Consequences of neonatal seizures in the rat: morphological and behavioral effects

Epilepsy Incidence and Developmental Outcomes After Early Discontinuation of Antiseizure Medication in Neonatal Hypoxic-Ischemic Encephalopathy

BACKGROUND

Neonatal seizures caused by hypoxic-ischemic encephalopathy (HIE) have significant morbidity and mortality. There is variability in clinical practice regarding treatment duration with antiseizure medication (ASM) after resolution of provoked neonatal seizures. We examined epilepsy incidence and developmental outcomes in post-HIE neonates discharged or not on ASM.

METHODS

We conducted a retrospective chart review of all HIE-admitted neonates to the University of Iowa Hospitals & Clinics neonatal intensive care unit between January 2008 and February 2021 who presented with encephalopathy, underwent therapeutic hypothermia, and developed seizures. Neonates were divided into two groups depending on whether ASM was continued or discontinued on discharge. We evaluated the incidence of epilepsy and developmental outcomes on follow-up in these two cohorts up to 12 months.

RESULTS

Sixty-nine neonates met the study criteria. ASM was continued on discharge in 41 neonates (59%) and discontinued before discharge in 28 (41%). At the 12-month follow-up, nine neonates (13%) had a diagnosis of epilepsy, out of which seven neonates had ASM continued on discharge (odds ratio [OR]: 2.84; 95% confidence interval [CI]: 0.48, 29.9)]. There was no statistical difference between the development of postneonatal epilepsy between the two groups (P value 0.29). There was no significant difference in developmental outcome between the two groups after adjusting for covariates like magnetic resonance imaging (MRI) brain abnormality and number of seizure days (OR: 0.68; 95% CI: 0.21, 2.22; P = 0.52).

CONCLUSION

We found no significant risk of seizure recurrence by age 12 months in infants who had discontinued ASM before discharge compared with those who had continued ASM. There was no difference in developmental outcomes at the 12-month follow-up between groups after adjusting for brain MRI abnormality and the number of seizure days during admission. Our results support early discontinuation of ASM after resolution of acute provoked seizures in neonates with HIE.

Maternal hyperhomocysteinemia increases seizures susceptibility of neonatal rats

AIMS

Neonatal seizures are severe pathologies which may result in long-term neurological consequences. High plasma concentrations of homocysteine - hyperhomocysteinemia (hHCy) - are associated with epilepsy. In the present study, we evaluated susceptibility to seizure of neonatal rats with prenatal hHCy.

MAIN METHODS

Prenatal hHCy was induced by feeding females with a high-methionine diet. Experiments were performed on pups during the first three postnatal weeks. Flurothyl-induced epileptic behavior was assessed according to Racine's scale. Epileptiform activity in the hippocampus was recorded using electrophysiological methods. The balance of excitation/inhibition, functional GABAergic inhibition and GABA reversal potential in hippocampal neurons were analyzed.

KEY FINDINGS

Rats with hHCy developed more severe stages of behavioral patterns during flurothyl-induced epilepsy with shorter latency. Electrophysiological recordings demonstrated higher background neuronal activity in rats with hHCy. Seizure-like events triggered by flurothyl (in vivo) or 4-aminopyridine (in vitro) showed shorter latency, higher power and amplitude. An increased glutamate/GABA synaptic ratio was shown in the pyramidal neurons of rats with hHCy and more slices demonstrated excitation by isoguvacine, a selective GABA(A) receptor agonist, during the first and second postnatal weeks. The GABA driving force and the reversal potential of GABA(A) currents were more positive during the second postnatal week for hHCy rats.

SIGNIFICANCE

The higher susceptibility to seizures in rats with prenatal hHCy due to a shift in the balance of excitation/inhibition toward excitation may underlie the clinical evidence about the association of hHCy with an increased risk of epilepsy.

An Introduction to Minimally Invasive Pediatric Epilepsy Surgery

The field of minimally invasive surgery has evolved over the past 50 years, including neurosurgery, with an evolution to “minimally invasive neurosurgery” when feasible. Epilepsy surgery has followed this trend, with a transition from standard neurosurgical techniques to minimally invasive techniques in all phases of neurosurgical involvement. These include the diagnostic intracranial electroencephalogram with a subdural exploration to stereoelectroencephalography, the actual resection from an open craniotomy to a less destructive technique, or the multiple modalities of neuromodulation instead of a destructive surgery.

The influence of these minimally invasive techniques has resulted in a change in the overall philosophy of pediatric epilepsy surgery. The expectations of what is considered “successful” epilepsy surgery has changed from total seizure control, in other words, a “cure,” to palliative epilepsy surgery with a decrease in the targeted seizures, especially “disabling seizures.” This has led to an overall greater acceptance of epilepsy surgery. This article summarizes the major reasons behind the explosion of minimally invasive pediatric epilepsy surgery, which are amplified in the subsequent articles. Some of this chapter includes the authors' opinions.

Epilepsy Characteristics in Neurodevelopmental Disorders: Research from Patient Cohorts and Animal Models Focusing on Autism Spectrum Disorder

Epilepsy, a heterogeneous group of brain-related diseases, has continued to significantly burden society and families. Epilepsy comorbid with neurodevelopmental disorders (NDDs) is believed to occur due to multifaceted pathophysiological mechanisms involving disruptions in the excitation and inhibition (E/I) balance impeding widespread functional neuronal circuitry. Although the field has received much attention from the scientific community recently, the research has not yet translated into actionable therapeutics to completely cure epilepsy, particularly those comorbid with NDDs. In this review, we sought to elucidate the basic causes underlying epilepsy as well as those contributing to the association of epilepsy with NDDs. Comprehensive emphasis is put on some key neurodevelopmental genes implicated in epilepsy, such as MeCP2, SYNGAP1, FMR1, SHANK1-3 and TSC1, along with a few others, and the main electrophysiological and behavioral deficits are highlighted. For these genes, the progress made in developing appropriate and valid rodent models to accelerate basic research is also detailed. Further, we discuss the recent development in the therapeutic management of epilepsy and provide a briefing on the challenges and caveats in identifying and testing species-specific epilepsy models.

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.

Early Life Events and Maturation of the Dentate Gyrus: Implications for Neurons and Glial Cells

The dentate gyrus (DG), an important part of the hippocampus, plays a significant role in learning, memory, and emotional behavior. Factors potentially influencing normal development of neurons and glial cells in the DG during its maturation can exert long-lasting effects on brain functions. Early life stress may modify maturation of the DG and induce lifelong alterations in its structure and functioning, underlying brain pathologies in adults. In this paper, maturation of neurons and glial cells (microglia and astrocytes) and the effects of early life events on maturation processes in the DG have been comprehensively reviewed. Early postnatal interventions affecting the DG eventually result in an altered number of granule neurons in the DG, ectopic location of neurons and changes in adult neurogenesis. Adverse events in early life provoke proinflammatory changes in hippocampal glia at cellular and molecular levels immediately after stress exposure. Later, the cellular changes may disappear, though alterations in gene expression pattern persist. Additional stressful events later in life contribute to manifestation of glial changes and behavioral deficits. Alterations in the maturation of neuronal and glial cells induced by early life stress are interdependent and influence the development of neural nets, thus predisposing the brain to the development of cognitive and psychiatric disorders.

Factors not considered in the study of drug-resistant epilepsy: Psychiatric comorbidities, age and gender

In basic research and clinical practice, the control of seizures has been the most important goal but it should not be the only one. There are factors that remain poorly understood in the study of refractory epilepsy such as the age and gender of patients and the presence of psychiatric comorbidities. It is known that in patients with drug-resistant epilepsy (DRE), the comorbidities contribute to the deterioration of the quality of life, increase the severity, and worsen the prognosis of epilepsy. Some studies have demonstrated that patients diagnosed with a co-occurrence of epilepsy and psychiatric disorders are more likely to present refractory seizures and the probability of seizure remission after pharmacotherapy is reduced. The evidence of this association suggests the presence of shared pathogenic mechanisms that may include endocrine disorders, neuroinflammatory processes, disturbances of neurotransmitters and mechanisms triggered by stress. Additionally, significant demographic, clinical and electrographic differences have been observed between women and men with epilepsy. Epilepsy affects the female gender in a greater proportion, although there are no studies that report whether refractoriness affects more females. The reasons behind these sex differences are unclear; however, it is likely that sex hormones and sex brain differences related to chromosomal genes play an important role. On the other hand, it has been shown in industrialized countries that prevalence of DRE is higher in the elderly when compared to youngsters. Conversely, this phenomenon is not observed in developing regions, where more cases are found in children and young adults. The correct identification and management of these factors is crucial in order to improve the quality of life of the patients.

Novel Concepts for the Role of Chloride Cotransporters in Refractory Seizures

Epilepsy is associated with a multitude of acquired or genetic neurological disorders characterized by a predisposition to spontaneous recurrent seizures. An estimated 15 million patients worldwide have ongoing seizures despite optimal management and are classified as having refractory epilepsy. Early-life seizures like those caused by perinatal hypoxic ischemic encephalopathy (HIE) remain a clinical challenge because although transient, they are difficult to treat and associated with poor neurological outcomes. Pediatric epilepsy syndromes are consistently associated with intellectual disability and neurocognitive comorbidities. HIE and arterial ischemic stroke are the most common causes of seizures in term neonates and account for 7.5-20% of neonatal seizures. Standard first-line treatments such as phenobarbital (PB) and phenytoin fail to curb seizures in ~50% of neonates. In the long-term, HIE can result in hippocampal sclerosis and temporal lobe epilepsy (TLE), which is the most common adult epilepsy, ~30% of which is associated with refractory seizures. For patients with refractory TLE seizures, a viable option is the surgical resection of the epileptic foci. Novel insights gained from investigating the developmental role of Cl- cotransporter function have helped to elucidate some of the mechanisms underlying the emergence of refractory seizures in both HIE and TLE. KCC2 as the chief Cl- extruder in neurons is critical for enabling strong hyperpolarizing synaptic inhibition in the brain and has been implicated in the pathophysiology underlying both conditions. More recently, KCC2 function has become a novel therapeutic target to combat refractory seizures.

Fenofibrate protects the neurovascular unit and ameliorates plasma corticosterone levels in pentylenetetrazole-induced kindling seizure in mice

Epileptic seizures are the most common neurological diseases that change the function of neurovascular unit at molecular levels accompanied by activation of a wide variety of neurodegenerative cascades. Based on the pleiotropic functions of peroxisome proliferator-activated receptor-alpha (PPARα), the current study evaluated the neuroprotective effects of fenofibrate (an effective PPARα agonist) on the brain injuries induced by pentylenetetrazole (PTZ)-induced kindling seizure. Adult male NMRI mice were randomly assigned into four groups (n = 14) as follows; control, untreated kindled mice (PTZ) and two fenofibrate-treated kindled groups. Repeated intraperitoneal injections of PTZ (45 mg/kg) were used to develop kindling seizure every 48 h for 21 days. Treated mice were administered orally fenofibrate at doses of 30 and 50 mg/kg/day during the study. Plasma corticosterone and brain levels of brain-derived neurotrophic factor (BDNF), malondialdehyde (MDA) and mRNA transcription of p53, as well as blood-brain barrier (BBB) permeability, were determined at termination of the study. Fenofibrate considerably improved seizure latency and anxiety-like behaviors in treated kindled mice. Fenofibrate at doses of 30 and 50 mg/kg significantly (P < 0.001) decreased plasma corticosterone (56.88 ± 0.80 and 54.81 ± 0.29 ng/mL, respectively) compared to PTZ group (74.96 ± 1.60 ng/mL). It also significantly (P < 0.05) decreased BDNF levels in both treatment groups (8.13 ± 0.14 and 8.74 ± 0.09 ng/mL, respectively) compared to PTZ group (9.68 ± 0.20 ng/mL). Fenofibrate particularly at higher dose significantly (P < 0.01) decreased MDA content and mRNA expression levels of p53 in treated kindled mice by 67% and 28%, respectively, compared to PTZ group. Similarly, 50 mg/kg fenofibrate significantly (P < 0.05) decreased Evans blue extravasation into brain in treated kindled mice (8.72 ± 0.96 µg/g) compared to PTZ group (15.31 ± 2.18 µg/g). Our results revealed the anticonvulsive and neuroprotective effects of fenofibrate in PTZ-induced kindling seizure in mice. Fenofibrate also improved the neurovascular functions at molecular levels in kindling seizure that might be associated with ameliorating the seizure behaviors.

Acute symptomatic neonatal seizures, brain injury, and long-term outcome: The role of neuroprotective strategies

INTRODUCTION

Neonatal seizures are frequent but underdiagnosed manifestations of acute brain dysfunction and an important contributor to unfavorable outcomes. Etiology and severity of brain injury are the single strongest outcome determinants.

AREAS COVERED

The authors will discuss the prognostic role of acute symptomatic seizures versus brain injury and the main neuroprotective and neurorestorative strategies for full-term and preterm infants.

EXPERT OPINION

Prolonged acute symptomatic seizures likely contribute to long-term outcomes by independently adding further brain injury to initial insults. Correct timing and dosing of therapeutic interventions, depending on etiology and gestational ages, need careful evaluation. Although promising strategies are under study, the only standard of care is whole-body therapeutic hypothermia in full-term newborns with hypoxic-ischemic encephalopathy.

Hippocampal Neural Stem Cell Grafting after Status Epilepticus Alleviates Chronic Epilepsy and Abnormal Plasticity, and Maintains Better Memory and Mood Function

Hippocampal damage after status epilepticus (SE) leads to multiple epileptogenic changes, which lead to chronic temporal lobe epilepsy (TLE). Morbidities such as spontaneous recurrent seizures (SRS) and memory and mood impairments are seen in a significant fraction of SE survivors despite the administration of antiepileptic drugs after SE. We examined the efficacy of bilateral intra-hippocampal grafting of neural stem/progenitor cells (NSCs) derived from the embryonic day 19 rat hippocampi, six days after SE for restraining SE-induced SRS, memory, and mood impairments in the chronic phase. Grafting of NSCs curtailed the progression of SRS at 3-5 months post-SE and reduced the frequency and severity of SRS activity when examined at eight months post-SE. Reduced SRS activity was also associated with improved memory function. Graft-derived cells migrated into different hippocampal cell layers, differentiated into GABA-ergic interneurons, astrocytes, and oligodendrocytes. Significant percentages of graft-derived cells also expressed beneficial neurotrophic factors such as the fibroblast growth factor-2, brain-derived neurotrophic factor, insulin-like growth factor-1 and glial cell line-derived neurotrophic factor. NSC grafting protected neuropeptide Y- and parvalbumin-positive host interneurons, diminished the abnormal migration of newly born neurons, and rescued the reelin+ interneurons in the dentate gyrus. Besides, grafting led to the maintenance of a higher level of normal neurogenesis in the chronic phase after SE and diminished aberrant mossy fiber sprouting in the dentate gyrus. Thus, intrahippocampal grafting of hippocampal NSCs shortly after SE considerably curbed the progression of epileptogenic processes and SRS, which eventually resulted in less severe chronic epilepsy devoid of significant cognitive and mood impairments.

Linking acute symptomatic neonatal seizures, brain injury and outcome in preterm infants

Neonatal seizures (NS) are the most frequent sign of neurological dysfunction in newborn infants. With increased survival of preterm neonates, the current clinical focus has shifted from preventing death to improving long-term neurological outcome. In the context of acute symptomatic NS, the main negative prognostic factors include etiology, and severity of brain injury, but also prolonged seizures and especially status epilepticus. However, the reasons for the detrimental contribution of seizures to outcome are still unclear, and evidence has been collected both in favor of seizures being an epiphenomenon of brain injury and of independently contributing to further damage. In this narrative focused review, we will discuss both hypotheses, with special emphasis on data relating to preterm infants. We will also identify present controversies and possible future lines of research.

The Transient Receptor Potential Melastatin 7 (TRPM7) Inhibitors Suppress Seizure-Induced Neuron Death by Inhibiting Zinc Neurotoxicity

Transient receptor potential melastatin 7 (TRPM7) is an ion channel that mediates monovalent cations out of cells, as well as the entry of divalent cations, such as zinc, magnesium, and calcium, into the cell. It has been reported that inhibitors of TRPM7 are neuroprotective in various neurological diseases. Previous studies in our lab suggested that seizure-induced neuronal death may be caused by the excessive release of vesicular zinc and the subsequent accumulation of zinc in the neurons. However, no studies have evaluated the effects of carvacrol and 2-aminoethoxydiphenyl borate (2-APB), both inhibitors of TRPM7, on the accumulation of intracellular zinc in dying neurons following seizure. Here, we investigated the therapeutic efficacy of carvacrol and 2-APB against pilocarpine-induced seizure. Carvacrol (50 mg/kg) was injected once per day for 3 or 7 days after seizure. 2-APB (2 mg/kg) was also injected once per day for 3 days after seizure. We found that inhibitors of TRPM7 reduced seizure-induced TRPM7 overexpression, intracellular zinc accumulation, and reactive oxygen species production. Moreover, there was a suppression of oxidative stress, glial activation, and the blood–brain barrier breakdown. In addition, inhibitors of TRPM7 remarkably decreased apoptotic neuron death following seizure. Taken together, the present study demonstrates that TRPM7-mediated zinc translocation is involved in neuron death after seizure. The present study suggests that inhibitors of TRPM7 may have high therapeutic potential to reduce seizure-induced neuron death.

Increased Seizure Susceptibility for Rats Subject to Early Life Hypoxia Might Be Associated with Brain Dysfunction of NRG1-ErbB4 Signaling in Parvalbumin Interneurons

Neuregulin 1 (NRG1)-induced activation of ErbB4 in parvalbumin (PV) inhibitory interneurons is reported to serve as a critical endogenous negative-feedback mechanism to repress brain epileptogenesis. Here, we investigated the seizure susceptibility and the role of NRG1-ErbB4 signaling in PV interneurons in the suppression of epileptic seizures for rats subject to early life hypoxia. Neonatal postnatal day 5 (P5) rats were exposed to intermittent hypoxia (IH) or control (CON) room air for 10 days. In the prefrontal cortex (PFC) of P54 rats, we determined the impact of neonatal IH exposures on the expression of PV, NRG1, ErbB4, and phosphorylated ErbB4 (p-ErbB4) during the seizure induction. Seizure susceptibility tests with the common convulsant agent pentylenetetrazole (PEN) at P54 revealed that rats subject to neonatal hypoxia exposure developed faster and more serious epileptic seizures. Neonatal IH exposures (1) decreased the number of PV cells in the PFC of P54 rats; (2) interrupted the expression of NRG1 gene; and (3) altered the activity of NRG1 on PV interneurons in the PFC after the seizure induction. Intracerebroventricular delivery of exogenous NRG1 before seizure induction by PEN significantly reduced the seizure susceptibility for neonatal IH-exposed rats. The ErbB4 inhibitor AG1478 inhibited the exogenous NRG1's effects on seizure susceptibility. Environmental enrichment (EE) rescued the abovementioned pathophysiological alterations and significantly attenuated the epileptic seizures after the seizure induction for neonatal IH-exposed rats. Our study indicated early life hypoxia exposure might increase the seizure susceptibility for rats and contribute to pathophysiological dysfunction of NRG1-ErbB4 signaling in PV interneurons in the suppression of epileptic seizures. EE might attenuate the increased seizure susceptibility for neonatal IH-exposed rats through rescuing pathophysiological alterations of NRG1-ErbB4 signaling in PV interneurons.

Early Chronic Carbamazepine-in-Food Administration to MAM/Pilocarpine Rats Does Not Affect Convulsive Motor Seizures

Antiepileptic drug-resistance is a major health problem in patients with cortical dysplasia (CD). Whether drug-resistant epilepsy is associated with progressive brain damage is still debated. We previously generated a rat model of acquired CD, the methylazoxymethanol-pilocarpine (MP) rat, in which the occurrence of status epilepticus and subsequent spontaneous seizures induce progressive brain damage (Nobili et al., 2015). The present study tested the outcome of early-chronic carbamazepine (CBZ) administration on both seizure activity and brain damage in MP rats. We took advantage of the non-invasive CBZ-in-food administration protocol, established by Ali (2012), which proved effective in suppressing generalized convulsive seizures in kainic acid rat model of epilepsy. MP rats were treated immediately after the onset of the first spontaneous seizure with 300 mg/kg/day CBZ formulated in pellets for a two-months-trial. CBZ-treated rats were continuously video-monitored to detect seizure activity and were compared with untreated epileptic MP rats. Despite CBZ serum levels in treated rats were within the suggested therapeutic range for humans, CBZ affected spontaneous convulsive seizures in 2 out of 10 treated rats (responders), whereas the remaining animals (non-responders) did not show any difference when compared to untreated MP rats. Histological analysis revealed cortical thinning paralleled by robust staining of Fluoro-Jade⁺ (FJ⁺) degenerating neurons and diffuse tissue necrosis in CBZ-non-responder vs CBZ-responder rats. Data reported here suggest that MP rat model represents suitable experimental setting where to investigate mechanisms of CD-related drug-resistant epilepsy and to verify if modulation of seizures, with appropriate treatment, may reduce seizure-induced brain damage.

Reigning in Excitatory Signaling in CDKL5 Deficiency

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High seizure load during sensitive periods of development leads to broad shifts in ultrasonic vocalization behavior in neonatal male and female C57BL/6J mice

There is increasing evidence that seizures during early development can impact ultrasonic vocalizations (USVs) emitted from neonatal mice. However, most of the effects of early-life seizures have been reported using chemoconvulsants that produce continuous seizures (status epilepticus). In the present study, we evaluated the impact of different seizure frequency loads during early-life vocalization development in C57BL/6J male and female mice. For the high seizure load (HSL) paradigm, we administered 3 flurothyl seizures to mice on postnatal day (PD) 7 through PD11, and recorded USVs on PD12. We found that the induction of seizures across PD7-11 resulted in increased average duration (P < 0.05) and cumulative duration (P < 0.05) of USVs across both sexes. Call-type analyses indicated several call-type changes, including reduced production of complex call-types from males' HSL condition. For the low seizure load (LSL) paradigm, we induced 3 flurothyl seizures only on PD10 and recorded USVs on PD12. We found no change in any spectral or temporal features of USVs. However, call-type production analyses indicated that both male and female animals from the LSL paradigm also produced changes in call-types. This study provides evidence that the magnitude of communication impairment following seizures is significantly impacted by seizure frequency load early in development.

How Early Can a Seizure Happen? Pathophysiological Considerations of Extremely Premature Infant Brain Development

Seizures in neonates represent a neurologic emergency requiring prompt recognition, determination of etiology, and treatment. Yet, the definition and identification of neonatal seizures remain challenging and controversial, in part due to the unique physiology of brain development at this life stage. These issues are compounded when considering seizures in premature infants, in whom the complexities of brain development may engender different clinical and electrographic seizure features at different points in neuronal maturation. In extremely premature infants (< 28 weeks gestational age), seizure pathophysiology has not been explored in detail. This review discusses the physiological and structural development of the brain in this developmental window, focusing on factors that may lead to seizures and their consequences at this early time point. We hypothesize that the clinical and electrographic phenomenology of seizures in extremely preterm infants reflects the specific pathophysiology of brain development in that age window.

Outcome in preterm infants with seizures

Most neonatal seizures in preterm newborns are of acute symptomatic origin with a prevalence higher than in full-term infants. To date, recommendations for management of seizures in preterm newborns are scarce and do not differ from those in full-term newborns. Mortality in preterm newborns with seizures has significantly declined over the last decades, from figures of 84%-94% in the 1970s and 1980s to 22%-45% in the last years. However, mortality is significantly higher in those with a birth weight<1000g and a gestational age<28 weeks. Seizures are a strong predictor of unfavorable outcomes, including not only cerebral palsy, epilepsy, and intellectual disability, but also vision, hearing impairment, and microcephaly. The majority of patients with developmental delay are severely affected and this is usually associated with cerebral palsy. Furthermore, the incidence of epilepsy after neonatal seizures seems to be lower in preterm than in full-term infants but the risk is approximately 40 times greater than in the general population. Clinical studies cannot disentangle the specific and independent contributions of seizure-induced functional changes and the role of etiology and brain damage severity in determining the long-term outcomes in these newborns.

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.

Treatment of early life status epilepticus: What can we learn from animal models?

Treatment of status epilepticus (SE) in infants and children is challenging. There is a recognition that a broad set of developmental processes need to be considered to fully appreciate the physiologic complexity of severe seizures, and seizure outcomes, in infants and children. The development and use of basic models to elucidate important mechanisms will help further our understanding of these processes. Here we review some of the key experimental models and consider several areas relevant to treatment that could lead to productive translational research. Terminating seizures quickly is essential. Understanding pharmacoresistance of SE as it relates to receptor trafficking will be critical to seizure termination. Once a severe seizure is terminated, how will the developing brain respond? Basic studies suggest that there are important acute and long‐term histopathologic, and pathophysiologic, consequences that, if left unaddressed, will produce long‐lasting deficits on the form and function of the central nervous system. To fully utilize the evidence that basic models produce, age‐ and development‐ and model‐specific frameworks have to be considered carefully. Studies have demonstrated that severe seizures can cause perturbations to developmental processes during critical periods of development that lead to life‐long deficits. Unfortunately, some of the drugs that are commonly used to treat seizures may also produce negative outcomes by enhancing Cl^‐‐mediated depolarization, or by accelerating programmed cell death. More research is needed to understand these phenomena and their relevance to the human condition, and to develop rational drugs that protect the developing brain from severe seizures to the fullest extent possible.

Planar coil-based contact-mode magnetic stimulation: synaptic responses in hippocampal slices and thermal considerations

Implantable magnetic stimulation is an emerging type of neuromodulation using coils that are small enough to be implanted in the brain. A major advantage of this method is that stimulation performance could be sustained even though the coil is encapsulated by gliosis due to foreign body reactions. Magnetic fields can induce indirect electric fields and currents in neurons. Compared to transcranial magnetic stimulation, the coil size used in implantable magnetic stimulation can be greatly reduced. However, the size reduction is accompanied by an increase in coil resistance. Hence, the coil could potentially damage neurons from the excess heat generated. Therefore, it is necessary to study the stimulation performance and possible thermal damage by implantable magnetic stimulation. Here, we devised contact-mode magnetic stimulation (CMS), wherein magnetic stimulation was applied to hippocampal slices through a customized planar-type coil underneath the slice in the contact mode. With acute hippocampal slices, we investigated the synaptic responses to examine the field excitatory postsynaptic responses of CMS and the temperature rise during CMS. A long-lasting synaptic depression was exhibited in the CA1 stratum radiatum after CMS, while the temperature remained in a safe range so as not to seriously affect the neural responses.

Regulation of seizure-induced MeCP2 Ser421 phosphorylation in the developing brain

Neonatal seizures disrupt normal synaptic maturation and often lead to later-life epilepsy and cognitive deficits. During early life, the brain exhibits heightened synaptic plasticity, in part due to a developmental overabundance of Ca_V1.2 L-type voltage gated calcium (Ca²⁺) channels (LT-VGCCs) and Ca²⁺-permeable AMPARs (CP-AMPARs) lacking GluA2 subunits. We hypothesized that early-life seizures overactivate these channels, in turn dysregulating Ca²⁺-dependent signaling pathways including that of methyl CPG binding protein 2 (MeCP2), a transcription factor implicated in the autism spectrum disorder (ASD) Rett Syndrome. Here, we show that in vivo hypoxia-induced seizures (HS) in postnatal day (P)10 rats acutely induced phosphorylation of the neuronal-specific target of activity-dependent MeCP2 phosphorylation, S421, as well as its upstream activator CaMKII T286. We next identified mechanisms by which activity-dependent Ca²⁺ influx induced MeCP2 phosphorylation using in vitro cortical and hippocampal neuronal cultures at embryonic day (E)18 + 10 days in vitro (DIV). In contrast to the prevalent role of NMDARs in the adult brain, we found that both CP-AMPARs and LT-VGCCs mediated MeCP2 S421 and CaMKII T286 phosphorylation induced by kainic acid (KA) or high potassium chloride (KCl) stimulation. Furthermore, in vivo post-seizure treatment with the broad-spectrum AMPAR antagonist NBQX, the CP-AMPAR blocker IEM-1460, or the LT-VGCC antagonist nimodipine blocked seizure-induced MeCP2 phosphorylation. Collectively, these results demonstrate that early-life seizures dysregulate critical activity-dependent developmental signaling pathways, in part via CP-AMPAR and LT-VGCC activation, providing novel age-specific therapeutic targets for convergent pathways underlying epilepsy and ASDs.

Predicting seizure by modeling synaptic plasticity based on EEG signals - a case study of inherited epilepsy

This paper explores the internal dynamical mechanisms of epileptic seizures through quantitative modeling based on full brain electroencephalogram (EEG) signals. Our goal is to provide seizure prediction and facilitate treatment for epileptic patients. Motivated by an earlier mathematical model with incorporated synaptic plasticity, we studied the nonlinear dynamics of inherited seizures through a differential equation model. First, driven by a set of clinical inherited electroencephalogram data recorded from a patient with diagnosed Glucose Transporter Deficiency, we developed a dynamic seizure model on a system of ordinary differential equations. The model was reduced in complexity after considering and removing redundancy of each EEG channel. Then we verified that the proposed model produces qualitatively relevant behavior which matches the basic experimental observations of inherited seizure, including synchronization index and frequency. Meanwhile, the rationality of the connectivity structure hypothesis in the modeling process was verified. Further, through varying the threshold condition and excitation strength of synaptic plasticity, we elucidated the effect of synaptic plasticity to our seizure model. Results suggest that synaptic plasticity has great effect on the duration of seizure activities, which support the plausibility of therapeutic interventions for seizure control.

Role of Neuroinflammation in Evolution of Childhood Epilepsy

Until a decade ago, epilepsy research had focused mainly on alterations of neuronal activities and excitability. Such neurocentric emphasis has neglected the role of glia and involvement of inflammation in the pathogenesis of epilepsy. It is becoming clear that immune and inflammatory reactions do occur in the brain despite the brain's lack of conventional lymphatic drainage and graft acceptance and the presence of vascular brain barrier that tightly regulates infiltration of blood monocytes and lymphocytes. The critical roles of brain-resident immune mediators and of brain-infiltrating peripheral leukocytes are increasingly recognized. Inflammatory processes, including activation of microglia and astrocytes and production of proinflammatory cytokines and related molecules, occur in human epilepsy as well as in experimental models of epilepsy. Immune mechanism that underlies evolution of drug-resistant epilepsy and epileptic encephalopathy represents a new target and will aid in development of novel immunotherapeutic drugs and therapies against the key constituents in immune pathways.

Unexpected Effects of Acetylcholine Precursors on Pilocarpine Seizure- Induced Neuronal Death

BACKGROUND

Choline alfoscerate (α-GPC) and Cytidine 5'-diphosphocholine (CDPCholine) are both acetylcholine precursors and are considered to act as pro-cholinergic nootropic agents. Acetylcholine precursors have also recently found frequent use in the neurology clinic. Stroke and many types of dementia have been shown to respond favorably after treatment with these agents, not only in terms of cognitive dysfunction but also behavioral and psychological symptoms. The primary mechanisms of Acetylcholine precursors are the following: 1) Acetylcholine precursors themselves are used in the biosynthesis of acetylcholine and 2) byproducts like glycerophosphate have protective functions for neuronal phospholipids. However, whether acetylcholine precursors have a similar effect in treating cognitive impairment in patients with epilepsy remains controversial.

METHODS

Our previous studies investigating acetylcholine precursors in seizure-experienced animals have produced variable results that were dependent on the timing of administration.

RESULTS

Early administration of CDP-choline immediately after seizure increased neuronal death, blood-brain barrier (BBB) disruption and microglial activation in the hippocampus. However, administration of α-GPC starting 3 weeks after seizure (late administration) improved cognitive function through reduced neuronal death and BBB disruption, and increased neurogenesis in the hippocampus.

CONCLUSION

These seemingly contradictory results may be attributed to both epileptogenic features and neuroprotective functions of several acetylcholine precursors.

Modulation of Neocortical Development by Early Neuronal Activity: Physiology and Pathophysiology

Animal and human studies revealed that patterned neuronal activity is an inherent feature of developing nervous systems. This review summarizes our current knowledge about the mechanisms generating early electrical activity patterns and their impact on structural and functional development of the cerebral cortex. All neocortical areas display distinct spontaneous and sensory-driven neuronal activity patterns already at early phases of development. At embryonic stages, intermittent spontaneous activity is synchronized within small neuronal networks, becoming more complex with further development. This transition is accompanied by a gradual shift from electrical to chemical synaptic transmission, with a particular role of non-synaptic tonic currents before the onset of phasic synaptic activity. In this review article we first describe functional impacts of classical neurotransmitters (GABA, glutamate) and modulatory systems (e.g., acetylcholine, ACh) on early neuronal activities in the neocortex with special emphasis on electrical synapses, nonsynaptic and synaptic currents. Early neuronal activity influences probably all developmental processes and is crucial for the proper formation of neuronal circuits. In the second part of our review, we illustrate how specific activity patterns might interfere with distinct neurodevelopmental processes like proliferation, migration, axonal and dendritic sprouting, synapse formation and neurotransmitter specification. Finally, we present evidence that transient alterations in neuronal activity during restricted perinatal periods can lead to persistent changes in functional connectivity and therefore might underlie the manifestation of neurological and neuropsychiatric diseases.

Sex differences in hippocampal area CA3 pyramidal cells

Numerous studies have demonstrated differences between males and females in hippocampal structure, function, and plasticity. There also are many studies about the different predisposition of a males and females for disorders where the hippocampus plays an important role. Many of these reports focus on area CA1, but other subfields are also very important, and unlikely to be the same as area CA1 based on what is known. Here we review basic studies of male and female structure, function, and plasticity of area CA3 pyramidal cells of adult rats. The data suggest that the CA3 pyramidal cells of males and females are distinct in structure, function, and plasticity. These sex differences cannot be simply explained by the effects of circulating gonadal hormones. This view agrees with previous studies showing that there are substantial sex differences in the brain that cannot be normalized by removing the gonads and depleting peripheral gonadal hormones. Implications of these comparisons for understanding sex differences in hippocampal function and dysfunction are discussed. © 2016 Wiley Periodicals, Inc.

Diverse Effects of an Acetylcholinesterase Inhibitor, Donepezil, on Hippocampal Neuronal Death after Pilocarpine-Induced Seizure

Epileptic seizures are short episodes of abnormal brain electrical activity. Many survivors of severe epilepsy display delayed neuronal death and permanent cognitive impairment. Donepezil is an acetylcholinesterase inhibitor and is an effective treatment agent for Alzheimer’s disease. However, the role of donepezil in seizure-induced hippocampal injury remains untested. Temporal lobe epilepsy (TLE) was induced by intraperitoneal injection of pilocarpine (25 mg/kg). Donepezil (2.5 mg/kg/day) was administered by gavage in three different settings: (1) pretreatment for three days before the seizure; (2) for one week immediately after the seizure; and (3) for three weeks from three weeks after the seizure. We found that donepezil showed mixed effects on seizure-induced brain injury, which were dependent on the treatment schedule. Pretreatment with donepezil aggravated neuronal death, oxidative injury, and microglia activation. Early treatment with donepezil for one week showed neither adverse nor beneficial effects; however, a treatment duration of three weeks starting three weeks after the seizure showed a significant reduction in neuronal death, oxidative injury, and microglia activation. In conclusion, donepezil has therapeutic effects when injected for three weeks after seizure activity subsides. Therefore, the present study suggests that the therapeutic use of donepezil for epilepsy patients requires a well-conceived strategy for administration.

Progressive changes in hippocampal cytoarchitecture in a neurodevelopmental rat model of epilepsy: implications for understanding presymptomatic epileptogenesis, predictive diagnosis, and targeted treatments

Epilepsies affect about 4% of the population and are frequently characterized by a prolonged "silent" period before the onset of spontaneous seizures. Most current animal models of epilepsy either involve acute seizure induction or kindling protocols that induce repetitive seizures. We have developed a rat model of epilepsy that is characterized by a slowly progressing series of behavioral abnormalities prior to the onset of behavioral seizures. In the current study, we further describe an accompanying progression of cytoarchitectural changes in the hippocampal formation. Groups of male and female SD rats received serial injections of a low dose of domoic acid (0.020 mg/kg) (or vehicle) throughout the second week of life. Postmortem hippocampal tissue was obtained on postnatal days 29, 64, and 90 and processed for glial fibrillary acidic protein (GFAP), NeuN, and calbindin expression. The data revealed no significant changes on postnatal day (PND) 29 but a significant increase in hilar NeuN-positive cells in some regions on PND 64 and 90 that were identified as ectopic granule cells. Further, an increase in GFAP positive cell counts and evidence of reactive astrogliosis was found on PND 90 but not at earlier time points. We conclude that changes in cellular expression, possibly due to on-going non-convulsive seizures, develop slowly in this model and may contribute to progressive brain dysfunction that culminates in a seizure-prone phenotype.

The importance of constructive feedback: Implications of top-down regulation in the development of neural circuits

Neural circuits in sensory pathways develop through a general strategy of overproduction of synapses followed by activity-driven pruning to fine-tune connectivity for optimal function. The early visual pathway, consisting of the retina → visual thalamus → primary visual cortex, has served for decades as a powerful model system for probing the mechanisms and logic of this process. In addition to these feedforward projections, the early visual pathway also includes a substantial feedback component in the form of corticothalamic projections from the deepest layer of primary visual cortex. The role of this feedback in visual processing has been studied extensively in mature animals, yet historically, its role in development has received comparatively little attention. Recent technological advances allowing for selective manipulation of neural activity in development led to the uncovering of a role for feedback in guiding the refinement of the forward projection from retina to visual thalamus. Here we discuss the implications of feedback exerting influence on the development of sensory pathways. We propose several possible advantages to constructing neural circuits with top-down regulation, and discuss the potential significance of this finding for certain neurologic disorders.

Early-life status epilepticus induces long-term deficits in anxiety and spatial learning in mice

Background

One of the most devastating aspects of developmental epilepsy is the long-term impact on behavior. Children with epilepsy show a high co-morbidity with anxiety disorders and autism.

Methods

To examine whether early-life status epilepticus results in altered anxiety, repetitive behavior, social behavior, and learning and memory, we induced status epilepticus in male C57BL/6 mice on postnatal day (PD) 10. The mice received intraperitoneal injections of either kainic acid (2mg/kg) or 0.9% normal saline. We also included a nontreated control group. Kainic acid induced status epilepticus for approximately 1.5 hrs. At PD60, the adult mice were then tested in a battery of behavioral tasks, including open field activity, elevated-plus maze, light-dark test, marble burying, social chamber, social partition, conditioned fear, novel object recognition, and Morris water maze.

Results

The early-life seizure group showed consistent increases in anxiety in the open field test (p < 0.05), elevated plus maze (p < 0.05), and light-dark task (p < 0.01). The seizure group showed significant (p < 0.01) impairment in the Morris water maze. There were no differences observed in marble burying, social partition, social chamber, novel object recognition, or delay fear conditioning tasks.

Conclusions

These results demonstrate that a single insult of status epilepticus during the neonatal period is sufficient to cause specific, long-term impairments in anxiety and spatial learning.

Why Are Children With Epileptic Encephalopathies Encephalopathic?

The epileptic encephalopathies are devastating conditions characterized by frequent seizures, severely abnormal electroencephalograms (EEGs), and cognitive slowing or regression. The cognitive impairment in the epileptic encephalopathies may be more concerning to the patient and parents than the epilepsy itself. There is increasing recognition that the cognitive comorbidity can be both chronic, primarily due to the underlying etiology of the epilepsy, and dynamic or evolving because of recurrent seizures, interictal spikes, and antiepileptic drugs. Much of scholars' understanding of the neurophysiological underpinnings of cognitive dysfunction in the epileptic encephalopathies comes from rodent studies. Frequent seizures and interictal EEG discharges in rats lead to considerable spatial and social-cognitive deficits. Paralleling these cognitive deficits are dyscoordination of dynamic neural activity within and between the neural networks that subserve normal cognitive processes.

Neurodevelopmental alterations and seizures developed by mouse model of infantile hypophosphatasia are associated with purinergic signalling deregulation

Hypomorphic mutations in the gene encoding the tissue-nonspecific alkaline phosphatase (TNAP) enzyme, ALPL in human or Akp2 in mice, cause hypophosphatasia (HPP), an inherited metabolic bone disease also characterized by spontaneous seizures. Initially, these seizures were attributed to the impairment of GABAergic neurotransmission caused by altered vitamin B6 (vit-B6) metabolism. However, clinical cases in human newborns and adults whose convulsions are refractory to pro-GABAergic drugs but controlled by the vit-B6 administration, suggest that other factors are involved. Here, to evaluate whether neurodevelopmental alterations are underlying the seizures associated to HPP, we performed morphological and functional characterization of postnatal homozygous TNAP null mice, a model of HPP. These analyses revealed that TNAP deficient mice present an increased proliferation of neural precursors, an altered neuronal morphology, and an augmented neuronal activity. We found that these alterations were associated with a partial downregulation of the purinergic P2X7 receptor (P2X7R). Even though deficient P2X7R mice present similar neurodevelopmental alterations, they do not develop neonatal seizures. Accordingly, we found that the additional blockage of P2X7R prevent convulsions and extend the lifespan of mice lacking TNAP. In agreement with these findings, we also found that exogenous administration of ATP or TNAP antagonists induced seizures in adult wild-type mice by activating P2X7R. Finally, our results also indicate that the anticonvulsive effects attributed to vit-B6 may be due to its capacity to block P2X7R. Altogether, these findings suggest that the purinergic signalling regulates the neurodevelopmental alteration and the neonatal seizures associated to HPP.

Spatial cognition following early-life seizures in rats: Performance deficits are dependent on task demands

Cognitive impairment is a common comorbidity in childhood epilepsy. Studies in rodents have demonstrated that frequent seizures during the first weeks of life result in impaired spatial cognition when the rats are tested as juvenile or adults. To determine if spatial cognitive deficits following early-life seizures are task-specific or similar across spatial tasks, we compared the effects of early-life seizures in two spatial assays: 1) the Morris water maze, a hippocampal-dependent task of spatial cognition and 2) the active avoidance task, a task that associates an aversive shock stimulus with a static spatial location that requires intact hippocampal-amygdala networks. Rats with early-life seizures tested as adults did not differ from control rats in the water maze. However, while animals with early-life seizures showed some evidence of learning the active avoidance task, they received significantly more shocks in later training trials, particularly during the second training day, than controls. One possibility for the performance differences between the tasks is that the active avoidance task requires multiple brain regions and that interregional communication could be affected by alterations in white matter integrity. However, there were no measurable group differences with regard to levels of myelination. The study suggests that elucidation of mild cognitive deficits seen following early-life seizures may be dependent on task features of active avoidance.

What is more harmful, seizures or epileptic EEG abnormalities? Is there any clinical data?

Cognitive impairment is a common and often devastating co-morbidity of childhood epilepsy. While the aetiology of the epilepsy is a critical determinant of cognitive outcome, there is considerable evidence from both rodent and human studies that indicate that seizures and interictal epileptiform abnormalities can contribute to cognitive impairment. A critical feature of childhood epilepsy is that the seizures and epileptiform activity occur in a brain with developing, plastic neuronal circuits. The consequences of seizures and interictal epileptiform activity in the developing brain differ from similar paroxysmal events occurring in the relatively fixed circuitry of the mature brain. In animals, it is possible to study interictal spikes independently from seizures, and it has been demonstrated that interictal spikes are as detrimental as seizures during brain development. In the clinic, distinguishing the differences between interictal spikes and seizures is more difficult, since both typically occur together. However, both seizures and interictal spikes result in transient cognitive impairment. Recurrent seizures, particularly when frequent, can lead to cognitive regression. While the clinical data linking interictal spikes to persistent cognitive impairment is limited, interictal spikes occurring during the formation and stabilization of neuronal circuits likely contribute to aberrant connectivity. There is insufficient clinical literature to indicate whether interictal spikes are more detrimental than seizures during brain development.

Effect of Seizures on the Developing Brain and Cognition

Epilepsy is a complex disorder, which involves much more than seizures, encompassing a range of associated comorbid health conditions that can have significant health and quality-of-life implications. Of these comorbidities, cognitive impairment is one of the most common and distressing aspects of epilepsy. Clinical studies have demonstrated that refractory seizures, resistant to antiepileptic drugs, and occurring early in life have significant adverse effects on cognitive function. Much of what has been learned about the neurobiological underpinnings of cognitive impairment following early-life seizures has come from animal models. Although early-life seizures in rodents do not result in cell loss, seizures cause in changes in neurogenesis and synaptogenesis and alteration of excitatory or inhibitory balance, network connectivity and temporal coding. These morphological and physiological changes are accompanied by parallel impairment in cognitive skills. This increased understanding of the pathophysiological basis of seizure-induced cognitive deficits should allow investigators to develop novel targets for therapeutic interventions.

Anticonvulsant drug-induced cell death in the developing white matter of the rodent brain

OBJECTIVE

During critical periods of brain development, both seizures and anticonvulsant medications can affect neurodevelopmental outcomes. In rodent models, many anticonvulsants trigger neuronal apoptosis. However, white matter apoptosis (WMA) has not been examined after anticonvulsant drug treatment. Herein, we sought to determine if anticonvulsant drugs induced apoptosis in the developing white matter (WM) in a rodent model.

METHODS

Postnatal day (P)7 rats were treated with phenobarbital (PB-75), MK-801 (dizocilpine, 0.5), lamotrigine (LTG-20), carbamazepine (CBZ-100), phenytoin (PHT-50), levetiracetam (LEV-250), or saline; all doses are mg/kg. Brain tissue collected 24 h after treatment was stained using the terminal deoxynucleotidyl transferase dUTP nick end labeling method. The number of degenerating cells within WM, that is, anterior commissure (AC), corpus callosum, cingulum, and hippocampus-associated WM tracts, was quantified.

RESULTS

Saline-treated rats showed low baseline level of apoptosis in developing WM on P8 in all the areas examined. PB, PHT, and MK-801 significantly increased apoptosis in all four brain areas examined. Exposure to CBZ, LTG, or LEV failed to increase apoptosis in all regions.

SIGNIFICANCE

Commonly used anticonvulsants (PB, PHT) cause apoptosis in the developing WM in a rat model; the N-methyl-d-aspartate (NMDA) receptor antagonist MK-801 has a similar effect. These results are consistent with reports of anesthesia-induced WMA during brain development. Consistent with the lack of neuronal apoptosis caused by LTG, LEV, and CBZ, these drugs did not cause WMA. Many infants treated with anticonvulsant drugs have underlying neurologic injury, including WM damage (e.g., following intraventricular hemorrhage [IVH] or hypoxic-ischemic encephalopathy [HIE]). The degree to which anticonvulsant drug treatment will alter outcomes in the presence of underlying injury remains to be examined, but avoiding drugs (when possible) that induce WMA may be beneficial.

Neonatal seizures in preterm newborns: A predictive model for outcome

BACKGROUND

With a reported prevalence of 22.2%, seizures in preterm newborns represent an emergent challenge, because they are often related to adverse outcome. The electroclinical features of preterm infants with neonatal seizures were evaluated in order to predict outcome.

METHODS

From 154 newborns with video-EEG confirmed neonatal seizures admitted to Parma University Hospital between January 1999 and December 2012, we collected 76 preterm newborns with neonatal seizures. Outcome was assessed at least at one year. Student t-test for unpaired data was used to compare means of continuous variables. We applied the χ(2) test to compare nominal data between preterm newborns with favorable versus adverse outcome, and between those with seizures versus those with status epilepticus. Then we determined the independent risk factors for adverse outcome with multivariate logistic regression analysis.

RESULTS

Birth weight, Apgar at 1st minute, neurologic examination, EEG, US brain scans and the presence of neonatal status epilepticus were different between preterm newborns with favorable and adverse outcome (p ≤ .049). Furthermore, birth weight, seizure onset, neurologic examination and EEG were different between the group with or without status (p ≤ .031). None of the infants with status epilepticus had a favorable outcome compared to 22.3% of those with neonatal seizures (p = .004). We also identified a predictive model that correctly classified outcome in 85.5% of subjects, with a high sensitivity for adverse outcome (>91.5%).

CONCLUSION

The presence of neonatal seizures in preterm newborns is highly related to an adverse outcome that can be predicted since the first days of life.

The Ever-Changing Morphology of Hippocampal Granule Neurons in Physiology and Pathology

Newborn neurons are continuously added to the hippocampal dentate gyrus throughout adulthood. In this review, we analyze the maturational stages that newborn granule neurons go through, with a focus on their unique morphological features during each stage under both physiological and pathological circumstances. In addition, the influence of deleterious (such as schizophrenia, stress, Alzheimer's disease, seizures, stroke, inflammation, dietary deficiencies, or the consumption of drugs of abuse or toxic substances) and neuroprotective (physical exercise and environmental enrichment) stimuli on the maturation of these cells will be examined. Finally, the regulation of this process by proteins involved in neurodegenerative and neurological disorders such as Glycogen synthase kinase 3β, Disrupted in Schizophrenia 1 (DISC-1), Glucocorticoid receptor, pro-inflammatory mediators, Presenilin-1, Amyloid precursor protein, Cyclin-dependent kinase 5 (CDK5), among others, will be evaluated. Given the recently acquired relevance of the dendritic branch as a functional synaptic unit required for memory storage, a full understanding of the morphological alterations observed in newborn neurons may have important consequences for the prevention and treatment of the cognitive and affective alterations that evolve in conjunction with impaired adult hippocampal neurogenesis.

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.

Widespread neuronal injury in a model of cholinergic status epilepticus in postnatal day 7 rat pups

OBJECTIVE

Status Epilepticus (SE) is common in neonates and infants, and is associated with neuronal injury and adverse developmental outcomes. However, the role of SE in this injury is uncertain. Until now, we have lacked an animal model in which seizures result in neuronal injury in rodent models at ages below postnatal day 12 (P12) unless seizures are combined with inflammatory stressors.

METHODS

We induced SE with high-dose lithium and pilocarpine in P7 rats, which are developmentally close to human neonates. Several EEG measures and O2 saturation were recorded during the 6h following initiation of SE. We assessed neuronal injury at 6 and 24h post-SE onset using Fluoro-Jade B staining (FJB) and caspase-3a immunoreactivity (IR).

RESULTS

EEGs showed continuous polyspikes activity for 54.3 ± 6.7 min, while O2 saturation showed no significant hypoxemia. By 24h after SE onset, significant neuronal injury was observed in CA1/subiculum, CA3, dentate gyrus, thalamus, neocortex, amygdala, piriform cortex, lateral entorhinal cortex, hypothalamus, caudate putamen, globus pallidus, ventral pallidum, and nucleus accumbens. At 24h post-SE, caspase-3a IR was significantly increased in CA1/subiculum, thalamus, and neocortex compared to sham, and caspase-3a IR neurons had fragmented nuclei, suggesting that SE triggered an irreversible form of cell injury.

SIGNIFICANCE

In conclusion, we have developed a model of cholinergic SE in P7 rat pups, which combines high survival (69.9% survival at 24h) and widespread brain injury. These studies suggest that the immature brain is vulnerable to severe forms of SE.

Subclinical seizures identified by postoperative electroencephalographic monitoring are common after neonatal cardiac surgery

OBJECTIVES

The American Clinical Neurophysiology Society recommends continuous electroencephalographic monitoring after neonatal cardiac surgery because seizures are common, often subclinical, and associated with worse neurocognitive outcomes. We performed a quality improvement project to monitor for postoperative seizures in neonates with congenital heart disease after surgery with cardiopulmonary bypass.

METHODS

We implemented routine continuous electroencephalographic monitoring and reviewed the results for an 18-month period. Clinical data were collected by chart review, and continuous electroencephalographic tracings were interpreted using standardized American Clinical Neurophysiology Society terminology. Electrographic seizures were classified as electroencephalogram-only or electroclinical seizures. Multiple logistic regression was used to assess associations between seizures and potential clinical and electroencephalogram predictors.

RESULTS

A total of 161 of 172 eligible neonates (94%) underwent continuous electroencephalographic monitoring. Electrographic seizures occurred in 13 neonates (8%) beginning at a median of 20 hours after return to the intensive care unit after surgery. Neonates with all types of congenital heart disease had seizures. Seizures were electroencephalogram only in 11 neonates (85%). Status epilepticus occurred in 8 neonates (62%). In separate multivariate models, delayed sternal closure or longer deep hypothermic circulatory arrest duration was associated with an increased risk for seizures. Mortality was higher among neonates with than without seizures (38% vs 3%, P < .001).

CONCLUSIONS

Continuous electroencephalographic monitoring identified seizures in 8% of neonates after cardiac surgery with cardiopulmonary bypass. The majority of seizures had no clinical correlate and would not have been otherwise identified. Seizure occurrence is a marker of greater illness severity and increased mortality. Further study is needed to determine whether seizure identification and management lead to improved outcomes.

Age-dependent changes in intrinsic neuronal excitability in subiculum after status epilepticus

Kainic acid-induced status epilepticus (KA-SE) in mature rats results in the development of spontaneous recurrent seizures and a pattern of cell death resembling hippocampal sclerosis in patients with temporal lobe epilepsy. In contrast, KA-SE in young animals before postnatal day (P) 18 is less likely to cause cell death or epilepsy. To investigate whether changes in neuronal excitability occur in the subiculum after KA-SE, we examined the age-dependent effects of SE on the bursting neurons of subiculum, the major output region of the hippocampus. Patch-clamp recordings were used to monitor bursting in pyramidal neurons in the subiculum of rat hippocampal slices. Neurons were studied either one or 2-3 weeks following injection of KA or saline (control) in immature (P15) or more mature (P30) rats, which differ in their sensitivity to KA as well as the long-term sequelae of the KA-SE. A significantly greater proportion of subicular pyramidal neurons from P15 rats were strong-bursting neurons and showed increased frequency-dependent bursting compared to P30 animals. Frequency-dependent burst firing was enhanced in P30, but not in P15 rats following KA-SE. The enhancement of bursting induced by KA-SE in more mature rats suggests that the frequency-dependent limitation of repetitive burst firing, which normally occurs in the subiculum, is compromised following SE. These changes could facilitate the initiation of spontaneous recurrent seizures or their spread from the hippocampus to other parts of the brain.

Behavioral changes following a single episode of early-life seizures support the latent development of an autistic phenotype

We probed the developmental and behavioral consequences of a single episode of kainic acid-induced early-life seizures (KA-ELS) in the rat on postnatal day 7. Correlates of developmental trajectory were not altered, demonstrating that long-term consequences following KA-ELS are not initiated by secondary causes, such as malnourishment or alterations in maternal care. We report reduced marble burying in adult rats, suggestive of restricted interests, a trait common to experimental and clinical autism. We did not detect increased repetitive grooming during habituated cage behavior. However, we did detect reduced grooming in adult KA-ELS rats in the presence of an unfamiliar rat, supporting altered social anxiety following KA-ELS. Reanalysis of a social approach task further indicated abnormal social interactions. Taken together with previous physiological and behavioral data, these data support the hypothesis that KA-ELS lead to a latent autistic phenotype in adult rats not attributable to other early alterations in development.

Personalized medicine approaches in epilepsy

Epilepsy affects 50 million persons worldwide, a third of whom continue to experience debilitating seizures despite optimum anti-epileptic drug (AED) treatment. Twelve-month remission from seizures is less likely in female patients, individuals aged 11-36 years and those with neurological insults and shorter time between first seizure and starting treatment. It has been found that the presence of multiple seizures prior to diagnosis is a risk factor for pharmacoresistance and is correlated with epilepsy type as well as intrinsic severity. The key role of neuroinflammation in the pathophysiology of resistant epilepsy is becoming clear. Our work in this area suggests that high-mobility group box 1 isoforms may be candidate biomarkers for treatment stratification and novel drug targets in epilepsy. Furthermore, transporter polymorphisms contributing to the intrinsic severity of epilepsy are providing robust neurobiological evidence on an emerging theory of drug resistance, which may also provide new insights into disease stratification. Some of the rare genetic epilepsies enable treatment stratification through testing for the causal mutation, for example SCN1A mutations in patients with Dravet's syndrome. Up to 50% of patients develop adverse reactions to AEDs which in turn affects tolerability and compliance. Immune-mediated hypersensitivity reactions to AED therapy, such as toxic epidermal necrolysis, are the most serious adverse reactions and have been associated with polymorphisms in the human leucocyte antigen (HLA) complex. Pharmacogenetic screening for HLA-B*15:02 in Asian populations can prevent carbamazepine-induced Stevens-Johnson syndrome. We have identified HLA-A*31:01 as a potential risk marker for all phenotypes of carbamazepine-induced hypersensitivity with applicability in European and other populations. In this review, we explore the currently available key stratification approaches to address the therapeutic challenges in epilepsy.