Influences of brain tumor-associated pH changes and hypoxia on epileptogenesis

Antiepileptic drug-loaded and multifunctional iron oxide@silica@gelatin nanoparticles for acid-triggered drug delivery

The current study developed an innovative design for the production of smart multifunctional core-double shell superparamagnetic nanoparticles (NPs) with a focus on the development of a pH-responsive drug delivery system tailored for the controlled release of Phenytoin, accompanied by real-time monitoring capabilities. In this regard, the ultra-small superparamagnetic iron oxide@silica NPs (IO@Si MNPs) were synthesized and then coated with a layer of gelatin containing Phenytoin as an antiepileptic drug. The precise saturation magnetization value for the resultant NPs was established at 26 emu g-1. The polymeric shell showed a pH-sensitive behavior with the capacity to regulate the release of encapsulated drug under neutral pH conditions, simultaneously, releasing more amount of the drug in a simulated tumorous-epileptic acidic condition. The NPs showed an average size of 41.04 nm, which is in the desired size range facilitating entry through the blood-brain barrier. The values of drug loading and encapsulation efficiency were determined to be 2.01 and 10.05%, respectively. Moreover, kinetic studies revealed a Fickian diffusion process of Phenytoin release, and diffusional exponent values based on the Korsmeyer-Peppas equation were achieved at pH 7.4 and pH 6.3. The synthesized NPs did not show any cytotoxicity. Consequently, this new design offers a faster release of PHT at the site of a tumor in response to a change in pH, which is essential to prevent epileptic attacks.

The Prevalence of Seizures in Brain Metastasis Patients on Anticonvulsant Prophylaxis: A Systematic Review and Meta-Analysis

BACKGROUND

Brain metastasis (BM) prognosis is incredibly poor and is often associated with considerable morbidity. Seizures are commonly present in these patients, and their biopsychosocial impact can be dangerous. The use of antiepileptic drugs (AEDs) as primary prophylaxis remains controversial. This systematic review and meta-analysis aim to evaluate the efficacy of AED prophylaxis in patients with BM.

METHODS

MEDLINE via PubMed, Web of Science, EMBASE, and Cochrane were searched for articles pertinent to AED prophylaxis use in patients with BM. Patients with BM previously treated for cancer who were seizure naive at the time of inclusion were included. Data regarding patient characteristics, type of AED, prior treatments, and groups at a high risk of seizure were extracted. Seizure prevalence was obtained.

RESULTS

Eight studies were included in this systematic review and meta-analysis; 1902 total patients with BM were included, with 381 receiving antiepileptic prophylaxis, and 1521 receiving no prophylaxis. Although the odds of a seizure in the treatment group was found to be 1.158 times the odds of a seizure in the control group, the odds ratio was not statistically significant (t-statistic = 0.62, P value = 0.5543).

CONCLUSIONS

There was no significant difference in the odds of seizure development in control groups compared to patients receiving prophylactic antiepileptic therapy. As patients with BM present with heterogeneity in tumor characteristics and receive various treatment modalities, future research is needed to identify groups that may benefit more significantly from AED prophylaxis.

Differential metabolic alterations in IDH1 mutant vs. wildtype glioma cells promote epileptogenesis through distinctive mechanisms

Glioma-related epilepsy (GRE) is a hallmark clinical presentation of gliomas with significant impacts on patient quality of life. The current standard of care for seizure management is comprised of anti-seizure medications (ASMs) and surgical resection. Seizures in glioma patients are often drug-resistant and can often recur after surgery despite total tumor resection. Therefore, current research is focused on the pro-epileptic pathological changes occurring in tumor cells and the peritumoral environment. One important contribution to seizures in GRE patients is metabolic reprogramming in tumor and surrounding cells. This is most evident by the significantly heightened seizure rate in patients with isocitrate dehydrogenase mutated (IDHmut) tumors compared to patients with IDH wildtype (IDHwt) gliomas. To gain further insight into glioma metabolism in epileptogenesis, this review compares the metabolic changes inherent to IDHmut vs. IDHwt tumors and describes the pro-epileptic effects these changes have on both the tumor cells and the peritumoral environment. Understanding alterations in glioma metabolism can help to uncover novel therapeutic interventions for seizure management in GRE patients.

RICH2 decreases the mitochondrial number and affects mitochondrial localization in diffuse low-grade glioma-related epilepsy

Epilepsy, a common complication of diffuse low-grade gliomas (DLGGs; diffuse oligodendroglioma and astrocytoma collectively), severely compromises the quality of life of patients. DLGG epileptogenicity may primarily be generated by interactions between the tumor and the neocortex. Neuronal uptake of dysfunctional mitochondria from the extracellular environment can lead to abnormal neuronal discharge. Mitochondrial dysfunction is frequently observed in gliomas that can transmigrate across the plasma membranes. Here, we examined the role of the Rho GTPase-activating protein 44 (RICH2) in mitochondrial dynamics and DLGG-related epilepsy. We investigated the association between mitochondrial and RICH2 expression in human DLGG tissues using immunohistochemistry. We examined the association between RICH2 and epilepsy in nude mouse glioma models by electrophysiology. The effect of RICH2 on mitochondrial morphology and calcium motility were assessed by single cell fluorescence microscopy. Quantitative RT-PCR (qRT-PCR) and Western blot analysis were performed to characterize RICH2 induced expression changes in the genes related to mitochondrial dynamics, mitogenesis and mitochondrial function. We found that RICH2 expression was higher in oligodendroglioma than in astrocytoma and was correlated with better prognosis and higher epilepsy rate in patients. The expression of mitochondria may be associated with clinical DLGG-related epilepsy and reduced by RICH2 overexpression. And RICH2 could promote DLGG-related epilepsy in tumorigenic nude mice. RICH2 overexpression decreased calcium flow and the mitochondria released from glioma cells (SW1088 and U251) into the extracellular environment, potentially via downregulation of MFN-1/MFN-2 levels which suggests reduced mitochondrial fusion. In addition, we observed decreased mitochondrial trafficking into neurons (released from glioma cells and trafficked into neurons), which could explain the higher incidence of DLGG-related epilepsy due to reduced neuroprotection. Furthermore, RICH2 downregulated MAPK/ERK/HIF-1 pathway. In conclusion, these results suggest that RICH2 could promote epilepsy by (i) inhibiting mitochondrial fusion via MFN downregulation and Drp-1 upregulation; (ii) altering the MAPK/ERK/Hif-1 signaling axis. RICH2 may be a potential target in the treatment of DLGG-related epilepsy.

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.

Ion Channels in Gliomas-From Molecular Basis to Treatment

Ion channels provide the basis for the nervous system's intrinsic electrical activity. Neuronal excitability is a characteristic property of neurons and is critical for all functions of the nervous system. Glia cells fulfill essential supportive roles, but unlike neurons, they also retain the ability to divide. This can lead to uncontrolled growth and the formation of gliomas. Ion channels are involved in the unique biology of gliomas pertaining to peritumoral pathology and seizures, diffuse invasion, and treatment resistance. The emerging picture shows ion channels in the brain at the crossroads of neurophysiology and fundamental pathophysiological processes of specific cancer behaviors as reflected by uncontrolled proliferation, infiltration, resistance to apoptosis, metabolism, and angiogenesis. Ion channels are highly druggable, making them an enticing therapeutic target. Targeting ion channels in difficult-to-treat brain tumors such as gliomas requires an understanding of their extremely heterogenous tumor microenvironment and highly diverse molecular profiles, both representing major causes of recurrence and treatment resistance. In this review, we survey the current knowledge on ion channels with oncogenic behavior within the heterogeneous group of gliomas, review ion channel gene expression as genomic biomarkers for glioma prognosis and provide an update on therapeutic perspectives for repurposed and novel ion channel inhibitors and electrotherapy.

The gene expression patterns as surrogate indices of pH in the brain

Hydrogen ion (H⁺) is one of the most potent intrinsic neuromodulators in the brain in terms of concentration. Changes in H⁺ concentration, expressed as pH, are thought to be associated with various biological processes, such as gene expression, in the brain. Accumulating evidence suggests that decreased brain pH is a common feature of several neuropsychiatric disorders, including schizophrenia, bipolar disorder, autism spectrum disorder, and Alzheimer's disease. However, it remains unclear whether gene expression patterns can be used as surrogates for pH changes in the brain. In this study, we performed meta-analyses using publicly available gene expression datasets to profile the expression patterns of pH-associated genes, whose expression levels were correlated with brain pH, in human patients and mouse models of major central nervous system (CNS) diseases, as well as in mouse cell-type datasets. Comprehensive analysis of 281 human datasets from 11 CNS disorders revealed that gene expression associated with decreased pH was over-represented in disorders including schizophrenia, bipolar disorder, autism spectrum disorders, Alzheimer's disease, Huntington's disease, Parkinson's disease, and brain tumors. Expression patterns of pH-associated genes in mouse models of neurodegenerative disease showed a common time course trend toward lower pH over time. Furthermore, cell type analysis identified astrocytes as the cell type with the most acidity-related gene expression, consistent with previous experimental measurements showing a lower intracellular pH in astrocytes than in neurons. These results suggest that the expression pattern of pH-associated genes may be a surrogate for the state- and trait-related changes in pH in brain cells. Altered expression of pH-associated genes may serve as a novel molecular mechanism for a more complete understanding of the transdiagnostic pathophysiology of neuropsychiatric and neurodegenerative disorders.

Historical Overview of the "Firing" Liaison between Brain Tumors and Epilepsy

This review addresses, in a critical historical perspective, the link between seizures and endocranic neoplasms. Folkloric descriptions of epilepsy can be found in writings from ancient cultures. Hippocrates first provided a medical interpretation. In 1770, Tissot published Traité de l'épilepsie, a milestone in epileptology, whereas the 19th century is considered the golden era of epileptic studies. In 1882, the father of modern epileptology, Jackson, in his article Localized Convulsions from Tumour of the Brain, reported a case of a patient affected by typical Jacksonian seizures in the presence of a brain tumor. However, he did not establish a direct correlation between brain tumors and epilepsy, and an explanation for his clinical case was lacking. Before Jackson's article, other authors reported similar cases, but only Gairdner in 1834 published a report suggesting the concept of a direct relationship between epilepsy and a brain tumor. From the beginning until the mid of the 20th century several authors reported seizures attributed to intracranial tumors, and in recent years studies have focused on the pathogenesis of tumor-related seizures. Biochemical and molecular changes in brain tumors and their environment opened unprecedented working hypotheses on epileptogenesis and on treatment of epilepsy associated with brain tumors.

Radiomics Nomogram Improves the Prediction of Epilepsy in Patients With Gliomas

Purpose

To investigate the association between clinic-radiological features and glioma-associated epilepsy (GAE), we developed and validated a radiomics nomogram for predicting GAE in WHO grade II~IV gliomas.

Methods

This retrospective study consecutively enrolled 380 adult patients with glioma (266 in the training cohort and 114 in the testing cohort). Regions of interest, including the entire tumor and peritumoral edema, were drawn manually. The semantic radiological characteristics were assessed by a radiologist with 15 years of experience in neuro-oncology. A clinic-radiological model, radiomic signature, and a combined model were built for predicting GAE. The combined model was visualized as a radiomics nomogram. The AUC was used to evaluate model classification performance, and the McNemar test and Delong test were used to compare the performance among the models. Statistical analysis was performed using SPSS software, and p < 0.05 was regarded as statistically significant.

Results

The combined model reached the highest AUC with the testing cohort (training cohort, 0.911 [95% CI, 0.878-0.942]; testing cohort, 0.866 [95% CI, 0.790-0.929]). The McNemar test revealed that the differences among the accuracies of the clinic-radiological model, radiomic signature, and combined model in predicting GAE in the testing cohorts (p > 0.05) were not significantly different. The DeLong tests showed that the difference between the performance of the radiomic signature and the combined model was significant (p < 0.05).

Conclusion

The radiomics nomogram predicted seizures in patients with glioma non-invasively, simply, and practically. Compared with the radiomics models, comprehensive clinic-radiological imaging signs observed by the naked eye have non-discriminatory performance in predicting GAE.

Reappearance of Neurological Deficits in Pathologic Brain: Are Sedatives and Opioids Culprits? A Systematic Review

Following a brain insult, focal neurological deficits may develop. Despite resolution of these deficits with time, the subsequent administration of sedative medications and opioids may lead to recrudescence of previous neurological deficits. Therefore, the present systematic review aims to explore the role of different sedatives and opioid analgesics at reproducing focal neurological deficits in patients with previous brain insults undergoing surgery. Our PRISMA compliant systematic review covering the literature from 1990 to 2020 showed a consistent reoccurrence of neurological deficits following administration of benzodiazepines and opioids across 12 studies. It appears that in all studies, the manifestations were transient and affected mostly middle-aged patients (45 to 67 y of age). In addition, benzodiazepines and opioid antagonism by naloxone and flumazenil reverses the unmasking of prior neurological deficits. In contrast, it is not clear based on our study whether the unmasking or worsening of neurological deficits occurs following recent injuries or an older brain insult, although for most patients it appears to be the former. Future studies are needed to elucidate the mechanisms involved in unmasking prior deficits and/or extension of prior injuries by sedative and opioid analgesics. This review will aid in developing prospective studies on individual sedative medications and their effects on unmasking neurological deficits in patients with multiple brain pathologies.

Radiomics for the Prediction of Epilepsy in Patients With Frontal Glioma

Objective

This study was conducted in order to investigate the association between radiomics features and frontal glioma-associated epilepsy (GAE) and propose a reliable radiomics-based model to predict frontal GAE.

Methods

This retrospective study consecutively enrolled 166 adult patients with frontal glioma (111 in the training cohort and 55 in the testing cohort). A total 1,130 features were extracted from T2 fluid-attenuated inversion recovery images, including first-order statistics, 3D shape, texture, and wavelet features. Regions of interest, including the entire tumor and peritumoral edema, were drawn manually. Pearson correlation coefficient, 10-fold cross-validation, area under curve (AUC) analysis, and support vector machine were adopted to select the most relevant features to build a clinical model, a radiomics model, and a clinical-radiomics model for GAE. The receiver operating characteristic curve (ROC) and AUC were used to evaluate the classification performance of the models in each cohort, and DeLong's test was used to compare the performance of the models. A two-sided t-test and Fisher's exact test were used to compare the clinical variables. Statistical analysis was performed using SPSS software (version 22.0; IBM, Armonk, New York), and p <0.05 was set as the threshold for significance.

Results

The classification accuracy of seven scout models, except the wavelet first-order model (0.793) and the wavelet texture model (0.784), was <0.75 in cross-validation. The clinical-radiomics model, including 17 magnetic resonance imaging-based features selected among the 1,130 radiomics features and two clinical features (patient age and tumor grade), achieved better discriminative performance for GAE prediction in both the training [AUC = 0.886, 95% confidence interval (CI) = 0.819-0.940] and testing cohorts (AUC = 0.836, 95% CI = 0.707-0.937) than the radiomics model (p = 0.008) with 82.0% and 78.2% accuracy, respectively.

Conclusion

Radiomics analysis can non-invasively predict GAE, thus allowing adequate treatment of frontal glioma. The clinical-radiomics model may enable a more precise prediction of frontal GAE. Furthermore, age and pathology grade are important risk factors for GAE.

Medical and Neurological Management of Brain Tumor Complications

PURPOSE OF REVIEW

The diagnosis of brain tumors often leads to complications that are either related to the tumor itself or the tumor-directed and supportive therapies, increasing the burden on the patients' quality of life and even survival. This article reviews the medical and neurological conditions that commonly complicate the disease course of brain tumors patients.

RECENT FINDINGS

Various mechanisms have been newly identified to be involved in the pathophysiology of seizures and brain edema and can help advance the treatment of such complications. There have also been new developments in the management of thromboembolic disease and cognitive impairment. Medical and neurological complications are being identified more often in brain tumor patients with the improved survival provided by therapeutic advances. Early and proper identification and management of such complications are crucial for a better survival and quality of life.

Epileptogenesis and oncogenesis: An antineoplastic role for antiepileptic drugs in brain tumours?

The first description of epileptic seizures due to brain tumours occurred in 19th century. Nevertheless, after over one hundred years, scientific literature is still lacking on how epilepsy and its treatment can affect tumour burden, progression and clinical outcomes. In patients with brain tumours, epilepsy dramatically impacts their quality of life (QoL). Even antiepileptic therapy seems to affect tumor lesion development. Numerous studies suggest that certain actors involved in epileptogenesis (inflammatory changes, glutamate and its ionotropic and metabotropic receptors, GABA-A and its GABA-AR receptor, as well as certain ligand- and voltage-gated ion channel) may also contribute to tumorigenesis. Although some antiepileptic drugs (AEDs) are known operating on such mechanisms underlying epilepsy and tumor development, few preclinical and clinical studies have tried to investigate them as targets of pharmacological tools acting to control both phenomena. The primary aim of this review is to summarize known determinants and pathophysiological mechanisms of seizures, as well as of cell growth and spread, in patients with brain tumors. Therefore, a special focus will be provided on the anticancer effects of commonly prescribed AEDs (including levetiracetam, valproic acid, oxcarbazepine and others), with an overview of both preclinical and clinical data. Potential clinical applications of this finding are discussed.

Correlation between glioma location and preoperative seizures: a systematic review and meta-analysis

Epilepsy is a common manifestation of glioma patients and negatively impacts on quality of life and neurocognitive function. The risk of preoperative seizures in patients with glioma is currently under discussion. We aimed to evaluate the relationship between tumor locations in the cerebrum and preoperative seizures in patients with glioma. PubMed, EMBASE, Web of Science, China Biology Medicine, and the Cochrane Library were systematically searched from inception to July 15, 2017, for original studies including reports of preoperative seizures in patients with gliomas in different brain regions. The pooled odds ratio (OR) and 95% confidence interval (CI) of the meta-analysis for preoperative seizure risk stratified by cerebrum regions were calculated. The quality of evidence was assessed per outcome, using the approach of the Grades of Recommendation, Assessment, Development and Evaluation. Overall, 4323 participants in 16 population-based studies were included in this meta-analysis. The meta-analysis indicated that gliomas in the frontal lobe (OR = 1.51, 95% CI = 1.09-2.09, P = 0.013) were associated with a higher risk for preoperative seizure compared to occipital lobe involved (OR = 0.53, 95% CI = 0.32-0.88, P = 0.014). Regarding the other three lobe involved gliomas, no difference was found between the incidence of preoperative seizures and tumor location. Current limited data suggest that frontal gliomas were associated with a higher risk of preoperative seizures, while gliomas in the occipital lobe were associated with a lower seizure risk. Further RCT studies recruiting larger sample sizes are required to validate these results and guide clinical practice.

Descriptive epidemiology: prevalence, incidence, sociodemographic factors, socioeconomic domains, and quality of life of epilepsy: an update and systematic review

INTRODUCTION

The purpose of this study was to investigate the contributions of quality of life (QOL), sociodemographic factors (age, sex, etc.), residential areas, general attitudes toward epilepsy, socioeconomic domains, prevalence and incidence in epileptic patients from Iran.

MATERIAL AND METHODS

A systematic literature search was conducted, including database searches in PubMed, Medline, Embase, ScienceDirect, Scopus, ISC, Health, Web of Science, and the Cochrane Library Database of relevant articles, personal files and systematic reviews to identify studies examining risk factors in epilepsy.

RESULTS

This review article shows that certain socio-demographic and socio-economic factors, geographic variation in epidemiologic patterns of epilepsy as well as clinical factors may be crucial in determining QOL in epilepsy patients and provides further evidence supporting the validity of the scale in QOL based on consideration of different target groups in different areas.

CONCLUSIONS

Prevalence of epilepsy appears to be correlated with socioeconomic status in the lower socioeconomic groups. Also demographic characteristics, socio-economic factors and clinical presentation are linked to different QOL of these patients among nations. The educational program has a beneficial effect on self-management behaviors in patients with epilepsy. More work needs to be done to improve tools that help to evaluate efficiently the health-related quality of life of people with epilepsy.

Molecular imaging for stem cell therapy in the brain

Molecular imaging is one of the methods to follow-up stem cell therapy by visualization in the brain. In a recent article in Stem Cell Research & Therapy, Micci et al. offer a thorough discussion of the advantages and disadvantages of this method and their roles in the future. The authors are among the very first who have implemented recently introduced molecular imaging techniques in experimental research and clinical practice.

Relationship between apathy and tumor location, size, and brain edema in patients with intracranial meningioma

BACKGROUND

The purpose of this study is to assess the relationship between apathy and tumor location, size, and brain edema in patients with intracranial meningioma.

METHODS

We enrolled 65 consecutive patients with meningioma and 31 normal controls matched for age, gender, and education. The patients were divided into frontal or non-frontal (NF) meningioma groups based on magnetic resonance imaging; the frontal group was then subdivided to dorsolateral frontal (DLF), medial frontal (MF), and ventral frontal (VF) groups. Tumor size and brain edema were also recorded. Apathy was assessed by the Apathy Evaluation Scale (AES). Assessments were carried out 1 week before and 3 months after surgery, respectively. Logistic regression analysis was performed to identify the predictive effect of tumor size, location, and brain edema on apathy. Analysis of variance and chi-square analysis were applied to compare apathy scores and apathy rates among the frontal, NF, and normal control groups, and all subgroups within the frontal group.

RESULTS

Compared with the NF and control groups, the mean AES score was much higher in the frontal group (34.0±8.3 versus 28.63±6.0, P=0.008, and 26.8±4.2, P<0.001). Subgroup analysis showed that AES scores in the MF group (42.1±6.6) and VF group (34.7±8.0) were higher than in the DLF group (28.5±4.36), NF group, and control group (P<0.05). The apathy rate was 63.6% in the MF group and 25% in the VF group, and significantly higher than in the DLF (5.6%), NF (5.3%), and control (0%) groups (P<0.001). A moderate correlation was found between AES score and mean diameter of the meningioma in all patient groups. Further analysis demonstrated that the correlation existed in the DLF (r=0.52, P=0.032), MF (r=0.84, P<0.001), and VF (r=0.64, P=0.008) groups, but not in the NF group (r=0.19, P=0.448). The AES score was much higher in patients with brain edema than in those without brain edema (34.73±8.28 versus 28.77±4.20, t=3.545, P=0.001). In subgroups within frontal meningioma patients, the statistical significance above only existed in the MF group (43.50±5.26 versus 25.67±6.03, P=0.001). Also, we examined the effect of related factors, such as age, sex, education, tumor size, tumor location and edema on the occurrence of apathy. The binary logistic regression analysis showed that MF [P=0.023, Exp(B) =145.6] and size [P=0.012, Exp(B) =1.20] got into the regression equation. Thirty-two patients underwent follow-up post-surgery. A significant reduction in AES was found in the MF group (AES1 - AES2 =6.86±6.82, t=2.68, P=0.04), but not in any of the other groups.

CONCLUSION

Apathy occurs frequently in patients with frontal meningioma, and is more severe, especially in the MF region. Apathy is probably correlated with tumor location and size. Brain edema might increase the severity of apathy.

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.

Epilepsy in glioblastoma patients: basic mechanisms and current problems in treatment

Glioblastoma-related epilepsy requires paying careful attention to a combination of factors with an integrated approach. Major interrelated issues must be considered in the seizure care of glioblastoma patients. Seizure control frequently requires the administration of antiepileptic drugs simultaneously with other treatments, including surgery, radiotherapy and chemotherapy, with complete seizure relief often being difficult to achieve. The pharmacological interactions between antiepileptic drugs and antineoplastic agents can modify the activity of both treatments, compromising their efficacy and increasing the probability of developing adverse events related to both therapies. This review summarizes the new pathophysiological pathways involved in the epileptogenesis of glioblastoma-related seizures and the interactions between antiepileptic drugs and oncological treatment, paying special attention to its impact on survival and the current evidence of the antiepileptic treatment efficacy, including the potential usefulness of new third-generation compounds.

Decreased inhibitory neuronal activity in patients with frontal lobe brain tumors with seizure presentation: Preliminary study using magnetoencephalography

BACKGROUND

Although 30-50 % of patients with brain tumors experience epileptic seizure as the presenting clinical symptom, and another 10-30 % are at risk for developing epilepsy in the later stages of the disease, the mechanisms of tumor-related epileptogenesis are poorly understood. We used magnetoencephalography (MEG) to investigate sensory evoked fields (SEFs) in patients with frontal lobe brain tumors as a means of evaluating the neuronal activity of peri-tumoral cortex.

METHODS

Twelve patients with frontal lobe brain tumors underwent MEG. We calculated the equivalent current dipole strength of two components of the primary sensory cortical response (N20m and P35m) and compared the P35m/N20m ratio in the tumor hemisphere vs. the normal hemisphere. There were two subsets of patients: group I, in which P35m/N20m was higher in the tumor hemisphere (n= 7), and group II, in which P35m/N20m was higher in the normal hemisphere (n=5). We looked for associations between clinical factors and P35m/N20m within each group.

RESULTS

All patients with seizure presentation were in group I, whereas only two patients without seizure presentation were in group I (Fisher exact test, p=0.028). No other clinical factors were related to P35m/N20m. The mean ratio of P35m/N20m equivalent current dipole strength in patients with seizure presentation was 4.07 ± 2.38 in the tumor hemisphere and 2.00 ± 0.55 in the normal hemisphere. This difference was statistically significant (Mann-Whitney test, p=0.030).

CONCLUSION

The paradoxical increase in P35m/N20m in patients with seizure presentation suggests that decreased inhibitory neuronal activity is a potential cause of tumorrelated epilepsy.

Higher incidence of epilepsy in meningiomas located on the premotor cortex: a voxel-wise statistical analysis

BACKGROUND

A substantial number of patients with brain tumors develop recurrent seizures, known as tumor-associated epilepsy. It is important to identify specific subgroups of brain tumor patients with higher incidences of epilepsy because a meta-analysis failed to certify the effectiveness of prophylactic anti-epileptic drugs (AEDs) to abort tumor-associated epilepsy as a whole.

METHODS

To investigate the relationship between tumor location and incidence of epilepsy, we performed voxel-wise comparison between 3D MRI scans obtained from patients with meningioma-associated epilepsy and those from control patients using spatial normalization techniques on neuroimaging data. Variables such as age, tumor size, the degree of edema, and pathological diagnosis were also compared between the two groups.

RESULTS

Our results showed the highest incidence of epilepsy when the tumor was located on the premotor cortex in the frontal lobe (Z-scores >2.0, Liebermeister's quasi-exact test). The stepwise multiple regression analysis on the clinical data revealed that the tumor diameter (p < 0.001) and the patient's age (p = 0.024) were positive and negative predictors, respectively, for the onset of epilepsy.

CONCLUSIONS

The incidence of epilepsy was higher in meningiomas located on the premotor cortex than on the other cortex. Larger volume also contributed to the onset of epilepsy. We suggest that variations of epilepsy incidence dependent on tumor characteristics can be considered when treating tumor-associated epilepsy.

Deep brain stimulation for refractory epilepsy

Deep brain stimulation (DBS) is a method of treatment utilized to control medically refractory epilepsy (RE). Patients with medically refractory epilepsy who do not achieve satisfactory control of seizures with pharmacological treatment or surgical resection of the epileptic focus and those who do not qualify for surgery could benefit from DBS. The most frequently used stereotactic targets for DBS are the anterior thalamic nucleus, subthalamic nucleus, central-medial thalamic nucleus, hippocampus, amygdala and cerebellum. The DBS is believed to be an effective method of treatment for various types of epilepsy among adults and adolescents. Side effects may be associated with implantation of electrodes and with the stimulation itself. An increasing number of publications and growing interest in DBS application for RE may result in standardization of the qualification and treatment protocol for RE with DBS.

Intractable epilepsy in paralimbic Word Health Organization Grade II gliomas: should the hippocampus be resected when not invaded by the tumor?

OBJECT

Beyond its oncological benefit, surgery could improve seizure control in paralimbic frontotemporoinsular or temporoinsular WHO Grade II gliomas generating intractable seizures. However, no studies have examined the impact of hippocampal resection on chronic epilepsy when the hippocampus is not invaded by Grade II gliomas. Here, the authors compared the epileptological outcomes and return to work in 2 groups of patients who underwent surgery with or without hippocampectomy for paralimbic Grade II gliomas eliciting intractable epilepsy despite no tumoral involvement of the hippocampus.

METHODS

Surgery was performed in 15 consecutive patients who were unable to work (median Karnofsky Performance Scale [KPS] Score 70) because of refractory epilepsy due to paralimbic Grade II gliomas that were not invading the hippocampus. In Group A (8 patients), the hippocampus was preserved. In Group B (7 patients), glioma removal was associated with hippocampectomy.

RESULTS

No patient died or suffered a permanent deficit after surgery. Postoperatively, in Group A, no patients were seizure free (4 patients were in Engel Class II and 4 were in Class III). In Group B, all 7 patients were seizure free (Class I) (p = 0.02). Only 62.5% of patients returned to work in Group A, whereas all patients are working full time in Group B. The postsurgical median KPS score was 85 in Group A, that is, not significantly improved in comparison with the preoperative score, while the postsurgical median KPS was 95 in Group B, that is, significantly improved in comparison with the preoperative score (p = 0.03).

CONCLUSIONS

The authors' data support, for the first time, the significant impact of hippocampectomy in patients with intractable epilepsy generated by a paralimbic Grade II glioma, even if it does not invade the hippocampus. Hippocampal resection allowed seizure control in all patients, with an improvement in KPS scores, since all patients resumed their social and professional activities. Thus, the authors suggest performing a resection of the nontumoral hippocampus in addition to resection of the tumor in patients with refractory epilepsy due to paralimbic Grade II gliomas.

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.

Seizure characteristics and outcomes in 508 Chinese adult patients undergoing primary resection of low-grade gliomas: a clinicopathological study

Seizure is a common presenting manifestation and plays an important role in the clinical presentation and quality of life for patients with low-grade gliomas (LGGs). The authors set out to identify factors that influence preoperative seizure characteristics and postoperative seizure control. Cases involving adult patients who had undergone initial surgery for LGGs in a single institution between 2005 and 2009 were retrospectively reviewed. Univariate and multivariate logistic regression analyses were used to identify factors associated with preoperative seizures and postoperative seizure control. Of the 508 patients in the series, 350 (68.9%) presented with seizures. Age less than 38 years and cortical involvement of tumor were more likely to be associated with seizures (P = .003 and .001, respectively, multivariate logistic analysis). For the cohort of 350 patients with seizures, Engel classification was used to evaluate 6- and 12-month outcome after surgery: completely seizure free (Engel class I), 65.3% and 62.5%; not seizure free (Engel classes II, III, IV), 34.7% and 37.5%. After multivariate logistic analysis, favorable seizure prognosis was more common in patients with secondary generalized seizure (P = .006) and with calcification on MRI (.031). With respect to treatment-related variables, patients achieved much better seizure control after gross total resection than after subtotal resection (P < .0001). Ki67 was an independent molecular marker predicting poor seizure control in the patients with a history of seizure if overexpressed but was not a predictor for those without preoperative seizures. These factors may provide insight into developing effective treatment strategies aimed at prolonging patients' survival.

Molecular imaging for stem cell transplantation in neuroregenerative medicine

Stem cell transplantation is a promising new therapeutic option in different neurological diseases. However, it was not yet possible to translate its potential from animal models to clinical application. One of the main problems of applying stem cell transplantation in clinical medium is the difficulty of detection, localization, and examination of the stem cells in vivo at both cellular and molecular levels. State-of-the-art molecular imaging techniques provide new and better means for noninvasive, repeated, and quantitative tracking of stem cell implant or transplant. From initial deposition to the survival, migration, and differentiation of the transplant/implanted stem cells, current molecular imaging methods allow monitoring of the infused cells in the same live recipient over time. The present review briefly summarizes and compares these molecular imaging methods for cell labeling and imaging in animal models as well as in clinical application and sheds light on consecutive new therapeutic options if appropriate.

Current molecular imaging of spinal tumors in clinical practice

Energy metabolism measurements in spinal cord tumors, as well as in osseous spinal tumors/metastasis in vivo, are rarely performed only with molecular imaging (MI) by positron emission tomography (PET). This imaging modality developed from a small number of basic clinical science investigations followed by subsequent work that influenced and enhanced the research of others. Apart from precise anatomical localization by coregistration of morphological imaging and quantification, the most intriguing advantage of this imaging is the opportunity to investigate the time course (dynamics) of disease-specific molecular events in the intact organism. Most importantly, MI represents one of the key technologies in translational molecular neuroscience research, helping to develop experimental protocols that may later be applied to human patients. PET may help monitor a patient at the vertebral level after surgery and during adjuvant treatment for recurrent or progressive disease. Common clinical indications for MI of primary or secondary CNS spinal tumors are: (i) tumor diagnosis, (ii) identification of the metabolically active tumor compartments (differentiation of viable tumor tissue from necrosis) and (iii) prediction of treatment response by measurement of tumor perfusion or ischemia. While spinal PET has been used under specific circumstances, a question remains as to whether the magnitude of biochemical alterations observed by MI in CNS tumors in general (specifically spinal tumors) can reveal any prognostic value with respect to survival. MI may be able to better identify early disease and to differentiate benign from malignant lesions than more traditional methods. Moreover, an adequate identification of treatment effectiveness may influence patient management. MI probes could be developed to image the function of targets without disturbing them or as treatment to modify the target's function. MI therefore closes the gap between in vitro and in vivo integrative biology of disease. At the spinal level, MI may help to detect progression or recurrence of metastatic disease after surgical treatment. In cases of nonsurgical treatments such as chemo-, hormone- or radiotherapy, it may better assess biological efficiency than conventional imaging modalities coupled with blood tumor markers. In fact, PET provides a unique possibility to correlate topography and specific metabolic activity, but it requires additional clinical and experimental experience and research to find new indications for primary or secondary spinal tumors.

Epilepsy in the cancer patient

PURPOSE

Epileptic seizures in patients with malignancies usually occur as a consequence of brain metastases from systemic cancer or the presence of a primary brain tumor. Other less-frequent causes include metabolic disorders such as electrolyte abnormalities, hypoglycemia, hypoxia and liver failure, paraneoplastic encephalitis, leptomeningeal carcinomatosis, side effects of certain chemotherapeutic agents, central nervous system infections, and pre-existing epilepsy.

METHODS

We reviewed all published literature in the English language regarding the use of antiepileptic drugs in patients with cancer.

RESULTS

In patients with brain metastases or primary brain tumors that had never experienced seizures, prophylactic anticonvulsant treatment is justified only for a period up to 6 months postoperatively after surgical excision of a cerebral tumor, since approximately half of the patients will never develop seizures and the anti-epileptic drugs may cause toxicity and interactions with antineoplastic therapies. For brief prophylaxis, newer antiepileptic drugs such as levetiracetam and oxcarbazepine are superior to older agents like phenytoin. In patients with a malignancy and seizures, certain antiepileptic drugs that express tumor inhibitory properties should be used such as valproic acid and levetiracetam, followed by oxcarbazepine and topiramate that exhibit good tolerance, efficient seizure control and absence of significant interactions with the chemotherapy.

CONCLUSIONS

Future clinical trials in patients with cancer and epilepsy should focus on combinations of chemotherapeutic interventions with antiepileptic drugs that demonstrate antineoplastic activities.

Stem cell transplantation in brain tumors: a new field for molecular imaging?

Neural stem cells have been proposed as a new and promising treatment modality in various pathologies of the central nervous system, including malignant brain tumors. However, the underlying mechanism by which neural stem cells target tumor areas remains elusive. Monitoring of these cells is currently done by use of various modes of molecular imaging, such as optical imaging, magnetic resonance imaging and positron emission tomography, which is a novel technology for visualizing metabolism and signal transduction to gene expression. In this new context, the microenvironment of (malignant) brain tumors and the blood-brain barrier gains increased interest. The authors of this review give a unique overview of the current molecular-imaging techniques used in different therapeutic experimental brain tumor models in relation to neural stem cells. Such methods for molecular imaging of gene-engineered neural stem/progenitor cells are currently used to trace the location and temporal level of expression of therapeutic and endogenous genes in malignant brain tumors, closing the gap between in vitro and in vivo integrative biology of disease in neural stem cell transplantation.

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.

Management of epilepsy in oncological patients

INTRODUCTION

Comorbidity between epilepsy and cancer is elevated. As a life-time condition, it is not impossible for a patient with epilepsy to have a cancer at some point. Besides, at least 30% of patients with primary brain tumors have epileptic seizures, but also in patients with metastatic infiltrating lesions of the central nervous system and with extracerebral tumors, epilepsy can be related. Seizures may also appear associated with paraneoplastic syndromes, such as limbic encephalitis and metabolic and infectious complications of chemotherapy and radiotherapy.

RESULTS

The precise mechanisms by which brain tumors and the other conditions mentioned above produce seizures are not fully understood, but are reviewed in this article, as well as the many different therapeutic options that may be used in the treatment of epileptic seizures. Pharmacological treatment poses various controversies, such as the utility of prophylactic treatment, interactions between antiepileptic drugs (AEDs) and chemotherapeutic drugs and the complications derived from the adverse effects of AEDs in this population. Finally, other treatments are proposed such as chemotherapy, radiotherapy and surgery, the rational application of which allows for an improvement in the patients' quality of life.

CONCLUSION

In order to arrive at a diagnosis, the different causes that could condition the appearance of epileptic seizures in cancer patients must be known. After this, the most adequate treatment should be chosen, thus ensuring the comprehensive treatment of cancer and epilepsy.

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.

Epilepsy in patients with brain tumours: epidemiology, mechanisms, and management

Epilepsy is common in patients with brain tumours and can substantially affect daily life, even if the tumour is under control. Several factors affect the mechanism of seizures in brain tumours, including tumour type, tumour location, and peritumoral and genetic changes. Prophylactic use of antiepileptic drugs is not recommended, and potential interactions between antiepileptic and chemotherapeutic agents persuades against the use of enzyme-inducing antiepileptic drugs. Multidrug-resistance proteins prevent the access of antiepileptic drugs into brain parenchyma, which partly explains why seizures are frequently refractory to treatment. Lamotrigine, valproic acid, and topiramate are first-line treatments of choice; if insufficient, add-on treatment with levetiracetam or gabapentin can be recommended. On the basis of clinical studies, we prefer to start treatment with valproic acid, adding levetiracetam if necessary. Risks of cognitive side-effects with antiepileptic drugs can add to previous damage by surgery or radiotherapy, and therefore appropriate choice and dose of antiepileptic drug is crucial.

Molecular Imaging of Brain Tumors: A Bridge Between Clinical and Molecular Medicine?

As the research on cellular changes has shed invaluable light on the pathophysiology and biochemistry of brain tumors, clinical and experimental use of molecular imaging methods is expanding and allows quantitative assessment. The term molecular imaging is defined as the in vivo characterization and measurement of biologic processes at the cellular and molecular level. Molecular imaging sets forth to probe the molecular abnormalities that are the basis of disease rather than to visualize the end effects of these molecular alterations and, therefore, provides different additional biochemical or molecular information about primary brain tumors compared to histological methods "classical" neuroradiological diagnostic studies. Common clinical indications for molecular imaging contain primary brain tumor diagnosis and identification of the metabolically most active brain tumor reactions (differentiation of viable tumor tissue from necrosis), prediction of treatment response by measurement of tumor perfusion, or ischemia. The interesting key question remains not only whether the magnitude of biochemical alterations demonstrated by molecular imaging reveals prognostic value with respect to survival, but also whether it identifies early disease and differentiates benign from malignant lesions. Moreover, an early identification of treatment success or failure by molecular imaging could significantly influence patient management by providing more objective decision criteria for evaluation of specific therapeutic strategies. Specially, as molecular imaging represents a novel technology for visualizing metabolism and signal transduction to gene expression, reporter gene assays are used to trace the location and temporal level of expression of therapeutic and endogenous genes. Molecular imaging probes and drugs are being developed to image the function of targets without disturbing them and in mass amounts to modify the target's function as a drug. Molecular imaging helps to close the gap between in vitro and in vivo integrative biology of disease.

Intracranial neoplasia in 61 cats: localisation, tumour types and seizure patterns

The purpose of this study was to analyse retrospectively a feline population with intracranial neoplastic diseases, to document seizure patterns in these animals and to determine whether partial seizures were more frequently associated with structural brain lesions then generalised seizures. In addition, a comparison was made within the population with intracranial neoplasia between two groups of cats: one with and one without seizures. Special emphasis was given to the evaluation of tumour type, localisation and size of the lesion and its correlation with seizure prevalence. Sixty-one cats with histopathological diagnosis of intracranial tumour were identified. Fourteen cats (23%; group A) had a history of seizure(s). Forty-seven cats (77%; group B) had no history of seizure(s). Generalised tonic-clonic seizures were seen in eight cats (57%) and were the most common seizure pattern in our cats with intracranial neoplasia. Clusters of seizures were observed in six cats. Status epilepticus was observed in one patient. The mean age of the cats was 7.9 years within group A (median 8.5) and 9.3 years (median 10) within group B. The cats with lymphoma within both groups were significantly younger than cats with meningioma. In both groups meningioma and lymphoma were confirmed to be the most frequent tumour type, followed by glial cell tumours. The prevalence of the seizures in patients with glial cell tumours was 26.7%, 26.3% in patients with lymphomas and 15% in cases with meningiomas. In 33 cases (54.1%) the tumours were localised in the forebrain, 15 tumours (24.6%) were in the brainstem, four (6.6%) in the cerebellum and nine tumours (14.7%) had multifocal localisation. Parietal lobe and basal ganglia mostly affected group A. In group B tumours were most frequently located in the parietal and frontal lobes as well as in the diencephalon. A positive association was documented between the localisation of a tumour in the forebrain and seizure occurrence.

Neuroprotection in primary brain tumors: sense or nonsense?

Primary brain tumors are generally difficult to treat because of the unique location of the lesions. In addition, normal brain structures are often destroyed by the growing neoplasm. Even with effective therapy to surgically resect and destroy the neoplastic tissues, the brain is sometimes still injured, which can leave the patient in a debilitated state. The hemodynamic and metabolic state of such peritumoral brain tissue is not yet well understood, and there are only a small number of experimental hypotheses of its reaction and changes to the growing primary brain tumor. In addition, primary brain tumors may be influenced by certain anticancer drugs, which cause oxidative stress and consecutive cell death, or by gamma-irradiation. Currently, no established diagnostic methods exist to demonstrate and/or quantify the metabolic condition of the peritumoral tissue. The therapeutic strategy for possible pharmacological neuroprotection should, in the future, still be related to metabolic parameters, as well as in the peritumor tissue to treat primary brain tumors without risk to sensitive normal tissue. To achieve this aim, there has been particular emphasis on the biological behavior of primary brain tumors and peritumor tissue, as well as the potential correlation among them. Thus, priority should be given to identifying more target antigens in primary brain tumors and defining those cells present in the brain parenchyma that are essential to maintain a neuroprotective effect. However, at this time, the postinjury enhancement of neurogenesis appears to offer the best hope for long-lasting functional recovery following surgery of primary brain tumors.