Neonatal seizures and their treatment:

Early life seizures and olfactory communication in rats

OBJECTIVE

Early life seizures (ELS) are commonly associated with autism spectrum disorder (ASD); however, the exact role of ELS in the pathology is unknown. Prior studies have demonstrated social deficits, a core feature of ASD, following ELS; consequently, alterations in sensory modalities may contribute to the overall social deficits. Considering the speculated contribution of sensory deficit to social communication, we examined the developmental consequences of early postnatal kainic acid (KA)-induced seizures on olfactory preference and neural markers in the olfactory bulb in both male and female Sprague Dawley rats.

METHODS

KA-induced seizures or saline was administered. Rats were then exposed to a series of biologically relevant scents including male scent, female scent, nest scent, and phenylethylamine during the juvenile period and again during adulthood. Alterations in sensory modalities were expected to be expressed via abnormal preference for certain scents and/or production of abnormal ultrasonic vocalizations in response to scents. The olfactory bulbs were also assessed for the biologically relevant markers glial fibrillary acidic protein (GFAP) and calcium/calmodulin-dependent protein kinase II (CAMKII).

RESULTS

Our findings resulted in no significant differences in olfactory preference following ELS for juveniles or adults compared to controls. Similarly, there were no differences in GFAP expression or the ratio of phosphorylated CAMKII to CAMKII in either olfactory bulb. Interestingly, despite a lack of treatment differences, different scents were shown to elicit different responses in juvenile rats, yet these differences subsided in adulthood.

SIGNIFICANCE

Overall, the results of this study suggest that olfaction does not contribute to socialization deficit following ELS within the KA model.

Timing of interventions to control neuronal chloride elevation in a model of neonatal seizures after hippocampal injury

OBJECTIVE

Following hypoxic-ischemic (HI) brain injury, neuronal cytoplasmic chloride concentration ([Cl-]i) increases, potentially contributing to depolarizing γ-aminobutyric acid (GABA) responses, onset of seizures, and the failure of antiepileptic drugs that target inhibitory chloride-permeable GABAA receptors. Post-HI seizures characteristically begin hours after injury, by which time substantial accumulation of [Cl-]i may have already occurred. In immature neurons, a major pathway for Cl- influx is the reversible Na+-K+-2Cl- cotransporter NKCC1.

METHODS

Spontaneous neuronal network, neuronal [Cl-]i, and GABA activity were determined in hippocampal preparations from neonatal Clomeleon and SuperClomeleon/DLX-cre mice to test whether blocking NKCC1 earlier after oxygen-glucose deprivation (OGD) injury would more effectively ameliorate the increase in [Cl-]i, ictallike epileptiform discharges (ILDs), and the failure of the GABAergic anticonvulsant phenobarbital.

RESULTS

In vitro, murine intact hippocampi were free of ILDs for 12 h after preparation. Transient OGD resulted in a gradual increase in [Cl-]i, depolarizing action of GABA, and facilitation of neuronal network activity. Spontaneous ILDs began 3-5 h after injury. Blocking NKCC1 with 2-10 μmol·L-1 bumetanide reduced [Cl-]i equally well when applied up to 10 h after injury. Whereas phenobarbital or bumetanide applied separately were less effective when applied later after injury, ILDs were successfully suppressed by the combination of phenobarbital and bumetanide regardless of the number of prior ILDs or delay in application.

SIGNIFICANCE

The present age-specific group studies demonstrate that after OGD, NKCC1 transport activity significantly contributes to progressive [Cl-]i accumulation, depolarizing action of GABA, and delayed onset of ILDs. In this neonatal model of neuronal injury and ILDs, earlier treatment with bumetanide alone more efficiently recovered control baseline [Cl-]i and depressed epileptiform discharges. However, there was no time dependency to the anti-ictal efficacy of the combination of phenobarbital and bumetanide. These in vitro results suggest that after perinatal injury, early pre-emptive treatment with phenobarbital plus bumetanide would be as efficacious as late treatment after seizures are manifest.

Rapid Genome Sequencing: Consent for New Technologies in the Neonatal Intensive Care Context

The clinical utility of rapid genome sequencing (rGS) in critically unwell infants has been consistently demonstrated, and there are calls for rGS to be implemented as a first-line test in the NICU. A diagnosis from rGS can enable rapid initiation of precision treatment, making it potentially lifesaving. However, in many patients rGS leads to the diagnosis of severe and life-limiting conditions, prompting discussion with families about withdrawal of life-sustaining treatment. The complexity of information about rGS, together with the heightened emotions of parents in the NICU, poses significant challenges for informed decision making in this context. We present a case where both parents are unable to provide informed consent, and the treating team must decide whether to proceed with rGS. Our discussion highlights the important differences between genome sequencing and other types of genetic testing, and the crucial role played by pre-test counseling in facilitating informed consent and preparing parents for a range of possible outcomes. We then discuss the consent paradigms at play in NICUs; whereas admission generally comes with an understanding that the treating team will perform interventions thought to be in the best interest of the child, rGS is substantially different because of its long-term implications for patients and family members. Finally, we look at the ethical interplay between parental consent and the interests of the child. We conclude by showing how cases like this are resolved at our tertiary center and how they may be resolved differently in future.

Why won't it stop? The dynamics of benzodiazepine resistance in status epilepticus

Status epilepticus is a life-threatening neurological emergency that affects both adults and children. Approximately 36% of episodes of status epilepticus do not respond to the current preferred first-line treatment, benzodiazepines. The proportion of episodes that are refractory to benzodiazepines is higher in low-income and middle-income countries (LMICs) than in high-income countries (HICs). Evidence suggests that longer episodes of status epilepticus alter brain physiology, thereby contributing to the emergence of benzodiazepine resistance. Such changes include alterations in GABA_A receptor function and in the transmembrane gradient for chloride, both of which erode the ability of benzodiazepines to enhance inhibitory synaptic signalling. Often, current management guidelines for status epilepticus do not account for these duration-related changes in pathophysiology, which might differentially impact individuals in LMICs, where the average time taken to reach medical attention is longer than in HICs. In this Perspective article, we aim to combine clinical insights and the latest evidence from basic science to inspire a new, context-specific approach to efficiently managing status epilepticus.

Early-life seizures modify behavioral response to ultrasonic vocalization playback in adult rats

Early-life seizures (ELS) are associated with autism spectrum disorder (ASD); however, due to a lack of effective treatments for ELS, it is not clear whether ELS plays a causal role, potentiates the ASD phenotype, or is the result of a common pathophysiology. Deficits in communications are a core feature of ASD. To isolate the impact of ELS on communication, we probed the behavioral consequences of a single episode of kainic acid-induced early-life seizures (KA-ELS) in male and female Sprague-Dawley (CD) rats. Deficits in auditory communication were observed in adult male rats as assessed by behavioral response to ultrasonic vocalization (USV) playback. Ultrasonic vocalizations are classified into two major categories - 50-kHz (positive) calls and 22-kHz (aversive) calls. Behavioral response was assessed via rat preference for different USV playback in a radial arm maze. Response to 22-kHz calls was not impacted by ELS while response to 50-kHz calls was impacted. All rats demonstrated positional preference for the arms adjacent to where 50-kHz calls were playing compared to background noise; however, male ELS rats demonstrated a greater positional preference for the arms adjacent to where 50-kHz calls were playing compared to male control rats. These studies demonstrate that responses to socially relevant auditory cues are chronically altered in adult male rats following a single episode of ELS. We speculate that these changes contribute to previously reported social deficits associated with ELS.

Neonatal Clonazepam Administration Induced Long-Lasting Changes in GABAA and GABAB Receptors

Benzodiazepines (BZDs) are widely used in patients of all ages. Unlike adults, neonatal animals treated with BZDs exhibit a variety of behavioral deficits later in life; however, the mechanisms underlying these deficits are poorly understood. This study aims to examine whether administration of clonazepam (CZP; 1 mg/kg/day) in 7-11-day-old rats affects Gama aminobutyric acid (GABA)ergic receptors in both the short and long terms. Using RT-PCR and quantitative autoradiography, we examined the expression of the selected GABA_A receptor subunits (α1, α2, α4, γ2, and δ) and the GABA_B B2 subunit, and GABA_A, benzodiazepine, and GABA_B receptor binding 48 h, 1 week, and 2 months after treatment discontinuation. Within one week after CZP cessation, the expression of the α2 subunit was upregulated, whereas that of the δ subunit was downregulated in both the hippocampus and cortex. In the hippocampus, the α4 subunit was downregulated after the 2-month interval. Changes in receptor binding were highly dependent on the receptor type, the interval after treatment cessation, and the brain structure. GABA_A receptor binding was increased in almost all of the brain structures after the 48-h interval. BZD-binding was decreased in many brain structures involved in the neuronal networks associated with emotional behavior, anxiety, and cognitive functions after the 2-month interval. Binding of the GABA_B receptors changed depending on the interval and brain structure. Overall, the described changes may affect both synaptic development and functioning and may potentially cause behavioral impairment.

Neonatal Clonazepam Administration Induces Long-Lasting Changes in Glutamate Receptors

γ-aminobutyric acid (GABA) pathways play an important role in neuronal circuitry formation during early postnatal development. Our previous studies revealed an increased risk for adverse neurodevelopmental consequences in animals exposed to benzodiazepines, which enhance GABA inhibition via GABA_A receptors. We reported that administration of the benzodiazepine clonazepam (CZP) during postnatal days 7-11 resulted in permanent behavioral alterations. However, the mechanisms underlying these changes are unknown. We hypothesized that early CZP exposure modifies development of glutamatergic receptors and their composition due to the tight developmental link between GABAergic functions and maturation of glutamatergic signaling. These changes may alter excitatory synapses, as well as neuronal connectivity and function of the neural network. We used quantitative real-time PCR and quantitative autoradiography to examine changes in NMDA and AMPA receptor composition and binding in response to CZP (1 mg/kg/day) administration for five consecutive days, beginning on P7. Brains were collected 48 h, 1 week, or 60 days after treatment cessation, and mRNA subunit expression was assessed in the hippocampus and sensorimotor cortex. A separate group of animals was used to determine binding to NMDA in different brain regions. Patterns of CZP-induced alterations in subunit mRNA expression were dependent on brain structure, interval after CZP cessation, and receptor subunit type. In the hippocampus, upregulation of GluN1, GluN3, and GluR2 subunit mRNA was observed at the 48-h interval, and GluN2A and GluR1 mRNA expression levels were higher 1 week after CZP cessation compared to controls, while GluN2B was downregulated. CZP exposure increased GluN3 and GluR2 subunit mRNA expression levels in the sensorimotor cortex 48 h after treatment cessation. GluA3 was higher 1 week after the CZP exposure, and GluN2A and GluA4 mRNA were significantly upregulated 2 months later. Expression of other subunits was not significantly different from that of the controls. NMDA receptor binding increased 1 week after the end of exposure in most hippocampal and cortical areas, including the sensorimotor cortex at the 48-h interval. CZP exposure decreased NMDA receptor binding in most evaluated hippocampal and cortical areas 2 months after the end of administration. Overall, early CZP exposure likely results in long-term glutamatergic receptor modulation that may affect synaptic development and function, potentially causing behavioral impairment.

Model-based clinical dose optimization for phenobarbital in neonates: An illustration of the importance of data sharing and external validation

BACKGROUND

Particularly in the pediatric clinical pharmacology field, data-sharing offers the possibility of making the most of all available data. In this study, we utilize previously collected therapeutic drug monitoring (TDM) data of term and preterm newborns to develop a population pharmacokinetic model for phenobarbital. We externally validate the model using prospective phenobarbital data from an ongoing pharmacokinetic study in preterm neonates.

METHODS

TDM data from 53 neonates (gestational age (GA): 37 (24-42) weeks, bodyweight: 2.7 (0.45-4.5) kg; postnatal age (PNA): 4.5 (0-22) days) contained information on dosage histories, concentration and covariate data (including birth weight, actual weight, post-natal age (PNA), postmenstrual age, GA, sex, liver and kidney function, APGAR-score). Model development was carried out using NONMEM^® 7.3. After assessment of model fit, the model was validated using data of 17 neonates included in the DINO (Drug dosage Improvement in NeOnates)-study.

RESULTS

Modelling of 229 plasma concentrations, ranging from 3.2 to 75.2mg/L, resulted in a one compartment model for phenobarbital. Clearance (CL) and volume (V_d) for a child with a birthweight of 2.6kg at PNA day 4.5 was 0.0091L/h (9%) and 2.38L (5%), respectively. Birthweight and PNA were the best predictors for CL maturation, increasing CL by 36.7% per kg birthweight and 5.3% per postnatal day of living, respectively. The best predictor for the increase in V_d was actual bodyweight (0.31L/kg). External validation showed that the model can adequately predict the pharmacokinetics in a prospective study.

CONCLUSION

Data-sharing can help to successfully develop and validate population pharmacokinetic models in neonates. From the results it seems that both PNA and bodyweight are required to guide dosing of phenobarbital in term and preterm neonates.

Chloride Dysregulation, Seizures, and Cerebral Edema: A Relationship with Therapeutic Potential

Pharmacoresistant seizures and cytotoxic cerebral edema are serious complications of ischemic and traumatic brain injury. Intraneuronal Cl^- concentration ([Cl^-]_i) regulation impacts on both cell volume homeostasis and Cl^--permeable GABA_A receptor-dependent membrane excitability. Understanding the pleiotropic molecular determinants of neuronal [Cl^-]_i - cytoplasmic impermeant anions, polyanionic extracellular matrix (ECM) glycoproteins, and plasmalemmal Cl^- transporters - could help the identification of novel anticonvulsive and neuroprotective targets. The cation/Cl^- cotransporters and ECM metalloproteinases may be particularly druggable targets for intervention. We establish here a paradigm that accounts for recent data regarding the complex regulatory mechanisms of neuronal [Cl^-]_i and how these mechanisms impact on neuronal volume and excitability. We propose approaches to modulate [Cl^-]_i that are relevant for two common clinical sequela of brain injury: edema and seizures.

AMPA GluA1-flip targeted oligonucleotide therapy reduces neonatal seizures and hyperexcitability

Glutamate-activated α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPA-Rs) mediate the majority of excitatory neurotransmission in brain and thus are major drug targets for diseases associated with hyperexcitability or neurotoxicity. Due to the critical nature of AMPA-Rs in normal brain function, typical AMPA-R antagonists have deleterious effects on cognition and motor function, highlighting the need for more precise modulators. A dramatic increase in the flip isoform of alternatively spliced AMPA-R GluA1 subunits occurs post-seizure in humans and animal models. GluA1-flip produces higher gain AMPA channels than GluA1-flop, increasing network excitability and seizure susceptibility. Splice modulating oligonucleotides (SMOs) bind to pre-mRNA to influence alternative splicing, a strategy that can be exploited to develop more selective drugs across therapeutic areas. We developed a novel SMO, GR1, which potently and specifically decreased GluA1-flip expression throughout the brain of neonatal mice lasting at least 60 days after single intracerebroventricular injection. GR1 treatment reduced AMPA-R mediated excitatory postsynaptic currents at hippocampal CA1 synapses, without affecting long-term potentiation or long-term depression, cellular models of memory, or impairing GluA1-dependent cognition or motor function in mice. Importantly, GR1 demonstrated anti-seizure properties and reduced post-seizure hyperexcitability in neonatal mice, highlighting its drug candidate potential for treating epilepsies and other neurological diseases involving network hyperexcitability.

NKCC1 up-regulation contributes to early post-traumatic seizures and increased post-traumatic seizure susceptibility

Traumatic brain injury (TBI) is not only a leading cause for morbidity and mortality in young adults (Bruns and Hauser, Epilepsia 44(Suppl 10):210, 2003), but also a leading cause of seizures. Understanding the seizure-inducing mechanisms of TBI is of the utmost importance, because these seizures are often resistant to traditional first- and second-line anti-seizure treatments. The early post-traumatic seizures, in turn, are a contributing factor to ongoing neuropathology, and it is critically important to control these seizures. Many of the available anti-seizure drugs target gamma-aminobutyric acid (GABA_A) receptors. The inhibitory activity of GABA_A receptor activation depends on low intracellular Cl⁻, which is achieved by the opposing regulation of Na⁺–K⁺–Cl⁻ cotransporter 1 (NKCC1) and K⁺–Cl⁻–cotransporter 2 (KCC2). Up-regulation of NKCC1 in neurons has been shown to be involved in neonatal seizures and in ammonia toxicity-induced seizures. Here, we report that TBI-induced up-regulation of NKCC1 and increased intracellular Cl⁻ concentration. Genetic deletion of NKCC1 or pharmacological inhibition of NKCC1 with bumetanide suppresses TBI-induced seizures. TGFβ expression was also increased after TBI and competitive antagonism of TGFβ reduced NKKC1 expression, ameliorated reactive astrocytosis, and inhibited seizures. Thus, TGFβ might be an important pathway involved in NKCC1 up-regulation after TBI. Our findings identify neuronal up-regulation of NKCC1 and its mediation by TGFβ, as a potential and important mechanism in the early post-traumatic seizures, and demonstrate the therapeutic potential of blocking this pathway.

Diazepam effect during early neonatal development correlates with neuronal Cl(.)

Objective

Although benzodiazepines and other GABA_A receptors allosteric modulators are used to treat neonatal seizures, their efficacy may derive from actions on subcortical structures. Side effects of benzodiazepines in nonseizing human neonates include myoclonus, seizures, and abnormal movements. Excitatory actions of GABA may underlie both side effects and reduced anticonvulsant activity of benzodiazepines. Neocortical organotypic slice cultures were used to study: (1) spontaneous cortical epileptiform activity during early development; (2) developmental changes in [Cl⁻]_i and (3) whether diazepam's anticonvulsant effect correlated with neuronal [Cl⁻]_i.

Methods

Epileptiform activity in neocortical organotypic slice cultures was measured by field potential recordings. Cl⁻ changes during development were assessed by multiphoton imaging of neurons transgenically expressing a Cl‐sensitive fluorophore. Clinically relevant concentrations of diazepam were used to test the anticonvulsant effectiveness at ages corresponding to premature neonates through early infancy.

Results

(1) Neocortical organotypic slices at days in vitro 5 (DIV5) exhibited spontaneous epileptiform activity. (2) Epileptiform event duration decreased with age. (3) There was a progressive decrease in [Cl⁻]_i over the same age range. (4) Diazepam was ineffective in decreasing epileptiform activity at DIV5‐6, but progressively more effective at older ages through DIV15. (5) At DIV5‐6, diazepam worsened epileptiform activity in 50% of the slices.

Interpretation

The neocortical organotypic slice is a useful model to study spontaneous epileptiform activity. Decreasing [Cl⁻]_i during development correlates with decreasing duration of spontaneous epileptiform activity and increasing anticonvulsant efficacy of diazepam. We provide a potential explanation for the reports of seizures and myoclonus induction by benzodiazepines in newborn human neonates and the limited electrographic efficacy of benzodiazepines for the treatment of neonatal seizures.

Models of hypoxia and ischemia-induced seizures

Despite greater understanding and improved management, seizures continue to be a major problem in childhood. Neonatal seizures are often refractory to conventional antiepileptic drugs, and can result in later life epilepsy and cognitive deficits, conditions for which there are no specific treatments. Hypoxic and/or ischemic encephalopathy (HIE) is the most common cause for neonatal seizures, and accounts for more than two-thirds of neonatal seizure cases. A better understanding of the cellular and molecular mechanisms is essential for identifying new therapeutic strategies that control the neonatal seizures and its cognitive consequences. This heavily relies on animal models that play a critical role in discovering novel mechanisms underlying both epileptogenesis and associated cognitive impairments. To date, a number of animal models have provided a tremendous amount of information regarding the pathophysiology of HIE-induced neonatal seizures. This review provides an overview on the most important features of the main animal models of HIE-induced seizures. In particular, we focus on the methodology of seizure induction and the characterizations of post-HIE injury consequences. These aspects of HIE-induced seizure models are discussed in the light of the suitability of these models in studying human HIE-induced seizures.

Early life seizures: evidence for chronic deficits linked to autism and intellectual disability across species and models

Recent work in Exp Neurol by Lugo et al. (2014b) demonstrated chronic alterations in sociability, learning and memory following multiple early life seizures (ELS) in a mouse model. This work adds to the growing body of evidence supporting the detrimental nature of ELS on the developing brain to contribute to aspects of an autistic phenotype with intellectual disability. Review of the face validity of behavioral testing and the construct validity of the models used informs the predictive ability and thus the utility of these models to translate underlying molecular and cellular mechanisms into future human studies.

Na⁺/H⁺ exchangers and intracellular pH in perinatal brain injury

Encephalopathy consequent on perinatal hypoxia–ischemia occurs in 1–3 per 1,000 term births in the UK and frequently leads to serious and tragic consequences that devastate lives and families, with huge financial burdens for society. Although the recent introduction of cooling represents a significant advance, only 40 % survive with normal neurodevelopmental function. There is thus a significant unmet need for novel, safe, and effective therapies to optimize brain protection following brain injury around birth. The Na⁺/H⁺ exchanger (NHE) is a membrane protein present in many mammalian cell types. It is involved in regulating intracellular pH and cell volume. NHE1 is the most abundant isoform in the central nervous system and plays a role in cerebral damage after hypoxia–ischemia. Excessive NHE activation during hypoxia–ischemia leads to intracellular Na⁺ overload, which subsequently promotes Ca²⁺ entry via reversal of the Na⁺/Ca²⁺ exchanger. Increased cytosolic Ca²⁺ then triggers the neurotoxic cascade. Activation of NHE also leads to rapid normalization of pH_i and an alkaline shift in pH_i. This rapid recovery of brain intracellular pH has been termed pH paradox as, rather than causing cells to recover, this rapid return to normal and overshoot to alkaline values is deleterious to cell survival. Brain pH_i changes are closely involved in the control of cell death after injury: an alkalosis enhances excitability while a mild acidosis has the opposite effect. We have observed a brain alkalosis in 78 babies with neonatal encephalopathy serially studied using phosphorus-31 magnetic resonance spectroscopy during the first year after birth (151 studies throughout the year including 56 studies of 50 infants during the first 2 weeks after birth). An alkaline brain pH_i was associated with severely impaired outcome; the degree of brain alkalosis was related to the severity of brain injury on MRI and brain lactate concentration; and a persistence of an alkaline brain pH_i was associated with cerebral atrophy on MRI. Experimental animal models of hypoxia–ischemia show that NHE inhibitors are neuroprotective. Here, we review the published data on brain pH_i in neonatal encephalopathy and the experimental studies of NHE inhibition and neuroprotection following hypoxia–ischemia.

EphA/ephrin A reverse signaling promotes the migration of cortical interneurons from the medial ganglionic eminence

Inhibitory interneurons control the flow of information and synchronization in the cerebral cortex at the circuit level. During embryonic development, multiple subtypes of cortical interneurons are generated in different regions of the ventral telencephalon, such as the medial and caudal ganglionic eminence (MGE and CGE), as well as the preoptic area (POA). These neurons then migrate over long distances towards their cortical target areas. Diverse families of diffusible and cell-bound signaling molecules, including the Eph/ephrin system, regulate and orchestrate interneuron migration. Ephrin A3 and A5, for instance, are expressed at the borders of the pathway of MGE-derived interneurons and prevent these cells from entering inappropriate regions via EphA4 forward signaling. We found that MGE-derived interneurons, in addition to EphA4, also express ephrin A and B ligands, suggesting Eph/ephrin forward and reverse signaling in the same cell. In vitro and in vivo approaches showed that EphA4-induced reverse signaling in MGE-derived interneurons promotes their migration and that this effect is mediated by ephrin A2 ligands. In EphA4 mutant mice, as well as after ephrin A2 knockdown using in utero electroporation, we found delayed interneuron migration at embryonic stages. Thus, besides functions in guiding MGE-derived interneurons to the cortex through forward signaling, here we describe a novel role of the ephrins in driving these neurons to their target via reverse signaling.

Pediatric seizures

Seizures are a commonly encountered condition within the emergency department and, because of this, can engender complacency on the part of the physicians and staff. Unfortunately, there is significant associated morbidity and mortality with seizures, and they should never be regarded as routine. This point is particularly important with respect to seizures in pediatric patients. The aim of this review is to provide a current view of the various issues that make pediatric seizures unique and to help elucidate emergent evaluation and management strategies.

Population pharmacokinetic analysis during the first 2 years of life: an overview

Three decades after its introduction, pharmacokinetic population approaches have become a reference method for drug modelling, particularly in paediatrics. The main practical limitation in this specific population is the collected blood volume. Pharmacokinetic population approaches using sparse sampling may resolve this issue. The pharmacokinetics of many drugs have been studied during the last 25 years using such methods. This review summarizes all of the published studies concerning population pharmacokinetic approaches in paediatric subjects from neonate to 2 years old. A literature search was conducted using the PubMed database, from 1985 to December 2010, using the following terms: pharmacokinetic(s), population, paediatric/pediatric and neonate(s). Articles were excluded if they were not pertinent according to our criteria. References of all relevant articles were also evaluated. Ninety-eight studies were included in this review. The following information was extracted from the articles: drug name, therapeutic class, population size, age of patients, number of samples per patient, covariates used for clearance and volume of distribution estimates, software used for modelling and validation methods. An increasing rate of publications over the years was observed; 44 different drugs were studied using a pharmacokinetic population approach. Antibacterials were the most studied class of drugs, including a large number of studies devoted to vancomycin and gentamicin. It must be underlined that few studies have been performed on anticonvulsant drugs and anaesthetics used in clinical daily practice conditions.

Acid extrusion via blood-brain barrier causes brain alkalosis and seizures after neonatal asphyxia

Birth asphyxia is often associated with a high seizure burden that is predictive of poor neurodevelopmental outcome. The mechanisms underlying birth asphyxia seizures are unknown. Using an animal model of birth asphyxia based on 6-day-old rat pups, we have recently shown that the seizure burden is linked to an increase in brain extracellular pH that consists of the recovery from the asphyxia-induced acidosis, and of a subsequent plateau level well above normal extracellular pH. In the present study, two-photon imaging of intracellular pH in neocortical neurons in vivo showed that pH changes also underwent a biphasic acid–alkaline response, resulting in an alkaline plateau level. The mean alkaline overshoot was strongly suppressed by a graded restoration of normocapnia after asphyxia. The parallel post-asphyxia increase in extra- and intracellular pH levels indicated a net loss of acid equivalents from brain tissue that was not attributable to a disruption of the blood–brain barrier, as demonstrated by a lack of increased sodium fluorescein extravasation into the brain, and by the electrophysiological characteristics of the blood–brain barrier. Indeed, electrode recordings of pH in the brain and trunk demonstrated a net efflux of acid equivalents from the brain across the blood–brain barrier, which was abolished by the Na/H exchange inhibitor, N-methyl-isobutyl amiloride. Pharmacological inhibition of Na/H exchange also suppressed the seizure activity associated with the brain-specific alkalosis. Our findings show that the post-asphyxia seizures are attributable to an enhanced Na/H exchange-dependent net extrusion of acid equivalents across the blood–brain barrier and to consequent brain alkalosis. These results suggest targeting of blood–brain barrier-mediated pH regulation as a novel approach in the prevention and therapy of neonatal seizures.

Risk factors affecting Tests of Infant Motor Performance (TIMP) in pre-term infants at post-conceptional age of 40 weeks

OBJECTIVE

The purpose of this study is to correlate clinical factors with the Test of Infant Motor Performance (TIMP) in pre-term infants at a post-conceptional age of 40 weeks.

METHODS

The study enrolled 80 pre-term infants admitted to the Neonatal Intensive Care Unit (NICU). Data on birth weight, multiple birth, sex, delivery type, Apgar scores at 1 minute and 5 minutes, neonatal seizures and Intraventricular Haemorrhage (IVH) as assessed by echoencephalography were retrospectively analysed through a review of relevant medical records.

RESULTS

IVH was the clinical factor most strongly correlated with the TIMP scores. Other clinical factors which significantly affected the TIMP scores were caesarean section, neonatal seizures, low birth weight and multiple births.

CONCLUSIONS

When pre-term infants exhibit risk factors of developmental delay, it is suggestd that TIMP is performed early in life among pre-term infants and the results can be used to select infants for early interventions.

GABA through the ages: regulation of cortical function and plasticity by inhibitory interneurons

Inhibitory interneurons comprise only about 20% of cortical neurons and thus constitute a clear minority compared to the vast number of excitatory projection neurons. They are, however, an influential minority with important roles in cortical maturation, function, and plasticity. In this paper, we will highlight the functional importance of cortical inhibition throughout brain development, starting with the embryonal formation of the cortex, proceeding by the regulation of sensory cortical plasticity in adulthood, and finishing with the GABA involvement in sensory information processing in old age.

Neurodevelopmental outcome in full-term newborns with refractory neonatal seizures

AIM

This retrospective study describes the prognosis of full-term newborns with refractory neonatal seizures, comparing the need for treatment with two versus three or more antiepileptic drugs.

METHODS

We reviewed our database (January 2002-December 2007) to include newborns with refractory neonatal seizures and abnormal electroencephalogram. Group A consisted of 17 newborns with two antiepileptic drugs. Group B consisted of 29 newborns with three or more antiepileptic drugs. Outcome was determined at 2 years of age using the Dutch Bayley Scales of Infant Development or a neurodevelopmental classification scheme.

RESULTS

Group A and group B were comparable regarding to a variety of demographic and aetiologic factors. Thirteen newborns died before 2 years of age and one was lost to follow-up. Normal development at 2 years of age was found in 50% and 5% for group A and B, respectively. Severe neurodevelopmental delay at 2 years of age was found in 30% and 68% for group A and B, respectively.

CONCLUSION

The number of antiepileptic drugs probably reflects increased seizure burden and is--in that way--related to poor outcome. This may be useful information for early prediction of adverse neurological outcome in the first days of life.

Long-term neurological outcome of term-born children treated with two or more anti-epileptic drugs during the neonatal period

BACKGROUND

Neonatal seizures may persist despite treatment with multiple anti-epileptic drugs (AEDs).

OBJECTIVE

To determine in term-born infants with seizures that required two or more AEDs, whether treatment efficacy and/or the underlying disorder were related to neurological outcome.

DESIGN/METHODS

We included 82 children (born 1998-2006) treated for neonatal seizures. We recorded mortality, aetiology of seizures, the number of AEDs required, achievement of seizure control, and amplitude-integrated-EEG (aEEG) background patterns. Follow-up consisted of an age-adequate neurological examination. Surviving children were classified as normal, having mild neurological abnormalities, or cerebral palsy (CP).

RESULTS

Forty-seven infants (57%) had status epilepticus. The number of AEDs was not related to neurological outcome. Treatment with three or four AEDs as opposed to two showed a trend towards an increased risk of a poor outcome, i.e., death or CP, odds ratio (OR) 2.74; 95% confidence interval (CI) 0.98-7.69; P=.055. Failure to achieve seizure control increased the risk of poor outcome, OR 6.77; 95%-CI 1.42-32.82, P=.016. Persistently severely abnormal aEEG background patterns also increased this risk, OR 3.19; 95%-CI 1.90-5.36; P<.001. In a multivariate model including abnormal aEEG background patterns, failure to achieve seizure control nearly reached significance towards an increased risk of poor outcome, OR 5.72, 95%-CI 0.99-32.97, P=.051. We found no association between seizure aetiology and outcome.

CONCLUSIONS

In term-born infants with seizures that required two or more AEDs outcome was poorer if seizure control failed. The number of AEDs required to reach seizure control and seizure aetiology had limited prognostic value.

Clinical seizures in neonatal hypoxic-ischemic encephalopathy have no independent impact on neurodevelopmental outcome: secondary analyses of data from the neonatal research network hypothermia trial

It remains controversial as to whether neonatal seizures have additional direct effects on the developing brain separate from the severity of the underlying encephalopathy. Using data collected from infants diagnosed with hypoxic-ischemic encephalopathy, and who were enrolled in an National Institute of Child Health and Human Development trial of hypothermia, we analyzed associations between neonatal clinical seizures and outcomes at 18 months of age. Of the 208 infants enrolled, 102 received whole body hypothermia and 106 were controls. Clinical seizures were generally noted during the first 4 days of life and rarely afterward. When adjustment was made for study treatment and severity of encephalopathy, seizures were not associated with death, or moderate or severe disability, or lower Bayley Mental Development Index scores at 18 months of life. Among infants diagnosed with hypoxic-ischemic encephalopathy, the mortality and morbidity often attributed to neonatal seizures can be better explained by the underlying severity of encephalopathy.

Brain alkalosis causes birth asphyxia seizures, suggesting therapeutic strategy

OBJECTIVE

The mechanisms whereby birth asphyxia leads to generation of seizures remain unidentified. To study the possible role of brain pH changes, we used a rodent model that mimics the alterations in systemic CO(2) and O(2) levels during and after intrapartum birth asphyxia.

METHODS

Neonatal rat pups were exposed for 1 hour to hypercapnia (20% CO(2) in the inhaled gas), hypoxia (9% O(2)), or both (asphyxic conditions). CO(2) levels of 10% and 5% were used for graded restoration of normocapnia. Seizures were characterized behaviorally and utilizing intracranial electroencephalography. Brain pH and oxygen were measured with intracortical microelectrodes, and blood pH, ionized calcium, carbon dioxide, oxygen, and lactate with a clinical device. The impact of the postexposure changes in brain pH on seizure burden was assessed during 2 hours after restoration of normoxia and normocapnia. N-methyl-isobutyl-amiloride, an inhibitor of Na(+) /H(+) exchange, was given intraperitoneally.

RESULTS

Whereas hypercapnia or hypoxia alone did not result in an appreciable postexposure seizure burden, recovery from asphyxic conditions was followed by a large seizure burden that was tightly paralleled by a rise in brain pH, but no change in brain oxygenation. By graded restoration of normocapnia after asphyxia, the alkaline shift in brain pH and the seizure burden were strongly suppressed. The seizures were virtually blocked by preapplication of N-methyl-isobutyl-amiloride.

INTERPRETATION

Our data indicate that brain alkalosis after recovery from birth asphyxia plays a key role in the triggering of seizures. We question the current practice of rapid restoration of normocapnia in the immediate postasphyxic period, and suggest a novel therapeutic strategy based on graded restoration of normocapnia.

Neurodevelopmental outcomes in neonates with seizures: a numerical score of background encephalography to help prognosticate

There is a high incidence of mortality and neurodevelopmental sequelae in babies with neonatal seizures. The electroencephalography (EEG) background has been shown to be an excellent predictor of outcome by most studies, with a few suggesting limited value in prognostication. Previous studies suggest poor prognosis with severely abnormal backgrounds, but prediction was difficult with moderate abnormalities. The proposed numerical scoring system for the EEG background provides an objective method of evaluation with improved reproducibility, categorization, and prognostication. Our study showed that the numerical score of EEG background was a good predictor of outcome. Higher numerical scores reflecting greater abnormality of background EEG were associated with increasing incidence of mortality, neurodevelopmental impairment, cerebral palsy, vision and hearing impairment, and epilepsy. The numerical score also correlated with neuroimaging abnormalities. A numerical EEG score can help target interventional strategies for neonatal seizures.

Neonatal seizures in a rural Kenyan District Hospital: aetiology, incidence and outcome of hospitalization

BACKGROUND

Acute seizures are common among children admitted to hospitals in resource poor countries. However, there is little data on the burden, causes and outcome of neonatal seizures in sub-Saharan Africa. We determined the minimum incidence, aetiology and immediate outcome of seizures among neonates admitted to a rural district hospital in Kenya.

METHODS

From 1st January 2003 to 31st December 2007, we assessed for seizures all neonates (age 0-28 days) admitted to the Kilifi District Hospital, who were resident in a defined, regularly enumerated study area. The population denominator, the number of live births in the community on 1 July 2005 (the study midpoint) was modelled from the census data.

RESULTS

Seizures were reported in 142/1572 (9.0%) of neonatal admissions. The incidence was 39.5 [95% confidence interval (CI) 26.4-56.7] per 1000 live-births and incidence increased with birth weight. The main diagnoses in neonates with seizures were sepsis in 85 (60%), neonatal encephalopathy in 30 (21%) and meningitis in 21 (15%), but only neonatal encephalopathy and bacterial meningitis were independently associated with seizures. Neonates with seizures had a longer hospitalization [median period 7 days - interquartile range (IQR) 4 to10] -compared to 5 days [IQR 3 to 8] for those without seizures, P = 0.02). Overall, there was no difference in inpatient case fatality between neonates with and without seizures but, when this outcome was stratified by birth weight, it was significantly higher in neonates >or= 2.5 kg compared to low birth weight neonates [odds ratio 1.59 (95%CI 1.02 to 2.46), P = 0.037]. Up to 13% of the surviving newborn with seizures had neurological abnormalities at discharge.

CONCLUSION

There is a high incidence of neonatal seizures in this area of Kenya and the most important causes are neonatal encephalopathy and meningitis. The high incidence of neonatal seizures may be a reflection of the quality of the perinatal and postnatal care available to the neonates.

Levetiracetam in the treatment of neonatal seizures: a pilot study

PURPOSE

At present, neonatal seizures are usually treated with Phenobarbital (PB) despite the limited efficacy and the potential risk this treatment holds for the developing brain. We report here a prospective pilot feasibility study on the use of Levetiracetam as monotherapy in the treatment of neonatal seizures.

METHODS

Six newborns (body weight>2000 g, gestational age>30 weeks) presenting with neonatal seizures were enrolled. Patients whose seizures were caused by electrolyte disturbances or hypoglycemia, or whose seizures did respond to pyridoxine were excluded. Patients previously treated with other antiepileptic drugs (AEDs), with the exception of single PB doses before and during titration, were excluded. LEV was administered orally, increasing the dose by 10mg/(kg day) over 3 days. Endpoint was the need of any additional AEDs (or PB) after day 3, or 3 months of LEV treatment. A decision regarding further treatment was made on an individual basis and follow-up was documented up to 8 months of age.

RESULTS

No severe adverse effects were observed. Mild sedation was reported in one infant. All six patients treated with oral LEV became seizure free within 6 days. Five patients remained seizure free after 3 months with ongoing LEV monotherapy. One infant developed pharmacoresistant epilepsy. Seizures relapsed later in the clinical course of two more patients, one of whom was no longer under LEV therapy.

DISCUSSION

Results from our small patient group indicate that LEV may be an alternative therapeutic option in neonatal seizures.

Seizures are associated with brain injury severity in a neonatal model of hypoxia-ischemia

Hypoxia-ischemia is a significant cause of brain damage in the human newborn and can result in long-term neurodevelopmental disability. The loss of oxygen and glucose supply to the developing brain leads to excitotoxic neuronal cell damage and death; such over-excitation of nerve cells can also manifest as seizures. The newborn brain is highly susceptible to seizures although it is unclear what role they have in hypoxic-ischemic (H/I) injury. The aim of this study was to determine an association between seizures and severity of brain injury in a piglet model of perinatal H/I and, whether injury severity was related to type of seizure, i.e. sub-clinical (electrographic seizures only) or clinical (electrographic seizures+physical signs). Hypoxia (4% O(2)) was induced in anaesthetised newborn piglets for 30 min with a final 10 min period of hypotension; animals were recovered and survived to 72 h. Animals were monitored daily for seizures both visually and with electroencephalogram (EEG) recordings. Brain injury was assessed with magnetic resonance imaging (MRI), (1)H-MR spectroscopy ((1)H-MRS), EEG and by histology (haematoxylin and eosin). EEG seizures were observed in 75% of all H/I animals, 46% displayed clinical seizures and 29% sub-clinical seizures. Seizure animals showed significantly lower background amplitude EEG across all post-insult days. Presence of seizures was associated with lower cortical apparent diffusion coefficient (ADC) scores and changes in (1)H-MRS metabolite ratios at both 24 and 72 h post-insult. On post-mortem examination animals with seizures showed the greatest degree of neuropathological injury compared to animals without seizures. Furthermore, clinical seizure animals had significantly greater histological injury compared with sub-clinical seizure animals; this difference was not apparent on MRI or (1)H-MRS measures. In conclusion we report that both sub-clinical and clinical seizures are associated with increased severity of H/I injury in a term model of neonatal H/I.

Differences in cortical versus subcortical GABAergic signaling: a candidate mechanism of electroclinical uncoupling of neonatal seizures

Electroclinical uncoupling of neonatal seizures refers to electrographic seizure activity that is not clinically manifest. Uncoupling increases after treatment with Phenobarbital, which enhances the GABA(A) receptor (GABA(A)R) conductance. The effects of GABA(A)R activation depend on the intracellular Cl(-) concentration ([Cl(-)](i)) that is determined by the inward Cl(-) transporter NKCC1 and the outward Cl(-) transporter KCC2. Differential maturation of Cl(-) transport observed in cortical versus subcortical regions should alter the efficacy of GABA-mediated inhibition. In perinatal rat pups, most thalamic neurons maintained low [Cl(-)](i) and were inhibited by GABA. Phenobarbital suppressed thalamic seizure activity. Most neocortical neurons maintained higher [Cl(-)](i), and were excited by GABA(A)R activation. Phenobarbital had insignificant anticonvulsant responses in the neocortex until NKCC1 was blocked. Regional differences in the ontogeny of Cl(-) transport may thus explain why seizure activity in the cortex is not suppressed by anticonvulsants that block the transmission of seizure activity through subcortical networks.

The bumetanide-sensitive Na-K-2Cl cotransporter NKCC1 as a potential target of a novel mechanism-based treatment strategy for neonatal seizures

Seizures that occur during the neonatal period do so with a greater frequency than at any other age, have profound consequences for cognitive and motor development, and are difficult to treat with the existing series of antiepileptic drugs. During development, gamma-aminobutyric acid (GABA)ergic neurotransmission undergoes a switch from excitatory to inhibitory due to a reversal of neuronal chloride (Cl()) gradients. The intracellular level of chloride ([Cl()](i)) in immature neonatal neurons, compared with mature adult neurons, is about 20-40 mM higher due to robust activity of the chloride-importing Na-K-2Cl cotransporter NKCC1, such that the binding of GABA to ligand-gated GABA(A) receptor-associated Cl() channels triggers Cl() efflux and depolarizing excitation. In adults, NKCC1 expression decreases and the expression of the genetically related chloride-extruding K-Cl cotransporter KCC2 increases, lowering [Cl()](i) to a level such that activation of GABA(A) receptors triggers Cl() influx and inhibitory hyperpolarization. The excitatory action of GABA in neonates, while playing an important role in neuronal development and synaptogenesis, accounts for the decreased seizure threshold, increased seizure propensity, and poor efficacy of GABAergic anticonvulsants in this age group. Bumetanide, a furosemide-related diuretic already used to treat volume overload in neonates, is a specific inhibitor of NKCC1 at low doses, can switch the GABA equilibrium potential of immature neurons from depolarizing to hyperpolarizing, and has recently been shown to inhibit epileptic activity in vitro and in vivo in animal models of neonatal seizures. The fundamental role of NKCC1 in establishing excitatory GABAergic neurotransmission in the neonate makes it a tempting target of a novel mechanism-based anticonvulsant strategy that could utilize the well-known pharmacology of bumetanide to help treat neonatal seizures.

Chloride regulation in the pain pathway

Melzack and Wall's Gate Control Theory of Pain laid the theoretical groundwork for a role of spinal inhibition in endogenous pain control. While the Gate Control Theory was based on the notion that spinal inhibition is dynamically regulated, mechanisms underlying the regulation of inhibition have turned out to be far more complex than Melzack and Wall could have ever imagined. Recent evidence indicates that an exquisitely sensitive form of regulation involves changes in anion equilibrium potential (E(anion)), which subsequently impacts fast synaptic inhibition mediated by GABA(A), and to a lesser extent, glycine receptor activation, the prototypic ligand gated anion channels. The cation-chloride co-transporters (in particular NKCC1 and KCC2) have emerged as proteins that play a critical role in the dynamic regulation of E(anion) which in turn appears to play a critical role in hyperalgesia and allodynia following peripheral inflammation or nerve injury. This review summarizes the current state of knowledge in this area with particular attention to how such findings relate to endogenous mechanisms of hyperalgesia and allodynia and potential applications for therapeutics based on modulation of intracellular Cl(-) gradients or pharmacological interventions targeting GABA(A) receptors.

Neonatal seizures: treatment and treatment variability in 31 United States pediatric hospitals

Neonatal seizures are one of the most common neurological disorders in infants. However, the optimal treatment strategy for neonatal seizures remains controversial and there is little data regarding current treatment of neonatal seizures. In this study we describe the current treatment of neonatal seizures and variation in practice among 31 pediatric hospitals in the United States. We retrospectively identified 6099 infants hospitalized in the first month of life in one of 31 pediatric hospitals participating in the Pediatric Health Information System, with a discharge diagnosis of seizure. As expected, most treated infants received phenobarbital. However, there was significant interhospital variability for all treatments studied including any antiepileptic drug treatment, phenytoin treatment, antiepileptic drug treatment through discharge, number of antiepileptic drugs used, and treatment with pyridoxine (P < .001). These findings highlight the need for rigorous controlled outcome studies to determine optimal therapy for neonatal seizures and devise treatment standards.

A single early-life seizure impairs short-term memory but does not alter spatial learning, recognition memory, or anxiety

The impact of a single seizure on cognition remains controversial. We hypothesized that a single early-life seizure (sELS) on rat Postnatal Day (P) 7 would alter only hippocampus-dependent learning and memory in mature (P60) rats. The Morris water maze, the novel object and novel place recognition tasks, and contextual fear conditioning were used to assess learning and memory associated with hippocampus/prefrontal cortex, perirhinal/hippocampal cortex, and amygdala function, respectively. The elevated plus maze and open-field test were used to assess anxiety associated with the septum. We report that sELS impaired hippocampus-dependent short-term memory, but not spatial learning or recall. sELS did not disrupt performance in the novel object and novel place recognition tasks. Contextual fear conditioning performance suggested intact amydgala function. sELS did not change anxiety levels as measured by the elevated plus maze or open-field test. Our data suggest that the long-term cognitive impact of sELS is limited largely to the hippocampus/prefrontal cortex.

Ephrin-A5 acts as a repulsive cue for migrating cortical interneurons

Cortical interneurons are born in the germinative zones of the ganglionic eminences in the subpallium, and migrate tangentially in spatially and temporally well-defined corridors into the neocortex. Because ephrin-A5 is expressed in the ventricular zone (VZ) of the ganglionic eminences at these developmental stages, we examined the possible effects of this molecule on interneuron migration. Double-immunocytochemistry of dissociated neurons from the medial ganglionic eminences (MGE) revealed that calbindin-positive cells express the EphA4-receptor. In situ, EphA4 is strongly expressed in the subventricular zone of the ganglionic eminences. Using different in vitro assays, we found that ephrin-A5 acts as a repellent cue for MGE neurons. We then examined interneuron migration in slice overlay experiments, where MGE-derived explants from enhanced green fluorescent protein-expressing transgenic mice were homotopically grafted into host slices from wild-type littermate embryos. In these in vitro preparations, interneurons recapitulated in vivo cell migration in several respects. However, interneurons in brain slices also migrated in the VZ of the ganglionic eminences, a region that is strictly avoided in vivo. In situ hybridizations revealed that ephrin-A5 became downregulated in the VZ in vitro. When recombinant ephrin-A5-Fc was added to the slices, it preferentially bound to the VZ, and migrating MGE neurons avoided the VZ as in vivo. The restoration of the normal migration pathway in slices required ephrin-A5 clustering and signalling of Src family kinases. Together, these experiments suggest that ephrin-A5 acts as an inhibitory flank that contributes to define the pathway of migrating interneurons.

Prophylactic phenobarbital administration after resolution of neonatal seizures: survey of current practice

OBJECTIVE

Child neurologists and neonatologists often discharge newborn infants with phenobarbital treatment for weeks to months despite the absence of continuing seizure activity. We conducted a national survey to determine the degree of variation in this practice.

METHODS

Surveys were sent to a randomly generated list of board-certified child neurologists (N = 609) and neonatologists (N = 579). The survey consisted of 3 parts, that is, questions related to overall attitudes and practices, specific patient scenarios, and respondent demographic characteristics. Responses were tabulated and analyzed for all respondents combined and for child neurologists and neonatologists separately. Variation in practices between respondents and the consistency between the respondents' stated use of phenobarbital in practice and their answers to various clinical scenarios were evaluated.

RESULTS

Responses were received from 118 child neurologists (20.7%) and 125 neonatologists (23.1%). There was wide variation in practices, with little difference in the response frequencies between child neurologists and neonatologists. Physicians were more likely to respond yes to continuation of phenobarbital treatment in a given clinical situation than would be predicted on the basis of their answers regarding overall frequency of use.

CONCLUSIONS

Since the survey of practices 15 years ago, child neurologists and neonatologists are reporting less frequent and shorter phenobarbital treatment after resolution of neonatal seizures, although there remains considerable variation in practices. Moreover, what physicians report as their practice in general is inconsistent with how they respond to specific clinical cases of neonatal seizures.

Layer-specific generation and propagation of seizures in slices of developing neocortex: role of excitatory GABAergic synapses

The neonatal period is critical for seizure susceptibility, and neocortical networks are central in infantile epilepsies. We report that application of 4-aminopyridine (4-AP) to immature (P6-P9) neocortical slices generates layer-specific interictal seizures (IISs) that transform after recurrent seizures to ictal seizures (ISs). During IISs, cell-attached recordings show action potentials in interneurons and pyramidal cells in L5/6 and interneurons but not pyramidal neurons in L2/3. However, L2/3 pyramidal neurons also fire during ISs. Using single N-methyl-d-aspartate (NMDA) channel recordings for measuring the cell resting potential (Em), we show that transition from IISs to ISs is associated with a gradual Em depolarization of L2/3 and L5/6 pyramidal neurons that enhances their excitability. Bumetanide, a NKCC1 co-transporter antagonist, inhibits generation of IISs and prevents their transformation to ISs, indicating the role excitatory GABA in epilepsies. Therefore deep layer neurons are more susceptible to seizures than superficial ones. The initiating phase of seizures is characterized by IISs generated in L5/6 and supported by activation of both L5/6 interneurons and pyramidal cells. IISs propagate to L2/3 via activation of L2/3 interneurons but not pyramidal cells, which are mostly quiescent at this phase. In superficial layers, a persistent increase in excitability of pyramidal neurons caused by Em depolarization is associated with a transition from largely confined GABAergic IIS to ictal events that entrain the entire neocortex.

Comparison of continuous drip of midazolam or lidocaine in the treatment of intractable neonatal seizures

Seizures constitute the most common neurological symptom in the neonatal period. Treatment usually involves the administration of intravenous benzodiazepines followed by either phenobarbital or phenytoin. For nonresponsive cases, continuous intravenous drip of either midazolam or lidocaine has been suggested for seizure control. Some reports suggest that seizures themselves may have a deleterious effect on long-term neurological outcome. Therefore, there is a need to find treatment regimens with better efficacy to provide maximum seizure control. The authors compared the effectiveness of lidocaine and midazolam in the treatment of intractable seizures in newborn infants born at or after 36 weeks of gestation who suffered from hypoxic-ischemic encephalopathy and who had their cerebral activity monitored. Thirty infants were included in the study: 22 received lidocaine, and 8 received midazolam. Seventeen (77%) infants had a good or partial response to lidocaine, and 4 (50%) had a partial response to midazolam. Of 20 infants diagnosed with hypoxic-ischemic encephalopathy grade 2, 18 (90%) responded to second-line treatment (14 [93%] of 15 to lidocaine and 4 [80%] of 5 to midazolam). Among 10 infants with hypoxic-ischemic encephalopathy grade 3, only 3 (30%) responded to second-line treatment (all 3 to lidocaine, none to midazolam). The findings suggest that lidocaine may be more effective than midazolam in reducing or controlling refractory neonatal seizures. The lower response rate to midazolam was more evident in infants with severe hypoxic-ischemic encephalopathy (grade 3).

Regulation of membrane protein function by lipid bilayer elasticity-a single molecule technology to measure the bilayer properties experienced by an embedded protein

Membrane protein function is generally regulated by the molecular composition of the host lipid bilayer. The underlying mechanisms have long remained enigmatic. Some cases involve specific molecular interactions, but very often lipids and other amphiphiles, which are adsorbed to lipid bilayers, regulate a number of structurally unrelated proteins in an apparently non-specific manner. It is well known that changes in the physical properties of a lipid bilayer (e.g., thickness or monolayer spontaneous curvature) can affect the function of an embedded protein. However, the role of such changes, in the general regulation of membrane protein function, is unclear. This is to a large extent due to lack of a generally accepted framework in which to understand the many observations. The present review summarizes studies which have demonstrated that the hydrophobic interactions between a membrane protein and the host lipid bilayer provide an energetic coupling, whereby protein function can be regulated by the bilayer elasticity. The feasibility of this 'hydrophobic coupling mechanism' has been demonstrated using the gramicidin channel, a model membrane protein, in planar lipid bilayers. Using voltage-dependent sodium channels, N-type calcium channels and GABA(A) receptors, it has been shown that membrane protein function in living cells can be regulated by amphiphile induced changes in bilayer elasticity. Using the gramicidin channel as a molecular force transducer, a nanotechnology to measure the elastic properties experienced by an embedded protein has been developed. A theoretical and technological framework, to study the regulation of membrane protein function by lipid bilayer elasticity, has been established.

Seizures in children

Seizures are the most common pediatric neurologic disorder. Four to ten percent of children suffer at least one seizure in the first 16 years of life. The incidence is highest in children less than 3 years of age, with a decreasing frequency in older children. Epidemiologic studies reveal that approximately 150,000 children will sustain a first-time unprovoked seizure each year, and of those, 30,000 will develop epilepsy. This article describes the types, diagnoses, and management and disposition of this pediatric neurologic disorder.

Brain injury in the infant: the old, the new, and the uncertain

Although neonatal brain injury occurs most frequently after a perinatal hypoxic-ischemic insult, recently studies have noted that variable causes such as metabolic and reperfusion events can result in, or aggravate, a brain insult. Current data suggest that about 2 to 5 of 1,000 live births in the United States and more so in developing countries experience a brain injury Approximately 20% to 40% of infants who survive the brain injury develop significant neurological and developmental impairments. The resulting impact on the child, family, and society presents a formidable challenge to health care professionals. Although several important insights have been gained in the last several years about the epidemiology, diagnosis, and mechanism of brain injury, management remains mostly a cocktail of controversial trials. This article provides a comprehensive review of the pathology, clinical manifestations, and timely management of infants with brain injury.

Slow endogenous activity transients and developmental expression of K+-Cl- cotransporter 2 in the immature human cortex

Spontaneous transients of correlated activity are a characteristic feature of immature brain structures, where they are thought to be crucial for the establishment of precise neuronal connectivity. Studies on experimental animals have shown that this kind of early activity in cortical structures is composed of long-lasting, intermittent network events, which undergo a developmental decline that is closely paralleled by the maturation of GABAergic inhibition. In order to examine whether similar events occur in the immature human cortex, we performed direct current-coupled electroencephalography (EEG) recordings from sleeping preterm babies. We show now that much of the preterm EEG activity is confined to spontaneous, slow activity transients. These transients are characterized by a large voltage deflection that nests prominent oscillatory activity in several frequency bands covering the whole frequency spectrum of the preterm EEG (<0.1-30 Hz). The slow voltage deflections had an amplitude of up to 800 microV. Most of these 'giant' events originated in the temporo-occipital areas, with a maximum rate of about 8/min, and their occurrence as well as amplitude showed a decline by the time of normal birth. In age-matched fetal brain tissue, this decrease in the spontaneous activity transients was associated with a developmental up-regulation of the neuronal chloride extruder K+-Cl- cotransporter 2, a crucial molecule for the generation of inhibitory GABAergic Cl- currents. Our work indicates that slow endogenous activity transients in the immature human neocortex are mostly confined to the prenatal stage and appear to be terminated in parallel with the maturation of functional GABAergic inhibition.