Sookyong Koh

NBQX or topiramate treatment after perinatal hypoxia-induced seizures prevents later increases in seizure-induced neuronal injury

Summary:  Purpose: To evaluate the efficacy of NBQX (2,3‐dihydroxy‐6‐nitro‐7‐sulfamoylbenzo(f) quinoxaline‐2,3‐dione) and topiramate (TPM) given after hypoxia‐induced seizures in preventing the delayed effect of hypoxia on subsequent susceptibility to seizures and neuronal injury.

Temperature-Sensitive Cav1.2 Calcium Channels Support Intrinsic Firing of Pyramidal Neurons and Provide a Target for the Treatment of Febrile Seizures

Febrile seizures are associated with increased brain temperature and are often resistant to treatments with antiepileptic drugs, such as carbamazepine and phenytoin, which are sodium channel blockers. Although they are clearly correlated with the hyperthermic condition, the precise cellular mechanisms of febrile seizures remain unclear. We performed patch-clamp recordings from pyramidal cells in acute rat brain slices at temperatures up to 40°C and found that, at ≥37°C, L-type calcium channels are active at unexpectedly hyperpolarized potentials and drive intrinsic firing, which is also supported by a temperature-dependent, gadolinium-sensitive sodium conductance. Pharmacological data, RT-PCR, and the current persistence in Cav1.3 knock-out mice suggested a critical contribution of Cav1.2 subunits to the temperature-dependent intrinsic firing, which was blocked by nimodipine. Because intrinsic firing may play a critical role in febrile seizures, we tested the effect of nimodipine in an in vivo model of febrile seizures and found that this drug dramatically reduces both the incidence and duration of febrile seizures in rat pups, suggesting new possibilities of intervention for this important pathological condition.

Early-life epilepsies and the emerging role of genetic testing

Importance Early-life epilepsies are often a consequence of numerous neurodevelopmental disorders, most of which are proving to have genetic origins. The role of genetic testing in the initial evaluation of these epilepsies is not established. Objective To provide a contemporary account of the patterns of use and diagnostic yield of genetic testing for early-life epilepsies. Design, Setting, and Participants In this prospective cohort, children with newly diagnosed epilepsy with an onset at less than 3 years of age were recruited from March 1, 2012, to April 30, 2015, from 17 US pediatric hospitals and followed up for 1 year. Of 795 families approached, 775 agreed to participate. Clinical diagnosis of the etiology of epilepsy were characterized based on information available before genetic testing was performed. Added contributions of cytogenetic and gene sequencing investigations were determined. Exposures Genetic diagnostic testing. Main Outcomes and Measures Laboratory-confirmed pathogenic variant. Results Of the 775 patients in the study (367 girls and 408 boys; median age of onset, 7.5 months [interquartile range, 4.2-16.5 months]), 95 (12.3%) had acquired brain injuries. Of the remaining 680 patients, 327 (48.1%) underwent various forms of genetic testing, which identified pathogenic variants in 132 of 327 children (40.4%; 95% CI, 37%-44%): 26 of 59 (44.1%) with karyotyping, 32 of 188 (17.0%) with microarrays, 31 of 114 (27.2%) with epilepsy panels, 11 of 33 (33.3%) with whole exomes, 4 of 20 (20.0%) with mitochondrial panels, and 28 of 94 (29.8%) with other tests. Forty-four variants were identified before initial epilepsy presentation. Apart from dysmorphic syndromes, pathogenic yields were highest for children with tuberous sclerosis complex (9 of 11 [81.8%]), metabolic diseases (11 of 14 [78.6%]), and brain malformations (20 of 61 [32.8%]). A total of 180 of 446 children (40.4%), whose etiology would have remained unknown without genetic testing, underwent some testing. Pathogenic variants were identified in 48 of 180 children (26.7%; 95% CI, 18%-34%). Diagnostic yields were greater than 15% regardless of delay, spasms, and young age. Yields were greater for epilepsy panels (28 of 96 [29.2%]; P < .001) and whole exomes (5 of 18 [27.8%]; P = .02) than for chromosomal microarray (8 of 101 [7.9%]). Conclusions and Relevance Genetic investigations, particularly broad sequencing methods, have high diagnostic yields in newly diagnosed early-life epilepsies regardless of key clinical features. Thorough genetic investigation emphasizing sequencing tests should be incorporated into the initial evaluation of newly presenting early-life epilepsies and not just reserved for those with severe presentations and poor outcomes.

Child Neurology: Dravet syndrome When to suspect the diagnosis

Dravet syndrome (DS), previously known as severe myoclonic epilepsy in infancy (SMEI), is an epileptic encephalopathy that presents with prolonged seizures in the first year of life. The seizures often occur with fever or illness, and are frequently initially categorized as febrile seizures. The correct diagnosis of DS and appropriate follow-up are typically delayed. The EEG is normal at onset, and neuroimaging reveals no structural lesion. Early development is normal, but signs of regression appear in the second year of life and are often accompanied by convulsive status epilepticus, alternating hemiconvulsions, and myoclonic seizures. Diagnosis can be confirmed by genetic testing that is now available, and shows mutations within the SCN1A gene. Early recognition and diagnosis of DS and management with appropriate anticonvulsants and treatment plan may reduce the seizure burden and improve long-term developmental outcome.

Neuroinflammatory targets and treatments for epilepsy validated in experimental models

A large body of evidence that has accumulated over the past decade strongly supports the role of inflammation in the pathophysiology of human epilepsy. Specific inflammatory molecules and pathways have been identified that influence various pathologic outcomes in different experimental models of epilepsy. Most importantly, the same inflammatory pathways have also been found in surgically resected brain tissue from patients with treatment‐resistant epilepsy. New antiseizure therapies may be derived from these novel potential targets. An essential and crucial question is whether targeting these molecules and pathways may result in anti‐ictogenesis, antiepileptogenesis, and/or disease‐modification effects. Therefore, preclinical testing in models mimicking relevant aspects of epileptogenesis is needed to guide integrated experimental and clinical trial designs. We discuss the most recent preclinical proof‐of‐concept studies validating a number of therapeutic approaches against inflammatory mechanisms in animal models that could represent novel avenues for drug development in epilepsy. Finally, we suggest future directions to accelerate preclinical to clinical translation of these recent discoveries.

A postnatal peak in microglial development in the mouse hippocampus is correlated with heightened sensitivity to seizure triggers

Explosive synaptogenesis and synaptic pruning occur in the hippocampus during the first two weeks of postnatal life, coincident with a heightened susceptibility to seizures in rodents. To determine the temporal correlation between microglial development and age‐dependent susceptibility and response to seizures, we quantified developmental changes in basal microglia levels and seizure‐induced microglial activation in the hippocampus of Cx3Cr1GFP/+ transgenic mice.

Characterization of a commonly used mouse model of SMA reveals increased seizure susceptibility and heightened fear response in FVB/N mice

The SMN2 transgenic mouse, Tg(SMN2)89Ahmb, has emerged as the most widely used in spinal muscular atrophy (SMA) research. Here we clone the genomic integration site of the transgene and demonstrate it to be in intron 4 of the metabotropic glutamate receptor 7 (mGluR7) gene. We found that the integration of this transgene significantly reduced both mGluR7 mRNA and protein levels (24% and 9%, respectively). To determine if phenotypes associated with mGluR7 knockout mice were present in Tg(SMN2)89Ahmb containing mice, we subjected mice homozygous for the transgene to open field and seizure susceptibility tests. When compared to wild type FVB/N mice, Tg(SMN2)89Ahmb(tg/tg) mice exhibited significantly longer times in finding a safe wall-adjacent square (+54s if Smn(+/+), +90s if Smn(+/-)), as well as a significantly higher frequency of generalized seizure in response to a subthreshold dose of pentylenetrazol (0.11 vs 0.45). These findings aid in explaining the sudden unexpected death that occurs within SMA mouse colonies that contain a homozygous Tg(SMN2)89Ahmb transgene. This should be taken into account in pre-clinical studies that utilize this transgene, especially in therapy-treated SMA mice that have extended survival.

Early-life experience alters response of developing brain to seizures

Prolonged seizures during childhood are associated with behavior problems, memory impairment and school failure. No effective treatment currently exists after seizures to mitigate neuronal injury and long-term neurological sequelae for children with epilepsy. We studied the therapeutic efficacy of early-life environment on seizure-induced behavioral deficits, neuronal injury and the inflammatory reaction using the kainic acid (KA) seizure model. Two rearing conditions, maternal separation for 3 h daily versus maternal care in an enriched environment, were followed by single housing for the former (Deprived) and group housing in an enriched environment for the latter (Enriched). To examine the influence of differential rearing on the behavioral effects of early-life seizures, KA was injected on P21. On P28, marked reduction in exploratory behavior was noted after seizures only in the Deprived group. To investigate seizure-induced hippocampal injury, a separate group of rats were injected with KA on P35 since consistent seizure-induced neuronal injury is observed only in mature rats. Brains of rats sacrificed on P37 displayed a significant reduction in DNA fragmentation and microglial activation in Enriched compared to Deprived animals. Our results suggest that a nurturing early environment can enhance the ability of the developing brain to recover from seizures and provide a buffer against their damaging effects. While the nurturing environment was neuroprotective, the combination of deprived rearing and the insult of early-life seizures resulted in significant behavioral deficits, an increase in neuronal injury and activation of microglia in young rats.

Ictal ontogeny in Dravet syndrome.

OBJECTIVE To define seizure characteristics of Dravet syndrome (DS) with video-electroencephalographic (EEG) recording in different age groups. METHODS We reviewed 23 patients with 63 seizures in different age groups: group 1 (0-5years old); group 2 (6-10years old); and group 3 (11 or above). RESULTS We included 7, 11 and 5 patients in groups 1, 2, and 3 respectively. Younger children had seizures while awake (p=0.005), provoked seizures (p=0.05), focal seizure semiology (p=0.02) and long seizure duration (p=0.0004). Older children had seizures from sleep (p=0.004), generalized seizure semiology (p=0.01) and short seizure duration (p=0.0007). A generalized ictal discharge was the most commonly observed EEG pattern (15/23, 65%), more frequently found in older children (p=0.01). Ten patients (43%) had unclassified seizures or seizures with discordant EEG results. Postictal EEG suppression was found in 9 (39%). CONCLUSION The phenotype of seizures and ictal EEG patterns in DS vary with age. SIGNIFICANCE These findings will enhance the recognition of DS in the adolescent population. The incidence of postictal EEG suppression seen in DS is significant because it is a possible biomarker for sudden unexpected death in epilepsy.

Lipopolysaccharide potentiates hyperthermia-induced seizures.

Prolonged febrile seizures (FS) have both acute and long‐lasting effects on the developing brain. Because FS are often associated with peripheral infection, we aimed to develop a preclinical model of FS that simulates fever and immune activation in order to facilitate the implementation of targeted therapy after prolonged FS in young children.