0.02). Likewise, less patients exposed to LEV required a coadjuvant drug (p = 0.04). Additionally, patients receiving LEV had significantly less adverse effects compared to patients treated with another AED. OS was significantly higher in the group treated with LEV compared to other AEDs (25.5 vs. 17.9 months; p = 0.047). Patients treated with LEV had better seizure control and longer OS compared to other AEDs.

Clinical considerations and surgical approaches for low-grade gliomas in deep hemispheric locations: insular lesions

Insula and paralimbic region represent a common location for gliomas in adulthood. However, limbic and paralimbic tumors are rare in children. Reports of pediatric insular tumors are scarce in literature, and most of them are included in adult's series, so their management and outcome can be outlined only after extracting data from these reports. Due to their predominantly low grade, they usually have a benign course for some time, what make them ideal candidates for total resection. However, their intricate location and spread to key areas, including the temporal lobe, make them a surgical challenge. The transsylvian route, with or without resection of the frontal and/or temporal operculae, which requires exposure of part or all of the insula is commonly selected for insular tumor approaches. Intraoperative functional mapping is a standard procedure for resection of central region tumors in adults. In children and young individuals, awake craniotomy is not always possible and surgical planning usually relay on functional and anatomical preoperative studies. The main goal when approaching an insular tumor is to achieve the largest extent of resection to increase overall patient survival while preserving the functional status, minimizing postoperative morbidity and increasing the quality of life. The extent of resection seems to be correlated also with the control of associated (and usually intractable) epilepsy.

Long-term outcomes after supratotal resection of diffuse low-grade gliomas: a consecutive series with 11-year follow-up

BACKGROUND

Total or subtotal surgical resection of WHO grade II glioma (diffuse low-grade glioma, DLGG) can significantly increase survival. Moreover, a supratotal resection, i.e., an extended resection with a margin beyond MR imaging abnormalities, could decrease the risk of malignant transformation. Here, the goal is to analyze the long-term functional and oncological outcomes following supratotal resection for DLGG.

METHODS

Sixteen consecutive patients who underwent supratotal resection for a DLGG with a minimum follow-up of 8 years after surgery were included. The resection was continued up to functional cortical and subcortical structures defined by intrasurgical electrical mapping. The extent of resection was evaluated on postoperative FLAIR-weighted MR imaging. Data regarding clinicoradiological features, therapeutic management, and outcomes were analyzed.

RESULTS

Seven men and nine women (mean age, 41.3 years, range, 26-63 years) were included (seizure in 15 cases, one incidental discovery). All patients resumed a normal life after surgery (no neurological deficits, no epilepsy). The volume of postoperative cavity was larger than the preoperative tumor volume in the 16 patients. Neuropathological examination confirmed the diagnosis of WHO grade II glioma in all cases. No adjuvant treatment was administrated after resection. The mean duration of postoperative follow-up was 132 months (range, 97-198 months). There was no relapse in eight cases. Eight patients experienced tumor recurrence, with an average time to relapse of 70.3 months (range, 32-105 months), but without malignant transformation. Five of them have been re-treated, with a reoperation (two cases), chemotherapy (three cases) and radiotherapy (two cases). All patients continue to enjoy a normal life.

CONCLUSIONS

This is the first series demonstrating the prolonged impact of supratotal resection on malignant transformation of DLGG. These original data may suggest to remove a margin around the FLAIR-weighted MR imaging abnormalities in a more systematic manner for DLGG not involving eloquent structures.

Epilepsy in glioma patients: mechanisms, management, and impact of anticonvulsant therapy

Seizures are a well-recognized symptom of primary brain tumors, and anticonvulsant use is common. This paper provides an overview of epilepsy and the use of anticonvulsants in glioma patients. Overall incidence and mechanisms of epileptogenesis are reviewed. Factors to consider with the use of antiepileptic drugs (AEDs) including incidence during the disease trajectory and prophylaxis along with considerations in the selection of anticonvulsant use (ie, potential side effects, drug interactions, adverse effects, and impact on survival) are also reviewed. Finally, areas for future research and exploring the pathophysiology and use of AEDs in this population are also discussed.

Animal models of tumour-associated epilepsy

Brain tumours cause a sizeable proportion of epilepsies in adulthood, and actually can be etiologically responsible also for childhood epilepsies. Conversely, seizures are often first clinical signs of a brain tumour. Nevertheless, several issues of brain-tumour associated seizures and epilepsies are far from understood, or clarified regarding clinical consensus. These include both the specific mechanisms of epileptogenesis related to different tumour types, the possible relationship between malignancy and seizure emergence, the interaction between tumour mass and surrounding neuronal networks, and - not least - the best treatment options depending on different tumour types. To investigate these issues, experimental models of tumour-induced epilepsies are necessary. This review concentrates on the description of currently used models, focusing on methodological aspects. It highlights advantages and shortcomings of these models, and identifies future experimental challenges.

Cortical GABAergic excitation contributes to epileptic activities around human glioma

Brain gliomas are highly epileptogenic. Excitatory glutamatergic mechanisms are involved in the generation of epileptic activities in the neocortex surrounding gliomas. However, chloride homeostasis is known to be perturbed in glioma cells. Thus, the contribution of γ-aminobutyric acidergic (GABAergic) mechanisms that depend on intracellular chloride merits closer study. We studied the occurrence, networks, cells, and signaling basis of epileptic activities in neocortical slices from the peritumoral surgical margin resected around human brain gliomas. Postoperative glioma tissue from 69% of patients spontaneously generated interictal-like discharges, synchronized, with a high-frequency oscillation signature, in superficial layers of neocortex around areas of glioma infiltration. Interictal-like events depended both on glutamatergic AMPA receptor-mediated transmission and on depolarizing GABAergic signaling. GABA released by interneurons depolarized 65% of pyramidal cells, in which chloride homeostasis was perturbed because of changes in expression of neuronal chloride cotransporters: KCC2 (K-Cl cotransporter 2) was reduced by 42% and expression of NKCC1 (Na-K-2Cl cotransporter 1) increased by 144%. Ictal-like activities were initiated by convulsant stimuli exclusively in these epileptogenic areas. This study shows that epileptic activities are sustained by excitatory effects of GABA in human peritumoral neocortex, as reported in temporal lobe epilepsies, suggesting that both glutamate and GABA signaling and cellular chloride regulation processes, all also involved in oncogenesis as already shown, induce an imbalance between synaptic excitation and inhibition underlying epileptic discharges in glioma patients. Thus, the control of chloride in neurons and glioma cells may provide a therapeutic target for patients with epileptogenic gliomas.

Peritumoral epilepsy: relating form and function for surgical success

Seizures are a prominent symptom in patients with both primary and secondary brain tumors. Medical management of seizure control in this patient group is problematic as the mechanisms linking tumorigenesis and epileptogenesis are poorly understood. It is possible that several mechanisms contribute to tumor-associated epileptic zone formation. In this review, we discuss key candidates that may be implicated in peritumoral epileptogenesis and, in so doing, hope to highlight areas for future research. Furthermore, we summarize the current role of antiepileptic medications in this type of epilepsy and examine the changes in surgical practice which may lead to improved seizure rates after tumor surgery. Lastly, we speculate on possible future preoperative and intraoperative considerations for improving seizure control after tumor resection.

Tumor associated seizures in glioblastomas are influenced by survival gene expression in a region-specific manner: a gene expression imaging study

Tumor associated seizures (TAS) are common and cause significant morbidity. Both imaging and gene expression features play significant roles in determining TAS, with strong interactions between them. We describe gene expression imaging tools which allow mapping of brain regions where gene expression has significant influence on TAS, and apply these methods to study 77 patients who underwent surgical evaluation for supratentorial glioblastomas. Tumor size and location were measured from MRI scans. A 9-set gene expression profile predicting long-term survivors was obtained from RNA derived from formalin-fixed paraffin embedded tissue. A total of 32 patients (42%) experienced preoperative TAS. Tumor volume was smaller (31.1 vs. 58.8 cubic cm, p<0.001) and there was a trend toward median survival being higher (48.4 vs. 32.7 months, p=0.055) in patients with TAS. Although the expression of only OLIG2 was significantly lower in patients with TAS in a groupwise analysis, gene expression imaging analysis revealed regions with significantly lower expression of OLIG2 and RTN1 in patients with TAS. Gene expression imaging is a powerful technique that demonstrates that the influence of gene expression on TAS is highly region specific. Regional variability should be evaluated with any genomic or molecular markers of solid brain lesions.

Modulatory effects of activation of metabotropic glutamate receptors on GABAergic circuits in the mouse cortex

Metabotropic glutamate receptors (mGluRs) have a ubiquitous distribution in the central nervous system and often serve to regulate the release of neurotransmitters. We have previously shown that activation of both presynaptic and postsynaptic mGluRs can affect the gain of glutamatergic inputs in both thalamus and cortex. In the present study, we sought to determine the effect of mGluR activation on GABAergic inputs in cortex. Using whole cell recordings in a mouse slice preparation of either primary visual or auditory cortex (V1 or A1), we tested the effects on mGluRs by applying various agonists to the slice. Two pathways were tested in each area: the GABAergic inputs in layers 2/3 activated from layer 4 and the GABAergic inputs in layer 4 activated from adjacent layer 4. In both of these pathways, we found that activation of mGluRs significantly reduced the amplitude of the evoked inhibitory postsynaptic currents. Because the effects were not blocked by the addition of GDPβS to the recording electrode, and because mGluR agonists did not affect responses to photostimulation of GABA in a low-Ca(2+) and high-Mg(2+) bathing solution, we concluded this reduction was due to activation of presynaptic mGluRs. Furthermore, using specific mGluR agonists, we found that group II mGluRs, but not group I mGluRs, were involved in these modulatory effects. Because similar results were found in both pathways in V1 and A1, a possible cortical pattern for these effects is suggested.

Rates and predictors of seizure freedom in resective epilepsy surgery: an update

Epilepsy is a debilitating neurological disorder affecting approximately 1 % of the world's population. Drug-resistant focal epilepsies are potentially surgically remediable. Although epilepsy surgery is dramatically underutilized among medically refractory patients, there is an expanding collection of evidence supporting its efficacy which may soon compel a paradigm shift. Of note is that a recent randomized controlled trial demonstrated that early resection leads to considerably better seizure outcomes than continued medical therapy in patients with pharmacoresistant temporal lobe epilepsy. In the present review, we provide a timely update of seizure freedom rates and predictors in resective epilepsy surgery, organized by the distinct pathological entities most commonly observed. Class I evidence, meta-analyses, and individual observational case series are considered, including the experiences of both our institution and others. Overall, resective epilepsy surgery leads to seizure freedom in approximately two thirds of patients with intractable temporal lobe epilepsy and about one half of individuals with focal neocortical epilepsy, although only the former observation is supported by class I evidence. Two common modifiable predictors of postoperative seizure freedom are early operative intervention and, in the case of a discrete lesion, gross total resection. Evidence-based practice guidelines recommend that epilepsy patients who continue to have seizures after trialing two or more medication regimens should be referred to a comprehensive epilepsy center for multidisciplinary evaluation, including surgical consideration.

Epileptic seizures in diffuse low-grade gliomas in adults

Diffuse low-grade gliomas are highly epileptogenic brain tumours. We aimed to explore the natural course of epileptic seizures, their predictors and the prognostic significance of their occurrence in adult patients harbouring a diffuse low-grade glioma. An observational retrospective multicentre study examined 1509 patients with diffuse low-grade gliomas to identify mutual interactions between tumour characteristics, tumour course and epileptic seizures. At diagnosis, 89.9% of patients had epileptic seizures. Male gender (P = 0.003) and tumour location within functional areas (P = 0.001) were independent predictors of a history of epileptic seizures at diagnosis. Tumour volume, growth velocity, cortical location, histopathological subtype or molecular markers did not significantly affect epileptic seizure occurrence probability. Prolonged history of epileptic seizures (P < 0.001), insular location (P = 0.003) and tumour location close to functional areas (P = 0.038) were independent predictors of uncontrolled epileptic seizures at diagnosis. Occurrence of epileptic seizures (P < 0.001), parietal (P = 0.029) and insular (P = 0.002) locations were independent predictors of uncontrolled epileptic seizures after oncological treatment. Patient age (P < 0.001), subtotal (P = 0.007) and total (P < 0.001) resections were independent predictors of total epileptic seizure control after oncological treatment. History of epileptic seizures at diagnosis and total surgical resection were independently associated with increased malignant progression-free (P < 0.001 and P < 0.001) and overall (P < 0.001 and P = 0.016) survivals. Epileptic seizures are independently associated with diffuse low-grade glioma prognosis. Patients diagnosed with epileptic seizures and those with complete and early surgical resections have better oncological outcomes. Early and maximal surgical resection is thus required for diffuse low-grade gliomas, both for oncological and epileptological purposes.

Neurocognitive functioning in adult WHO grade II gliomas: impact of old and new treatment modalities

In the treatment of patients with low-grade glioma, there still is controversy on how surgical intervention, radiation therapy, and chemotherapy contribute to an ameliorated progression-free survival, overall survival, and treatment-related neurotoxicity. With the ongoing changes in treatment options for these patients, neurocognitive functioning is an increasingly important outcome measure, because neurocognitive impairments can have a large impact on self-care, social and professional functioning, and consequently, health-related quality of life. Many factors contribute to neurocognitive outcome, such as direct and indirect tumor effects, seizures, medication, and oncological treatment. Although the role of radiotherapy has been studied extensively, the adverse effects on neurocognitive function of other treatment-related factors remain elusive. This holds for both resective surgery, in which the use of intraoperative stimulation mapping has a high potential benefit concerning survival and patient functioning, and the use of chemotherapy that might have some interesting new applications, such as the facilitation of total resection for initially primary or recurrent diffuse low-grade glioma tumors. This article will discuss these treatment options in patients with low-grade glioma and their potential effects on neurocognitive functioning.

Characteristics and treatment of seizures in patients with high-grade glioma: a review

High-grade gliomas (HGGs), including anaplastic astrocytoma and glioblastoma multiforme, are the most common primary brain tumors, and are often associated with seizures. Seizure control is a critical but often underappreciated goal in the treatment of patients harboring these malignant lesions. Patients with HGG who also have medically intractable seizures should be considered for a palliative resection guided by electrocorticography and functional mapping. Antiepileptic drugs remain the mainstay of seizure treatment in HGG, and antiepileptic medication should be started after a tumor-related seizure, but should not be used prophylactically in the absence of seizure activity.

MR imaging-based correction for partial volume effect improves detectability of intractable epileptogenic foci on iodine 123 iomazenil brain SPECT images: an extended study with a larger sample size

BACKGROUND AND PURPOSE

It has been suggested, on the basis of a previous pilot study conducted in a small number of patients, that MR imaging-based PVE correction in I-123 iomazenil brain SPECT improves the detectability of cortical epileptogenic foci. In the present study, we performed an investigation by using a larger sample size to establish the effectiveness of the PVE correction and to conduct a detailed evaluation based on the histologic classification of lesions.

MATERIALS AND METHODS

Seventy-five patients (male/female, 37/38; age, 28 ± 12 years) with intractable epilepsy who had undergone surgical treatment were enrolled in this study. I-123 iomazenil SPECT and MR imaging examinations were performed before the operation in all patients. I-123 iomazenil SPECT images with and without MR imaging-based PVE correction were assessed visually and by semiquantitative analysis based on the AI(%) of the SPECT count in the resected lesions.

RESULTS

The sensitivity, specificity, and accuracy of foci detection by visual assessment were significantly higher after PVE correction compared with the values obtained before the correction. The results of the semiquantitative analysis revealed that the asymmetry of the SPECT counts was significantly increased after the PVE correction in the surgically resected lesions in cases of mesial temporal sclerosis, tumor, and malformations of cortical development.

CONCLUSIONS

The effectiveness of MR imaging-based PVE correction in I-123 iomazenil brain SPECT in improving the detection of cortical epileptogenic foci with abnormal histologic findings was established by our investigation conducted on a large sample size.

The pathogenesis of tumor-related epilepsy and its implications for clinical treatment

Approximately 30-50% of patients with brain tumors present with seizures as the initial symptom. Seizures play a very important role in the quality of life, particularly in patients with slow-growing primary brain tumors. Tumor-related seizures are often refractory to antiepileptic treatment. Despite the importance of this subject to the fields of neurology, neurosurgery and neurooncology, the pathogenesis of tumor-related epilepsy remains poorly understood. This review summarizes possible mechanisms underlying the pathogenesis of tumor-related epilepsy, including both tumoral and peri-tumoral aspects. Tumor cells themselves may create intrinsic epileptogenicity, and inadequate homeostasis in the peri-tumoral tissues may lead to seizure susceptibility. Other local changes in electrolytes, perfusion, metabolism, and enzymes could also contribute. It is generally accepted that changes in amino acid neurotransmission are the most important mechanism underlying tumor-related seizures, and changes in extracellular ions also play an important role. Hypoxia, acidosis, and metabolic, immunological, and inflammatory changes may also be involved in the occurrence of seizures. Knowledge of these mechanisms may provide guidance in the search for new strategies for the surgical and medical treatment of tumor-related epilepsy.

2D MR Spectroscopy Combined with Prior-Knowledge Fitting Is Sensitive to HCV-Associated Cerebral Metabolic Abnormalities

There is an evidence of neurocognitive dysfunction even in the absence of advanced liver disease in chronic hepatitis C virus (HCV) infection. Brain metabolism has been investigated non-invasively using one-dimensional (1D) in vivo Magnetic Resonance Spectroscopy (MRS) over three decades. Even though highly concentrated cerebral metabolites (N-acetylaspartate, creatine, choline, glutamate/glutamine, myo-inositol) have been detected using MRS, other metabolites at low concentrations (~1-3 mM or less) including glutathione, aspartate and GABA are quite difficult to observe using 1D MRS. In order to resolve overlapping resonances from a number of metabolites, a remedy is to add a second spectral dimension to the existing 1D MRS. Localized two-dimensional correlated spectroscopy (L-COSY) has been developed over the last decade to enhance the spectral dispersion by using the second spectral dimension. We have evaluated this L-COSY technique in the frontal white/gray matter regions of 14 HCV+ (mean age of 56.2 years) and 14 HCV- (mean age of 46.6 years) subjects. Our preliminary results showed significantly increased myo-inositol and glutathione in the HCV+ compared to the HCV- subjects. Hence, glutathione and myo-inositol should be considered along with other metabolites as important markers of inflammation.

Electrocorticography and seizure outcomes in children with lesional epilepsy

PURPOSE

The use of electrocorticographically (ECoG)-guided cortical resection in children with lesional epilepsy is controversial. Given the important developmental issues associated with recurrent childhood seizures, sustained seizure control is a key therapeutic goal. We therefore evaluated the effect of the decision to perform lesionectomy or ECoG-guided cortical resection on seizure outcome and surgical morbidity in the pediatric population.

METHODS

We retrospectively analyzed seizure outcomes in 67 patients between the ages of 3 months and 16 years who underwent surgery for lesional epilepsy at British Columbia Children's Hospital. Thirty-four patients underwent ECoG, and 33 patients had lesionectomy without ECoG.

RESULTS

One year post-operatively, 80% of patients who had ECoG-guided cortical resection or lesionectomy were seizure free. However, there was a trend toward improved seizure freedom in patients who had ECoG at most recent follow-up (79% patients with ECoG seizure free, vs. 61% with lesionectomy only; mean follow-up time 5.8 year, P=0.078). There was no increase in neurological morbidity in patients who had ECoG-guided cortical resection, and these patients were less likely to experience repeat epilepsy surgery.

CONCLUSIONS

Overall, using ECoG to guide additional cortical resection may lead to more robust seizure freedom in children with lesional epilepsy without increasing their risk of surgical morbidity.

Impact of temozolomide chemotherapy on seizure frequency in patients with low-grade gliomas

OBJECT

Seizures occur in approximately 80% of patients with low-grade gliomas (LGGs). The majority of patients are treated with anticonvulsant monotherapy; however, many patients require multidrug therapy, or their seizures are refractory to antiepileptic drugs altogether. The oral alkylating agent temozolomide has emerged as a potential initial treatment option for LGG. A few reports suggest an association between temozolomide and reduced seizure frequency in patients with intractable epilepsy.

METHODS

Using their clinical database, the authors identified adult patients whose LGGs were treated using temozolomide as the initial antineoplastic therapy at the University of Virginia Health System. As a control group, the authors assessed patients whose LGGs were under observation. All patients had seizure disorders that were treated with anticonvulsants. Seizure frequency in patients with intractable epilepsy was analyzed before and after treatment with temozolomide. Age at diagnosis, sex, antiepileptic drugs, pathological subtype, surgical treatment, and follow-up until progression were also assessed. Interval seizure frequency was meticulously analyzed at each neurooncology clinic visit. A meaningful difference in seizures was defined as a reduction in seizure frequency of greater than 50% per month.

RESULTS

Thirty-nine patients were identified in the temozolomide cohort and 30 patients in the control cohort. The median age at diagnosis was 46 years for the former cohort and 41.5 years for the latter. The median length of follow-up was 39 months for the temozolomide group and 37 months for the control group. There was a significant difference in reduced seizure frequency between patients receiving temozolomide (59%) and those who did not receive temozolomide (13%, p < 0.001). Seven patients (18%) in the temozolomide group displayed this improvement independent of antiepileptic drug adjustment compared with no patient in the control group (p < 0.001).

CONCLUSIONS

The authors' data suggest that a subset of patients with LGGs experience improvement in seizure frequency during treatment with temozolomide independent of antiepileptic drug adjustment. This decrease in seizure frequency appears independent of the natural history of seizures in patients whose tumors are under observation. Consequently, seizures in patients with LGGs may be better controlled with the combination of AEDs and temozolomide.

Pediatric epileptogenic gangliogliomas: seizure outcome and surgical results

OBJECT

Ganglioglioma is the most common neoplasm causing focal epilepsy, accounting for approximately 40% of all epileptogenic tumors and for 1-4% of all pediatric CNS tumors. The optimal surgical treatment for pediatric epileptogenic ganglioglioma has not been fully established. The authors present their experience in the surgical management of these lesions.

METHODS

The authors retrospectively analyzed seizure outcome and surgical results of pediatric patients with ganglioglioma treated with resection. The patients' charts were reviewed for demographic data, clinical presentation, surgical therapy, and follow-up.

RESULTS

The 30 patients (17 boys, 13 girls) had a history of medically intractable epilepsy. Total resection of tumor was achieved with or without adjacent epileptogenic tissue resection in all patients except 1, who underwent cyst fenestration and biopsy. Intraoperative electrocorticography (ECoG) was used in 21 patients. If an active spike focus or profound attenuation was observed in adjacent tissues, resection of those tissues was performed in addition to complete tumor resection (lesionectomy). The interval between onset of seizures and surgery ranged from 1 month to 9 years (mean 1.6 years). Patient age at the time of surgery ranged from 9 months to 16.3 years (mean 8.6 years). Twenty-five patients (83.3%) had complex partial seizures and 5 (16.7%) had simple partial seizures. Eighteen tumors (60%) were temporal (14 temporomesial, 4 temporolateral), and 12 (40%) were extratemporal. The mean follow-up period was 3.4 years (range 1 month-8.16 years). In 2 cases (6.7%), tumor recurrence was observed. Outcome was Engel Class I in 27 cases (90.0%; 14 temporomesial, 4 temporolateral, 9 extratemporal) and Engel Class II in 3 (10.0%; all extratemporal). Tumor resection allowed good seizure control, especially in the 18 cases of temporal ganglioglioma (all Engel Class I postoperatively). Eleven patients underwent removal of extratumoral epileptogenic tissue (anterior temporal neocortex resection in 10, anterior temporal neocortex resection with anterior hippocampectomy in 1) in addition to lesionectomy using intraoperative ECoG.

CONCLUSIONS

Lesionectomy with adjacent temporal neocortex resection using intraoperative ECoG provided good seizure control of pediatric temporal ganglioglioma. For extratemporal ganglioglioma, lesionectomy alone can provide fairly good seizure control. Considering the memory function of the hippocampus, lesionectomy with adjacent temporal neocortical resection can be a safe, feasible, and effective treatment option for epileptogenic gangliogliomas in pediatric patients.

Epilepsy and insular Grade II gliomas: an interdisciplinary point of view from a retrospective monocentric series of 46 cases

OBJECT

There are few data in the literature concerning a multimodal approach to insular WHO Grade II gliomas (GIIGs) and the control of epilepsy after treatment. In this paper, the authors describe a monocentric series of 46 cases in which patients underwent various sequential treatments for insular GIIGs. On the basis of global results with regard to epilepsy, the respective interests in the various treatments are discussed.

METHODS

Available data on 46 patients harboring insular GIIGs were extracted from a local database of 288 GIIGs. The various therapeutic sequences were analyzed in parallel with the course of seizure frequency.

RESULTS

Despite the usual difficulties with seizure quantification in retrospective studies, the authors showed that 1) the negative course of seizure frequency was mostly connected to tumor progression, 2) surgery almost always had a favorable effect on epilepsy, and 3) chemotherapy had a mostly favorable effect with acceptable tolerance. The authors were unable to draw conclusions about the role of radiotherapy given the too few cases.

CONCLUSIONS

This extensive experience with insular GIIGs tends to confirm interest in their surgical removal and supports interest in chemotherapy from an epileptological point of view.

Tumor-associated epilepsy

Tumor-associated epilepsy is an important contributor to morbidity in patients with brain tumors. Proposed pathophysiological mechanisms to explain these effects range from neuronal and glial dysfunction to deranged vascular homeostasis, to ionic and pH changes. Perilesional tissue alterations play a vital role in the generation of tumor-associated seizures. Clinical studies have determined that tumor-associated seizures are usually focal with secondary generalization and often resistant to antiepileptic drugs. Tumor histopathological characteristics and location are independent factors that impact seizure burden. Further understanding of the mechanisms of tumor-associated epilepsy may lead to new types of treatments targeted at perilesional tissue alterations.

Long-term seizure outcomes in adult patients undergoing primary resection of malignant brain astrocytomas

Object

Seizures are a common presenting symptom and cause of morbidity for patients with malignant astrocytomas. The authors set out to determine preoperative seizure characteristics, effects of surgery on seizure control, and factors associated with prolonged seizure control in patients with malignant astrocytomas.

Methods

Cases involving adult patients who underwent primary resection of a hemispheric anaplastic astrocytoma (AA) or glioblastoma multiforme (GBM) at the Johns Hopkins Medical Institutions between 1996 and 2006 were retrospectively reviewed. Multivariate logistical regression analysis was used to identify associations with pre-operative seizures, and multivariate proportional hazards regression analyses were used to identify associations with prolonged seizure control following resection.

Results

Of the 648 patients (505 with GBM, 143 with AA) in this series, 153 (24%) presented with seizures. The factors more commonly associated with preoperative seizures were AA pathology (p = 0.03), temporal lobe involvement (p = 0.04), and cortical location (p = 0.04), while the factors less commonly associated with preoperative seizures were greater age (p = 0.03) and larger tumor size (p ≤ 0.001). Among those patients with a history of seizures, outcome 12 months after surgery was Engel Class I (seizure free) in 77%, Class II (rare seizures) in 12%, Class III (meaningful improvement) in 6%, and Class IV (no improvement) in 5%. Postoperative seizures were rare in patients without a history of preoperative seizures. The factor positively associated with prolonged seizure control was increased Karnofsky Performance Scale score (p = 0.002), while the factors negatively associated with seizure control were preoperative uncontrolled seizures (p = 0.03) and parietal lobe involvement (p = 0.005). Seizure recurrence in patients with postoperative seizure control was independently associated with tumor recurrence (p = 0.006).

Conclusions

The identification and consideration of factors associated with prolonged seizure control may help guide treatment strategies aimed at improving the quality of life for patients with malignant astrocytomas.

Brain tumors and epilepsy: pathophysiology of peritumoral changes

Epilepsy commonly develops among patients with brain tumors, frequently even as the presenting symptom, and such patients consequently experience substantial morbidity from both the seizures and the underlying disease. At clinical presentation, these seizures are most commonly focal with secondary generalization and conventional medical management is often met with less efficacy. The molecular pathophysiology of these seizures is being elucidated with findings that both the tumoral and peritumoral microenvironments may exhibit epileptogenic phenotypes owing to disordered neuronal connectivity and regulation, impaired glial cell function, and the presence of altered vascular supply and permeability. Neoplastic tissue can itself be the initiation site of seizure activity, particularly for tumors arising from neuronal cell lines, such as gangliogliomas or dysembryoblastic neuroepithelial tumors. Conversely, a growing intracranial lesion can both structurally and functionally alter the surrounding brain tissue with edema, vascular insufficiency, inflammation, and release of metabolically active molecules, hence also promoting seizure activity. The involved mechanisms are certain to be multifactorial and depend on specific tumor histology, integrity of the blood brain barrier, and characteristics of the peritumoral environment. Understanding these changes that underlie tumor-related epilepsy may have roles in both optimal medical management for the seizure symptom and optimal surgical objective and management of the underlying disease.

Intracranial EEG findings in patients with lesional lateral temporal lobe epilepsy

PURPOSE

Intracranial EEG in patients with lesional lateral temporal lobe epilepsy is rarely reported. Therefore, the number of patients with seizures arising independently from ipsilateral mesial structures or contralateral hemisphere has not been clarified. We analyzed the intracranial EEG of cases with localized lesion in the lateral temporal cortex.

METHODS

We studied 15 patients who satisfied the following criteria: (1) MRI depicted a lesion less than 4cm in diameter located lateral to the collateral sulcus and at least 3cm posterior to the temporal pole; (2) intracranial EEG with electrodes placed on bilateral temporal lobes captured at least one complex partial seizure; and (3) postoperative follow-up period of 2 years or longer. The mean age of seizure onset was 16.6 years (range, 11-25) and that at surgery was 26.7 years (range, 16-36).

RESULTS

A total of 147 complex partial seizures, 51 simple partial seizures, 16 secondarily generalized seizures, and over 80 subclinical seizures were recorded. On the lesional side, many clinical seizures were recorded from the lateral cortex. Independent of the lateral temporal onset seizures, ictal discharges originating from the mesial temporal structures were recorded in 7 of 15 patients (47%). Moreover, onset of ictal discharges from the contralateral temporal lobe was recorded in 7 of 15 patients (47%). Interictal spikes from ipsilateral mesial structures were recorded in all patients. The presence of ipsilateral mesial onset seizures was not associated with hippocampal neuron losses.

CONCLUSION

Intracranial EEG analysis revealed that approximately one-half of the patients with structural lesions in the lateral cortex showed independent epileptogenic areas in ipsilateral mesial structures. Although ictal discharges originating from the contralateral temporal lobe were recorded in a half of these patients, this finding does not constitute a contraindication of resective surgery. Interictal spike is not an indicator of whether mesial structures should be resected.

Seizure characteristics and control following resection in 332 patients with low-grade gliomas

OBJECT

Seizures play an important role in the clinical presentation and postoperative quality of life of patients who undergo surgical resection of low-grade gliomas (LGGs). The aim of this study was to identify factors that influenced perioperative seizure characteristics and postoperative seizure control.

METHODS

The authors performed a retrospective chart review of all cases involving adult patients who underwent initial surgery for LGGs at the University of California, San Francisco between 1997 and 2003.

RESULTS

Three hundred and thirty-two cases were included for analysis; 269 (81%) of the 332 patients presented with >or=1 seizures (generalized alone, 33%; complex partial alone, 16%; simple partial alone, 22%; and combination, 29%). Cortical location and oligodendroglioma and oligoastrocytoma subtypes were significantly more likely to be associated with seizures compared with deeper midline locations and astrocytoma, respectively (p=0.017 and 0.001, respectively; multivariate analysis). Of the 269 patients with seizures, 132 (49%) had pharmacoresistant seizures before surgery. In these patients, seizures were more likely to be simple partial and to involve the temporal lobe, and the period from seizure onset to surgery was likely to have been longer (p=0.0005, 0.0089, and 0.006, respectively; multivariate analysis). For the cohort of patients that presented with seizures, 12-month outcome after surgery (Engel class) was as follows: seizure free (I), 67%; rare seizures (II), 17%; meaningful seizure improvement (III), 8%; and no improvement or worsening (IV), 9%. Poor seizure control was more common in patients with longer seizure history (p<0.001) and simple partial seizures (p=0.004). With respect to treatment-related variables, seizure control was far more likely to be achieved after gross-total resection than after subtotal resection/biopsy alone (odds ratio 16, 95% confidence interval 2.2-124, p=0.0064). Seizure recurrence after initial postoperative seizure control was associated with tumor progression (p=0.001).

CONCLUSIONS

The majority of patients with LGG present with seizures; in approximately half of these patients, the seizures are pharmacoresistant before surgery. Postoperatively, >90% of these patients are seizure free or have meaningful improvement. A shorter history of seizures and gross-total resection appear to be associated with a favorable prognosis for seizure control.

SURGERY OF INTRINSIC CEREBRAL TUMORS

TUMORS AND OTHER structural lesions located with and adjacent to the cerebral cortex present certain challenges in terms of the overall management and design of surgical strategies. This comprehensive analysis attempts to define the current understanding of cerebral localization and function and includes the latest advances in functional imaging, as well as surgical technique, including localization of tumors and neurophysiological mapping to maximize extent of resection while minimizing morbidity. Finally, it remains to be seen whether or not stimulation mapping will be the most useful way to identify function within the cortex in the future. Another potential paradigm would be to actually record baseline oscillatory rhythms within the cortex and, following presentation of a given task, determine if those rhythms are disturbed enough to identify eloquent cortex as a means of functional localization. This would be a paradigm shift away from stimulation mapping, which currently deactivates the cortex, as opposed to identifying an activation function which identifies functional cortex.

Inhibitory networks in epilepsy-associated gangliogliomas and in the perilesional epileptic cortex

Developmental glioneuronal lesions, such as gangliogliomas (GG) are increasingly recognized causes of chronic pharmaco-resistant epilepsy. It has been postulated that chronic epilepsy in patients with malformations of cortical development is associated with dysfunction of the inhibitory GABA-ergic system. We aimed to identify the subtypes of interneurons present within GG specimens and the expression and cellular distribution patterns of GABA receptors (GABAR) and GABA transporter 1 (GAT1). The expression of the various components of the GABA-ergic system were also analyzed in the perilesional cortex. We investigated the expression of parvalbumin, calbindin, calretinin, GABA(A)R (a1 subunit)(,) GABA(B) (R1 and R2) and GAT-1 using immunocytochemistry in 30 specimens of GG obtained during epilepsy surgery, including 10 cases with sufficient amount of perilesional cortex. Immunocytochemistry for calbindin (CB), calretinin (CR) and parvalbumin (PV) demonstrate the presence of inhibitory neurons of different subtypes within the GG specimens. Calcium-binding protein-positive interneurons represent a small fraction of the total neuronal population. Both GABA(A)R and GABA(B)R (R1 and R2) subtypes were detected within the neuronal component of GG specimens. In addition, GABA(B)R2 immunoreactivity (IR) was observed in glial cells. GG specimens displayed also expression of GAT-1 IR. Compared to normal cortex, the density of PV- and CB-immunoreactive interneurons was reduced in the perilesional cortex of GG patients, whereas CR-labeling was similar to that observed in normal cortex. GAT-1 IR was also significantly reduced in the perilesional specimens. The cellular distribution of components of the GABA-ergic system in GG, together with the perilesional changes suggest that alterations of the GABA-ergic system may contribute to the complex abnormal functional network of these highly epileptogenic developmental lesions.

Symptom management and supportive care of the patient with brain metastases

The focus of care for patients with brain metastases will always be on therapeutic options such as surgery, radiotherapy, and chemotherapy. However, proper symptom management and supportive care of non-therapeutic issues will be equally as important, including treatment of seizures, use of anticonvulsants, corticosteroids, and gastric acid inhibitors, assessment of swallowing dysfunction, treatment of thromboembolic events, appropriate use, and safe application of anticoagulation, and evaluation of psychiatric issues. Appropriate management of these supportive aspects of patient care will improve overall quality of life and allow the patient and family to more easily concentrate on treatment.

Clinical features and epileptogenesis of dysembryoplastic neuroepithelial tumor

INTRODUCTION

Dysembryoplastic neuroepithelial tumor (DNT) frequently causes medically intractable epilepsy.

OBJECTIVE

The aim of this study was to investigate the basic mechanism of epileptogenecity of the tumor.

MATERIALS AND METHODS

Clinicopathological data in 13 cases of DNT and immunohistochemical changes of ionotropic glutamate receptor subunits in the tumor and peritumoral epileptogenic cortex were studied.

CONCLUSIONS

Magnetic resonance imaging combined with electroencephalography (EEG), electrocorticography, and depth-electrode EEG was valuable to localize complicated epileptogenic zones of the patients with DNT. Neuropathological examinations of the peritumoral cerebral cortex presenting abnormal spikes showed different histopathological grades of neuronal migration disorder (NMD). The tumor cells in DNT disclosed increased immunopositivities of N-methyl-D: -aspartate receptor 1 (NR1) and NR2A/B, and peritumoral epileptogenic NMD revealed increased immunopositivities of GluR2 and GluR3. The amplification of ionotropic glutamate receptor subunits in the tumor and peritumoral NMD may be the underlying cause of epileptic seizures in DNT patients.

Cerebral cavernous malformations and epilepsy

✓Seizures and epilepsy are frequent clinical manifestations of cerebral cavernous malformations (CCMs) and represent the most common symptomatic presentation of supratentorial lesions. Clinicians often diagnose CCMs in patients after a first seizure, or in some cases after obtaining neuroimaging studies in patients suffering from chronic epilepsy previously thought to be idiopathic. In some cases, the lesion is clinically significant solely because of its epileptogenicity, but in others there may be concern about potential hemorrhage or focal neurological deficits from a similar lesion.

The authors present current pathophysiological concepts related to epilepsy associated with CCMs. They discuss the spectrum of seizure disorders associated with these lesions and review the natural history, prognosis, and options for therapeutic intervention.

Surgery for epilepsy

Epilepsy surgery in general is viewed with many misconceptions about its safety and efficacy, and it is an under-used modality worldwide. This deficiency is particularly relevant to children, who stand to benefit the most from early remission of seizures and elimination of the need for potentially toxic AEDs. Advancements in the field and the ability to further sway public opinion toward the established safety and efficacy of epilepsy surgery will come through less invasive techniques to map the epileptogenic zone (eg, EEG, fMRI, MEG) and reversible strategies such as neurostimulation/neuromodulation to control seizures. Two multicenter trials are underway to test the efficacy of thalamic and cortical stimulation via more sophisticated technology and devices than those available in the past.

Loss of neuronal integrity: a cause of hypometabolism in patients with traumatic brain injury without MRI abnormality in the chronic stage

PURPOSE

Traumatic brain injury (TBI) causes brain dysfunction in many patients. However, some patients have severe brain dysfunction but display no abnormalities on magnetic resonance imaging (MRI). There have been some reports of hypometabolism even in such patients. The purpose of this study was to investigate the relationship between metabolic abnormality and loss of neuronal integrity in TBI patients with some symptoms but without MRI abnormalities.

METHODS

The study population comprised ten patients with TBI and ten normal volunteers. All of the patients were examined at least 1 year after the injury. ( 15)O-labelled gas PET and [(11)C]flumazenil (FMZ) positron emission tomography (PET) were carried out. The cerebral metabolic rate of oxygen (CMRO(2)) and binding potential (BP) images of FMZ were calculated. Axial T2WI, T2*WI and FLAIR images were obtained. Coronal images were added in some cases.

RESULTS

All of the patients had normal MRI findings, and all showed areas with abnormally low CMRO(2). Low uptake on BP images was observed in six patients (60%). No lesions that showed low uptake on BP images were without low CMRO(2). On the other hand, there were 14 lesions with low CMRO(2) but without BP abnormalities.

CONCLUSION

These results indicate that there are metabolic abnormalities in TBI patients with some symptoms after brain injury but without abnormalities on MRI. Some of the hypometabolic lesions showed low BP, indicating a loss of neuronal integrity. Thus, FMZ PET may have potential to distinguish hypometabolism caused by neuronal loss from that caused by other factors.

Frequent association of cortical dysplasia in dysembryoplastic neuroepithelial tumor treated by epilepsy surgery

BACKGROUND

We report on our experience with epilepsy surgery in the treatment of localization-related epilepsy caused by dysembryoplastic neuroepithelial tumor (DNT) aimed at achieving the best seizure control.

METHODS

A retrospective analysis was performed on the pathological reports as well as on clinical data of 24 case patients with medically intractable epilepsy with DNT treated surgically between 1995 and 2000 at the Samsung Medical Center. Resective surgery was performed using subdural electrodes or intraoperative electrocorticography in all patients.

RESULTS

The mean follow-up period was 57.2 months. Two patients had rare seizures transiently after surgery but remained free from seizures after 6 months. Others remained completely free from seizures. There was a strong tendency of temporal lobe involvement (19 cases; 79.2%). Size of tumors located at medial temporal regions was significantly smaller than those at lateral temporal or frontal lobes (P < .05). A rather radical resection (tumor plus surrounding tissue showing active epileptogenicity) was performed in all but one case where only focal lesionectomy was done. In 20 of the 24 cases (83.3%), association of cortical dysplasia (CD) was found on pathological examination.

CONCLUSIONS

We conclude that DNT is frequently associated with CD, with a wide area of epileptogenic activity that might be related to the presence of CD around the DNT. Comprehensive preoperative investigations for accurate localization of epileptogenic activity, meticulous brain mapping, and a rather radical resection of pathological areas might be essential for the achievement of excellent seizure control in DNT-associated epilepsy.

Distribution, characterization and clinical significance of microglia in glioneuronal tumours from patients with chronic intractable epilepsy

Cells of the microglia/macrophage lineage represent an important component of different brain tumours. However, there is little information about the microglia/macrophage cell system in glioneuronal tumours and its possible contribution to the high epileptogenecity of these lesions. In the present study, the distribution of cells of the microglia/macrophage lineage was studied by immunocytochemistry for CD68 and human leucocyte antigen (HLA)-DR in a group of glioneuronal tumours, including gangliogliomas (GG, n = 30), and dysembryoplastic neuroepithelial tumours (DNT, n = 17), from patients with chronic intractable epilepsy. A significant number of microglia/macrophage cells were observed in the large majority of glioneuronal tumours, both within the tumour and in the peritumoral region. Activated microglial cells positive for HLA-DR were localized around blood vessels and clustered around tumour neuronal cells. The density of activated microglial cells correlated with the duration of epilepsy, as well as with the frequency of seizures prior to surgical resection. These observations indicate that the presence of cells of the microglial/macrophage cell system is a feature of glioneuronal tumours and is functionally related to epilepsy, either directly in epileptogenesis or through activation following seizure activity.