Epileptic Encephalopathies in Infants and Children

Late infantile epileptic encephalopathy: A distinct developmental and epileptic encephalopathy syndrome

OBJECTIVE

Within the spectrum of developmental and epileptic encephalopathy (DEE), there are a group of infants with features that are distinct from the well-recognized syndromes of early infantile developmental and epileptic encephalopathy (EIDEE), infantile epileptic spasm syndrome (IESS), and Lennox-Gastaut syndrome (LGS). We refer to this condition as late infantile epileptic encephalopathy (LIEE). Our objective was to highlight the characteristics of this group by analyzing patients who exhibit prototypical features.

METHODS

From July 2022 to May 2023, we searched for LIEE features in pediatric patients who underwent epilepsy follow-up at the University of Chicago Comer Children's Hospital.

RESULTS

Out of 850 patients evaluated, thirty patients (3.5%) were identified with LIEE based on electroclinical characteristics. These patients had an average onset of epilepsy at 6.8 months and an average onset of LIEE features at 18.1 months. The epilepsy etiology was most commonly genetic and metabolic (50%), followed by congenital cortical malformations (23%), acquired structural abnormalities (20%), and unknown (7%). The predominant seizure types were myoclonic-tonic (70%), spasm-tonic (50%), epileptic spasms (47%), tonic (43%), and myoclonic (43%) seizures. All patients reported a history of either spasm-tonic or myoclonic-tonic seizures in addition to other types. All patients had EEGs showing discontinuity, electrodecrements, or both along with diffuse slowing, background voltages between 100 and 300 μV, and superimposed multifocal, diffuse epileptiform discharges. Every patient, except one, fulfilled the definition of drug-resistant epilepsy, and all reported either moderate-to-severe or severe developmental delay.

SIGNIFICANCE

Late infantile epileptic encephalopathy (LIEE) is characterized by several unique clinical and electrographic features. Typically, LIEE manifests in patients during the second year of life and occurs before two years of age, hence late infantile onset. The condition is commonly observed in infants with symptomatic epilepsy. Myoclonic-tonic and spasm-tonic seizures are the quintessential seizure types. The inter-ictal EEG exhibits more organization and lower voltages than seen with hypsarrhythmia and lacks the defining EEG characteristics of EIDEE, IESS, or LGS. We propose that LIEE is a distinct electroclinical syndrome within the spectrum of developmental and epileptic encephalopathies.

Resting-state fMRI in patients with refractory epilepsy with and without drop attacks: exploring the connectivity of sensorimotor cortex

OBJECTIVE

Patients with multifocal or generalized epilepsies manifesting with drop attacks have severe refractory seizures and significant cognitive and behavioural abnormalities. It is unclear to what extent these features relate to network abnormalities and how networks in sensorimotor cortex differ from those in patients with refractory focal epilepsies. Thus, in this study we sought to provide preliminary data on connectivity of sensorimotor cortex in patients with epileptic drop attacks, in comparison to patients with focal refractory epilepsies.

METHODS

Resting-state fMRI (rs-fMRI) data was available for 5 patients with epileptic drop attacks and 15 with refractory focal epilepsies undergoing presurgical evaluation. Functional connectivity was analyzed with a seed-based protocol, with primary seeds placed at the precentral gyrus, the postcentral gyrus and the premotor cortex. For each seed, the subjects' timeseries were extracted and transformed to Z scores. Between-group analysis was then performed using the 3dttest+ + AFNI program.

RESULTS

Two clusters of reduced connectivity in the group with drop attacks (DA group) in relation to those with focal epilepsies were found in the between-group analysis: the precentral seed showed reduced connectivity in the surrounding motor area, and the postcentral seed, reduced connectivity with the ipsilateral posterior cingulate gyrus. In the intra-group analyses, sensorimotor and premotor networks were abnormal in the DA group, whereas patients with focal epilepsies had the usual connectivity maps with each seed.

CONCLUSION

This pilot study shows differences in the cerebral connectivity in the sensorimotor cortex of patients with generalized epilepsies and drop attacks which should be further explored to better understand the biological bases of the seizure generation and cognitive changes in these people.

Clinical and electroencephalography characteristics of 41 children with epileptic spasms onset after 1 year of age

The incidence of epileptic spasms (ES) that begin after the first year of life is much lower than that before 1 year of age. The aim of this study was to identify clinical and electroencephalography (EEG) characteristics, etiologies, treatments, and prognoses in pediatric patients with ES onset after 1 year of age. Forty-one children were retrospectively identified in Children's Hospital of Chongqing Medical University between January 1, 2020 and December 1, 2021. ES onset after 1 year of age have diverse presentations. Although most occur in clusters, are symmetrical and flexional, and occur frequently during awakening, some are characterized as isolated and asymmetrical, have a tonic component, and can also occur during sleep. The hypsarrhythmia variants and focal or multifocal discharges occur alternately in the interictal period, and the focal spikes and slow waves predominated in the unilateral temporal or frontotemporal areas. These patients had diverse etiologies, including structural (51.2 % of patients) and genetic (22.0 %) ones, and 11 patients (26.8 %) had an unknown etiology. No patients in our study had an infectious or immune-mediated etiology. Forty-eight percent of patients responded to hydrocortisone and/or adrenocorticotropic hormone. The efficacy of antiepileptic drug therapy was lower in patients who did not receive concurrent steroid therapy. However, ES onset after 1 year of age caused by a tumor, brain malformation, or other focal lesions, may be cured by focal cortical resection despite a lack of clearly localized EEG surface anomalies. Delays in motor, language, and cognitive development, or behavioral problems were observed in all but three patients.

A companion to the preclinical common data elements for rodent models of pediatric acquired epilepsy: A report of the TASK3-WG1B, Pediatric and Genetic Models Working Group of the ILAE/AES Joint Translational Task Force

Epilepsy syndromes during the early years of life may be attributed to an acquired insult, such as hypoxic-ischemic injury, infection, status epilepticus, or brain trauma. These conditions are frequently modeled in experimental rodents to delineate mechanisms of epileptogenesis and investigate novel therapeutic strategies. However, heterogeneity and subsequent lack of reproducibility of such models across laboratories is an ongoing challenge to maintain scientific rigor and knowledge advancement. To address this, as part of the TASK3-WG1B Working Group of the International League Against Epilepsy/American Epilepsy Society Joint Translational Task Force, we have developed a series of case report forms (CRFs) to describe common data elements for pediatric acquired epilepsy models in rodents. The "Rodent Models of Pediatric Acquired Epilepsy" Core CRF was designed to capture cohort-general information; while two Specific CRFs encompass physical induction models and chemical induction models, respectively. This companion manuscript describes the key elements of these models and why they are important to be considered and reported consistently. Together, these CRFs provide investigators with the tools to systematically record critical information regarding their chosen model of acquired epilepsy during early life, for improved standardization and transparency across laboratories. These outcomes will support the ultimate goal of such research; that is, to understand the childhood onset-specific biology of epileptogenesis after acquired insults, and translate this knowledge into therapeutics to improve pediatric patient outcomes and minimize the lifetime burden of epilepsy.

Approach to Neurological Channelopathies and Neurometabolic Disorders in Newborns

Ion channel disorders (channelopathies) can affect any organ system in newborns before 2 months of life, including the skeletal muscle and central nervous system. Channelopathies in newborns can manifest as seizure disorders, which is a critical issue as early onset seizures can mimic the presentation of neurometabolic disorders. Seizures in channelopathies can either be focal or generalized, and range in severity from benign to epileptic encephalopathies that may lead to developmental regression and eventually premature death. The presenting symptoms of channelopathies are challenging for clinicians to decipher, such that an extensive diagnostic survey through a precise step-by-step process is vital. Early diagnosis of a newborn's disease, either as a channelopathy or neurometabolic disorder, is important for the long-term neurodevelopment of the child.

New avenues in molecular genetics for the diagnosis and application of therapeutics to the epilepsies

Genetic epidemiology studies have shown that most epilepsies involve some genetic cause. In addition, twin studies have helped strengthen the hypothesis that in most patients with epilepsy, a complex inheritance is involved. More recently, with the development of high-density single-nucleotide polymorphism (SNP) microarrays and next-generation sequencing (NGS) technologies, the discovery of genes related to the epilepsies has accelerated tremendously. Especially, the use of whole exome sequencing (WES) has had a considerable impact on the identification of rare genetic variants with large effect sizes, including inherited or de novo mutations in severe forms of childhood epilepsies. The identification of pathogenic variants in patients with these childhood epilepsies provides many benefits for patients and families, such as the confirmation of the genetic nature of the diseases. This process will allow for better genetic counseling, more accurate therapy decisions, and a significant positive emotional impact. However, to study the genetic component of the more common forms of epilepsy, the use of high-density SNP arrays in genome-wide association studies (GWAS) seems to be the strategy of choice. As such, researchers can identify loci containing genetic variants associated with the common forms of epilepsy. The knowledge generated over the past two decades about the effects of the mutations that cause the monogenic epilepsy is tremendous; however, the scientific community is just starting to apply this information in order to generate better target treatments.

Role of pulse methylprednisolone in epileptic encephalopathy: A retrospective observational analysis

OBJECTIVES

To study the effect of monthly pulses of intravenous methylprednisolone (IVMP) on seizure and global outcomes in children with epileptic encephalopathy (EE).

METHODS

This retrospective study was undertaken in a tertiary care epilepsy center in India. Consecutive patients with EE who had received IVMP as adjunctive therapy for a minimum of 3 months and had at least one pre-and post-steroid EEG each, were identified and a structured questionnaire was used to collect information including outcomes at 3 months post-steroid course completion and beyond, as available.

RESULTS

Ninety-seven patients (M:F=71:26) fulfilling the inclusion criteria with a mean age at onset of seizures being 20.52 ± 25.69 months were included. Commonest seizure types were myoclonic (66%); Lennaux-Gastaut and West Syndromes accounted for 57 % and 24 % patients respectively. The etiology was unknown in 52 %. All children were on a combination of standard anti-seizure drugs. The duration of IVMP pulse therapy was 7.72 ± 6.25 months. One-fourth (26 %) patients experienced minor adverse events. Greater than 50 % seizure burden reduction was seen in 66 % patients at 3 months with seizure-freedom in 25 %. A total of 45 (46 %) patients became seizure-free in the cohort eventually with continuation of steroids beyond 3 months. Children with idiopathic EEs, normal neuroimaging, myoclonic jerks, and West syndrome showed the best response. The presence of burst-suppression and generalized paroxysmal fast activity (GPFA) predicted inadequate response.

CONCLUSIONS

Adjunct pulse doses of IVMP are safe, well-tolerated, and effective in reducing seizures and improving global outcomes in children with idiopathic EEs, West syndrome, normal neuroimaging, and myoclonic jerks. Seizure freedom might be delayed in a subset of these patients, hence duration of therapy beyond 3 months may be warranted.

Postnatal Arx transcriptional activity regulates functional properties of PV interneurons

The transcription factor Aristaless-related X-linked gene (Arx) is a monogenic factor in early onset epileptic encephalopathies (EOEEs) and a fundamental regulator of early stages of brain development. However, Arx expression persists in mature GABAergic neurons with an unknown role. To address this issue, we generated a conditional knockout (CKO) mouse in which postnatal Arx was ablated in parvalbumin interneurons (PVIs). Electroencephalogram (EEG) recordings in CKO mice revealed an increase in theta oscillations and the occurrence of occasional seizures. Behavioral analysis uncovered an increase in anxiety. Genome-wide sequencing of fluorescence activated cell sorted (FACS) PVIs revealed that Arx impinged on network excitability via genes primarily associated with synaptic and extracellular matrix pathways. Whole-cell recordings revealed prominent hypoexcitability of various intrinsic and synaptic properties. These results revealed important roles for postnatal Arx expression in PVIs in the control of neural circuits and that dysfunction in those roles alone can cause EOEE-like network abnormalities.

Pathogenic variants identified by whole-exome sequencing in 43 patients with epilepsy

Background

Epilepsy is a group of neurological disorders characterized by recurrent epileptic seizures. Epilepsy is affected by many factors, approximately 20–30% of cases are caused by acquired conditions, but in the remaining cases, genetic factors play an important role. Early establishment of a specific diagnosis is important to treat and manage this disease.

Methods

In this study, we have recruited 43 epileptic encephalopathy patients and the molecular genetic analysis of those children was performed by whole-exome sequencing (WES).

Results

Fourteen patients (32.6%, 14/43) had positive genetic diagnoses, including fifteen mutations in fourteen genes. The overall diagnostic yield was 32.6%. A total of 9 patients were diagnosed as pathogenic mutations, including 4 variants had been reported as pathogenic previously and 6 novel variants that had not been reported previously. Therefore, WES heralds promise as a tool for clinical diagnosis of patients with genetic disease.

Conclusion

Early establishment of a specific diagnosis, on the one hand, is necessary for providing an accurate prognosis and recurrence risk as well as optimizing management and treatment options. On the other hand, to unveil the genetic architecture of epilepsy, it is of vital importance to investigate the phenotypic and genetic complexity of epilepsy.

Cannabis for Pediatric Epilepsy

Epilepsy is a chronic disease characterized by recurrent unprovoked seizures. Up to 30% of children with epilepsy will be refractory to standard anticonvulsant therapy, and those with epileptic encephalopathy can be particularly challenging to treat. The endocannabinoid system can modulate the physiologic processes underlying epileptogenesis. The anticonvulsant properties of several cannabinoids, namely Δ-tetrahydrocannabinol and cannabidiol (CBD), have been demonstrated in both in vitro and in vivo studies. Cannabis-based therapies have been used for millennia to treat a variety of diseases including epilepsy. Several studies have shown that CBD, both in isolation as a pharmaceutical-grade preparation or as part of a CBD-enriched cannabis herbal extract, is beneficial in decreasing seizure frequency in children with treatment-resistant epilepsy. Overall, cannabis herbal extracts appear to provide greater efficacy in decreasing seizure frequency, but the studies assessing cannabis herbal extract are either retrospective or small-scale observational studies. The two large randomized controlled studies assessing the efficacy of pharmaceutical-grade CBD in children with Dravet and Lennox-Gastaut syndromes showed similar efficacy to other anticonvulsants. Lack of data regarding appropriate dosing and pediatric pharmacokinetics continues to make authorization of cannabis-based therapies to children with treatment-resistant epilepsy challenging.

Compliance With Standard Therapies and Remission Rates After Implementation of an Infantile Spasms Management Guideline

BACKGROUND

We implemented an infantile spasms management guideline recommending standard therapies and, early start of next treatment. After six years, we determined (1) our compliance with standard therapies, (2) time to next treatment, and (3) rate of initial and three-month electroclinical remission with first, second, and third treatments.

METHODS

This is a retrospective record review of newly diagnosed spasms from September 2012 to September 2018, with the onset age of two months to two years.

RESULTS

Standard therapies (hormone or vigabatrin) were the first treatments in 114 of 115 consecutive patients. The second and third treatments were started within 14 days of failed treatment in only 21% and 24%, respectively. Remission with the first and second treatments was similar (41% and 40%). Remission was lower for the third treatment (15%), although higher if standard therapy was used (36%). Initial and three-month remission by the first treatment was significantly higher for adrenocorticotropic hormone (ACTH, 66% and 79%, respectively) and prednisolone (53% and 83%, respectively) than for vigabatrin (19% and 40%, respectively). There were no significant differences in patient characteristics or rates of remission between ACTH and prednisolone.

CONCLUSIONS

Although we achieved excellent compliance with standard therapies as initial treatment, a next treatment often started after two weeks. Given the superiority of hormone therapies over vigabatrin and standard therapies over nonstandard therapies, as well as the potentially negative impact of delays in effective treatment, future interventions need to focus on increasing the use of hormone over vigabatrin (for patients without tuberous sclerosis complex), use of standard therapies as second and third treatments, and reducing delays to next treatment.

Whole-genome analysis for effective clinical diagnosis and gene discovery in early infantile epileptic encephalopathy

Early infantile epileptic encephalopathy (EIEE) is a devastating epilepsy syndrome with onset in the first months of life. Although mutations in more than 50 different genes are known to cause EIEE, current diagnostic yields with gene panel tests or whole-exome sequencing are below 60%. We applied whole-genome analysis (WGA) consisting of whole-genome sequencing and comprehensive variant discovery approaches to a cohort of 14 EIEE subjects for whom prior genetic tests had not yielded a diagnosis. We identified both de novo point and INDEL mutations and de novo structural rearrangements in known EIEE genes, as well as mutations in genes not previously associated with EIEE. The detection of a pathogenic or likely pathogenic mutation in all 14 subjects demonstrates the utility of WGA to reduce the time and costs of clinical diagnosis of EIEE. While exome sequencing may have detected 12 of the 14 causal mutations, 3 of the 12 patients received non-diagnostic exome panel tests prior to genome sequencing. Thus, given the continued decline of sequencing costs, our results support the use of WGA with comprehensive variant discovery as an efficient strategy for the clinical diagnosis of EIEE and other genetic conditions.

[Gene mutations in unexplained infantile epileptic encephalopathy: an analysis of 47 cases]

OBJECTIVE

To investigate the characteristics of gene mutations in unexplained infantile epileptic encephalopathy (EE).

METHODS

A total of 47 infants with unexplained infantile EE were enrolled, and next-generation sequencing was used to analyze gene mutations in these infants and their parents.

RESULTS

Of all 47 infants, 23 were found to have gene mutations, among whom 13 had de novo mutations and 10 had heterozygous mutations inherited from their father or mother. Among the 23 infants with gene mutations, 17 were found to have the gene mutations related to EE (among whom 14 had ion channel gene mutations), 2 had the gene mutations related to congenital inherited metabolic diseases, 2 had the gene mutations related to brain structural abnormality, and 2 had the gene mutations related to mental retardation.

CONCLUSIONS

Unexplained infantile EE may have gene mutations, mainly ion channel gene mutations.

Ketogenic diet poses a significant effect on imbalanced gut microbiota in infants with refractory epilepsy

AIM

To investigate whether patients with refractory epilepsy and healthy infants differ in gut microbiota (GM), and how ketogenic diet (KD) alters GM.

METHODS

A total of 14 epileptic and 30 healthy infants were recruited and seizure frequencies were recorded. Stool samples were collected for 16S rDNA sequencing using the Illumina Miseq platform. The composition of GM in each sample was analyzed with MOTHUR, and inter-group comparison was conducted by R software.

RESULTS

After being on KD treatment for a week, 64% of epileptic infants showed an obvious improvement, with a 50% decrease in seizure frequency. GM structure in epileptic infants (P1 group) differed dramatically from that in healthy infants (Health group). Proteobacteria, which had accumulated significantly in the P1 group, decreased dramatically after KD treatment (P2 group). Cronobacter predominated in the P1 group and remained at a low level both in the Health and P2 groups. Bacteroides increased significantly in the P2 group, in which Prevotella and Bifidobacterium also grew in numbers and kept increasing.

CONCLUSION

GM pattern in healthy infants differed dramatically from that of the epileptic group. KD could significantly modify symptoms of epilepsy and reshape the GM of epileptic infants.

Pediatric Epileptic Encephalopathies: Pathophysiology and Animal Models

Epileptic encephalopathies are syndromes in which seizures or interictal epileptiform activity contribute to or exacerbate brain function, beyond that caused by the underlying pathology. These severe epilepsies begin early in life, are associated with poor lifelong outcome, and are resistant to most treatments. Therefore, they represent an immense challenge for families and the medical care system. Furthermore, the pathogenic mechanisms underlying the epileptic encephalopathies are poorly understood, hampering attempts to devise novel treatments. This article reviews animal models of the three classic epileptic encephalopathies-West syndrome (infantile spasms), Lennox-Gastaut syndrome, and continuous spike waves during sleep or Landau-Kleffner syndrome-with discussion of how animal models are revealing underlying pathophysiological mechanisms that might be amenable to targeted therapy.

Recent developments in the genetics of childhood epileptic encephalopathies: impact in clinical practice

Recent advances in molecular genetics led to the discovery of several genes for childhood epileptic encephalopathies (CEEs). As the knowledge about the genes associated with this group of disorders develops, it becomes evident that CEEs present a number of specific genetic characteristics, which will influence the use of molecular testing for clinical purposes. Among these, there are the presence of marked genetic heterogeneity and the high frequency of de novo mutations. Therefore, the main objectives of this review paper are to present and discuss current knowledge regarding i) new genetic findings in CEEs, ii) phenotype-genotype correlations in different forms of CEEs; and, most importantly, iii) the impact of these new findings in clinical practice. Accompanying this text we have included a comprehensive table, containing the list of genes currently known to be involved in the etiology of CEEs.

Genetic mutations associated with status epilepticus

This paper reports the results of a preliminary search of the literature aimed at identifying the genetic mutations reported to be strongly associated with status epilepticus. Genetic mutations were selected for inclusion if status epilepticus was specifically mentioned as a consequence of the mutation in standard genetic databases or in a case report or review article. Mutations in 122 genes were identified. The genetic mutations identified were found in only rare conditions (sometimes vanishingly rare) and mostly in infants and young children with multiple other handicaps. Most of the genetic mutations can be subdivided into those associated with cortical dysplasias, inborn errors of metabolism, mitochondrial disease, or epileptic encephalopathies and childhood syndromes. There are no identified 'pure status epilepticus genes'. The range of genes underpinning status epilepticus differs in many ways from the range of genes underpinning epilepsy, which suggests that the processes underpinning status epilepticus differ from those underpinning epilepsy. It has been frequently postulated that status epilepticus is the result of a failure of 'seizure termination mechanisms', but the wide variety of genes affecting very diverse biochemical pathways identified in this survey makes any unitary cause unlikely. The genetic influences in status epilepticus are likely to involve a wide range of mechanisms, some related to development, some to cerebral energy production, some to diverse altered biochemical pathways, some to transmitter and membrane function, and some to defects in networks or systems. The fact that many of the identified genes are involved with cerebral development suggests that status epilepticus might often be a system or network phenomenon. To date, there are very few genes identified which are associated with adult-onset status epilepticus (except in those with preexisting neurological damage), and this is disappointing as the cause of many adult-onset status epilepticus cases remains obscure. It has been suggested that idiopathic adult-onset status epilepticus might often have an immunological cause but no gene mutations which relate to immunological mechanisms were identified. Overall, the clinical utility of what is currently known about the genetics of status epilepticus is slight and the findings have had little impact on clinical treatment despite what has been a very large investment in money and time. New genetic technologies may result in the identification of further genes, but if the identified genetic defects confer only minor susceptibility, this is unlikely to influence therapy. It is also important to recognize that genetics has social implications in a way that other areas of science do not. This article is part of a Special Issue entitled "Status Epilepticus".

Genetics of pediatric epilepsy

As the genetic etiologies of an expanding number of epilepsy syndromes are revealed, the complexity of the phenotype genotype correlation increases. As our review will show, multiple gene mutations cause different epilepsy syndromes, making identification of the specific mutation increasingly more important for prognostication and often more directed treatment. Examples of that include the need to avoid specific drugs in Dravet syndrome and the ongoing investigations of the potential use of new directed therapies such as retigabine in KCNQ2-related epilepsies, quinidine in KCNT1-related epilepsies, and memantine in GRIN2A-related epilepsies.

Analysis of mutations in 7 genes associated with neuronal excitability and synaptic transmission in a cohort of children with non-syndromic infantile epileptic encephalopathy

Epileptic Encephalopathy (EE) is a heterogeneous condition in which cognitive, sensory and/or motor functions deteriorate as a consequence of epileptic activity, which consists of frequent seizures and/or major interictal paroxysmal activity. There are various causes of EE and they may occur at any age in early childhood. Genetic mutations have been identified to contribute to an increasing number of children with early onset EE which had been previously considered as cryptogenic. We identified 26 patients with Infantile Epileptic Encephalopathy (IEE) of unknown etiology despite extensive workup and without any specific epilepsy syndromic phenotypes. We performed genetic analysis on a panel of 7 genes (ARX, CDKL5, KCNQ2, PCDH19, SCN1A, SCN2A, STXBP1) and identified 10 point mutations [ARX (1), CDKL5 (3), KCNQ2 (2), PCDH19 (1), SCN1A (1), STXBP1 (2)] as well as one microdeletion involving both SCN1A and SCN2A. The high rate (42%) of mutations suggested that genetic testing of this IEE panel of genes is recommended for cryptogenic IEE with no etiology identified. These 7 genes are associated with channelopathies or synaptic transmission and we recommend early genetic testing if possible to guide the treatment strategy.

Vagus nerve stimulation in children less than 3 years with medically intractable epilepsy

OBJECTIVE

To describe the characteristics of children less than three years of age with medically intractable epilepsy, who underwent Vagus Nerve Stimulator (VNS) therapy at Children's Hospital of Pittsburgh between 2004 and 2011.

METHODS

Retrospective chart review.

RESULTS

Seventeen patients were identified; adequate follow-up was available for 15. Median follow up duration was 4.3 years (1.4-10.2 years). 12/15 (80%) had a known etiology for their epilepsy. All patients had more than 1 seizure per week prior to VNS and a history of status epilepticus was frequent (40%, 6/15). Five patients (33%) reported improved seizure frequency at one year after VNS. A normal MRI was associated with seizure improvement (p=0.007). No patient had status epilepticus after VNS at one-year follow-up. At three years after VNS, four patients had experienced status epilepticus with only one patient experiencing multiple episodes. Complications were seen in 2/15 (13%) patients and in 2/21 (9.5%) procedures.

SIGNIFICANCE

A normal MRI was associated with seizure improvement at one year in children less than three years of age at the time of VNS implant. The degree of overall seizure reduction was modest, but the frequency of status epilepticus was decreased after VNS implant. VNS was tolerated well in this age group.

Detection of global DNA hypomethylation of peripheral blood lymphocytes in patients with infantile spasms

The pathogenesis of infantile spasms remains unclear. DNA methylation may play a pivotal role in the development of some types of neurological diseases, such as epilepsy. In this study, we aimed to investigate the relationship between global DNA methylation of peripheral blood leukocytes and cryptogenic infantile spasms. DNA from peripheral blood leukocytes was extracted from 20 patients with cryptogenic infantile spasms and 20 gender and age matched healthy controls. Global DNA methylation percentage of peripheral blood leukocytes was measured using a global DNA methylation quantification kit. Global DNA methylation levels of peripheral blood lymphocytes in patients with cryptogenic infantile spasms (23.4 ± 20.0%) were significantly lower than those in healthy controls (46.8 ± 8.4%). Furthermore, we did not find any association between the levels of DNA methylation and effectiveness of Adrenocorticotropic hormone treatment. Our study demonstrates that global DNA hypomethylation of peripheral blood lymphocytes is correlated with infantile spasms. This finding provides information for better understanding of the pathogenesis of infantile spasms.

Do seizures and epileptic activity worsen epilepsy and deteriorate cognitive function?

Relevant to the definition of epileptic encephalopathy (EE) is the concept that the epileptic activity itself may contribute to bad outcomes, both in terms of epilepsy and cognition, above and beyond what might be expected from the underlying pathology alone, and that these can worsen over time. The review of the clinical and experimental evidence that seizures or interictal electroencephalography (EEG) discharges themselves can induce a progression toward more severe epilepsy and a regression of brain function leads to the following conclusions: The possibility of seizure-dependent worsening is by no means a general one but is limited to some types of epilepsy, namely mesial temporal lobe epilepsy (MTLE) and EEs. Clinical and experimental data concur in indicating that prolonged seizures/status epilepticus (SE) are a risky initial event that can set in motion an epileptogenic process leading to persistent, possibly drug-refractory epilepsies. The mechanisms for SE-related epileptogenic process are incompletely known; they seem to involve inflammation and/or glutamatergic transmission. The evidence of the role of recurrent individual seizures in sustaining epilepsy progression is ambiguous. The correlation between high seizure frequency and bad outcome does not necessarily demonstrate a cause-effect relationship, rather high seizure frequency and bad outcome can both depend on a particularly aggressive epileptogenic process. The results of EE studies challenge the idea of a common seizure-dependent mechanism for epilepsy progression/intellectual deterioration.

The history of the concept of epileptic encephalopathy

The first description of epileptic encephalopathies dates back to Dr. West who, in 1857, described the syndrome that took his name. In addition to West syndrome, in the last century other epileptic syndromes entered into the chapter of epileptic encephalopathies. Henry Gastaut has the virtue of having created the modern concept of epileptic encephalopathy and entering it into the official terminology of the International League Against Epilepsy (ILAE). After the first proposal, it was further defined and refined over time.

Attention deficit associated with early life interictal spikes in a rat model is improved with ACTH

Children with epilepsy often present with pervasive cognitive and behavioral comorbidities including working memory impairments, attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder. These non-seizure characteristics are severely detrimental to overall quality of life. Some of these children, particularly those with epilepsies classified as Landau-Kleffner Syndrome or continuous spike and wave during sleep, have infrequent seizure activity but frequent focal epileptiform activity. This frequent epileptiform activity is thought to be detrimental to cognitive development; however, it is also possible that these IIS events initiate pathophysiological pathways in the developing brain that may be independently associated with cognitive deficits. These hypotheses are difficult to address due to the previous lack of an appropriate animal model. To this end, we have recently developed a rat model to test the role of frequent focal epileptiform activity in the prefrontal cortex. Using microinjections of a GABA(A) antagonist (bicuculline methiodine) delivered multiple times per day from postnatal day (p) 21 to p25, we showed that rat pups experiencing frequent, focal, recurrent epileptiform activity in the form of interictal spikes during neurodevelopment have significant long-term deficits in attention and sociability that persist into adulthood. To determine if treatment with ACTH, a drug widely used to treat early-life seizures, altered outcome we administered ACTH once per day subcutaneously during the time of the induced interictal spike activity. We show a modest amelioration of the attention deficit seen in animals with a history of early life interictal spikes with ACTH, in the absence of alteration of interictal spike activity. These results suggest that pharmacological intervention that is not targeted to the interictal spike activity is worthy of future study as it may be beneficial for preventing or ameliorating adverse cognitive outcomes.

Clinical whole-genome sequencing in severe early-onset epilepsy reveals new genes and improves molecular diagnosis

In severe early-onset epilepsy, precise clinical and molecular genetic diagnosis is complex, as many metabolic and electro-physiological processes have been implicated in disease causation. The clinical phenotypes share many features such as complex seizure types and developmental delay. Molecular diagnosis has historically been confined to sequential testing of candidate genes known to be associated with specific sub-phenotypes, but the diagnostic yield of this approach can be low. We conducted whole-genome sequencing (WGS) on six patients with severe early-onset epilepsy who had previously been refractory to molecular diagnosis, and their parents. Four of these patients had a clinical diagnosis of Ohtahara Syndrome (OS) and two patients had severe non-syndromic early-onset epilepsy (NSEOE). In two OS cases, we found de novo non-synonymous mutations in the genes KCNQ2 and SCN2A. In a third OS case, WGS revealed paternal isodisomy for chromosome 9, leading to identification of the causal homozygous missense variant in KCNT1, which produced a substantial increase in potassium channel current. The fourth OS patient had a recessive mutation in PIGQ that led to exon skipping and defective glycophosphatidyl inositol biosynthesis. The two patients with NSEOE had likely pathogenic de novo mutations in CBL and CSNK1G1, respectively. Mutations in these genes were not found among 500 additional individuals with epilepsy. This work reveals two novel genes for OS, KCNT1 and PIGQ. It also uncovers unexpected genetic mechanisms and emphasizes the power of WGS as a clinical tool for making molecular diagnoses, particularly for highly heterogeneous disorders.

Are there really "epileptogenic" mechanisms or only corruptions of "normal" plasticity?

Plasticity in the nervous system, whether for establishing connections and networks during development, repairing networks after injury, or modifying connections based on experience, relies primarily on highly coordinated patterns of neural activity. Rhythmic, synchronized bursting of neuronal ensembles is a fundamental component of the activity-dependent plasticity responsible for the wiring and rewiring of neural circuits in the CNS. It is therefore not surprising that the architecture of the CNS supports the generation of highly synchronized bursts of neuronal activity in non-pathological conditions, even though the activity resembles the ictal and interictal events that are the hallmark symptoms of epilepsy. To prevent such natural epileptiform events from becoming pathological, multiple layers of homeostatic control operate on cellular and network levels. Many data on plastic changes that occur in different brain structures during the processes by which the epileptogenic aggregate is constituted have been accumulated but their role in counteracting or promoting such processes is still controversial. In this chapter we will review experimental and clinical evidence on the role of neural plasticity in the development of epilepsy. We will address questions such as: is epilepsy a progressive disorder? What do we know about mechanism(s) accounting for progression? Have we reliable biomarkers of epilepsy-related plastic processes? Do seizure-associated plastic changes protect against injury and aid in recovery? As a necessary premise we will consider the value of seizure-like activity in the context of normal neural development.

Diagnosis and management of epileptic encephalopathies in children

Epileptic encephalopathies refer to a group of disorders in which the unremitting epileptic activity contributes to severe cognitive and behavioral impairments above and beyond what might be expected from the underlying pathology alone, and these can worsen over time leading to progressive cerebral dysfunction. Several syndromes have been described based on their electroclinical features (age of onset, seizure type, and EEG pattern). This review briefly describes the clinical evaluation and management of commonly encountered epileptic encephalopathies in children.