The search for circulating epilepsy biomarkers

Polygenic risk scores as a marker for epilepsy risk across lifetime and after unspecified seizure events

A diagnosis of epilepsy has significant consequences for an individual but is often challenging in clinical practice. Novel biomarkers are thus greatly needed. Here, we investigated how common genetic factors (epilepsy polygenic risk scores, [PRSs]) influence epilepsy risk in detailed longitudinal electronic health records (EHRs) of > 700k Finns and Estonians. We found that a high genetic generalized epilepsy PRS (PRSGGE) increased risk for genetic generalized epilepsy (GGE) (hazard ratio [HR] 1.73 per PRSGGE standard deviation [SD]) across lifetime and within 10 years after an unspecified seizure event. The effect of PRSGGE was significantly larger on idiopathic generalized epilepsies, in females and for earlier epilepsy onset. Analogously, we found significant but more modest focal epilepsy PRS burden associated with non-acquired focal epilepsy (NAFE). Here, we outline the potential of epilepsy specific PRSs to serve as biomarkers after a first seizure event.

Circulating microRNAs from plasma as preclinical biomarkers of epileptogenesis and epilepsy

Epilepsy frequently develops as a result of brain insult; however, there are no tools allowing to predict which patients suffering from trauma will eventually develop epilepsy. microRNAs are interesting candidates for biomarkers, as several of them have been described to change their levels in the brains, and in the plasma of epileptic subjects. This study was conducted to evaluate the usefulness of plasma miRNAs as epileptogenesis/epilepsy biomarkers. In our studies, we used a rat model of temporal lobe epilepsy. An epileptogenic insult was status epilepticus evoked by stimulation of the left lateral nucleus of the amygdala. Next, animals were continuously video and EEG monitored for 3 months. Blood was collected at 14, 30, 60, and 90 days after stimulation. Blood plasma was separated and miRNA levels were analyzed. We compared miRNA levels between sham-operated and stimulated animals, and between animals with high and low numbers of seizures. We propose three miRNAs that could be biomarkers of epilepsy: miR-671, miR-9a-3p and miR-7a-5p. According to us, miR-206-5p is a potential biomarker of epileptogenesis, and miR-221-3p is a potential biomarker of epilepsy severity. We think that these five miRNAs can be considered in the future as potential treatment targets.

Polygenic risk scores as a marker for epilepsy risk across lifetime and after unspecified seizure events

A diagnosis of epilepsy has significant consequences for an individual but is often challenging in clinical practice. Novel biomarkers are thus greatly needed. Here, we investigated how common genetic factors (epilepsy polygenic risk scores, [PRSs]) influence epilepsy risk in detailed longitudinal electronic health records (EHRs) of > 360k Finns spanning up to 50 years of individuals' lifetimes. Individuals with a high genetic generalized epilepsy PRS (PRSGGE) in FinnGen had an increased risk for genetic generalized epilepsy (GGE) (hazard ratio [HR] 1.55 per PRSGGE standard deviation [SD]) across their lifetime and after unspecified seizure events. Effect sizes of epilepsy PRSs were comparable to effect sizes in clinically curated data supporting our EHR-derived epilepsy diagnoses. Within 10 years after an unspecified seizure, the GGE rate was 37% when PRSGGE > 2 SD compared to 5.6% when PRSGGE < -2 SD. The effect of PRSGGE was even larger on GGE subtypes of idiopathic generalized epilepsy (IGE) (HR 2.1 per SD PRSGGE). We further report significantly larger effects of PRSGGE on epilepsy in females and in younger age groups. Analogously, we found significant but more modest focal epilepsy PRS burden associated with non-acquired focal epilepsy (NAFE). We found PRSGGE specifically associated with GGE in comparison with >2000 independent diseases while PRSNAFE was also associated with other diseases than NAFE such as back pain. Here, we show that epilepsy specific PRSs have good discriminative ability after a first seizure event i.e. in circumstances where the prior probability of epilepsy is high outlining a potential to serve as biomarkers for an epilepsy diagnosis.

Protein profiling in plasma for biomarkers of seizure

PURPOSE

A biochemical way to measure seizures would greatly benefit epilepsy research and clinical follow-up. Short-term biomarkers like lactate exist, and interest in biomarkers representative of longer-term seizure burden is growing. In this exploratory study, we aimed to identify markers in blood plasma that differentiate persons with recent seizures from persons with epilepsy and long-standing seizure freedom.

METHODS

A proteomic analysis was performed on plasma samples of 120 persons with seizures using the Olink Neuro-exploratory panel. Participants were selected from a regional biobank study in Västra Götaland (Sweden) and categorized into two groups: recent seizure and seizure-free. The panel contained 92 proteins linked to neurological diseases and processes, and levels of these proteins were compared between the patient groups to identify potential markers of seizure activity.

RESULTS

We identified significant differences in protein levels between the recent seizure and seizure-free patient groups for Cadherin-15 [(CDH15; p = 0.008)], Latent transforming growth factor beta-binding protein 3 [(LTBP3; p = 0.002)], Phosphoethanolamine/phosphocholine phosphatase 1 [(PHOSPHO1; p = 0.011)], and Progestagen associated endometrial protein [(PAEP; p = 0.0005)].

CONCLUSION

The findings in this study present CDH15, LTBP3, PHOSPHO1 and PAEP as candidate markers of seizure activity. Further confirmatory studies are needed.

The Neuroprotective Effect of miR-136 on Pilocarpine-Induced Temporal Lobe Epilepsy Rats by Inhibiting Wnt/β-Catenin Signaling Pathway

Objective

To explore the effect of miR-136 on temporal lobe epilepsy (Ep) and its mechanism of action.

Methods

30 male rats were injected intraperitoneally with 30 mg/kg pilocarpine to construct a rat temporal lobe epilepsy model, and they were randomly divided into 5 groups (n = 6 per group): control group, Ep group, agomir NC group, miR-136 agomir group, and miR-136+LiCl group. The brain tissues of the rats were collected 7 days after the treatment. The expression of miR-136 in the hippocampus tissue was detected by qRT-PCR. H&E and Nissl staining were used to observe the histopathological changes and neuron damage in the hippocampus tissue. IL-1β, IL-6, and TNF-α levels in the hippocampus tissue were detected by ELISA. Flow cytometry was used to detect the apoptosis rate in the hippocampus tissue. Western blot was used to detect the expression levels of c-Caspase-3, Bcl-2, β-catenin, Cyclin D1, and c-myc protein in the hippocampus.

Results

The expression of miR-136 was significantly downregulated in the hippocampus tissue of epileptic rats. After overexpression of miR-136, the number of seizures and the duration of epilepsy in rats were significantly reduced. At the same time, hippocampal tissue damage was improved considerably, and the degree of neuronal damage decreased. Overexpression of miR-136 also significantly reduced the apoptosis rate in the hippocampus tissue and inhibited the levels of inflammatory factors. Meanwhile, miR-136 downregulates the expression of Wnt/β-catenin signaling pathway-related proteins. However, Wnt pathway activator LiCl could destroy the protective effect of miR-136.

Conclusion

miR-136 could exert its neuroprotective influence on temporal lobe epilepsy rats by inhibiting the Wnt/β-catenin signaling pathway.

Cortical Dysplasia in Rats Provokes Neurovascular Alterations, GLUT1 Dysfunction, and Metabolic Disturbances That Are Sustained Post-Seizure Induction

Focal cortical dysplasia (FCD) is associated with blood-brain barrier (BBB) dysfunction in patients with difficult-to-treat epilepsy. However, the underlying cellular and molecular factors in cortical dysplasia (CD) associated with progressive neurovascular challenges during the pro-epileptic phase, post-seizure, and during epileptogenesis remain unclear. We studied the BBB function in a rat model of congenital (in utero radiation-induced, first hit) CD and longitudinally examined the cortical brain tissues at baseline and the progressive neurovascular alterations, glucose transporter-1 (GLUT1) expression, and glucose metabolic activity at 2, 15, and 30 days following a second hit using pentylenetetrazole-induced seizure. Our study revealed through immunoblotting, immunohistochemistry, and biochemical analysis that (1) altered vascular density and prolongation of BBB albumin leakages in CD rats continued through 30 days post-seizure; (2) CD brain tissues showed elevated matrix metalloproteinase-9 levels at 2 days post-seizure and microglial overactivation through 30 days post-seizure; (3) BBB tight junction protein and GLUT1 levels were decreased and neuronal monocarboxylate transporter-2 (MCT2) and mammalian target of rapamycin (mTOR) levels were increased in the CD rat brain: (4) ATPase activity is elevated and a low glucose/high lactate imbalance exists in CD rats; and (5) the mTOR pathway is activated and MCT2 levels are elevated in the presence of high lactate during glucose starvation in vitro. Together, this study suggests that BBB dysfunction, including decreased GLUT1 expression and metabolic disturbance, may contribute to epileptogenesis in this CD rat model through multiple mechanisms that could be translated to FCD therapy in medically refractory epilepsy.

Liquid biopsies in epilepsy: biomarkers for etiology, diagnosis, prognosis, and therapeutics

Epilepsy is one of the most common diseases of the central nervous system, impacting nearly 50 million people around the world. Heterogeneous in nature, epilepsy presents in children and adults alike. Currently, surgery is one treatment approach that can completely cure epilepsy. However, not all individuals are eligible for surgical procedures or have successful outcomes. In addition to surgical approaches, antiepileptic drugs (AEDs) have also allowed individuals with epilepsy to achieve freedom from seizures. Others have found treatment through nonpharmacologic approaches such as vagus nerve stimulation, or responsive neurostimulation. Difficulty in accessing samples of human brain tissue along with advances in sequencing technology have driven researchers to investigate sampling liquid biopsies in blood, serum, plasma, and cerebrospinal fluid within the context of epilepsy. Liquid biopsies provide minimal or non-invasive sample collection approaches and can be assayed relatively easily across multiple time points, unlike tissue-based sampling. Various efforts have investigated circulating nucleic acids from these samples including microRNAs, cell-free DNA, transfer RNAs, and long non-coding RNAs. Here, we review nucleic acid-based liquid biopsies in epilepsy to improve understanding of etiology, diagnosis, prediction, and therapeutic monitoring.

Chronic electroencephalography in epilepsy with a responsive neurostimulation device: current status and future prospects

INTRODUCTION

Implanted neurostimulation devices are gaining traction as therapeutic options for people with certain forms of drug-resistant focal epilepsy. Some of these devices enable chronic electroencephalography (cEEG), which offers views of the dynamics of brain activity in epilepsy over unprecedented time horizons.

AREAS COVERED

This review focuses on clinical insights and basic neuroscience discoveries enabled by analyses of cEEG from an exemplar device, the NeuroPace RNS® System. Applications of RNS cEEG covered here include counting and lateralizing seizures, quantifying medication response, characterizing spells, forecasting seizures, and exploring mechanisms of cognition. Limitations of the RNS System are discussed in the context of next-generation devices in development.

EXPERT OPINION

The wide temporal lens of cEEG helps capture the dynamism of epilepsy, revealing phenomena that cannot be appreciated with short duration recordings. The RNS System is a vanguard device whose diagnostic utility rivals its therapeutic benefits, but emerging minimally invasive devices, including those with subscalp recording electrodes, promise to be more applicable within a broad population of people with epilepsy. Epileptology is on the precipice of a paradigm shift in which cEEG is a standard part of diagnostic evaluations and clinical management is predicated on quantitative observations integrated over long timescales.

Biomarkers for epileptogenesis and its treatment

There are no pharmacological interventions to prevent the development of epilepsy, although many promising compounds have been identified in the animal laboratory. Clinical trials to validate their effectiveness, however, would currently be prohibitively expensive due to the large subject population and duration of follow-up necessary. There is, therefore, the need to identify biomarkers of epileptogenesis that could identify patients at high risk for epilepsy following a potential epileptogenic insult to enrich the subject population, as well as biomarkers that could determine the effectiveness of therapeutic intervention without the need to wait for seizures to occur. Putative biomarkers under investigation for epileptogenesis and its treatment include genetic, molecular, cellular, imaging, and electrophysiological measures that might reliably predict the development or progression of an epileptic condition, the effects of antiepileptogenic treatment, or cure after surgery. To be clinically useful for most purposes, ideal biomarkers should be noninvasive, and it is anticipated that a profile of multiple biomarkers will likely be required. Ongoing animal research involves a number of experimental models of epileptogenesis, with traumatic brain injury, offering the best potential for translational clinical investigations. Collaborative and multicenter research efforts by multidisciplinary teams of basic and clinical neuroscientists with access to robust, well-defined animal models, extensive patient populations, standardized protocols, and cutting-edge analytical methodologies are likely to be most successful. Such biomarker research should also provide insights into fundamental neuronal mechanisms of epileptogenesis suggesting novel targets for antiepileptogenic treatments. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

MicroRNAs as biomarkers and treatment targets in status epilepticus

Microribonucleic acids (miRNAs) are short noncoding ribonucleic acids (RNAs) that have been proposed as potential biomarkers for epilepsy, acute seizures, and status epilepticus. Various properties support their potential in this regard, including relative stability and amenability to rapid quantitation in biofluids. Several miRNAs are enriched in the brain and within specific cell types. Dysregulation of miRNAs has been reported in brain regions damaged by status epilepticus and in resected brain tissue from patients with drug-resistant epilepsy. Silencing miRNAs using antisense-like oligonucleotides termed antagomirs has been reported to suppress evoked and spontaneous seizures in animal models, indicating therapeutic applications. The prospect of miRNAs as mechanistic biomarkers is supported by recent studies showing blood levels of brain-enriched miRNAs increase after status epilepticus in rodents, and clinical studies have identified miRNAs upregulated in human cerebrospinal fluid after status epilepticus. It remains unproven, however, whether there are miRNAs that uniquely identify acute seizures, chronic epilepsy, or the process of epileptogenesis. Finally, efforts have turned to the challenge of proving that some of the circulating miRNAs actually originate from the brain. New models that feature a biochemically-labeled protein involved in miRNA function and restricted to specific brain cell types offer opportunities to resolve this issue. This review summarizes recent progress on miRNAs as diagnostic biomarkers of status epilepticus and considers some of the unanswered questions and future directions. This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures.

Stem cells: A path towards improved epilepsy therapies

Despite the immense growth of new anti-seizure drugs (ASDs), approximately one-third of epilepsy patients remain resistant to current treatment options. Advancements in whole genome sequencing technology continues to identify an increasing number of epilepsy-associated genes at a rate that is outpacing the development of in vivo animal models. Patient-derived induced pluripotent stem cells (iPSCs) show promise in providing a platform for modeling genetic epilepsies, high throughput drug screening, and personalized medicine. This is largely due to the ease of collecting donor cells for iPSC reprogramming, and their ability to be maintained in vitro, while preserving the patient's genetic background. In this review, we summarize the current state of iPSC research in epilepsy and closely related syndromes, discuss the growing need for high-throughput drug screening (HTS), and review the use of stem cell technology for the purpose of autologous transplantation for epilepsy stem cell therapy. Although the use of iPSC technology, as it applies to ASD discovery, is in its infancy, we highlight the significant progress that has been made in phenotype and assay development to facilitate systematic HTS for personalized medicine. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Protein biomarkers of epileptogenicity after traumatic brain injury

Traumatic brain injury (TBI) is a major risk factor for acquired epilepsy. Post-traumatic epilepsy (PTE) develops over time in up to 50% of patients with severe TBI. PTE is mostly unresponsive to traditional anti-seizure treatments suggesting distinct, injury-induced pathomechanisms in the development of this condition. Moderate and severe TBIs cause significant tissue damage, bleeding, neuron and glia death, as well as axonal, vascular, and metabolic abnormalities. These changes trigger a complex biological response aimed at curtailing the physical damage and restoring homeostasis and functionality. Although a positive correlation exists between the type and severity of TBI and PTE, there is only an incomplete understanding of the time-dependent sequelae of TBI pathobiologies and their role in epileptogenesis. Determining the temporal profile of protein biomarkers in the blood (serum or plasma) and cerebrospinal fluid (CSF) can help to identify pathobiologies underlying the development of PTE, high-risk individuals, and disease modifying therapies. Here we review the pathobiological sequelae of TBI in the context of blood- and CSF-based protein biomarkers, their potential role in epileptogenesis, and discuss future directions aimed at improving the diagnosis and treatment of PTE.

Discovery and validation of blood microRNAs as molecular biomarkers of epilepsy: Ways to close current knowledge gaps

There is a major unmet need for biomarkers of epilepsy. Biofluids such as blood offer a potential source of molecular biomarkers. MicroRNAs (miRNAs) fulfill several key requirements for a blood‐based molecular biomarker being enriched in the brain and dysregulated in epileptic brain tissue, and manipulation of miRNAs can have seizure‐suppressive and disease‐modifying effects in preclinical models. Biofluid miRNAs also possess qualities that are favorable for translation, including stability and easy and cheap assay techniques. Herein we review findings from both clinical and animal models. Studies have featured a mix of unbiased profiling and hypothesis‐driven efforts. Blood levels of several brain‐enriched miRNAs are altered in patients with epilepsy and in patients with drug‐resistant compared to drug‐responsive seizures, with encouraging receiver‐operating characteristic (ROC) curve analyses, both in terms of sensitivity and specificity. Both focal and generalized epilepsies are associated with altered blood miRNA profiles, and associations with clinical parameters including seizure burden have been reported. Results remain preliminary, however. There is a need for continued discovery and validation efforts that include multicenter studies and attention to study design, sample collection methodology, and quality control. Studies focused on epileptogenesis as well as associations with covariables such as sex, etiology, and timing of sampling remain limited. We identify 10 knowledge gaps and propose experiments to close these. If adequately addressed, biofluid miRNAs may be an important future source of diagnostic biomarkers that could also support forthcoming trials of antiepileptogenesis or disease‐modifying therapies.

Cerebrospinal fluid microRNAs are potential biomarkers of temporal lobe epilepsy and status epilepticus

There is a need for diagnostic biomarkers of epilepsy and status epilepticus to support clinical examination, electroencephalography and neuroimaging. Extracellular microRNAs may be potentially ideal biomarkers since some are expressed uniquely within specific brain regions and cell types. Cerebrospinal fluid offers a source of microRNA biomarkers with the advantage of being in close contact with the target tissue and sites of pathology. Here we profiled microRNA levels in cerebrospinal fluid from patients with temporal lobe epilepsy or status epilepticus, and compared findings to matched controls. Differential expression of 20 microRNAs was detected between patient groups and controls. A validation phase included an expanded cohort and samples from patients with other neurological diseases. This identified lower levels of miR-19b in temporal lobe epilepsy compared to controls, status epilepticus and other neurological diseases. Levels of miR-451a were higher in status epilepticus compared to other groups whereas miR-21-5p differed in status epilepticus compared to temporal lobe epilepsy but not to other neurological diseases. Targets of these microRNAs include proteins regulating neuronal death, tissue remodelling, gliosis and inflammation. The present study indicates cerebrospinal fluid contains microRNAs that can support differential diagnosis of temporal lobe epilepsy and status epilepticus from other neurological and non-neurological diseases.

"TORNADO" - Theranostic One-Step RNA Detector; microfluidic disc for the direct detection of microRNA-134 in plasma and cerebrospinal fluid

Diagnosis of seizure disorders such as epilepsy currently relies on clinical examination and electroencephalogram recordings and is associated with substantial mis-diagnosis. The miRNA, miR-134 (MIR134 in humans), has been found to be elevated in brain tissue after experimental status epilepticus and in human epilepsy cells and their detection in biofluids may serve as unique biomarkers. miRNAs from unprocessed human plasma and human cerebrospinal fluid samples were used in a novel electrochemical detection based on electrocatalytic platinum nanoparticles inside a centrifugal microfluidic device where the sandwich assay is formed using an event triggered release system, suitable for the rapid point-of-care detection of low abundance biomarkers of disease. The device has the advantage of controlling the rotation speed of the centrifugal device to pump nanoliter volumes of fluid at a set time and manipulate the transfer of liquids within the device. The centrifugal platform improves reaction rates and yields by proposing efficient mixing strategies to overcome diffusion-limited processes and improve mass transport rates, resulting in reduced hybridization times with a limit of detection of 1 pM target concentration. Plasma and cerebrospinal fluid samples (unprocessed) from patients with epilepsy or who experienced status epilepticus were tested and the catalytic response obtained was in range of the calibration plot. This study demonstrates a rapid and simple detection for epilepsy biomarkers in biofluid.

Changes in serum miRNAs following generalized convulsive seizures in human mesial temporal lobe epilepsy

MicroRNAs (miRNAs) are key regulators of gene expression and are involved in the pathomechanisms of epilepsy. MiRNAs may also serve as peripheral biomarkers of epilepsy. We investigated the miRNA profile in the blood serum of patients suffering from mesial temporal lobe epilepsy (mTLE) following a single focal seizure evolving to a bilateral convulsive seizure (BCS) during video-EEG monitoring. Data of 15 patients were included in the final analysis. MiRNA expression was determined using Real Time-PCR followed by thorough bioinformatical analysis of expression levels. We found that more than 200 miRNAs were differentially expressed in the serum of patients within 30 min after a single seizure. Validation of the 20 top miRNA candidates confirmed that 4 miRNAs (miR-143, miR-145, miR-532, miR-365a) were significantly deregulated. Interestingly, in a sub-group of patients with seizures occurring during sleep, we found 10 miRNAs to be deregulated up to 20-28 h after the seizure. In this group of patients, miR-663b was significantly deregulated. We conclude that single seizures are associated with detectable transient miRNA alterations in blood serum in the early postictal phase. The significant upregulation of miR-663b following BCS arising during sleep indicates potential suitability of this miRNA as a potential biomarker for seizure diagnostics.

Extracellular Vesicles in Molecular Diagnostics: An Overview with a Focus on CNS Diseases

All known cells continuously release nanoscale lipid membrane-enclosed packets. These packets, termed extracellular vesicles (EVs), bear the signature of their cells of origin. These vesicles can be detected in just about every type of biofluid tested, including blood, urine, and cerebrospinal fluid. The majority comes from normal cells, but disease cells also release them. There is a great interest in collecting and analyzing EVs in biofluids as diagnostics for a wide spectrum of central nervous system diseases. Here, we will review the state of central nervous system EV research in terms of molecular diagnostics and biomarkers.

Plasma cysteine/cystine redox couple disruption in animal models of temporal lobe epilepsy

Currently the field of epilepsy lacks peripheral blood-based biomarkers that could predict the onset or progression of chronic seizures following an epileptogenic injury. Thiol/disulfide ratios have been shown to provide a sensitive means of assessing the systemic redox potential in tissue and plasma. In this study, we utilized a rapid, simple and reliable method for simultaneous determination of several thiol-containing amino acids in plasma using HPLC with electrochemical detection in kainic acid (KA) and pilocarpine rat models of epilepsy. In contrast to GSH and GSSG levels, the levels of cysteine (Cys) were decreased by 42% and 62% and cystine (Cyss) were increased by 46% and 23% in the plasma of KA- and pilocarpine-injected rats, respectively after 48 h. In chronically epileptic rats, plasma cysteine was decreased by 40.4% and 37.7%, and plasma GSSG increased by 33.8% and 35.0% following KA and pilocarpine, respectively. Treatment of rats with a catalytic antioxidant, 60 min after KA or pilocarpine significant attenuated the decrease of plasma Cys/Cyss ratios at the 48 h time point in both models. These observations suggest that the decreased cysteine and ratio of Cys/Cyss in plasma could potentially serve as redox biomarkers in temporal lobe epilepsy.

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HPLC method for determination thiol-containing amino acids in rat plasma.

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Decreased plasma cysteine/cystine in acute and chronic stages of chemoconvulsant-induced epilepsy.

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Depletion of plasma cysteine/cystine can be ameliorated by a catalytic antioxidant.

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Measurement of plasma cysteine/cystine could serve as redox biomarkers in epilepsy.

Neuronal antibodies in pediatric epilepsy: Clinical features and long-term outcomes of a historical cohort not treated with immunotherapy

OBJECTIVE

In autoimmune encephalitis the etiologic role of neuronal cell-surface antibodies is clear; patients diagnosed and treated early have better outcomes. Neuronal antibodies have also been described in patients with pediatric epilepsy without encephalitis. The aim was to assess whether antibody presence had any effect on long-term outcomes in these patients.

METHODS

Patients (n = 178) were recruited between 1988 and 1992 as part of the prospective Dutch Study of Epilepsy in Childhood; none received immunotherapy. Healthy age-matched bone-marrow donors served as controls (n = 112). All sera were tested for serum N-methyl-d-aspartate receptor (NMDAR), alpha amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, leucine rich glioma inactivated 1, contactin associated protein like 2 (CASPR2), contactin-2, glutamic acid decarboxylase, and voltage gated potassium channel (VGKC)-complex antibodies by standard techniques. No cerebrospinal fluid (CSF) samples were available. Results were correlated with clinical data collected over 15 years.

RESULTS

Seventeen patients (9.5%) were positive for VGKC complex (n = 3), NMDAR (n = 7), CASPR2 (n = 4), and contactin-2 (n = 3), compared to three (3/112; 2.6%) healthy controls (VGKC complex [n = 1], NMDAR [n = 2]; p = 0.03; Fisher's exact test). Titers were relatively low (≤1:100 for cell-surface antibodies), but 8 (47%) of the 17 positive samples bound to the surface of live hippocampal neurons consistent with a potential pathogenic antibody. Preexisting cognitive impairment was more frequent in antibody-positive patients (9/17 vs. 33/161; p = 0.01). Fourteen antibody-positive patients were treated with standard antiepileptic drugs (AEDs); three (17%) became intractable but this was not different from the 16 (10%) of 161 antibody-negative patients. In 96 patients with available follow-up samples at 6 and/or 12 months, 6 of 7 positive antibodies had disappeared and, conversely, antibodies had appeared for the first time in a further 7 patients.

SIGNIFICANCE

Neuronal antibodies were found at low levels in 9.5% of patients with new-onset pediatric epilepsy but did not necessarily persist over time, and the development of antibodies de novo in later samples suggests they could be due to a secondary response to neuronal damage or inflammation. Moreover, as the response to standard AEDs and the long-term outcome did not differ from those of antibody-negative pediatric patients, these findings suggest that routine neuronal antibody testing is unlikely to be helpful in pediatric epilepsy. However, the higher incidence of preexisting cognitive problems in the antibody-positive group, the CASPR2 and contactin-2 antibodies in 7 of 17 patients, and the binding of 8 of 17 of serum samples to live hippocampal neurons suggest that neuronal antibodies, even if secondary, could contribute to the comorbidities of pediatric epilepsy.

A genomic view on epilepsy and autism candidate genes

Epilepsy is a common complex disorder most frequently associated with psychiatric and neurological diseases. Massive parallel sequencing of individual or cohort genomes and exomes led the identification of several disease associated genes. We review here the candidate genes in epilepsy genetics with focus on exome and gene panel data. Together with the examination of brain expressed genes and post synaptic proteome the results show that: (1) Non-metabolic epilepsies and autism candidate genes tend to be AT-rich and (2) large transcript size and local AT-richness are characteristic features of genes involved in developmental brain disorders and synaptic functions. These results point to the preferential location of core epilepsy and autism candidate genes in late replicating, GC-poor chromosomal regions (isochores). These results indicate that the genomic alterations leading to some brain disorders are confined to responsive chromatin areas harboring brain critical genes.

microRNA targeting of the P2X7 purinoceptor opposes a contralateral epileptogenic focus in the hippocampus

The ATP-gated ionotropic P2X7 receptor (P2X7R) modulates glial activation, cytokine production and neurotransmitter release following brain injury. Levels of the P2X7R are increased in experimental and human epilepsy but the mechanisms controlling P2X7R expression remain poorly understood. Here we investigated P2X7R responses after focal-onset status epilepticus in mice, comparing changes in the damaged, ipsilateral hippocampus to the spared, contralateral hippocampus. P2X7R-gated inward currents were suppressed in the contralateral hippocampus and P2rx7 mRNA was selectively uploaded into the RNA-induced silencing complex (RISC), suggesting microRNA targeting. Analysis of RISC-loaded microRNAs using a high-throughput platform, as well as functional assays, suggested the P2X7R is a target of microRNA-22. Inhibition of microRNA-22 increased P2X7R expression and cytokine levels in the contralateral hippocampus after status epilepticus and resulted in more frequent spontaneous seizures in mice. The major pro-inflammatory and hyperexcitability effects of microRNA-22 silencing were prevented in P2rx7^−/− mice or by treatment with a specific P2X7R antagonist. Finally, in vivo injection of microRNA-22 mimics transiently suppressed spontaneous seizures in mice. The present study supports a role for post-transcriptional regulation of the P2X7R and suggests therapeutic targeting of microRNA-22 may prevent inflammation and development of a secondary epileptogenic focus in the brain.

Direct, non-amplified detection of microRNA-134 in plasma from epilepsy patients

We report a novel electrochemical detection of microRNA-134, a low-abundance human plasma microRNA, based on regioselective functionalised electrocatalytic nanoparticles.

Advances on genetic rat models of epilepsy

Considering the suitability of laboratory rats in epilepsy research, we and other groups have been developing genetic models of epilepsy in this species. After epileptic rats or seizure-susceptible rats were sporadically found in outbred stocks, the epileptic traits were usually genetically-fixed by selective breeding. So far, the absence seizure models GAERS and WAG/Rij, audiogenic seizure models GEPR-3 and GEPR-9, generalized tonic-clonic seizure models IER, NER and WER, and Canavan-disease related epileptic models TRM and SER have been established. Dissection of the genetic bases including causative genes in these epileptic rat models would be a significant step toward understanding epileptogenesis. N-ethyl-N-nitrosourea (ENU) mutagenesis provides a systematic approach which allowed us to develop two novel epileptic rat models: heat-induced seizure susceptible (Hiss) rats with an Scn1a missense mutation and autosomal dominant lateral temporal epilepsy (ADLTE) model rats with an Lgi1 missense mutation. In addition, we have established episodic ataxia type 1 (EA1) model rats with a Kcna1 missense mutation derived from the ENU-induced rat mutant stock, and identified a Cacna1a missense mutation in a N-Methyl-N-nitrosourea (MNU)-induced mutant rat strain GRY, resulting in the discovery of episodic ataxia type 2 (EA2) model rats. Thus, epileptic rat models have been established on the two paths: ‘phenotype to gene’ and ‘gene to phenotype’. In the near future, development of novel epileptic rat models will be extensively promoted by the use of sophisticated genome editing technologies.

Risk of venous thromboembolism in people with epilepsy

OBJECTIVE

Risk of venous thromboembolism (VTE) among people with epilepsy (PWEs) has not been previously reported. Standard VTE prevention methods may increase the risk of complications in this population. This statewide study assessed the risk of VTE in PWEs.

METHODS

Main risk categories were grouped into definite epilepsy (DE), probable epilepsy (PE), and migraine, a comparable neurologic condition. All inpatient, emergency department, and hospital-based outpatient encounters in South Carolina from January 1, 2000 through December 31, 2011, were evaluated for the primary outcome variable of VTE, defined as having a diagnosis of VTE at or after the diagnosis of epilepsy or migraine. Coagulopathies and common comorbidities of epilepsy were enumerated. Differences in VTE proportions were assessed using 95% confidence intervals (CIs). Association of VTE with epilepsy and migraine was evaluated with Cox proportional hazard modeling.

RESULTS

A total of 138,497 people with migraine (PWMs) and 67,900 PWEs (32,186 DE, 35,714 PE) were included. VTE occurred in 2.7% of PWEs (4.2% among DE), and 0.6% of PWMs. The hazard ratio for VTE in DE compared with PWMs was 3.08 (95% CI 2.76-3.42), adjusted for all covariables. Higher numbers of comorbidities were strongly associated with VTE. PWE had higher numbers of comorbidities (52% with 2+ comorbidities versus 23% of PWM), but the impact of comorbidities on VTE risk was larger in PWM.

SIGNIFICANCE

Higher VTE risk in PWE than PWM suggests risk factors associated with epilepsy, independent of chronic neurologic illness. VTE occurrence in PWE is comparable to published rates among people with cancer.