The epileptic hypothesis: developmentally related arguments based on animal models

Do vaccines cause epilepsy? Review of cases in the National Vaccine Injury Compensation Program

OBJECTIVE

The National Childhood Vaccine Injury Act of 1986 created the National Vaccine Injury Compensation Program (VICP), a no-fault alternative to the traditional tort system. Since 1988, the total compensation paid exceeds $5 billion. Although epilepsy is one of the leading reasons for filing a claim, there has been no review of the process and validity of the legal outcomes given current medical information. The objectives were to review the evolution of the VICP program in regard to vaccine-related epilepsy and assess the rationale behind decisions made by the court.

METHODS

Publicly available cases involving epilepsy claims in the VICP were searched through Westlaw and the US Court of Federal Claims websites. All published reports were reviewed for petitioner's theories supporting vaccine-induced epilepsy, respondent's counterarguments, the final decision regarding compensation, and the rationale underlying these decisions. The primary goal was to determine which factors went into decisions regarding whether vaccines caused epilepsy.

RESULTS

Since the first epilepsy case in 1989, there have been many changes in the program, including the removal of residual seizure disorder as a vaccine-related injury, publication of the Althen prongs, release of the acellular form of pertussis, and recognition that in genetic conditions the underlying genetic abnormality rather than the immunization causes epilepsy. We identified 532 unique cases with epilepsy: 105 with infantile spasms and 427 with epilepsy without infantile spasms. The petitioners' experts often espoused outdated, erroneous causation theories that lacked an acceptable medical or scientific foundation and were frequently criticized by the court.

SIGNIFICANCE

Despite the lack of epidemiological or mechanistic evidence indicating that childhood vaccines covered by the VICP result in or aggravate epilepsy, these cases continue to be adjudicated. After 35 years of intense litigation, it is time to reconsider whether epilepsy should continue to be a compensable vaccine-induced injury.

Alternations of neuromagnetic activity across neurocognitive core networks among benign childhood epilepsy with centrotemporal spikes: A multi-frequency MEG study

Objective

We aimed to investigate the alternations of neuromagnetic activity across neurocognitive core networks among early untreated children having benign childhood epilepsy with centrotemporal spikes (BECTS).

Methods

We recorded the Magnetoencephalography (MEG) resting-state data from 48 untreated children having BECTS and 24 healthy children. The fourth edition of the Wechsler Intelligence Scale for Children (WISC-IV) was utilized to divide the children with BECTS into two groups: the cognitive impairment (CI) group with a full-scale intelligence quotient (FSIQ) of < 90 and the cognitive non-impairment (CNI) group with an FSIQ of > 90. We selected 26 bilateral cognitive-related regions of interest based on the triple network model. The neurocognitive core network spectral power was estimated using a minimum norm estimate (MNE).

Results

In the CNI group, the spectral power inside the bilateral anterior cingulate cortex (ACC) and the bilateral caudal middle frontal cortex (CMF) enhanced within the delta band and reduced within the alpha band. Both the CI and the CNI group demonstrated enhanced spectral power inside the bilateral posterior cingulate cortex (PCC), bilateral precuneus (PCu) region, bilateral superior and middle temporal cortex, bilateral inferior parietal lobe (IPL), and bilateral supramarginal cortex (SM) region in the delta band. Moreover, there was decreased spectral power in the alpha band. In addition, there were consistent changes in the high-frequency spectrum (> 90 Hz). The spectral power density within the insula cortex (IC), superior temporal cortex (ST), middle temporal cortex (MT), and parahippocampal cortex (PaH) also decreased. Therefore, studying high-frequency activity could lead to a new understanding of the pathogenesis of BECTS.

Conclusion

The alternations of spectral power among neurocognitive core networks could account for CI among early untreated children having BECTS. The dynamic properties of spectral power in different frequency bands could behave as biomarkers for diagnosing new BECTS.

A novel de novo heterozygous variant of the KCNQ2 gene: Contribution to early‑onset epileptic encephalopathy in a female infant

Early-onset epileptic encephalopathy (EOEE) represents one of the most severe epilepsies, characterized by recurrent seizures during early infancy, electroencephalogram (EEG) abnormalities and varying degrees of neurodevelopmental delay. The KCNQ2 gene has been reported to have a major role in EOEE. In the present study, a 3-month-old female infant from the Chinese Lisu minority with EOEE was analyzed. Detailed clinical evaluations and next-generation sequencing were performed to investigate the clinical and genetic characteristics of this patient, respectively. Furthermore, the three-dimensional structure of the mutant protein was predicted by SWISS-Model and the expression of KCNQ2 protein in the patient was assessed by flow cytometry. It was observed that the patient presented with typical clinical features of EOEE, including repeated non-febrile seizures and significant EEG abnormalities. A novel heterozygous missense variant c.431G>C (p.R144P) in KCNQ2 was identified in the patient and the genotyping of KCNQ2 in the patient's parents suggested that this variant was de novo. Subsequently, the breakage of hydrogen bonds between certain amino acids was predicted by structural analysis of the mutant protein. Flow cytometric analysis detected a significant reduction buts not complete loss of native KCNQ2 protein expression in the patient (25.1%). In conclusion, a novel variant in KCNQ2 was confirmed as the genetic cause for EOEE in this patient. The present study expanded the pathogenic mutation spectrum of KCNQ2, enhanced the understanding of the molecular pathogenesis of EOEE and provided novel clues for research on the genotype-phenotype correlation in this disease.

Genetic and Phenotype Analysis of a Chinese Cohort of Infants and Children With Epilepsy

Background: Epilepsy in childhood is a common and diverse neurological disorder. We conducted a genetic and phenotype analysis of a Chinese cohort of infants and children with epilepsy.

Methods: We conducted a pedigree analysis of 260 Chinese patients with epilepsy onset during infancy or childhood by whole exome sequencing (WES).

Results: Of the 260 probands analyzed, a genetic diagnosis was established in 135 patients. One-hundred eighty-eight phenotypes were detected in those 135 positive/likely positive patients, 106 patients had more than two phenotypes, and 67 patients had more than three phenotypes. A total of 142 variants of 81 genes were detected among the positive/likely positive patients. Among these 142 variants, of which 87 of 66 genes were novel.

Conclusion: Our findings extend the variant spectrum of genes related to epilepsy. Our results will be useful for genetic testing and counseling for patients with epilepsy.

Disruption of functional connectivity among subcortical arousal system and cortical networks in temporal lobe epilepsy

Growing evidence has demonstrated widespread brain network alterations in temporal lobe epilepsy (TLE). However, the relatively accurate portrait of the subcortical-cortical relationship for impaired consciousness in TLE remains unclear. We proposed that consciousness-impairing seizures may invade subcortical arousal system and corresponding cortical regions, resulting in functional abnormalities and information flow disturbances between subcortical and cortical networks. We performed resting-state fMRI in 26 patients with TLE and 30 matched healthy controls. All included patients were diagnosed with impaired awareness during focal temporal lobe seizures. Functional connectivity density was adopted to determine whether local or distant network alterations occurred in TLE, and Granger causality analysis (GCA) was utilized to assess the direction and magnitude of causal influence among these altered brain networks further. Patients showed increased local functional connectivity in several arousal structures, such as the midbrain, thalamus, and cortical regions including bilateral prefrontal cortex (PFC), left superior temporal pole, left posterior insula, and cerebellum (P < 0.05, FDR corrected). GCA analysis revealed that the casual effects among these regions in patients were significantly sparser than those in controls (P < 0.05, uncorrected), including decreased excitatory and inhibitory effects among the midbrain, thalamus and PFC, and decreased inhibitory effect from the cerebellum to PFC. These findings suggested that consciousness-impairing seizures in TLE are associated with functional alterations and disruption of information process between the subcortical arousal system and cortical network. Understanding the functional networks and innervation pathway involved in TLE can provide insights into the mechanism underlying seizure-related loss of consciousness.

Efficacy of Intravenous Hydrocortisone Treatment in Refractory Neonatal Seizures: A Report on Three Cases

Neonatal seizures are the most common neurological emergency, and neonatal status epilepticus (NSE) remains a controversial entity, with no general consensus about its definition and treatment. Here, we report on three newborns with NSE refractory to first- and second-line antiepileptic drugs successfully treated with intravenous (IV) hydrocortisone. The patients had previously failed therapy with levetiracetam, phenobarbital and midazolam, showing persistent clinical and electrical seizures. Modulation of brain inflammation triggered during prolonged epileptic activity has been thought to potentially explain the beneficial effects of anti-inflammatory treatment.

The thalamic midline nucleus reuniens: potential relevance for schizophrenia and epilepsy

Anatomical, electrophysiological and behavioral studies in rodents have shown that the thalamic midline nucleus reuniens (RE) is a crucial link in the communication between hippocampal formation (HIP, i.e., CA1, subiculum) and medial prefrontal cortex (mPFC), important structures for cognitive and executive functions. A common feature in neurodevelopmental and neurodegenerative brain diseases is a dysfunctional connectivity/communication between HIP and mPFC, and disturbances in the cognitive domain. Therefore, it is assumed that aberrant functioning of RE may contribute to behavioral/cognitive impairments in brain diseases characterized by cortico-thalamo-hippocampal circuit dysfunctions. In the human brain the connections of RE are largely unknown. Yet, recent studies have found important similarities in the functional connectivity of HIP-mPFC-RE in humans and rodents, making cautious extrapolating experimental findings from animal models to humans justifiable. The focus of this review is on a potential involvement of RE in schizophrenia and epilepsy.

Can we and should we use animal models to study neurobehavioral comorbidities of epilepsy?

Animal systems have been widely used to examine mechanisms of neurobehavioral comorbidities of epilepsy and to help in developing their effective therapies. Despite the progress made in the field, animal studies have their limitations stemming both from issues with modeling neuropsychiatric disorders in the laboratory and from drawbacks of animal models of epilepsy themselves. This review discusses advantages and weaknesses of experimental paradigms and approaches used to model and to analyze neurobehavioral comorbidities of epilepsy, from the perspectives of their needs, interpretation, ways of improvement, and clinical relevance. Developmental studies are required to adequately address age-specific aspects of the comorbidities. The deployment of preclinical Common Data Elements (pCDEs) for epilepsy research should facilitate the standardization and the harmonization of studies in question, while the application of Research Domain Criteria (RDoC) to characterize neurobehavioral disorders in animals with epilepsy should help in closing the bench-to-bedside gap. Special Issue: Epilepsy & Behavior's 20th Anniversary.

Immunity and inflammation in status epilepticus and its sequelae: possibilities for therapeutic application

Status epilepticus (SE) is a life-threatening neurological emergency often refractory to available treatment options. It is a very heterogeneous condition in terms of clinical presentation and causes, which besides genetic, vascular and other structural causes also include CNS or severe systemic infections, sudden withdrawal from benzodiazepines or anticonvulsants and rare autoimmune etiologies. Treatment of SE is essentially based on expert opinions and antiepileptic drug treatment per se seems to have no major impact on prognosis. There is, therefore, urgent need of novel therapies that rely upon a better understanding of the basic mechanisms underlying this clinical condition. Accumulating evidence in animal models highlights that inflammation ensuing in the brain during SE may play a determinant role in ongoing seizures and their long-term detrimental consequences, independent of an infection or auto-immune cause; this evidence encourages reconsideration of the treatment flow in SE patients.

The influence of EEG-detected nocturnal centrotemporal discharges on the expression of core symptoms of ADHD in children with benign childhood epilepsy with centrotemporal spikes (BCECTS): A prospective study in a tertiary referral center

Benign childhood epilepsy with centrotemporal spikes (BCECTS) is the most frequent benign focal epilepsy in childhood. Although it is described as a benign epilepsy syndrome, many studies have revealed that a significant number of patients have some degree of neuropsychological impairment. Thirty-two patients with BCECTS aged 6-11years were included in the study. All patients (without any antiepileptic or psychiatric medication) underwent all-night EEG monitoring and complex neuropsychological testing to diagnose the presence of core symptoms of attention-deficit/hyperactivity disorder (ADHD). The spike index (number of spikes per minute) on awake and asleep EEG, age at seizure onset, family history of epilepsy, and perinatal risks were correlated with the results of neuropsychological testing. Of the 32 patients, 21 patients (65.6%) fulfilled the criteria for ADHD diagnosis. Children who were younger at epilepsy onset demonstrated lower IQ and higher attention deficit (P=0.004) and higher impulsivity (P=0.016). The occurence of epileptiform discharges on nocturnal EEG was positively related to higher attention deficit and higher impulsivity. The findings are discussed in terms of how interictal discharges in the centrotemporal region during sleep affect the development of cognitive functions in children during critical epochs of neuropsychological development.

Association Between Magnetoencephalographic Interictal Epileptiform Discharge and Cognitive Function in Young Children With Typical Development and With Autism Spectrum Disorders

Electroencephalograms of individuals with autism spectrum disorders (ASD) show higher rates of interictal epileptiform discharges (IEDs), which are known to have an inverse association with cognitive function in typically developed (TD) children. Nevertheless, that phenomenon has not been investigated adequately in children with ASD. From university and affiliated hospitals, 163 TD children (84 male, 79 female, aged 32-89 months) and 107 children (85 male, 22 female, aged 36-98 months) with ASD without clinical seizure were recruited. We assessed their cognitive function using the Kaufman Assessment Battery for Children (K-ABC) and recorded 10 min of MEG. Original waveforms were visually inspected. Then a linear regression model was applied to evaluate the association between the IED frequency and level of their cognitive function. Significantly higher rates of IEDs were found in the ASD group than in the TD group. In the TD group, we found significant negative correlation between mental processing scale scores (MPS) and the IED frequency. However, for the ASD group, we found significant positive correlation between MPS scores and the IED frequency. In terms of the achievement scale, correlation was not significant in either group. Although we found a correlative rather than a causal effect, typically developed children with higher IED frequency might better be followed up carefully. Furthermore, for children with ASD without clinical seizure, clinicians might consider IEDs as less harmful than those observed in TD children.

White matter disruption is associated with persistent seizures in tuberous sclerosis complex

BACKGROUND AND AIMS

White matter is diffusely altered in tuberous sclerosis complex (TSC), and these alterations appear to be more evident in subjects with a more severe neurologic phenotype. However, little is known on the correlation between white matter alterations and epilepsy in TSC. The aims of this study were to evaluate the effects of early onset and refractory seizures on white matter by using diffusion tensor imaging (DTI).

METHODS

We enrolled 20 children with TSC and epilepsy onset in the first 3years of life and grouped them according to seizure persistence or freedom. All patients underwent brain MRI with DTI. Specific ROIs have were placed to generate tracks to calculate fractional anisotropy (FA) and apparent diffusion coefficient (ADC). Statistical analysis was performed by ANOVA.

RESULTS

Children with persistent seizures presented an overall reduced FA, with statistically significant differences on the cingulum (right p=0.003, left p=0.016), the left cerebral peduncle (p=0.020), the superior cerebellar peduncles (right p=0.008, left p=0.002), the posterior limbs of internal capsule (right p=0.037, left p=0.015), the external capsule (right p=0.018, left p=0.031), the inferior frontooccipital fasciculus (right p=0.010, left p=0.026), and the temporal trunk (right p=0.017, left p=0.001).

CONCLUSIONS

Our study demonstrated that children with persistent seizures present more significant alterations of brain connectivity in areas crucial for global cognitive maturation, executive functions, and verbal abilities, implying a higher risk of cognitive impairment, attention-deficit hyperactivity disorder, and autism.

Should epileptiform discharges be treated?

To evaluate the impact of epileptiform discharges (EDs) that do not occur within seizure patterns--such as spikes, sharp waves or spike waves--on cognitive function and to discuss the circumstances under which treatment of EDs might be considered. Methods used in this article is "Review of the literature". EDs may disrupt short-term cognition in humans. Frequent EDs for a prolonged period can potentially impair long-term cognitive function in humans. However, there is conflicting evidence on the impact of EDs on long-term cognitive outcome because this relationship may be confounded by multiple factors such as underlying etiology, seizures, and medication effects. Limitations of existing studies include the lack of standardized ED quantification methods and of widely accepted automated spike quantification methods. Although there is no solid evidence for or against treatment of EDs, a non-evidence-based practical approach is suggested. EDs in otherwise asymptomatic individuals should not be treated because the risks of treatment probably outweigh its dubious benefits. A treatment trial for EDs may be considered when there is cognitive dysfunction or regression or neurologic symptoms that are unexplained by the underlying etiology, comorbid conditions, or seizure severity. In patients with cognitive or neurologic dysfunction with epilepsy or EDs, treatment may be warranted to control the underlying epileptic syndrome. EDs may cause cognitive or neurologic dysfunction in humans in the short term. There is conflicting evidence on the impact of EDs on long-term cognitive outcome. There is no evidence for or against treatment of asymptomatic ED.

Sex-specific consequences of early life seizures

Seizures are very common in the early periods of life and are often associated with poor neurologic outcome in humans. Animal studies have provided evidence that early life seizures may disrupt neuronal differentiation and connectivity, signaling pathways, and the function of various neuronal networks. There is growing experimental evidence that many signaling pathways, like GABAA receptor signaling, the cellular physiology and differentiation, or the functional maturation of certain brain regions, including those involved in seizure control, mature differently in males and females. However, most experimental studies of early life seizures have not directly investigated the importance of sex on the consequences of early life seizures. The sexual dimorphism of the developing brain raises the question that early seizures could have distinct effects in immature females and males that are subjected to seizures. We will first discuss the evidence for sex-specific features of the developing brain that could be involved in modifying the susceptibility and consequences of early life seizures. We will then review how sex-related biological factors could modify the age-specific consequences of induced seizures in the immature animals. These include signaling pathways (e.g., GABAA receptors), steroid hormones, growth factors. Overall, there are very few studies that have specifically addressed seizure outcomes in developing animals as a function of sex. The available literature indicates that a variety of outcomes (histopathological, behavioral, molecular, epileptogenesis) may be affected in a sex-, age-, region-specific manner after seizures during development. Obtaining a better understanding for the gender-related mechanisms underlying epileptogenesis and seizure comorbidities will be necessary to develop better gender and age appropriate therapies.

DREAM controls the on/off switch of specific activity-dependent transcription pathways

Changes in nuclear Ca(2+) homeostasis activate specific gene expression programs and are central to the acquisition and storage of information in the brain. DREAM (downstream regulatory element antagonist modulator), also known as calsenilin/KChIP-3 (K(+) channel interacting protein 3), is a Ca(2+)-binding protein that binds DNA and represses transcription in a Ca(2+)-dependent manner. To study the function of DREAM in the brain, we used transgenic mice expressing a Ca(2+)-insensitive/CREB-independent dominant active mutant DREAM (daDREAM). Using genome-wide analysis, we show that DREAM regulates the expression of specific activity-dependent transcription factors in the hippocampus, including Npas4, Nr4a1, Mef2c, JunB, and c-Fos. Furthermore, DREAM regulates its own expression, establishing an autoinhibitory feedback loop to terminate activity-dependent transcription. Ablation of DREAM does not modify activity-dependent transcription because of gene compensation by the other KChIP family members. The expression of daDREAM in the forebrain resulted in a complex phenotype characterized by loss of recurrent inhibition and enhanced long-term potentiation (LTP) in the dentate gyrus and impaired learning and memory. Our results indicate that DREAM is a major master switch transcription factor that regulates the on/off status of specific activity-dependent gene expression programs that control synaptic plasticity, learning, and memory.

NINDS epilepsy and autism spectrum disorders workshop report

The association of epilepsy and autism spectrum disorders (ASD), although well-recognized, is poorly understood. The purpose of this report is to summarize the discussion of a workshop sponsored by the National Institute of Neurological Disorders and Stroke, with support from the National Institute of Child Health and Human Development, Autism Speaks, and Citizens United for Research in Epilepsy, that took place in Bethesda, Maryland, on May 29 and 30, 2012. The goals of this workshop were to highlight the clinical and biological relationships between ASD and epilepsy, to determine both short- and long-term goals that address research and treatment conundrums in individuals with both ASD and epilepsy, and to identify resources that can further both clinical and basic research. Topics discussed included epidemiology, genetics, environmental factors, common mechanisms, neuroimaging, neuropathology, neurophysiology, treatment, and research gaps and challenges in this unique population.

Cognitive correlates of interictal epileptiform discharges in adult patients with epilepsy in China

OBJECTIVE

Learning difficulties or cognitive impairment has been observed in many patients with epilepsy. Evidence from neurophysiologic and functional neuroimaging suggests that epileptic seizures and/or epileptiform activity can be the dominant factors inhibiting specific brain areas. However, most previous studies were focused on cognitive performance in children. In this study, we analyzed a new cohort of adult patients with frequent interictal epileptiform discharges (IEDs).

METHODS

Data from 67 adult patients with epilepsy were reviewed. Electroencephalography (EEG)-video recording and cognitive testing were performed, and the IED index was estimated as a percentage assigned to one of four categories (<1%, 1-10%, 10-50%, and >50%) during either wakefulness or sleep. Correlations of cognitive test results and clinical characteristics of IED categories were analyzed. The effects of the frequency, duration, location, and sleep-wake cycles of IEDs on cognition (intelligence and memory capacity) were analyzed.

RESULTS

Patients with an IED index >10% showed impaired performance on the Chinese Wechsler Adult Intelligence Scale (WAIS-RC) and the Chinese Wechsler Memory Scale (WMS). This effect was detected independently from other IED frequencies and other IED-related variables, such as duration, distribution, and location. The impact of waking or sleeping IEDs was of equal importance in contributing to impaired WAIS-RC and WMS performance.

CONCLUSION

An IED frequency of more than 10% in both waking and sleeping EEGs is associated with impaired cognitive performance in adult patients. However, whether patients with a high IED frequency but low seizure frequency will benefit from antiepileptic treatment should be examined in future studies.

Neuropsychological development in children belonging to BECTS spectrum: long-term effect of epileptiform activity

Benign epilepsy with centrotemporal spikes (BECTS) is an idiopathic focal epileptic syndrome in childhood. It is called "benign" because the seizure and cognitive outcomes are usually favorable, but a significant number of children with BECTS present heterogeneous cognitive deficits correlated to NREM sleep epileptiform discharges. The atypical evolutions of BECTS form a spectrum of conditions suggesting that slow sleep nocturnal interictal epileptiform discharges (IEDs) specifically determine the neuropsychological deficit. Few follow-up studies of neuropsychological outcome in BECTS are available, and very often, slow sleep has not been recorded throughout night sleep. The present study analyzed the long-term effects of IEDs during NREM sleep on neuropsychological development in children with rolandic spikes. Thirty-three children with a diagnosis of BECTS were monitored for at least two years. Results show that these children are at higher risk for residual verbal difficulties, and the abnormal neuropsychological development is significantly correlated with a greater frequency of NREM sleep discharges, school-age epilepsy onset, and a higher number of antiepileptic drugs (AEDs). The findings are discussed in terms of how slow sleep IEDs affect the consolidation of verbal skills during critical epochs of neuropsychological development.

Cognitive effects of interictal epileptiform discharges in children

Frequent interictal epileptiform discharges (IEDs) may have effects on cognition. We analysed a group of 182 children with different epilepsy syndromes as well as children with IEDs without observed seizures [corrected], with 24-h ambulatory EEG and cognitive tests. The IED index was estimated, in wakefulness and in sleep, as percentage of time in five categories (0%, <1%, 1-10%, ≥10-50% and ≥50%). IEDs were defined as spikes or spike-wave complexes, isolated or occurring serially (in runs) without evident clinical signs of a seizure. The IED categories were correlated to cognitive test results and epilepsy characteristics. The group of patients with diurnal IEDs in ≥10% of the EEG record showed impaired central information processing speed, short-term verbal memory and visual-motor integration. This effect was seen independently from other EEG-related and epilepsy-related characteristics, and independently from epilepsy syndrome diagnosis. The impact of the nocturnal IEDs was of less importance; only contributing partially to the slowing of central information processing speed. We conclude that frequent IEDs (in more than 10% of the record) in the awake EEG can impair cognitive performance in children. Whether children with a high diurnal spike frequency and low seizure frequency can benefit from antiepileptic treatment should be examined in controlled trials.

Infantile spasms: treatment challenges

OPINION STATEMENT

Infantile spasms (IS) represent a major therapeutic challenge, as cessation of spasms and normalization of the electroencephalogram (elimination of hypsarrhythmia) are mandatory to prevent cognitive deterioration in previously healthy infants, or to preserve neurocognitive function among those neurologically affected prior to onset of IS. Traditionally, this epilepsy syndrome has been considered a "catastrophic" epilepsy, not only for its frequent refractoriness, but mostly due to its effect on cognition. Nevertheless, a change of attitude among pediatric epileptologists is probably warranted, as enough evidence and clinical experience demonstrate that early, aggressive therapy, especially with adrenocorticotropic hormone (ACTH), may not only lead to cessation of spasms, but often leads to the cure of infants with idiopathic/cryptogenic IS. Some ACTH protocols such as that prescribed in Israel (tetracosactide ACTH) appear to be highly efficacious in guarantying a good or even excellent prognosis in idiopathic IS. Moreover, oral prednisolone is a promising and much less expensive alternative to IM ACTH. Vigabatrin does have a role as a first-line agent, especially for tuberous sclerosis patients, but evidence supports hormonal therapy as the initial treatment. The role of pyridoxine and the ketogenic diet still needs to be established; given the efficacy of a much shorter tetracosactide ACTH protocol, there may be no need for the long-term diet, despite its efficacy. Finally, a very promising drug has been developed (CP-115) that may altogether replace the current therapeutic regimens in the near future.

Gliomas and seizures

Glial neoplasms account for nearly 50% of all adult primary brain tumors. They originate from glial cells in the brain and/or spinal cord and include low-grade diffuse astrocytomas, anaplastic-astrocytomas, and glioblastomas. Of all brain tumors, glioblastoma multiforme (GBM) is the most aggressive and is characterized by rapid glial cell growth, resistance to radio- and chemo- therapies, and relentless infiltration and spreading throughout the central nervous system (CNS). In glioblastomas, primary tumor growth and CNS invasion are associated with the activation of complex structural molecular and metabolic changes within the tumor tissue, which profoundly affect the surrounding neuronal networks and may in part explain induction of epilepsy. In fact, epileptic seizures are very common among patients with glial tumors, reaching nearly 50% in glioblastoma patients and almost 90% in low-grade astrocytomas. The overall hypothesis presented here discusses the possibility that the aberrant tumor cell metabolism may act directly on neuronal network, and this leads to seizure susceptibility. Further invasion and growth of the malignant glial cells exacerbate this initial pathologic state which promotes recurrent seizures (epileptogenesis).

The transient effect of interictal spikes from a frontal focus on language-related gamma activity

Interictal spike activity arising from an epileptic focus may cause transient subclinical changes in language function. We retrospectively studied four patients with a seizure focus of the left frontal lobe who underwent language mapping via electrocorticography. In three patients, we could group language task trials into 'spike' and 'non-spike' trials, based upon occurrence of spikes arising from the seizure onset zone during presentation of question stimuli. In one patient, we demonstrated a reduction in language-related gamma activity (80-100Hz) at one dorsal superior frontal site outside the seizure onset zone; reduction in mean peak amplitude of 58.4% of baseline reference (95% C.I.: 31.6% to 85.1%). This site was located near the seizure onset zone and was associated with the greatest spike rate among sites of similar function. This is the first preliminary study to show an effect of interictal spikes upon language-related gamma activity of the lateral frontal lobe.

Epilepsy and epileptic syndrome

Epilepsy is one of the most common neurological disorders. In most patients with epilepsy, seizures respond to available medications. However, a significant number of patients, especially in the setting of medically-intractable epilepsies, may experience different degrees of memory or cognitive impairment, behavioral abnormalities or psychiatric symptoms, which may limit their daily functioning. As a result, in many patients, epilepsy may resemble a neurodegenerative disease. Epileptic seizures and their potential impact on brain development, the progressive nature of epileptogenesis that may functionally alter brain regions involved in cognitive processing, neurodegenerative processes that relate to the underlying etiology, comorbid conditions or epigenetic factors, such as stress, medications, social factors, may all contribute to the progressive nature of epilepsy. Clinical and experimental studies have addressed the pathogenetic mechanisms underlying epileptogenesis and neurodegeneration.We will primarily focus on the findings derived from studies on one of the most common causes of focal onset epilepsy, the temporal lobe epilepsy, which indicate that both processes are progressive and utilize common or interacting pathways. In this chapter we will discuss some of these studies, the potential candidate targets for neuroprotective therapies as well as the attempts to identify early biomarkers of progression and epileptogenesis, so as to implement therapies with early-onset disease-modifying effects.

Genes of early-onset epileptic encephalopathies: from genotype to phenotype

Early-onset epileptic encephalopathies are severe disorders in which cognitive, sensory, and motor development is impaired by recurrent clinical seizures or prominent interictal epileptiform discharges during the neonatal or early infantile periods. They include Ohtahara syndrome, early myoclonic epileptic encephalopathy, West syndrome, Dravet syndrome, and other diseases, e.g., X-linked myoclonic seizures, spasticity and intellectual disability syndrome, idiopathic infantile epileptic-dyskinetic encephalopathy, epilepsy and mental retardation limited to females, and severe infantile multifocal epilepsy. We summarize recent updates on the genes and related clinical syndromes involved in the pathogenesis of early-onset epileptic encephalopathies: Aristaless-related homeobox (ARX), cyclin-dependent kinase-like 5 (CDKL5), syntaxin-binding protein 1 (STXBP1), solute carrier family 25 member 22 (SLC25A22), nonerythrocytic α-spectrin-1 (SPTAN1), phospholipase Cβ1 (PLCβ1), membrane-associated guanylate kinase inverted-2 (MAGI2), polynucleotide kinase 3'-phosphatase (PNKP), sodium channel neuronal type 1α subunit (SCN1A), protocadherin 19 (PCDH19), and pyridoxamine 5-prime-phosphate oxidase (PNPO).

Kainate administered to adult zebrafish causes seizures similar to those in rodent models

Glutamate is the major excitatory neurotransmitter of the central nervous system in vertebrates. Excitotoxicity, caused by over-stimulation of the glutamate receptors, is a major cause of neuron death in several brain diseases, including epilepsy. We describe here how behavioural seizures can be triggered in adult zebrafish by the administration of kainate and are very similar to those observed in rodent models. Kainate induced a dose-dependent sequence of behavioural changes culminating in clonus-like convulsions. Behavioural seizures were suppressed by DNQX (6,7-dinitroquinoxaline-2,3-dione) dose-dependently, whilst MK-801 (a non-competitive NMDA receptor antagonist) had a lesser effect. Kainate triggers seizures in adult zebrafish, and thus this species can be considered as a new model for studying seizures and subsequent excitotoxic brain injury.

Interictal spikes: harbingers or causes of epilepsy?

Interictal spikes are brief paroxysmal electrographic discharges observed between spontaneous recurrent seizures in epileptic patients. The relationship between interictal spikes and the seizures that define acquired epilepsy has been debated for decades. Recent studies using long-term continuous electrographic recordings from the hippocampus and cortex in rats with kainate-induced epilepsy suggest that electrographic spikes, with waveforms similar to interictal spikes, precede the occurrence of the first spontaneous epileptic seizure. These data raise the possibility that spikes might serve as a surrogate marker of ongoing chronic epileptogenesis. Additionally, electrographic spikes might actually contribute to the development and maintenance of the epileptic state (i.e., the increased probability of spontaneous recurrent seizures). Correlational evidence for such a causal relationship has recently also been obtained in an in vitro model of epileptogenesis using organotypic hippocampal slices. Testing for a causal relationship will ultimately require selective anti-spike medications. Although no such agents currently exist, this new preparation is amenable to moderate-throughput screening, which should accelerate their discovery. Anti-spike agents may also be of benefit in ameliorating the cognitive dysfunctions associated with epilepsy, to which spike activity may contribute.

Statistical mapping of ictal high-frequency oscillations in epileptic spasms

PURPOSE

We assessed 636 epileptic spasms seen in 11 children (median 44 spasms per child) and determined the spatial and temporal characteristics of ictal high-frequency oscillations (HFOs) in relation to the onset of spasms.

METHODS

Electrocorticography (ECoG) signals were sampled from 104-148 cortical sites per child, and the dynamic changes of ictal HFOs were animated on each individual's three-dimensional (3D) magnetic resonance (MR) image surface.

KEY FINDINGS

Visual assessment of ictal ECoG recordings revealed that each spasm event was characterized by augmentation of HFOs. Time-frequency analysis demonstrated that ictal augmentation of HFOs at 80-200 Hz was most prominent and generally preceded those at 210-300 Hz and at 70 Hz and slower. Recruitment of HFOs in the rolandic cortex preceded the clinical onset objectively visualized as electromyographic deflection. The presence or absence of ictal motor symptoms was related more to the amplitude of HFOs in the Rolandic cortex than in the seizure-onset zone. In a substantial proportion of epileptic spasms, seizure termination began at the seizure-onset zone and propagated to the surrounding areas; we referred to this observation as the "ictal doughnut phenomenon." Univariate analysis suggested that complete resection of the sites showing the earliest augmentation of ictal HFOs was associated with a good surgical outcome.

SIGNIFICANCE

Recruitment of HFOs at 80-200 Hz in the rolandic area may play a role in determining seizure semiology in epileptic spasms. Our study using macroelectrodes demonstrated that ictal HFOs at 80-200 Hz preceded those at 210-300 Hz.

Lessons from the laboratory: the pathophysiology, and consequences of status epilepticus

Status epilepticus (SE) is the most common neurologic emergency of childhood. Experimental models parallel several clinical features of SE including (1) treatment is complicated by an increasing probability that benzodiazepines will fail with increasing seizure duration and (2) outcome varies with age and etiology. Studies using these models showed that the activity-dependent trafficking of GABA(A) receptors contributes in part to the progressive decline in GABA-mediated inhibition and the failure of the benzodiazepines. Furthermore, laboratory studies have provided evidence that age and inciting stimulus interact to determine the neuronal circuits activated during SE (ie, functional anatomy) and that differences in functional anatomy can partially account for variations in SE outcome. Future laboratory studies are likely to provide an additional understanding of the cellular and molecular mechanisms that underlie SE and its consequences. Such studies are necessary in the development of rational emergent therapy for SE and its long-term outcomes.

Interictal spikes in developing rats cause long-standing cognitive deficits

Frequent interictal spikes are a common finding in the electroencephalograms of children with epileptic encephalopathies. While it is well recognized that interictal spikes are a biological marker of seizures and can lead to transitory cognitive impairment, whether interictal spikes can result in long-standing adverse effects on learning and memory in children is not known. Here we investigated the consequences of interictal spikes in rat pups without seizures on long-term learning and memory. Rat pups were given a low dose of flurothyl for 4h for 10 days during continuous electroencephalographic monitoring. Rats developed interictal spikes without seizures while age-matched controls under similar testing conditions had few interictal spikes. When rats were tested as adults, there was impairment in reference memory in the probe test of the Morris water maze, reference memory impairment in the four-trial radial-arm water maze and impaired long-term potentiation. Early-life interictal spikes resulted in impaired new cell formation and decreased cell counts in the hippocampus but did not cause an increase in apoptosis. This study, for the first time demonstrates that interictal spikes in rat pups without seizures can result in long-standing spatial cognitive impairment. Our findings suggest that suppressing IIS may be as important as treating seizures during brain development.