Effects of seizures on brain development: lessons from the laboratory

Spotlight on plasticity-related genes: Current insights in health and disease

The development of the central nervous system is highly complex, involving numerous developmental processes that must take place with high spatial and temporal precision. This requires a series of complex and well-coordinated molecular processes that are tighly controlled and regulated by, for example, a variety of proteins and lipids. Deregulations in these processes, including genetic mutations, can lead to the most severe maldevelopments. The present review provides an overview of the protein family Plasticity-related genes (PRG1-5), including their role during neuronal differentiation, their molecular interactions, and their participation in various diseases. As these proteins can modulate the function of bioactive lipids, they are able to influence various cellular processes. Furthermore, they are dynamically regulated during development, thus playing an important role in the development and function of synapses. First studies, conducted not only in mouse experiments but also in humans, revealed that mutations or dysregulations of these proteins lead to changes in lipid metabolism, resulting in severe neurological deficits. In recent years, as more and more studies have shown their involvement in a broad range of diseases, the complexity and broad spectrum of known and as yet unknown interactions between PRGs, lipids, and proteins make them a promising and interesting group of potential novel therapeutic targets.

Accessibility to formal education among persons with epilepsy in Mahenge, Tanzania

BACKGROUND

Epilepsy is estimated to affect 50 million people globally, with 80% living in sub-Saharan Africa (SSA). Children with epilepsy (CWE) in SSA are often socially isolated, and many do not get access to school. This study aimed to explore the barriers hindering accessibility to formal education among CWE in Mahenge, Tanzania.

METHODS

The study was conducted in June 2022 in four villages (Mdindo, Msogezi, Mzelezi and Sali) using quantitative and qualitative methods. The quantitative included 203 persons with epilepsy (PWE), while the qualitative involved six focus group discussions and 17 in-depth interviews. Quantitative and qualitative data were analyzed using Stata and Nvivo software, respectively.

RESULTS

Of the 203 PWE, 62 (30.5%) had never enrolled in school, while 77 (54.6%) of those enrolled dropped-out before completing it. The perceived barriers to accessing education were categorized as individual barriers (such as frequent seizures, learning difficulties, anti-seizure medication side effects and perceived stigma), Community barriers (such as stigma and discrimination, negative beliefs and misconceptions, relocation to farms and poor socio-economic status), and Institutional barriers (including lack of knowledge about epilepsy among stake-holders, topography and distance to schools).

CONCLUSION

There is a high rate of dropouts and non-enrolment of CWE in schools within the Mahenge area. Negative beliefs and low awareness of the community about epilepsy and formal education contribute to this issue. This calls for more advocacy to raise community awareness on epilepsy. The government should enforce an inclusive education policy and provide free and uninterrupted anti-seizure medication for seizure control.

Optical Monitoring in Neonatal Seizures

BACKGROUND

Neonatal seizures remain a significant cause of morbidity and mortality worldwide. The past decade has resulted in substantial progress in seizure detection and understanding the impact seizures have on the developing brain. Optical monitoring such as cerebral near-infrared spectroscopy (NIRS) and broadband NIRS can provide non-invasive continuous real-time monitoring of the changes in brain metabolism and haemodynamics.

AIM

To perform a systematic review of optical biomarkers to identify changes in cerebral haemodynamics and metabolism during the pre-ictal, ictal, and post-ictal phases of neonatal seizures.

METHOD

A systematic search was performed in eight databases. The search combined the three broad categories: (neonates) AND (NIRS) AND (seizures) using the stepwise approach following PRISMA guidance.

RESULTS

Fifteen papers described the haemodynamic and/or metabolic changes observed with NIRS during neonatal seizures. No randomised controlled trials were identified during the search. Studies reported various changes occurring in the pre-ictal, ictal, and post-ictal phases of seizures.

CONCLUSION

Clear changes in cerebral haemodynamics and metabolism were noted during the pre-ictal, ictal, and post-ictal phases of seizures in neonates. Further studies are necessary to determine whether NIRS-based methods can be used at the cot-side to provide clear pathophysiological data in real-time during neonatal seizures.

Sleep Disturbances in Chinese Children with Epilepsy: Associations with Behavioral Problems and Quality of Life

OBJECTIVE

To investigate the association between sleep disturbances and behavioral problems as well as quality of life (QOL) in Chinese children with epilepsy.

METHODS

Caregivers of 167 epileptic children aged 3 to 12 years completed the Child Sleep Habits Questionnaire (CSHQ), the Strengths and Difficulties Questionnaire (SDQ), and the Pediatric Quality of Life Inventory (PedsQL™, 4.0 Core).

RESULTS

The prevalence of sleep disturbances (CSHQ total score >41) in epileptic children was 73.7% [95% CI (66.9%.80.4%)]. Epileptic children with sleep disturbances demonstrated more behavioral problems and lower QOL compared to those without sleep disturbances. Sleep disturbances such as sleep anxiety and daytime sleepiness were associated with more behavioral problems and lower QOL (p <0.05). Linear regression analyses showed that higher disturbance in sleep duration domain were associated with more behavioral problems, while higher sleep disordered breathing domains was associated with lower QOL (p <0.05). The interaction between sleep disturbances and behavioral problems in predicting QOL was not significant. The sensitivity analysis using 48 as an alternative cutoff for CSHQ total score obtained consistent results.

CONCLUSION

Sleep disturbances occur frequently among Chinese children with epilepsy, and are associated with more behavioral problems and lower QOL. The sleep disturbance-QOL association is unlikely contingent on behavioral problems. This study highlights the necessity of evaluating and treating sleep disturbances multidimensionally among children with epilepsy to promote their whole health and wellbeing.

Multiple Early-Life Seizures Alters Neonatal Communicative Behavior in Fmr1 Knockout Mice

Fragile X syndrome (FXS) is the leading monogenic cause of intellectual disability and a significant contributor to Autism Spectrum Disorder. Individuals with FXS are subject to developing numerous comorbidities, one of the most prevalent being seizures. In the present study, we investigated how seizures affected neonatal communicative behavior in the FXS mouse model. On postnatal day (PD) 7 through 11, we administered 3 flurothyl seizures per day to both Fmr1 knockout and wild-type C57BL/6J male mice. Ultrasonic vocalizations were recorded on PD12. Statistically significant alterations were found in both spectral and temporal measurements across seizure groups. We found that induction of seizures across PD7-11 resulted in an increased fundamental frequency (pitch) of ultrasonic vocalizations produced (p < 0.05), a longer duration of calls (p < 0.05), and a greater cumulative duration of calls (p < 0.05) in both genotypes. Induction of seizures across PD7-11 also resulted in a decreased latency to the first emitted vocalization (p < 0.05) and a decrease in mean power (loudness) for their vocalizations (p < 0.05). Early-life seizures also resulted in an increase in the number of downward and frequency step call types (p < 0.05). There was a significant increase in the number of chevron calls emitted from the Fmr1 knockout mice that received seizures compared to knockout control and wild-type seizure mice (p < 0.05). Overall, this study provides evidence that early-life seizures result in communication impairments and that superimposing seizures in Fmr1 knockout mice does produce an additional deficit in vocalization.

Propofol and Sevoflurane Anesthesia in Early Childhood Do Not Influence Seizure Threshold in Adult Rats

Experimental studies have demonstrated that general anesthetics administered during the period of synaptogenesis may induce widespread neurodegeneration, which results in permanent cognitive and behavioral deficits. What remains to be elucidated is the extent of the potential influence of the commonly used hypnotics on comorbidities including epilepsy, which may have resulted from increased neurodegeneration during synaptogenesis. This study aimed to test the hypothesis that neuropathological changes induced by anesthetics during synaptogenesis may lead to changes in the seizure threshold during adulthood. Wistar rat pups were treated with propofol, sevoflurane, or saline on the sixth postnatal day. The long-term effects of prolonged propofol and sevoflurane anesthesia on epileptogenesis were assessed using corneal kindling, pilocarpine-, and pentylenetetrazole-induced seizure models in adult animals. Body weight gain was measured throughout the experiment. No changes in the seizure threshold were observed in the three models. A significant weight gain after exposure to anesthetics during synaptogenesis was observed in the propofol group but not in the sevoflurane group. The results suggest that single prolonged exposure to sevoflurane or propofol during synaptogenesis may have no undesirable effects on epileptogenesis in adulthood.

Development and Validation of Prediction Models for Developmental and Intellectual Outcome Following Pediatric Epilepsy Surgery

BACKGROUND AND OBJECTIVES

To (1) identify predictors of postoperative intelligence and developmental quotients (IQ/DQ) and (2) develop and validate clinically applicable IQ/DQ prediction models.

METHODS

We retrospectively analyzed neuropsychological outcomes and their possible determinants for children treated in Bethel and Utrecht since 1990. We performed separate analyses for patients with IQ and those with only DQ available. We developed prediction models based on presurgical determinants to predict dichotomized levels of performance (IQ≥85, IQ≥70, DQ≥50).

RESULTS

IQ/DQ data before and two years after surgery were available for 492 patients (IQ n=365, DQ n=127). At a cutoff-level ±10 points, the chance of improvement was considerably higher than the chance of deterioration (IQ 37.3% vs. 6.6% and DQ 31.5% vs. 15.0%, respectively). Presurgical IQ/DQ was the strongest predictor of postoperative cognition (IQ r=0.85, p<.001, DQ: r=0.57, p<.001).Two IQ models were developed in the Bethel cohort (n=258) and externally validated in the Utrecht cohort (n=102). For DQ, we developed the model in the Bethel cohort and used 10-fold cross-validation. Models allowed good prediction at all three cutoff-levels (correct classification for IQ≥85=86%, IQ≥70=91%, DQ≥50=76%). External validation of the IQ models showed high accuracy (IQ≥85: 0.82, CI 0.75-0.91, IQ≥70: 0.84, CI 0.77-0.92) and excellent discrimination (ROC curves IQ≥85: AUC 0.90, CI 0.84-0.96; IQ≥70: AUC 0.92, CI 0.87-0.97).

DISCUSSION

After epilepsy surgery in children, the risk of cognitive deterioration is very low. Presurgical development has a strong impact on the postoperative trajectory. The presented models can improve presurgical counseling of patients and parents by reliably predicting cognitive outcomes.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that for children undergoing epilepsy surgery presurgical IQ/DQ was the strongest predictor of postoperative cognition.

Seizures in the neonate: A review of etiologies and outcomes

Neonatal seizures occur in their majority in close temporal relation to an acute brain injury or systemic insult, and are accordingly defined as acute symptomatic or provoked seizures. However less frequently, unprovoked seizures may also present in the neonatal period as secondary to structural brain abnormalities, thus corresponding to structural epilepsies, or to genetic conditions, thus corresponding to genetic epilepsies. Unprovoked neonatal seizures should be thus considered as the clinical manifestation of early onset structural or genetic epilepsies that often have the characteristics of early onset epileptic encephalopathies. In this review, we address the conundrum of neonatal seizures including acute symptomatic, remote symptomatic, provoked, and unprovoked seizures, evolving to post-neonatal epilepsies, and neonatal onset epilepsies. The different clinical scenarios involving neonatal seizures, each with their distinct post-neonatal evolution are presented. The structural and functional impact of neonatal seizures on brain development and the concept of secondary epileptogenesis, with or without a following latent period after the acute seizures, are addressed. Finally, we underline the need for an early differential diagnosis between an acute symptomatic seizure and an unprovoked seizure, since it is associated with fundamental differences in clinical evolution. These are crucial aspects for neonatal management, counselling and prognostication. In view of the above aspects, we provide an outlook on future strategies and potential lines of research in this field.

Low-Dose Perampanel Rescues Cortical Gamma Dysregulation Associated With Parvalbumin Interneuron GluA2 Upregulation in Epileptic Syngap1+/- Mice

BACKGROUND

Loss-of-function SYNGAP1 mutations cause a neurodevelopmental disorder characterized by intellectual disability and epilepsy. SYNGAP1 is a Ras GTPase-activating protein that underlies the formation and experience-dependent regulation of postsynaptic densities. The mechanisms that contribute to this proposed monogenic cause of intellectual disability and epilepsy remain unresolved.

METHODS

We established the phenotype of the epileptogenesis in a Syngap1^+/- mouse model using 24-hour video electroencephalography (vEEG)/electromyography recordings at advancing ages. We administered an acute low dose of perampanel, a Food and Drug Administration-approved AMPA receptor (AMPAR) antagonist, during a follow-on 24-hour vEEG to investigate the role of AMPARs in Syngap1 haploinsufficiency. Immunohistochemistry was performed to determine the region- and location-specific differences in the expression of the GluA2 AMPAR subunit.

RESULTS

A progressive worsening of the epilepsy with emergence of multiple seizure phenotypes, interictal spike frequency, sleep dysfunction, and hyperactivity was identified in Syngap1^+/- mice. Interictal spikes emerged predominantly during non-rapid eye movement sleep in 24-hour vEEG of Syngap1^+/- mice. Myoclonic seizures occurred at behavioral-state transitions both in Syngap1^+/- mice and during an overnight EEG from a child with SYNGAP1 haploinsufficiency. In Syngap1^+/- mice, EEG spectral power analyses identified a significant loss of gamma power modulation during behavioral-state transitions. A significant region-specific increase of GluA2 AMPAR subunit expression in the somas of parvalbumin-positive interneurons was identified.

CONCLUSIONS

Acute dosing with perampanel significantly rescued behavioral state-dependent cortical gamma homeostasis, identifying a novel mechanism implicating Ca²⁺-impermeable AMPARs on parvalbumin-positive interneurons underlying circuit dysfunction in SYNGAP1 haploinsufficiency.

Emergency Department Implementation of the Brain Trauma Foundation's Pediatric Severe Brain Injury Guideline Recommendations

The "Guidelines for the Management of Pediatric Severe Traumatic Brain Injury, Third Edition: Update of the Brain Trauma Foundation Guidelines" published in Pediatric Critical Care Medicine in 2019 provides new and updated recommendations applicable to the emergency department management of children with severe traumatic brain injury. Practice-changing takeaways include specific recommendations for administration of 3% hypertonic saline, administration of seizure prophylaxis, and avoiding hyperventilation.

Reconfiguration of dynamic large-scale brain network functional connectivity in generalized tonic-clonic seizures

An increasing number of studies in patients with generalized tonic–clonic seizures (GTCS) have reported the alteration of functional connectivity (FC) in many brain networks. However, little is known about the underlying temporal variability of FC in large‐scale brain functional networks in patients. Recently, dynamic FC could provide novel insight into the physiological mechanisms in the brain. Here, we recruited 63 GTCS and 65 age‐ and sex‐matched healthy controls. Dynamic FC approaches were used to evaluate alterations in the temporal variability of FC in patients at the region‐ and network‐levels. In addition, two kinds of brain templates (>10² and > 10³ regions) and two kinds of temporal variability FC approaches were adopted to verify the stability of the results. Patients showed increased FC variability in regions of the default mode network (DMN), ventral attention network (VAN) and motor‐related areas. The DAN, VAN, and DMN illustrated enhanced FC variability at the within‐network level. In addition, increased FC variabilities between networks were found between the DMN and cognition‐related networks, including the VAN, dorsal attention network and frontal–parietal network in GTCS. Meanwhile, the alterations in FC variability were relatively consistent across different methods and templates. Therefore, the consistent alteration of FC variability would reflect a dynamic restructuring of the large‐scale brain networks in patients with GTCS. Overly frequent information communication among cognition‐related networks, especially in the DMN, might play a role in the epileptic activity and/or cognitive dysfunction in patients.

Comorbidities of early-onset temporal epilepsy: Cognitive, social, emotional, and morphologic dimensions

Epilepsy, the most common neurologic disorder in childhood, is associated with a subset of psychiatric dysfunctions, including cognitive deficits, and alterations in emotionality (e.g., anxiety and depression) and social functioning. In the present study, we evaluated an integrative set of behavioral responses, including cognitive/socio-cognitive and emotional dimensions, using a number of behavioral paradigms in the LiCl/pilocarpine model of status epilepticus (SE) in rats. The aims of the study were to examine whether SE affects: 1) non-associative learning (habituation of exploratory behavior); 2) investigatory response to an indifferent stimulus object; 3) sociability/social novelty preference; 4) social recognition or discrimination; and 4) short- and long-term memory in the Morris water maze (MWM). Finally, we investigated the morphology of key brain structures involved in the examined behavioral dysfunctions. SE did not affect habituation to an open-field arena in juvenile (P25), adolescent (P32), or adult (P80) rats. SE rats spent less time in the central part of the arena. SE adolescent rats (P32) displayed a higher number of rearings with a shorter duration. SE rats displayed a markedly attenuated investigatory response to an indifferent stimulus object. SE rats in all age groups demonstrated pronounced deficits in sociability and the preference for social novelty. In addition, SE rats spent a reduced amount of time investigating a juvenile rat upon first exposure. After 30 min re-exposure together with an additional, novel juvenile, the SE rats spent equal time investigating both juveniles. In the MWM task, acquisition was unimpaired but there was a deficit in delayed memory retention after 10 days. SE did not affect cognitive flexibility expressed by reversal learning. Together, these findings suggest that early-life SE leads to alterations in emotional/anxiety-related behavior and affects sociability/preference for social novelty and social discrimination. Early-life SE did not alter acquisition of spatial learning, but it impaired delayed retention. Using Fluoro Jade B staining performed 24 h after SE revealed apparent neurodegeneration in the dorsal hippocampus, mediodorsal thalamic nucleus and medial amygdala, brain areas that are critically involved in network underlying emotional behavior and cognitive functions.

[Assessment of neurodevelopment in children of different gestational age with neonatal seizures]

AIM

To assess psychomotor development in infants with neonatal seizures (NS) born with different gestational age, by means of Bayley-III scales of infant and toddler development, in their corrected age of 1 year.

MATERIAL AND METHODS

The study included 52 infants, who had NS and were born with different gestational age: 28 weeks or less (n=26) - group I, 29-32 weeks (n=16) - group II, 33-36 weeks (n=3) - group III, 37-41 weeks (n=7) - group IV. The infants' neurodevelopment was evaluated in their corrected age of 1 year by means of N. Bayley scales of infant and toddler development, third edition: Cognitive, Language, Motor, Social-Emotional, and Adaptive Behavior.

RESULTS AND CONCLUSION

Only 17 (32,7%) of 52 examined infants did not demonstrate any developmental delay on each of five Bayley-III scales. Significant developmental delay (composite score <70) on at least one scale was revealed in 23 (44,2%) patients, including 12 (46,2%) in group I, 5 (31,3%) in group II, 6 (60%) of 10 in the combined group III-IV. In most cases, neurodevelopmental delays were attributed to only one domain and could be indicated as partial. The conclusion about global developmental retardation (the composite scores 55 or less on all five scales) was done in 3 patients, each of whom had a co-morbidity of cerebral palsy and epilepsy.

The neuropsychological profile of parietal and occipital lobe epilepsy

Despite the extensive body of research in clinical neurology on the functional organization of posterior cortices, parietal and occipital lobe epilepsy (PLE and OLE) have not as yet received the attention afforded frontal and temporal lobe epilepsy (FLE and TLE), perhaps due to their low prevalence. Posterior epilepsies however, represent a challenge for epileptology in general and neuropsychological differential diagnosis in particular. Our main purpose was to examine the likely existence of a pattern of cognitive dysfunction characterizing patients suffering from seizures with a parietal and/or occipital ictal onset. We hypothesized that such patients would present difficulties in the visuospatial and visuoconstructive domains, since spatial analysis and synthesis is an inherent feature of posterior cortical systems. Participants were 14 patients with epilepsy and 14 healthy controls matched for demographic characteristics (gender, age, and education level). We used an extensive battery of neuropsychological tests to assess auditory-verbal memory and learning, episodic memory, attention and working memory, verbal abilities, haptic perception, arithmetic abilities, and executive functions. Special attention was given to visuospatial abilities. Depression and anxiety symptoms were assessed through a self-administered questionnaire. Nonparametric (Mann-Whitney U test) statistical tests were conducted. We found that patients with epilepsy performed significantly worse in visuoconstruction, verbal, and executive functions compared to their healthy matches. Finally, we interpret our findings from the perspective of Luria of mental functions organized into functional systems and the current trends in epileptology to view epilepsy as a system (network) problem.

Long-Term Effects of Early Life Seizures on Endogenous Local Network Activity of the Mouse Neocortex

Understanding the long term impact of early life seizures (ELS) is of vital importance both for researchers and clinicians. Most experimental studies of how seizures affect the developing brain have drawn their conclusions based on changes detected at the cellular or behavioral level, rather than on intermediate levels of analysis, such as the physiology of neuronal networks. Neurons work as part of networks and network dynamics integrate the function of molecules, cells and synapses in the emergent properties of brain circuits that reflect the balance of excitation and inhibition in the brain. Therefore, studying network dynamics could help bridge the cell-to-behavior gap in our understanding of the neurobiological effects of seizures. To this end we investigated the long-term effects of ELS on local network dynamics in mouse neocortex. By using the pentylenetetrazole (PTZ)-induced animal model of generalized seizures, single or multiple seizures were induced at two different developmental stages (P9-15 or P19-23) in order to examine how seizure severity and brain maturational status interact to affect the brain's vulnerability to ELS. Cortical physiology was assessed by comparing spontaneous network activity (in the form of recurring Up states) in brain slices of adult (>5 mo) mice. In these experiments we examined two distinct cortical regions, the primary motor (M1) and somatosensory (S1) cortex in order to investigate regional differences in vulnerability to ELS. We find that the effects of ELSs vary depending on (i) the severity of the seizures (e.g., single intermittent ELS at P19-23 had no effect on Up state activity, but multiple seizures induced during the same period caused a significant change in the spectral content of spontaneous Up states), (ii) the cortical area examined, and (iii) the developmental stage at which the seizures are administered. These results reveal that even moderate experiences of ELS can have long lasting age- and region-specific effects in local cortical network dynamics.

Efficacy of levetiracetam for neonatal seizures in preterm infants

Background

Neonatal seizures remain a significant clinical problem, and therapeutic options are still not diverse with limited efficacy. Levetiracetam (LEV) is a relatively new and wide spectrum anti-seizure medication with favorable pharmacokinetics and safety profile. In the recent decades, LEV has been increasingly used for the treatment of neonatal seizures. The aim of this study was to describe the experience of using LEV as the first line anti-seizure medication for preterm infants.

Methods

A retrospective analysis of 37 preterm infants who were treated with LEV as the first-line anti-seizure medication was performed.

Results

Mean gestational age of the 37 preterm infants was 31.5 ± 1.9 weeks (range, 26 to 36^+ 6 weeks). Twenty-one infants (57%) were seizure-free while given LEV at the end of the first week, and no additional anti-seizure medication was required. Loading doses of LEV ranged from 40 to 60 mg/kg (mean 56 mg/kg) and the maintenance dose ranged from 20 to 30 mg/kg (mean 23 mg/kg). No adverse effect was observed.

Conclusions

Levetiracetam can be a good and safe choice for treatment of neonatal seizures in preterm infants. Prospective double blind controlled studies are needed in the future.

Internalizing and externalizing symptoms in preschool and school-aged children with epilepsy: Focus on clinical and EEG features

INTRODUCTION

Psychiatric and behavioral problems are frequent comorbidities of epilepsy, although their clinical and electroencephalographic (EEG) correlates remain uncertain. In this study, we have assessed the frequency of psychopathological problems in a cohort of children with epilepsy, and established their main clinical and EEG-associated features.

METHODS

One hundred fifty-nine young patients with epilepsy were recruited and assessed through the Child Behavior Checklist for preschool-aged children (CBCL 1 1/2-5) or for school-aged children (CBCL 6-18). Child Behavior Checklist (CBCL) results were then correlated to the main clinical and EEG data.

RESULTS

We found emotional and behavioral problems in about half of the children in our sample. Internalizing, social, and attention problems were more common than externalizing features. Moderate intellectual disability, a nonidiopathic etiology of epilepsy, a poor control of seizures, and antiepileptic polytherapies, as well as an early age at seizure-onset and a longer duration of the disorder, were all associated with specific behavioral and emotional problems. A temporal site of interictal EEG abnormalities also enhanced the risk for psychiatric comorbidities, especially in the externalizing domain.

CONCLUSIONS

Several clinical and EEG features are associated with an increased risk for emotional and behavioral comorbidities in children with epilepsy. Their identification may foster an early diagnosis and appropriate care, limiting the worsening of psychiatric symptoms and their impact on quality of life and health status. A better understanding of the underlying clinical and molecular mechanisms is needed to further improve prevention and treatment interventions.

The Potential Application of Multiscale Entropy Analysis of Electroencephalography in Children with Neurological and Neuropsychiatric Disorders

Electroencephalography (EEG) is frequently used in functional neurological assessment of children with neurological and neuropsychiatric disorders. Multiscale entropy (MSE) can reveal complexity in both short and long time scales and is more feasible in the analysis of EEG. Entropy-based estimation of EEG complexity is a powerful tool in investigating the underlying disturbances of neural networks of the brain. Most neurological and neuropsychiatric disorders in childhood affect the early stage of brain development. The analysis of EEG complexity may show the influences of different neurological and neuropsychiatric disorders on different regions of the brain during development. This article aims to give a brief summary of current concepts of MSE analysis in pediatric neurological and neuropsychiatric disorders. Studies utilizing MSE or its modifications for investigating neurological and neuropsychiatric disorders in children were reviewed. Abnormal EEG complexity was shown in a variety of childhood neurological and neuropsychiatric diseases, including autism, attention deficit/hyperactivity disorder, Tourette syndrome, and epilepsy in infancy and childhood. MSE has been shown to be a powerful method for analyzing the non-linear anomaly of EEG in childhood neurological diseases. Further studies are needed to show its clinical implications on diagnosis, treatment, and outcome prediction.

Inflammation in epileptogenesis after traumatic brain injury

Background

Epilepsy is a common and debilitating consequence of traumatic brain injury (TBI). Seizures contribute to progressive neurodegeneration and poor functional and psychosocial outcomes for TBI survivors, and epilepsy after TBI is often resistant to existing anti-epileptic drugs. The development of post-traumatic epilepsy (PTE) occurs in a complex neurobiological environment characterized by ongoing TBI-induced secondary injury processes. Neuroinflammation is an important secondary injury process, though how it contributes to epileptogenesis, and the development of chronic, spontaneous seizure activity, remains poorly understood. A mechanistic understanding of how inflammation contributes to the development of epilepsy (epileptogenesis) after TBI is important to facilitate the identification of novel therapeutic strategies to reduce or prevent seizures.

Body

We reviewed previous clinical and pre-clinical data to evaluate the hypothesis that inflammation contributes to seizures and epilepsy after TBI. Increasing evidence indicates that neuroinflammation is a common consequence of epileptic seizure activity, and also contributes to epileptogenesis as well as seizure initiation (ictogenesis) and perpetuation. Three key signaling factors implicated in both seizure activity and TBI-induced secondary pathogenesis are highlighted in this review: high-mobility group box protein-1 interacting with toll-like receptors, interleukin-1β interacting with its receptors, and transforming growth factor-β signaling from extravascular albumin. Lastly, we consider age-dependent differences in seizure susceptibility and neuroinflammation as mechanisms which may contribute to a heightened vulnerability to epileptogenesis in young brain-injured patients.

Conclusion

Several inflammatory mediators exhibit epileptogenic and ictogenic properties, acting on glia and neurons both directly and indirectly influence neuronal excitability. Further research is required to establish causality between inflammatory signaling cascades and the development of epilepsy post-TBI, and to evaluate the therapeutic potential of pharmaceuticals targeting inflammatory pathways to prevent or mitigate the development of PTE.

Variation in seizure prophylaxis in severe pediatric traumatic brain injury

OBJECTIVE Posttraumatic seizure is a major complication following traumatic brain injury (TBI). The aim of this study was to determine the variation in seizure prophylaxis in select pediatric trauma centers. The authors hypothesized that there would be wide variation in seizure prophylaxis selection and use, within and between pediatric trauma centers. METHODS In this retrospective multicenter cohort study including 5 regional pediatric trauma centers affiliated with academic medical centers, the authors examined data from 236 children (age < 18 years) with severe TBI (admission Glasgow Coma Scale score ≤ 8, ICD-9 diagnosis codes of 800.0-801.9, 803.0-804.9, 850.0-854.1, 959.01, 950.1-950.3, 995.55, maximum head Abbreviated Injury Scale score ≥ 3) who received tracheal intubation for ≥ 48 hours in the ICU between 2007 and 2011. RESULTS Of 236 patients, 187 (79%) received seizure prophylaxis. In 2 of the 5 centers, 100% of the patients received seizure prophylaxis medication. Use of seizure prophylaxis was associated with younger patient age (p < 0.001), inflicted TBI (p < 0.001), subdural hematoma (p = 0.02), cerebral infarction (p < 0.001), and use of electroencephalography (p = 0.023), but not higher Injury Severity Score. In 63% cases in which seizure prophylaxis was used, the patients were given the first medication within 24 hours of injury, and 50% of the patients received the first dose in the prehospital or emergency department setting. Initial seizure prophylaxis was most commonly with fosphenytoin (47%), followed by phenytoin (40%). CONCLUSIONS While fosphenytoin was the most commonly used medication for seizure prophylaxis, there was large variation within and between trauma centers with respect to timing and choice of seizure prophylaxis in severe pediatric TBI. The heterogeneity in seizure prophylaxis use may explain the previously observed lack of relationship between seizure prophylaxis and outcomes.

Long-term expression of zinc transporters in hippocampus following penicillin-induced developmental seizures and its regulation by E-64d

Autophagy has been shown to be involved in the pathophysiology of developmental seizure-induced brain damage. The present study aimed to examine whether E-64d, an autophagy inhibitor, was able to facilitate developmental seizure-induced hippocampal mossy fiber sprouting, in particular sprouting-associated zinc transporter signals. Recurrent seizures were induced by penicillin every other day in Sprague-Dawley rats from postnatal day 21 (P21). Rats were randomly assigned into the control group (CONT), recurrent seizure group (RS) and the seizure plus E-64d group (E64D). The expression levels of beclin-1 and B-cell lymphoma 2 were analyzed at 1.5, 3, 6 and 24 h after the last seizures using western blot analysis. At P51, mossy fiber sprouting and the mRNA expression levels of zinc transporter 2 (ZnT-2), ZnT-4, ZnT-5, ZnT-6, ZnT-7, divalent cation transporter 1, Zrt-Irt-like protein 6 (ZIP-6), ZIP-7, cathepsin D and cathepsin L in the rat hippocampus were assessed using Timm staining and reverse transcription-quantitative polymerase chain reaction analysis, respectively. Reduced hippocampal mossy fiber sprouting were detected in the E-64d-treated rats compared with the non-treated control. In parallel with these observations, there was a marked reduction in the mRNA expression levels of ZnT-4 at P51 in the E-64d-treated rat hippocampus compared with the non-treated seizure group. Linear correlation analysis showed significant inter-relationship among ZIP-7, ZnT-4, ZnT-5, ZnT-7, cathepsin D and cathepsin L. These results indicate that the ZnT-4/ZIP-7/cathepsin signaling pathway serves a crucial function in the neuroprotective effects of E-64d. Thus, E-64d may offer a novel strategy for the development of therapeutic interventions for developmental seizure-induced brain damage.

Effects of an acute seizure on associative learning and memory

Past studies have demonstrated that inducing several seizures or continuous seizures in neonatal or adult rats results in impairments in learning and memory. The impact of a single acute seizure on learning and memory has not been investigated in mice. In this study, we exposed adult 129SvEvTac mice to the inhalant flurothyl until a behavioral seizure was induced. Our study consisted of 4 experiments where we examined the effect of one seizure before or after delay fear conditioning. We also included a separate cohort of animals that was tested in the open field after a seizure to rule out changes in locomotor activity influencing the results of memory tests. Mice that had experienced a single seizure 1h, but not 6h, prior to training showed a significant impairment in associative conditioning to the conditioned stimulus when compared with controls 24h later. There were no differences in freezing one day later for animals that experienced a single seizure 1h after associative learning. We also found that an acute seizure reduced activity levels in an open-field test 2h but not 24h later. These findings suggest that an acute seizure occurring immediately before learning can have an effect on the recall of events occurring shortly after that seizure. In contrast, an acute seizure occurring shortly after learning appears to have little or no effect on long-term memory. These findings have implications for understanding the acute effects of seizures on the acquisition of new knowledge.

Increased excitability and excitatory synaptic transmission during in vitro ischemia in the neonatal mouse hippocampus

OBJECTIVE

The present study tested the hypothesis that exposure to in vitro hypoxia-ischemia alters membrane properties and excitability as well as excitatory synaptic transmission of CA1 pyramidal neurons in the neonatal mouse.

METHODS

Experiments were conducted in hippocampal slices in P7-P9 C57Bl/6 mice using whole-cell patch clamp in current- and voltage-clamp mode. Passive membrane potential (Vm), input resistance (Rin) and active (action potential (AP) threshold and amplitude) membrane properties of CA1 pyramidal neurons were assessed at baseline, during 10 min in vitro ischemia (oxygen-glucose deprivation (OGD)) and during reoxygenation. Spontaneous and miniature excitatory post-synaptic currents (s and mEPSCs) were studied under similar conditions.

RESULTS

OGD caused significant depolarization of CA1 pyramidal neurons as well as decrease in AP threshold and increase in AP amplitude. These changes were blocked by the application of tetrodotoxin (TTX), indicating Na(+) channels' involvement. Following 10 min of reoxygenation, significant membrane hyperpolarization was noted and it was associated with a decrease in Rin. AP threshold and amplitude returned to baseline during that stage. sEPSC and mEPSC frequency increased during both OGD and reoxygenation but their amplitude remained unchanged. Additionally, we found that OGD decreases Ih (hyperpolarization activated current) in CA1 neurons from neonatal mice and this effect persists during reoxygenation.

SIGNIFICANCE

These results indicate that in vitro ischemia leads to changes in membrane excitability mediated by sodium and potassium channels. Further, it results in enhanced neurotransmitter release from presynaptic terminals. These changes are likely to represent one of the mechanisms of hypoxia/ischemia-mediated seizures in the neonatal period.

Neonatal status epilepticus: differences between preterm and term newborns

BACKGROUND

Despite the many studies on neonatal seizures, neonatal status epilepticus (NSE) remains a controversial entity, with no general consensus about its definition. We report the characteristics of newborns with NSE in order to assess whether they showed homogeneous features or displayed clinical and/or instrumental differences depending on gestational age (GA). Preterm and term neonates were compared and risk factors for adverse outcome evaluated.

METHODS

From 154 newborns with video-EEG confirmed neonatal seizures admitted to the NICU of Parma University Hospital between January 1999 and December 2012, we collected a cohort of 47 newborns (19 preterm, 28 full-term) with NSE. NSE was defined as continuous seizure activity for at least 30 min or recurrent seizures lasting a total of 30 min without definite return to the baseline neurologic condition between seizures. Outcome was assessed at least at one year. We applied the χ(2) test to compare nominal data, and multivariate logistic regression analysis to determine independent risk factors for adverse outcome.

RESULTS

Only Apgar scores and neurologic examination (p ≤ .02) were different between the groups. None of the preterm newborns had a favourable outcome compared to 25% of the full-term ones (p = .032). Moreover, 52.6% of preterm neonates died compared to 17.8% of the full-term newborns (p = .01; OR = 5.11). The only variable related to outcome was Apgar score at 5 min (p = .02).

CONCLUSION

Newborns with NSE represented a quite homogeneous group regardless of the GA. Outcome was unfavourable in most of the subjects; however adverse outcome and death were more represented in preterm newborns.

A rat model of nerve agent exposure applicable to the pediatric population: The anticonvulsant efficacies of atropine and GluK1 antagonists

Inhibition of acetylcholinesterase (AChE) after nerve agent exposure induces status epilepticus (SE), which causes brain damage or death. The development of countermeasures appropriate for the pediatric population requires testing of anticonvulsant treatments in immature animals. In the present study, exposure of 21-day-old (P21) rats to different doses of soman, followed by probit analysis, produced an LD50 of 62μg/kg. The onset of behaviorally-observed SE was accompanied by a dramatic decrease in brain AChE activity; rats who did not develop SE had significantly less reduction of AChE activity in the basolateral amygdala than rats who developed SE. Atropine sulfate (ATS) at 2mg/kg, administered 20 min after soman exposure (1.2×LD50), terminated seizures. ATS at 0.5mg/kg, given along with an oxime within 1 min after exposure, allowed testing of anticonvulsants at delayed time-points. The AMPA/GluK1 receptor antagonist LY293558, or the specific GluK1 antagonist UBP302, administered 1h post-exposure, terminated SE. There were no degenerating neurons in soman-exposed P21 rats, but both the amygdala and the hippocampus were smaller than in control rats at 30 and 90days post-exposure; this pathology was not present in rats treated with LY293558. Behavioral deficits present at 30 days post-exposure, were also prevented by LY293558 treatment. Thus, in immature animals, a single injection of atropine is sufficient to halt nerve agent-induced seizures, if administered timely. Testing anticonvulsants at delayed time-points requires early administration of ATS at a low dose, sufficient to counteract only peripheral toxicity. LY293558 administered 1h post-exposure, prevents brain pathology and behavioral deficits.

Neonatal Seizures: Impact on Neurodevelopmental Outcomes

Neonatal period is the most vulnerable time for the occurrence of seizures, and neonatal seizures often pose a clinical challenge both for their acute management and frequency of associated long-term co-morbidities. Etiologies of neonatal seizures are known to play a primary role in the anti-epileptic drug responsiveness and the long-term sequelae. Recent studies have suggested that burden of acute recurrent seizures in neonates may also impact chronic outcomes independent of the etiology. However, not many studies, either clinical or pre-clinical, have addressed the long-term outcomes of neonatal seizures in an etiology-specific manner. In this review, we briefly review the available clinical and pre-clinical research for long-term outcomes following neonatal seizures. As the most frequent cause of acquired neonatal seizures, we focus on the studies evaluating long-term effects of HIE-seizures with the goal to evaluate (1) what parameters evaluated during acute stages of neonatal seizures can reliably be used to predict long-term outcomes? and (2) what available clinical and pre-clinical data are available help determine importance of etiology vs. seizure burdens in long-term sequelae.

Cognitive impairment predicts social disability in persons with epilepsy

Introduction.Cognitive dysfunction is one of the main comorbidities of epilepsy which co-exists with seizures and contributes to the adverse impact of the disease on employment, education and interpersonal relationships. A fundamental question regarding cognitive dysfunction in epilepsy goes as follows: in comparison to seizures, what role does cognitive dysfunction play in causing social disability? The purpose of this review was to evaluate our understanding of the role cognitive impairment plays in social disability in persons with epilepsy (PWE). We systematically searched the medical literature and identified studies which assessed the impact of seizures and cognitive function on some aspect of social disability in PWE.

Results and Discussion.We identified 12 studies which adequately measured all variables in non-surgical cohorts, and 9 studies of cohorts following epilepsy surgery. We found evidence from non-surgical and from surgical series that cognitive variables strongly correlate with levels of social disability.

Conclusions.We conclude that efforts to better understand the origins of cognitive dysfunction in epilepsy and subsequently at developing treatment modalities will be needed in order to reduce the degree of social disability caused by the condition.

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.

Electrographic seizures and status epilepticus in critically ill children and neonates with encephalopathy

Electrographic seizures are seizures that are evident on EEG monitoring. They are common in critically ill children and neonates with acute encephalopathy. Most electrographic seizures have no associated clinical changes, and continuous EEG monitoring is necessary for identification. The effect of electrographic seizures on outcome is the focus of active investigation. Studies have shown that a high burden of electrographic seizures is associated with worsened clinical outcome after adjustment for cause and severity of brain injury, suggesting that a high burden of such seizures might independently contribute to secondary brain injury. Further research is needed to determine whether identification and management of electrographic seizures reduces secondary brain injury and improves outcome in critically ill children and neonates.

Intellectual development before and after the onset of infantile spasms: a controlled prospective longitudinal study in tuberous sclerosis

OBJECTIVE

Infantile spasms (IS) have long been suspected to be a risk factor for impairment in intellectual development, but there are no controlled, prospective longitudinal data in well-characterized conditions to confirm this suspicion. We tested the hypothesis in a longitudinal study of children with tuberous sclerosis (TS), who have a high risk of developing IS.

METHODS

Eleven infants with TS were recruited and studied longitudinally using the Mullen Scales of Early Learning. Seizure histories were assessed using a structured parent interview and by review of medical notes. Intellectual development was examined in relation to the onset and length of exposure to IS and other types of seizures.

RESULTS

Six children developed IS and five children developed other types of seizure disorders. Among those that developed IS, estimated mean IQ dropped significantly (nonparametric test for trend p = 0.002) from 92 (prior to onset of spasms) to 73 (after exposure to IS for a month or less) and 62 (after exposure to IS for more than a month). By contrast, there was no significant drop in estimated IQ among the five infants exposed to other types of seizure disorders (nonparametric test for trend p = 0.9). All six children exposed to infantile spasms developed clinically significant intellectual impairment.

SIGNIFICANCE

These data provide the first clear evidence of clinically significant, dose dependent, impairment in intellectual development following exposure to infantile spasms. The mechanisms underlying this developmental impairment and methods for preventing it require in depth study.

Risk factors and scoring system as a prognostic tool for epilepsy after neonatal seizures

BACKGROUND

Neonatal seizures may cause irreversible changes to the immature brain and. A scoring system for early prognostic information could be a useful clinical tool. The aim of the study was to analyze risk factors for epilepsy after neonatal seizures, to validate Garfinkle's scoring system, and to analyze whether a new scoring system is feasible.

METHODS

A retrospective study of 176 newborns (59.1% boys, 40.9% girls, 70.5% term, 29.5% preterm; mean birth weight 2820 g), admitted to the Department of Neonatology, Division of Pediatrics, University Medical Centre, Ljubljana, because of neonatal seizures (clinical and/or neurophysiological), was performed. Epilepsy rate between 2 and 12 years of follow-up was 18.1%. Five independent predictors from Garfinkle's study and other known predictors were entered into hierarchical binary logistic regression models and analyzed through four steps to identify independent predictors of epilepsy. We tested whether any of the predictors was an effect modifier.

RESULTS

Of five potential predictors from Garfinkle's score, electroencephalograph background findings and etiology were predictive. Etiologies, gestation, mode of delivery, duration of seizures, and other risk factors at birth were found to be independent predictors. Duration of seizures has a different effect on prognosis depending on the gestational age.

CONCLUSION

Gestational age determines the association between duration of seizures and epilepsy. Scoring systems to predict development of epilepsy after neonatal seizures need to limit interaction between important predictor variables.

While waiting: early recognition and initial management of neonatal hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) occurring during the perinatal period is one of the primary causes of severe, long-term neurological deficits in children. Initial systemic supportive therapy remains a critical aspect of HIE management. In addition to support therapy, the widespread use of hypothermia has demonstrated a reduction in death and neurodevelopmental disability in infants with moderate to severe HIE. Neonates with HIE born outside of tertiary care centers must be rapidly identified as hypothermia candidates and have emergent transport arranged. While waiting for the transport team to arrive, these neonates often require intensive stabilization, including meticulous temperature management. This article examines the need for HIE outreach teaching programs, assists in the identification of a neonate for hypothermia therapy, and supplies evidence-based recommendations for the initial stabilization and care of neonates delivered at nontertiary care facilities. The guidelines and materials supplied represent the outreach model used by our regional hypothermia center and disseminated to the surrounding referral hospitals.

Limbic system activation is affected by prenatal predator exposure and postnatal environmental enrichment and further moderated by dam and sex

Epilepsy is a relatively common and chronic neurological condition, affecting 1-2% of the population. However, understanding of the underlying pathophysiology remains incomplete. To identify potential factors in the early environment that may increase the risk for experiencing seizures, maternal stress and environmental enrichment (EE) were utilized. Pregnant Long-Evans rats were exposed to an ethologically relevant predator stress (PS) and maternal glucocorticoid (GC) response was assessed across the exposure period. At birth, litters were divided into standard care (SC) and EE groups until postnatal day 14 (PD14) when a model of febrile convulsions was used to determine seizure susceptibility of the various groups. Pup brains were then processed for immunohistochemical detection of FosB from several structures in the limbic system as a measure of neuronal activation. Maternal PS-induced GC levels were elevated early in the exposure period, and pup birth weights, in both sexes, were lower in litters from dams exposed to PS. Seizure scores at PD14 were highly individualized and litter dependent, suggesting a dam-dependent and variable effect of controlled pre- and postnatal environmental factors. Further, analysis of FosB-immunoreactive (-ir) patterns revealed an activity dependent distribution, reflecting individual seizure susceptibility. EE had a varying effect on FosB-ir that was dependent on region. In the hippocampus FosB-ir levels were greater in the EE groups while extra-hippocampal regions showed lower levels of FosB-ir. Our results support the concept that pre- and postnatal environmental influences affect fetal programming and neurodevelopment of processes that could underlie seizure susceptibility, but that the magnitude of these effects appears to be dam- or litter-dependent.

Continuous EEG monitoring in the neonatal intensive care unit

Continuous EEG monitoring provides an opportunity to both accurately identify seizures and monitor the neurologic status of critically ill neonates in the intensive care unit. The incidence of seizures is higher in the neonatal period than at any other time in life. Seizures and abnormalities of EEG background are associated with significant risk of mortality and long-term neurodevelopmental morbidities. In the neonatal population the majority of seizures are not clinically evident and go undetected without EEG monitoring. We review the incidence and risk factors for neonatal seizures, and the utility of continuous EEG monitoring in the neonatal intensive care unit for seizure detection and for analysis of background to allow prognostication. We consider the role of amplitude-integrated EEG in the neonatal population. We consider the utility of continuous EEG for frequently encountered neurologic indications and discuss the outcome data and some new developments in continuous EEG monitoring.

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.

Hippocampal interictal epileptiform activity disrupts cognition in humans

OBJECTIVE

We investigated whether interictal epileptiform discharges (IED) in the human hippocampus are related to impairment of specific memory processes, and which characteristics of hippocampal IED are most associated with memory dysfunction.

METHODS

Ten patients had depth electrodes implanted into their hippocampi for preoperative seizure localization. EEG was recorded during 2,070 total trials of a short-term memory task, with memory processing categorized into encoding, maintenance, and retrieval. The influence of hippocampal IED on these processes was analyzed and adjusted to account for individual differences between patients.

RESULTS

Hippocampal IED occurring in the memory retrieval period decreased the likelihood of a correct response when they were contralateral to the seizure focus (p < 0.05) or bilateral (p < 0.001). Bilateral IED during the memory maintenance period had a similar effect (p < 0.01), particularly with spike-wave complexes of longer duration (p < 0.01). IED during encoding had no effect, and reaction time was also unaffected by IED.

CONCLUSIONS

Hippocampal IED in humans may disrupt memory maintenance and retrieval, but not encoding. The particular effects of bilateral IED and those contralateral to the seizure focus may relate to neural compensation in the more functional hemisphere. This study provides biological validity to animal models in the study of IED-related transient cognitive impairment. Moreover, it strengthens the argument that IED may contribute to cognitive impairment in epilepsy depending upon when and where they occur.

Peroxynitrite alters GABAergic synaptic transmission in immature rat hippocampal slices

Increasing of peroxynitrite (ONOO(-)) production during ischemia in the immature brain was considered to be associated with impaired cognitive function. GABAergic synapses played an important role in memory formation including the induction of long-term potentiation (LTP) and long-term depression (LTD) in hippocampus. In the present study, we examined the effects of acute exposure of the ONOO(-) donor, SIN-1 on GABAergic synaptic transmission in immature rat hippocampal slices with whole-cell patch-clamp recordings. The results showed that SIN-1 increased the peak amplitude of evoked inhibitory postsynaptic currents (eIPSCs) and decreased paired pulse ratio via the formation of ONOO(-). In addition, it also increased the frequency of spontaneous (but not miniature) IPSCs in a dose-dependent manner without altering amplitudes or rise and decay times of both (sIPSCs and mIPSCs). It further demonstrated that the presynaptic action of SIN-1 was external calcium dependent and was not related to the changes of interneuron excitability. This study provides electrophysiological evidences from developing hippocampal slices to support that SIN-1 enhances action potential-dependent GABA release. It suggests that the potentiation effect of ONOO(-) may contribute to hyperexcitability and seizures and may underlie one of the mechanisms by which ischemia increases seizure susceptibility in the immature brain.

Leukocyte trafficking mechanisms in epilepsy

Epilepsy is a chronic disorder that affects 1% of the world population and is characterized by chronically reoccurring seizures. Seizures are initiated by abnormal excessive or synchronous neuronal activity in the brain. Epilepsy requires life long anti-convulsant therapy and current therapies for epilepsy selectively target neuronal activity. In the last decade, cytokines and vascular alterations have been discussed in relation to the pathogenesis of epilepsy, suggesting a potential role for inflammation mechanisms in seizure induction. More recently, it has been shown that leukocyte trafficking plays a key role in seizure generation, and that anti-leukocyte adhesion therapy has therapeutic and preventative effects in an experimental model of human epilepsy. These results were supported by evidence in humans showing that leukocytes accumulate in the brain parenchyma of patients with different types of epilepsy. Finally, recent clinical observations suggest that therapies able to interfere with leukocyte trafficking may have a therapeutic effect in epilepsy. The emerging role for leukocytes and leukocyte adhesion mechanisms in seizure generation provides insight into the mechanisms of brain damage and may contribute to the development of novel therapeutic strategies in epilepsy.

Epileptogenesis in the developing brain

The neonatal brain has poorly developed GABAergic circuits, and in many of them GABA is excitatory, favoring ictogenicity. Frequently repeated experimental seizures impair brain development in an age-dependent manner. At critical ages, they delay developmental milestones, permanently lower seizure thresholds, and can cause very specific cognitive and learning deficits, such as the permanent impairment of neuronal spatial maps. Some types of experimental status epilepticus cause neuronal necrosis and apoptosis, and are followed by chronic epilepsy with spontaneous recurrent seizures, others appear relatively benign, so that seizure-induced neuronal injury and epileptogenesis are highly age-, seizure model-, and species-dependent. Experimental febrile seizures can be epileptogenic, and hyperthermia aggravates both neuronal injury and epileptogenicity. Antiepileptic drugs, the mainstay of treatment, have major risks of their own, and can, at therapeutic or near-therapeutic doses, trigger neuronal apoptosis, which is also age-, drug-, cell type-, and species-dependent. The relevance of these experimental results to human disease is still uncertain, but while their brains are quite different, the basic biology of neurons in rodents and humans is strikingly similar. Further research is needed to elucidate the molecular mechanisms of epileptogenesis and of seizure- or drug-induced neuronal injury, in order to prevent their long-term consequences.

Expression profiles of hippocampal regenerative sprouting-related genes and their regulation by E-64d in a developmental rat model of penicillin-induced recurrent epilepticus

E-64d (a calpain and autophagy inhibitor) has previously been shown safe for the treatment of Alzheimer's disease in humans. In the present study, the potential protective mechanism of E-64d on hippocampal aberrant mossy fiber sprouting was examined in a developmental rat model of penicillin-induced recurrent epilepticus. A seizure was induced by penicillin every other day in Sprague-Dawley rats from postnatal day 21 (P21). The rats were randomly assigned into the control group (CONT1), the control plus E-64d (CONT2), the seizure group (EXP1) and the seizure plus E-64d (EXP2). On P51, mossy fiber sprouting and related gene expression in hippocampus were assessed by Timm staining and real-time RT-PCR methods, respectively. To validate the RT-PCR results, western blot analysis was performed on selected genes. E-64d obviously suppressed the aberrant mossy fiber sprouting in the supragranular region of dentate gyrus and CA3 subfield of hippocampus. Among the total twelve genes, six genes were strongly up- (MT-3, ACAT1, clusterin and ApoE) or down- (ZnT-1 and PRG-3) regulated by developmental seizures (EXP1) compared with that in the CONT1. Up-regulation of ApoE and Clusterin was blocked by pretreatment with E-64d both in mRNA and protein levels. Further, E-64d-pretreated seizure rats (EXP2) showed a significant downregulation of mRNA expression of PRG-1, PRG-3 and PRG-5, cathepsin B and ApoE, as well as up-regulated nSMase and ANX7 in hippocampus when compared with EXP1 rats. The results of the present study suggest that E-64d, an elective inhibitor of calpain and autophagy, is potentially useful in the treatment of developmental seizure-induced brain damage both by regulating abnormal zinc signal transduction and through the modulation of altered lipid metabolism via ApoE/clusterin pathway in hippocampus.

Mortality risk after neonatal seizures in very preterm newborns

We analyzed clinical and instrumental data of 403 consecutive newborns with gestational age from 24 to 32 weeks, admitted to the University-Hospital of Parma between January 2000 and December 2007, to evaluate the possible relationship between neonatal mortality and occurrence of neonatal seizures in very preterm newborns. Seventy-four subjects died during hospital stay. Seizures were present in 35 neonates, in whom the mortality rate was 37.1%. Multivariate analysis revealed that birth-weight <1000 g (odds ratio: 4.48; 95% confidence interval: 1.47-13.68; P < .01), cardiopulmonary resuscitation (odds ratio: 5.35; 95% confidence interval: 1.19-23.98; P = .02), and moderately and severely abnormal cerebral ultrasound scan findings (odds ratio: 2.48; 95% confidence interval: 1.02-6.05; P < .04; odds ratio: 9.56; 95% confidence interval: 3.45-26.51; P < .01, respectively) were related to the in-hospital mortality but not the presence of neonatal seizures. Our study suggests that neonatal seizures alone are not an independent risk factor for early death in very preterm newborns.

Cognitive outcome of status epilepticus in children

Epileptic encephalopathy encompasses conditions in which cognitive, motor, or sensory deficits result as a consequence of epileptic activity defining certain syndromes. It therefore represents a more severe subset of epilepsy, which can be generally characterized as frequent or severe seizures leading to cerebral dysfunction. This disturbance in cerebral functioning can in turn hinder, somewhat dramatically, cognitive development and further impact the future lives of patients. In this paper, we describe the cognitive consequences of status epilepticus in children and in adults in the context of plasticity theories. Recent studies maintain that consequences of SE may be severe cognitive sequelae, especially in early life. Since the residual consequences of SE in adulthood seem less detrimental and long-lasting, we argue that early life insults, such as those created by SE, during a rapid period of development and functional specialization, result in specific cognitive deficits dependent on the sensitive period at which SE occurred.

Cerebral oxygenation during subclinical seizures in neonatal hypoxic-ischaemic encephalopathy

Treatment of subclinical seizures in newborn HIE remains a contentious issue, especially in light of potential adverse effects of aggressive use of anticonvulsants. We report on the association of subclinical seizures with changes in cerebral oxygenation in an infant with HIE. Our results show that subclinical seizures of longer durations and with associated autonomic disturbance (increased blood pressure) are more likely to be associated with fluctuation in cerebral oxygenation, with some seizures resulting in cerebral hypoxia. Future studies should aim to delineate the effects of subclinical seizure and anticonvulsant treatment on cerebral oxygenation, and their relationships to developmental outcome. Level of cerebral oxygenation may play a role in refining anti-convulsant treatment and management of subclinical seizures in newborns.