Early and effective treatment ofKCNQ2encephalopathy

Epileptic Encephalopathy In A Patient With A Novel Variant In The Kv7.2 S2 Transmembrane Segment: Clinical, Genetic, and Functional Features

Kv7.2 subunits encoded by the KCNQ2 gene provide a major contribution to the M-current (I_KM), a voltage-gated K⁺ current crucially involved in the regulation of neuronal excitability. Heterozygous missense variants in Kv7.2 are responsible for epileptic diseases characterized by highly heterogeneous genetic transmission and clinical severity, ranging from autosomal-dominant Benign Familial Neonatal Seizures (BFNS) to sporadic cases of severe epileptic and developmental encephalopathy (DEE). Here, we describe a patient with neonatal onset DEE, carrying a previously undescribed heterozygous KCNQ2 c.418G > C, p.Glu140Gln (E140Q) variant. Patch-clamp recordings in CHO cells expressing the E140Q mutation reveal dramatic loss of function (LoF) effects. Multistate structural modelling suggested that the E140Q substitution impeded an intrasubunit electrostatic interaction occurring between the E140 side chain in S₂ and the arginine at position 210 in S₄ (R210); this interaction is critically involved in stabilizing the activated configuration of the voltage-sensing domain (VSD) of Kv7.2. Functional results from coupled charge reversal or disulfide trapping experiments supported such a hypothesis. Finally, retigabine restored mutation-induced functional changes, reinforcing the rationale for the clinical use of Kv7 activators as personalized therapy for DEE-affected patients carrying Kv7.2 LoF mutations.

[Epileptogenesis and consequences for treatment]

Epilepsy is a frequent and disabling neurological disease with a significant burden for patients and their relatives worldwide. Epileptogenesis is understood as the plastic process that after an insult (in acquired epilepsies) finally leads to seizures with a latent period. In some cases, epileptogenesis has been clarified down to the molecular level. In parallel, the discovery of genetic defects has decisively contributed to unravel epileptic disease mechanisms. Both research directions have enabled first personalized treatment options. In addition, genetic variants associated with epilepsy can not only directly cause seizures but likely also induce an epileptogenic process (similar as in acquired epilepsies) and interact with developmental processes of the brain, finally leading to the typical age-dependent manifestation of genetic epilepsy syndromes. This article describes these correlations and the consequences for personalized treatment possibilities.

KCNQ2 mutations in childhood nonlesional epilepsy: Variable phenotypes and a novel mutation in a case series

BACKGROUND

Epilepsy caused by a KCNQ2 gene mutation usually manifests as neonatal seizures during the first week of life. The genotypes and phenotypes of KCNQ2 mutations are noteworthy.

METHODS

The KCNQ2 sequencings done were selected from 131 nonconsanguineous pediatric epileptic patients (age range: 2 days to 18 years) with nonlesional epilepsy.

RESULTS

Seven (5%) index patients had verified KCNQ2 mutations: c.387+1 G>T (splicing), c.1741 C>T (p.Arg581*), c.740 C>T p.(Ser247Leu), c.853 C>A p.(Pro285Thr), c.860 C>T p.(Thr287Ile), c.1294 C>T p.(Arg432Cys), and c.1627 G>A p.(Val543Met). We found, after their paternity had been confirmed, that three patients had de novo p.(Ser247Leu), p.(Pro285Thr), and p.(Thr287Ile) mutations and neonatal-onset epileptic encephalopathy; however, their frequent seizures remitted after they turned 6 months old. Those with the c.387+1G>T (splicing), (p.Arg581*), and p.(Val543Met) mutations presented with benign familial neonatal convulsions. In addition to their relatives, 14 patients had documented KCNQ2 mutations, and 12 (86%) had neonatal seizures. The seizures of all five patients treated with oxcarbazepine remitted.

CONCLUSION

KCNQ2-related epilepsy led to varied outcomes (from benign to severe) in our patients. KCNQ2 mutations accounted for 13% of patients with seizure onset before 2 months old in our study. KCNQ2 mutations can cause different phenotypes in children. p.(Pro 285Thr) is a novel mutation, and the p.(Pro 285Thr), p.(Ser247Leu), and p.(Thr287Ile) variants can cause neonatal-onset epileptic encephalopathy.

Genetics of neonatal onset epilepsies: An overview

The weight of monogenic abnormalities in the possible causes of epilepsy has grown significantly in recent years, due to the emergence of next-generation sequencing (NGS) techniques. Especially notable in early neonatal and infantile epilepsies, which seem to be explained by monogenic abnormalities. This short review focuses on the major genes associated with very early-onset epilepsies, where NGS techniques are most cost-effective: early infantile epileptic encephalopathy, early myoclonic encephalopathy, and other neonatal epilepsies. The discovery of the genetic mutation often follows several weeks or months of management, and rarely modifies it. However, clinical studies can sometimes better define medical treatment. The genetic causes of these epilepsies are very numerous and the pathophysiological knowledge very minimal. The big challenge for the coming years is to develop more targeted treatments based on research on animal models.

Etiology of neonatal seizures and maintenance therapy use: a 10-year retrospective study at Toulouse Children's hospital

BACKGROUND

No guidelines exist concerning the maintenance antiepileptic drug to use after neonatal seizures. Practices vary from one hospital to another. The aim of this study was to investigate etiologies and to report on the use of maintenance antiepileptic therapy in our population of full-term neonates presenting neonatal seizures.

METHODS

From January 2004 to October 2014, we retrospectively collected data from all full-term neonates with neonatal seizures admitted to the Children's Hospital of Toulouse, France.

RESULTS

Two hundred and forty-three neonates were included (59% males, 48% electroencephalographic confirmation). The frequencies of etiologies of neonatal seizures were: hypoxic-ischemic encephalopathy (HIE) (n = 91; 37%), ischemic infarction (n = 36; 15%), intracranial hemorrhage (n = 29; 12%), intracranial infection (n = 19; 8%), metabolic or electrolyte disorders (n = 9; 3%), inborn errors of metabolism (n = 5; 2%), congenital malformations of the central nervous system (n = 11; 5%), epileptic syndromes (n = 27; 12%) and unknown (n = 16; 7%). A maintenance therapy was prescribed in 180 (72%) newborns: valproic acid (n = 123), carbamazepine (n = 28), levetiracetam (n = 17), vigabatrin (n = 2), and phenobarbital (n = 4). In our cohort, the choice of antiepileptic drug depended mainly on etiology. The average duration of treatment was six months.

CONCLUSIONS

In our cohort, valproic acid was the most frequently prescribed maintenance antiepileptic therapy. However, the arrival on the market of new antiepileptic drugs and a better understanding of the physiopathology of genetic encephalopathies is changing our practice.

TRIAL REGISTRATION

Retrospectively registered. Patient data were reported to the "Commission Nationale Informatique et Libertés" under the number 2106953 .

Case for genome sequencing in infants and children with rare, undiagnosed or genetic diseases

Up to 350 million people worldwide suffer from a rare disease, and while the individual diseases are rare, in aggregate they represent a substantial challenge to global health systems. The majority of rare disorders are genetic in origin, with children under the age of five disproportionately affected. As these conditions are difficult to identify clinically, genetic and genomic testing have become the backbone of diagnostic testing in this population. In the last 10 years, next-generation sequencing technologies have enabled testing of multiple disease genes simultaneously, ranging from targeted gene panels to exome sequencing (ES) and genome sequencing (GS). GS is quickly becoming a practical first-tier test, as cost decreases and performance improves. A growing number of studies demonstrate that GS can detect an unparalleled range of pathogenic abnormalities in a single laboratory workflow. GS has the potential to deliver unbiased, rapid and accurate molecular diagnoses to patients across diverse clinical indications and complex presentations. In this paper, we discuss clinical indications for testing and historical testing paradigms. Evidence supporting GS as a diagnostic tool is supported by superior genomic coverage, types of pathogenic variants detected, simpler laboratory workflow enabling shorter turnaround times, diagnostic and reanalysis yield, and impact on healthcare.

Neonatal seizures: Is there a relationship between ictal electroclinical features and etiology? A critical appraisal based on a systematic literature review

The aim of this study was to evaluate whether specific etiologies of neonatal seizures have distinct ictal electroclinical features. A systematic review of English articles using the PubMed database since 2004 (last update 9/26/16). Search terms included text words and Medical Subject Headings (MeSH) terms related to neonatal seizures. Eligible articles included reports of neonates with seizures with a full description of seizure semiology and electroclinical findings. Independent extraction of data was performed by 2 authors using predefined data fields, including study quality indicators. Data were collected for every individual patient described in the articles. The dataset was analyzed with the Fisher exact test. The initial search led to 8507 titles; using filters, 2910 titles and abstracts were identified, with 177 full texts selected to be read. Fifty-seven studies were included in the analysis with 151 neonates (37.7 male and 62.9% term). Genetic etiologies (51%) and sequential seizures (41.1%) predominated in this sample and hypoxic-ischemic encephalopathy (HIE) accounted for only 4%. The low prevalence of HIE observed was probably due to a publication bias. A significant association was found between etiology and seizure type: hemorrhage with autonomic seizures (P = 0.003), central nervous system (CNS) infection and stroke with clonic seizures (P = 0.042, P < 0.001, respectively), metabolic/vitamin-related disorders, and inborn errors of metabolism with myoclonic seizures (P < 0.001). There were also specific electroencephalography (EEG) patterns seen with certain etiologies: vascular disorders and electrolyte imbalance with focal ictal discharges (P < 0.001, P = 0.049 respectively), vitamin-related disorders with multifocal (P = 0.003), and all categories of genetic disorders with burst-suppression (P < 0.001). Clonic and autonomic seizures were more frequently present with focal EEG abnormalities (P = 0.001 and P < 0.001), whereas tonic and myoclonic seizures present with burst-suppression (P = 0.001, P = 0.005). In conclusion, our data suggest that specific associations of etiologies of neonatal seizures with distinct clinical features and EEG patterns might help in the decision to establish appropriate treatment.

A de novo KCNQ2 Gene Mutation Associated With Non-familial Early Onset Seizures: Case Report and Revision of Literature Data

Among neonatal epileptic syndromes, benign familial neonatal seizures (BFNS) are often due to autosomal-dominant mutations of the KCNQ2 gene. Seizures are usually characterized by asymmetric tonic posturing with apnea with onset in the first 7 days of life; they may even occur more than 10 times per day or evolve into status epilepticus. The delivery course of our patient was uneventful and family history was negative; on the second day of life the baby became pale, rigid, and apnoic during breastfeeding and appeared jittery and irritable when stimulated or examined. At age 3 days, she experienced clusters of generalized tonic seizures with pallor, desaturation, bradycardia, and partial response to intravenous phenobarbital; during her 4th and 5th days of life, three episodes of tonic seizures were noticed. At age 6 days, the patient experienced about 10 episodes of tonic seizures involving both sides of the body, which gradually responded to intravenous phenytoin. Electroencephalograms revealed abnormalities but brain MRI was normal. The patient is seizure-free since postnatal day 21; she is now 12 months old with cognitive development within normal limits at Bayley III Scale and mild motor delay. The patient is on maintenance therapy with phenobarbital since she was 7 months old. A de novo heterozygous mutation (c.853C>T/p.P285S) in the KCNQ2 gene was identified. We therefore describe a case of de novo KCNQ2-related neonatal convulsions with necessity of multiple anticonvulsants for the control of seizures, mutation occurring in the pore channel of the voltage-gated potassium channel subfamily Q member 2 associated with a likely benign course; furthermore, the same mutation of the KCNQ2 gene and a similar one (c.854C>A/p.P285H) have already been described in association with Ohtahara syndrome. Probably acquired environmental, perinatal and genetic risk factors are very important in determining the different phenotype; we hope that the rapid progress of analysis tools in molecular diagnosis can also be used in the search of an individualized therapeutic approach for these patients.

Genetics of neonatal-onset epilepsies

Although the majority of seizures in neonates are related to acute brain injury, a substantial minority are the first symptom of a neonatal-onset epilepsy often linked to a pathogenic genetic variant. Historically, studies on neonatal seizures including treatment response and long-term consequences have lumped all etiologies together. However, etiology has been consistently shown to be the most important determinant of outcome. In the past few years, an increasing number of monogenic disorders have been described and might explain up to a third of neonatal-onset epilepsy syndromes previously included under the umbrella of Ohtahara syndrome and early myoclonic encephalopathy. In this chapter, we define the concept of genetic epilepsy and review the classification. Then, we review the most relevant monogenic neonatal-onset epilepsies, detail their underlying pathophysiologic mechanisms, and present their electroclinical phenotypes. We highlight that, in some cases, such as neonates with KCNQ2 or KCNT1 gene mutations, the early recognition of the electroclinical phenotype can lead to targeted diagnostic testing and precision medicine treatment, enabling the possibility of improved outcome.

Generalized epilepsies

Idiopathic generalized epilepsies (IGE) are characterized by normal background EEG activity and generalized interictal spike-and-wave discharges in the absence of any evidence of brain lesion. Absence epilepsies are the prototypes of IGEs. In childhood and juvenile absence epilepsies, by definition, all patients manifest absence seizures associated with an EEG pattern of generalized spike-wave (GSW) discharges. In juvenile myoclonic epilepsy, myoclonic jerks, usually affecting shoulders and arms bilaterally and appearing upon awakening, are the most characteristic clinical feature. Myoclonic jerks are accompanied on the EEG by generalized spike/polyspike-and-wave (GSW, GPWS) complexes at 3.5-6Hz. Idiopathic generalized epilepsy with generalized tonic-clonic seizures only is a broad and nonspecific category including all patients with generalized tonic-clonic seizures and an interictal EEG pattern of GSW discharges. Despite the strong heritability and the recent advances in genetic technology, the genetic basis of IGEs remains largely elusive and only in a small minority of patients with classic IGE phenotypes is a monogenic cause identified. Early myoclonic encephalopathy (EME), early infantile encephalopathy with suppression bursts, West syndrome, and Lennox-Gastaut syndrome, once classified among the generalized epilepsies, are now considered to be epileptic encephalopathies. Among them, only Lennox-Gastaut syndrome is characterized by prominent generalized clinical and EEG features.

Homomeric Kv7.2 current suppression is a common feature in KCNQ2 epileptic encephalopathy

OBJECTIVE

To gain insight into the mechanisms underlying KCNQ2 encephalopathy by examining the electrophysiologic properties of mutant Kv7.2 channels in different multimeric configurations.

METHODS

We analyzed the genotype-phenotype relationship in 4 patients with KCNQ2 encephalopathy and performed electrophysiologic analysis of M-currents mediated by homomeric Kv7.2 or heteromeric Kv7.2/Kv7.3 channels.

RESULTS

Negligible or no current was recorded in cells expressing homomeric E130K, W270R, or G281R de novo mutants, and it was reduced by more than 90% for the L243F maternally inherited mutant. The E130K and G281R mutants presented a marked dominant-negative behavior, whereas the current density was partially reduced (L243F) or not affected (W270R) when coexpressed with wild-type Kv7.2 subunits. In contrast, the extent of Kv7.3 "rescue," which yields negligible currents on its own, followed the sequence E130K > L243F > W270R, whereas no rescue was observed with the G281R mutant. No significant effects on current density were observed when subunits were expressed in a 0.5:0.5:1.0 (Kv7.2:mutant:Kv7.3) DNA ratio to mimic the genetic balance. There was an increase in sensitivity to phosphatidylinositol 4,5-bisphosphate (PIP₂ ) depletion for W270R/Kv7.3, but no substantial differences were observed when the mutated subunits were coexpressed with Kv7.2 or both Kv7.2 and Kv7.3.

SIGNIFICANCE

There was a marked disparity of the impact of these mutations on Kv7.2 function, which varied on association with Kv7.2 or Kv7.3 subunits. Current density of homomeric channels was the most reliable property relating Kv7.2 function to encephalopathy, but other factors are required to explain the milder phenotype for some individuals carrying the maternally inherited L243F mutation. We hypothesize that the role of homomeric Kv7.2 channels for fine-tuning neuronal connections during development is critical for the severity of the KCNQ2 encephalopathy.

Evolution and course of early life developmental encephalopathic epilepsies: Focus on Lennox-Gastaut syndrome

OBJECTIVES

Developmental encephalopathic epilepsies (DEEs) are characterized by refractory seizures, disability, and early death. Opportunities to improve care and outcomes focus on West syndrome/infantile spasms (WS/IS). Lennox-Gastaut syndrome (LGS) is almost as common but receives little attention. We examined initial presentations of DEEs and their evolution over time to identify risk and indicators of developing LGS.

METHODS

Data are from the Connecticut Study of Epilepsy, a prospective, longitudinal study of 613 children with newly diagnosed epilepsy recruited in 1993-1997. Central review of medical records permitted classification of epilepsy syndromes at diagnosis and at reclassification 2, 5, and 9 years later. DEEs were compared to other epilepsies for seizure and cognitive outcomes and mortality. Analyses examined the evolution of DEE syndromes after initial presentation, with specific comparisons made between WS/IS and LGS. Statistical analyses were performed with t tests and chi-square tests.

RESULTS

Fifty-eight children (9.4%) had DEEs, median onset age = 1.1 years (interquartile range ([IQR] 0.3-1.3) in DEEs and 6.0 years (IQR 3.0-9.0) in other epilepsies (P < 0.001). DEEs vs other epilepsies had more pharmacoresistance (71% vs 18%), intellectual disability (84% vs 11%), and mortality (21% vs <1%; all P < 0.001). During follow-up, the form of epilepsy evolved in 33 children. WS/IS was the most common initial diagnosis (N = 23) and in 5 children WS/IS evolved later. LGS was diagnosed initially in 4 children (1 later revised) and in 22 by the end of follow-up, including 7 evolving from WS/IS and 12 from nonsyndromic generalized, focal, or undetermined epilepsies. Evolution to LGS took a median of 1.9 years. LGS developed in 13% of infants, including 9% of those who did not present initially with WS/IS.

SIGNIFICANCE

DEEs account for disproportionate amounts of pharmacoresistance, disability, and early mortality. LGS often has a window between initial presentation and full expression. LGS should become targeted for early detection and prevention.

Diagnostic work-up and rehabilitation of cerebral visual impairment in infancy: A case of epileptic perinatal encephalopathy due to KCNQ2-related channelopathy

BACKGROUND

There is evidence that channelopathies are the cause of many different neurological diseases. The epileptic perinatal encephalopathy due to mutation in the KCNQ2 gene is a rare disease involving severe tetraparesis and cerebral visual impairment. Diseases of this kind are associated with severe disability that involves multiple systems and requires accurate genetic diagnosis and early multidisciplinary care once clinical stability is reached.

CASE REPORT

We describe a case of a baby girl with KCNQ2 encephalopathy who came to our observation for rehabilitation at age 2 years and 6 months.

CLINICAL REHABILITATION IMPACT

We stress the importance of a correct clinical, pharmacological and visual diagnosis. Correct diagnosis made it possible to involve the baby girl and her care-giver in an early process of visual rehabilitation lasting 6 months, the effects of which proved to persist at follow-up after more than a year, making it possible to start a useful inter-professional rehabilitation plan.

Next-generation sequencing improves treatment efficacy and reduces hospitalization in children with drug-resistant epilepsy

BACKGROUND

The purposes of this study were three-fold: (i) to determine the contribution of known genes to the causation of a broad-spectrum of pediatric drug-resistant epilepsy (DRE), (ii) to compare the diagnostic yield and cost among different next-generation sequencing (NGS) approaches, and especially (iii) to assess how NGS approaches can benefit patients by improving diagnosis and treatment efficiency.

METHODS

This study enrolled 273 pediatric DRE patients with no obvious acquired etiology. Seventy-four patients underwent whole-exome sequencing (WES), 141 patients had epilepsy-related gene panel testing, and another 58 patients had clinical WES gene panel testing. We obtained these patients' seizure and hospitalization frequency by periodic follow-up phone calls and outpatient visits.

RESULTS

Genetic diagnosis was achieved in 86 patients (31.5%) and involved 93 likely disease-causing mutations in 33 genes. In this study, the detection rates of the epilepsy-related gene panel, the clinical WES gene panel, and WES were 32.6% (46/141), 44.8% (26/58), and 17.3% (13/74), respectively. Moreover, 34 patients accepted corrective therapy according to their mutant genes, after which 52.9% (18/34) became seizure-free and 38.2% (13/34) achieved seizure reduction. In the end, patients with either positive or negative genetic results had significantly fewer hospitalization incidents (times/half year) than before (positive genetic results group 0.58 ± 1.14 vs 0.10 ± 0.26; negative genetic results group 0.72 ± 1.65 vs 0.12 ± 0.33).

CONCLUSIONS

These results offer further proof that NGS approaches represent powerful tools for establishing a definitive diagnosis. Moreover, this study indicated how NGS can improve treatment efficacy and reduce hospitalization in children with DRE.

Neonatal epilepsy genetics

Neonatal epilepsy genetics is a rapidly expanding field with recent technological advances in genomics leading to an expanding list of genetic disorders associated with neonatal-onset epilepsy. The genetic causes of neonatal epilepsy can be grouped into the following categories: (i) malformations of cortical development, (ii) genetic-metabolic, (iii) genetic-vascular, (iv) genetic-syndromic, and (v) genetic-cellular. Clinically, epilepsy in the neonate shows phenotypic overlap with pathogenic variants in unrelated genes causing similar clinical presentation (locus heterogeneity) and variants in the same gene leading to a wide clinical spectrum ranging from benign familial neonatal seizures to more severe epileptic encephalopathies (variable expressivity). We suggest a diagnostic approach to obtaining a genetic diagnosis with emphasis on clinical features such as electro-clinical phenotype and magnetic resonance imaging findings. Rapid identification of genetic disorders with targeted treatments should be a clinical priority. Achieving a genetic diagnosis can be challenging in a rapidly changing genetic landscape, but is increasingly possible.

Neonatal epilepsies: Clinical management

Whereas the majority of seizures in neonates are related to acute brain injury, a substantial minority are the first symptom of a neonatal-onset epilepsy, often linked to a pathogenic genetic variant. This defect may disrupt cortical development (e.g., lissencephaly, focal cortical dysplasia), lead to metabolic changes (e.g., pyridoxine-dependent epilepsy, sulfite oxidase deficiency) or lead to cortical dysfunction without metabolic or macroscopic structural changes (e.g., channelopathies, STXBP1). Historically, studies on treatment response and long-term consequences of neonatal seizures have lumped all etiologies together. However, etiology has been consistently shown to be the most important determinant of outcome. Here, we address the elements differentiating neonatal-onset epilepsies from acute symptomatic seizures. We review some common neonatal-onset epilepsies and emphasize how pathognomonic electro-clinical phenotypes such as the ones associated with KCNQ2 or KCNT1 gene mutation, when recognized early, can lead to targeted diagnostic testing and precision medicine treatment, enabling the possibility of improved outcome.

Genetic diagnosis in neonatal-onset epilepsies: Back to the future

Seizures are more frequent in newborns than in any other period of life. In most cases they are due to acute dysfunction of the central nervous system; however some can be true epileptic disorders with an early onset. Although rare, diagnosis of neonatal-onset epilepsies is rising as genetic testing increases. The spectrum of clinical severity associated with specific genes can vary widely with difficulties in providing genotype-phenotype correlations. Therefore, clinicians should strive in order to clearly delineate the clinical features associated with pathogenic genetic variants with the aim to guide the increasing use of genetic testing and improve clinical management.

Rapid whole-genome sequencing decreases infant morbidity and cost of hospitalization

Genetic disorders are a leading cause of morbidity and mortality in infants. Rapid whole-genome sequencing (rWGS) can diagnose genetic disorders in time to change acute medical or surgical management (clinical utility) and improve outcomes in acutely ill infants. We report a retrospective cohort study of acutely ill inpatient infants in a regional children's hospital from July 2016-March 2017. Forty-two families received rWGS for etiologic diagnosis of genetic disorders. Probands also received standard genetic testing as clinically indicated. Primary end-points were rate of diagnosis, clinical utility, and healthcare utilization. The latter was modelled in six infants by comparing actual utilization with matched historical controls and/or counterfactual utilization had rWGS been performed at different time points. The diagnostic sensitivity of rWGS was 43% (eighteen of 42 infants) and 10% (four of 42 infants) for standard genetic tests (P = .0005). The rate of clinical utility of rWGS (31%, thirteen of 42 infants) was significantly greater than for standard genetic tests (2%, one of 42; P = .0015). Eleven (26%) infants with diagnostic rWGS avoided morbidity, one had a 43% reduction in likelihood of mortality, and one started palliative care. In six of the eleven infants, the changes in management reduced inpatient cost by $800,000-$2,000,000. These findings replicate a prior study of the clinical utility of rWGS in acutely ill inpatient infants, and demonstrate improved outcomes and net healthcare savings. rWGS merits consideration as a first tier test in this setting.

KCNQ2 encephalopathy: A case due to a de novo deletion

KCNQ2 encephalopathy is characterized by severely abnormal EEG, neonatal-onset epilepsy and developmental delay. It is caused by mutations (typically missense) in the KCNQ2 gene, encoding the voltage gated potassium channel Kv7.2 and leading to a negative-dominant effect. We present one case experiencing recurrent neonatal seizures with changing hemispheres of origin, reminiscent of epilepsy of infancy with migrating focal seizures. At 9months of age the patient is still seizure-free on carbamazepine, although he is developing a spastic-dystonic tetraplegia with severe dysphagia. He harbors a de novo deletion (c.913_915del [p.Phe305del)]), only described once in a couple of severely affected twins, and leading to the deletion of a phenylalanine residue in the pore domain of the channel. In conclusion, our case is the second described with encephalopathy due to this specific deletion (the one and only deletion so far reported in KCNQ2 encephalopathy). Thus, deletion is a newly described mechanism highlighting how not only missense mutations but also deletions in the channel hot spots can lead to a severe phenotype. Furthermore he presented ictal EEG features similar to epilepsy of infancy with migrating focal seizures not previously described.

A Case of KCNQ2-Associated Movement Disorder Triggered by Fever

The differential diagnosis of fever-induced movement disorders in childhood is broad. Whole exome sequencing has yielded new insights into those cases with a suspected genetic basis. We report the case of an 8-year-old boy with a history of neonatal seizures who presented with near-continuous hyperkinetic movements of his limbs during a febrile illness. Initial diagnostic testing did not explain his abnormalities; however, given the suspicion for a channelopathy, whole exome sequencing was performed and it demonstrated a de novo pathogenic heterozygous variant in KCNQ2. There is an expanding phenotypic spectrum of heterozygous alterations in KCNQ2; however, this report provides the first description of a pathogenic KCNQ2 variant fever-induced hyperkinetic movement disorder in childhood. We also review the literature of cases previously published with the same pathogenic variant.

Genetics update: Monogenetics, polygene disorders and the quest for modifying genes

The genetic channelopathies are a broad collection of diseases. Many ion channel genes demonstrate wide phenotypic pleiotropy, but nonetheless concerted efforts have been made to characterise genotype-phenotype relationships. In this review we give an overview of the factors that influence genotype-phenotype relationships across this group of diseases as a whole, using specific individual channelopathies as examples. We suggest reasons for the limitations observed in these relationships. We discuss the role of ion channel variation in polygenic disease and highlight research that has contributed to unravelling the complex aetiological nature of these conditions. We focus specifically on the quest for modifying genes in inherited channelopathies, using the voltage-gated sodium channels as an example. Epilepsy related to genetic channelopathy is one area in which precision medicine is showing promise. We will discuss the successes and limitations of precision medicine in these conditions. This article is part of the Special Issue entitled 'Channelopathies.'

Prospective cohort study for identification of underlying genetic causes in neonatal encephalopathy using whole-exome sequencing

PurposeNeonatal encephalopathy, which is characterized by a decreased level of consciousness, occurs in 1-7/1,000 live-term births. In more than half of term newborns, there is no identifiable etiological factor. To identify underlying genetic defects, we applied whole-exome sequencing (WES) in term newborns with neonatal encephalopathy as a prospective cohort study.MethodsTerm newborns with neonatal encephalopathy and no history of perinatal asphyxia were included. WES was performed using patient and both parents' DNA.ResultsNineteen patients fulfilling inclusion criteria were enrolled. Five patients were excluded owing to withdrawal of consent, no parental DNA samples, or a genetic diagnosis prior to WES. Fourteen patients underwent WES. We confirmed a genetic diagnosis in five patients (36%): epileptic encephalopathy associated with autosomal dominant de novo variants in SCN2A (p.Met1545Val), KCNQ2 (p.Asp212Tyr), and GNAO1 (p.Gly40Arg); lipoic acid synthetase deficiency due to compound heterozygous variants in LIAS (p.Ala253Pro and p.His236Gln); and encephalopathy associated with an X-linked variant in CUL4B (p.Asn211Ser).ConclusionWES is helpful at arriving genetic diagnoses in neonatal encephalopathy and/or seizures and brain damage. It will increase our understanding and probably enable us to develop targeted neuroprotective treatment strategies.

Barriers to Genetic Testing for Pediatric Medicaid Beneficiaries With Epilepsy

BACKGROUND

Children with public insurance (Medicaid) have increased barriers to specialty care in the United States. For children with epilepsy, the relationship between public insurance and barriers to genetic testing is understudied.

METHODS

We surveyed a sample of US child neurology clinicians. We performed quantitative and qualitative analysis of responses.

RESULTS

There were 302 responses (of 1982 surveyed; response rate 15%) from clinicians from 46 states, the District of Columbia, and Puerto Rico, including board-certified child neurologists (82%), resident physicians (6%), nurses (3%), and nurse practitioners (3%). Clinicians felt it was more difficult to get genetic testing for patients with Medicaid insurance compared with commercial insurance, (43% vs 12%, P < 0.05), although many felt it was about the same degree of difficulty (25%) or were not sure (20%). Increased availability of testing was associated with less complex testing (P < 0.001), in-house testing (P < 0.001), and no preauthorization requirements (P < 0.001). Qualitative responses described barriers related to cost, clinician familiarity and comfort, commercial laboratories, health care organization, payer, and patient concerns. Descriptions of facilitators included lowered cost, availability of clinical genetics expertise, clinician knowledge, commercial laboratory assistance, health care organizational changes, improved payer coverage, and increased interest by parents.

CONCLUSIONS

Pediatric Medicaid beneficiaries with epilepsy have barriers to genetic testing, compared with children with commercial insurance, particularly for more advanced testing. Potential strategies to improve access include broader coverage, lower co-pays, increased capacity for testing outside of specialty laboratories, fewer preauthorization requirements, improved clinician education, ongoing development and dissemination of guidelines, improved availability of clinical genetics services, and continued assistance programs from commercial laboratories.

WITHDRAWN: Genetics update: Monogenetics, polygene disorders and the quest for modifying genes

The Publisher regrets that this article is an accidental duplication of an article that has already been published, https://doi.org/10.1016/j.neuropharm.2017.10.013. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Profile of neonatal epilepsies: Characteristics of a prospective US cohort

OBJECTIVE

Although individual neonatal epilepsy syndromes are rare, as a group they represent a sizable subgroup of neonatal seizure etiologies. We evaluated the profile of neonatal epilepsies in a prospective cohort of newborns with seizures.

METHODS

Consecutive newborns with seizures were enrolled in the Neonatal Seizure Registry (an association of 7 US children's hospitals). Treatment and diagnostic testing were at the clinicians' discretion. Neonates with seizures related to epileptic encephalopathies (without structural brain abnormalities), brain malformations, or benign familial epilepsies were included in this analysis.

RESULTS

Among 611 consecutive newborns with seizures, 79 (13%) had epilepsy (35 epileptic encephalopathy, 32 congenital brain malformations, 11 benign familial neonatal epilepsy [BFNE], 1 benign neonatal seizures). Twenty-nine (83%) with epileptic encephalopathy had genetic testing and 24/29 (83%) had a genetic etiology. Pathogenic or likely pathogenic KCNQ2 variants (n = 10) were the most commonly identified etiology of epileptic encephalopathy. Among 23 neonates with brain malformations who had genetic testing, 7 had putative genetic etiologies. Six infants with BFNE had genetic testing; 3 had pathogenic KCNQ2 variants and 1 had a pathogenic KCNQ3 variant. Comorbid illnesses that predisposed to acute symptomatic seizures occurred in 3/35 neonates with epileptic encephalopathy vs 10/32 with brain malformations (p = 0.03). Death or discharge to hospice were more common among newborns with brain malformations (11/32) than those with epileptic encephalopathy (3/35, p = 0.01).

CONCLUSIONS

Neonatal epilepsy is often due to identifiable genetic causes. Genetic testing is now warranted for newborns with epilepsy in order to guide management and inform discussions of prognosis.

The role of genetic testing in epilepsy diagnosis and management

INTRODUCTION

Epilepsy is a common neurological disorder characterized by recurrent unprovoked seizures. More than 500 epilepsy-associated genes have been described in the literature. Most of these genes play an important role in neuronal excitability, cortical development or synaptic transmission. A growing number of genetic variations have implications on diagnosis and prognostic or therapeutic advice in terms of a personalized medicine. Area covered: The review presents the different forms of genetic epilepsies with respect to their underlying genetic and functional pathophysiology and aims to give advice for recommended genetic testing. Moreover, it discusses ethical and legal guidelines, costs and technical limitations which should be considered. Expert commentary: Genetic testing is an important component in the diagnosis and treatment of many forms of epilepsy.

Variable expressivity of a likely pathogenic variant in KCNQ2 in a three-generation pedigree presenting with intellectual disability with childhood onset seizures

KCNQ2 has been reported as a frequent cause of autosomal dominant benign familial neonatal seizures. De novo likely pathogenic variants in KCNQ2 have been described in neonatal or early infantile onset epileptic encephalopathy patients. Here, we report a three-generation family with six affected patients with a novel likely pathogenic variant (c.628C>T; p.Arg210Cys) in KCNQ2. Four family members, three adults and a child, presented with a childhood seizure onset with variability in the severity of seizures and response to treatment, intellectual disability (ID) as well as behavioral problems. The two youngest affected patients had a variable degree of global developmental delay with no seizures at their current age. This three-generation family with six affected members expands the phenotypic spectrum of KCNQ2 associated encephalopathy to KCNQ2 associated ID and or childhood onset epileptic encephalopathy. We think that KCNQ2 associated epileptic encephalopathy should be included in the differential diagnosis of childhood onset epilepsy and early onset global developmental delay, cognitive dysfunction, or ID. Furthermore, whole exome sequencing in families with ID and history of autosomal dominant inheritance pattern with or without seizures, may further broaden the phenotypic spectrum of KCNQ2 associated epileptic encephalopathy or encephalopathy.

Gene panel analysis for nonsyndromic cryptogenic neonatal/infantile epileptic encephalopathy

Objective

Epileptic encephalopathy (EE) is a heterogeneous condition associated with deteriorations of cognitive, sensory and/or motor functions as a consequence of epileptic activity. The phenomenon is the most common and severe in infancy and early childhood. Genetic-based diagnosis in EE patients is challenging owing to genetic and phenotypic heterogeneity of numerous monogenic disorders and the fact that thousands of genes are involved in neurodevelopment. Therefore, high-throughput next-generation sequencing (NGS) was used to investigate the genetic causes of non-syndromic cryptogenic neonatal/infantile EE (NIEE).

Methods

We have selected a cohort of 31 patients with seizure cryptogenic NIEE and seizure onset before 24 months. All investigations including metabolic work-up, were negative. Using NGS, we distinguished a panel of 430 epilepsy-associated genes by NGS was utilized to identify possible pathogenic variants in the patients. Segregation analysis and multiple silico analysis prediction tools were used for pathogenicity assessment. The identified variants were classified as "pathogenic," "likely pathogenic" and "uncertain significance," according to the American College of Medical Genetics (ACMG) guidelines.

Results

Pathogenic or likely pathogenic variants were identified in six genes (ALG13 [1], CDKL5 [2], KCNQ2 [2], PNPO [1], SCN8A [1], SLC9A6 [2]) in 9 NIEE patients (9/31; 29%). Variants of uncertain significance (VUS) were found in DNM1 and TUBA8 in 2 NIEE patients (2/31; 6%). Most phenotypes in our cohort matched with those reported cases.

Significance

The diagnostic rate (29%) of pathogenic and likely pathogenic variants was comparable to the recent studies of early-onset epileptic encephalopathy, indicating that gene panel analysis through NGS is a powerful tool to investigate cryptogenic NIEE in patients. Six percent of patients had neurometabolic disorders. Some of our diagnosed cases illustrated that successful molecular investigation may allow a better treatment strategy and avoid unnecessary and even invasive investigations. Functional analysis could be performed to further study the pathogenicity of the VUS identified in DNM1 and TUBA8.

Severe methemoglobinemia caused by continuous lidocaine infusion in a term neonate

Neonates and young infants are especially prone to develop drug-induced methemoglobinemia. Therefore, lidocaine is not licensed as local anesthetic in children below the age of 3 months. However, its systemic use is advocated for neonatal seizures. Cardiac arrhythmia has been reported as sole major side effect. Here we report a case of severe methemoglobinemia caused by continuous infusion of lidocaine in a term neonate with neonatal seizures. The increase of methemoglobin up to 13.8% was accompanied by hypoxemia and cyanosis, necessitating additional inspired oxygen and CPAP ventilation. After stopping lidocaine infusion methemoglobin levels fell and the neonate could be weaned from ventilation. Neonates treated with lidocaine for seizures must be monitored for the occurrence of methemoglobinemia.

Genetics and genotype-phenotype correlations in early onset epileptic encephalopathy with burst suppression

OBJECTIVE

We sought to identify genetic causes of early onset epileptic encephalopathies with burst suppression (Ohtahara syndrome and early myoclonic encephalopathy) and evaluate genotype-phenotype correlations.

METHODS

We enrolled 33 patients with a referral diagnosis of Ohtahara syndrome or early myoclonic encephalopathy without malformations of cortical development. We performed detailed phenotypic assessment including seizure presentation, electroencephalography, and magnetic resonance imaging. We confirmed burst suppression in 28 of 33 patients. Research-based exome sequencing was performed for patients without a previously identified molecular diagnosis from clinical evaluation or a research-based epilepsy gene panel.

RESULTS

In 17 of 28 (61%) patients with confirmed early burst suppression, we identified variants predicted to be pathogenic in KCNQ2 (n = 10), STXBP1 (n = 2), SCN2A (n = 2), PNPO (n = 1), PIGA (n = 1), and SEPSECS (n = 1). In 3 of 5 (60%) patients without confirmed early burst suppression, we identified variants predicted to be pathogenic in STXBP1 (n = 2) and SCN2A (n = 1). The patient with the homozygous PNPO variant had a low cerebrospinal fluid pyridoxal-5-phosphate level. Otherwise, no early laboratory or clinical features distinguished the cases associated with pathogenic variants in specific genes from each other or from those with no prior genetic cause identified.

INTERPRETATION

We characterize the genetic landscape of epileptic encephalopathy with burst suppression, without brain malformations, and demonstrate feasibility of genetic diagnosis with clinically available testing in >60% of our cohort, with KCNQ2 implicated in one-third. This electroclinical syndrome is associated with pathogenic variation in SEPSECS. Ann Neurol 2017;81:419-429.

Epilepsy-Associated KCNQ2 Channels Regulate Multiple Intrinsic Properties of Layer 2/3 Pyramidal Neurons

KCNQ2 potassium channels are critical for normal brain function, as both loss-of-function and gain-of-function KCNQ2 variants can lead to various forms of neonatal epilepsy. Despite recent progress, the full spectrum of consequences as a result of KCNQ2 dysfunction in neocortical pyramidal neurons is still unknown. Here, we report that conditional ablation of Kcnq2 from mouse neocortex leads to hyperexcitability of layer 2/3 (L2/3) pyramidal neurons, exhibiting an increased input resistance and action potential frequency, as well as a reduced medium afterhyperpolarization (mAHP), a conductance partly mediated by KCNQ2 channels. Importantly, we show that introducing the KCNQ2 loss-of-function variant KCNQ2I205V into L2/3 pyramidal neurons using in utero electroporation also results in a hyperexcitable phenotype similar to the conditional knock-out. KCNQ2I205V has a right-shifted conductance-to-voltage relationship, suggesting loss of KCNQ2 channel activity at subthreshold membrane potentials is sufficient to drive large changes in L2/3 pyramidal neuronal excitability even in the presence of an intact mAHP. We also found that the changes in excitability following Kcnq2 ablation are accompanied by alterations at action potential properties, including action potential amplitude in Kcnq2-null neurons. Importantly, partial inhibition of Nav1.6 channels was sufficient to counteract the hyperexcitability of Kcnq2-null neurons. Therefore, our work shows that loss of KCNQ2 channels alters the intrinsic neuronal excitability and action potential properties of L2/3 pyramidal neurons, and identifies Nav1.6 as a new potential molecular target to reduce excitability in patients with KCNQ2 encephalopathy.

SIGNIFICANCE STATEMENT

KCNQ2 channels are critical for the development of normal brain function, as KCNQ2 variants could lead to epileptic encephalopathy. However, the role of KCNQ2 channels in regulating the properties of neocortical neurons is largely unexplored. Here, we find that Kcnq2 ablation or loss-of-function at subthreshold membrane potentials leads to increased neuronal excitability of neocortical layer 2/3 (L2/3) pyramidal neurons. We also demonstrate that Kcnq2 ablation unexpectedly leads to a larger action potential amplitude. Importantly, we propose the Nav1.6 channel as a new molecular target for patients with KCNQ2 encephalopathy, as partial inhibition of these channels counteracts the increased L2/3 pyramidal neuron hyperexcitability of Kcnq2-null neurons.

Pharmacogenomics in epilepsy

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Genetic variation can influence response to antiepileptic drug (AED) treatment through various effector processes.

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Metabolism of many AEDs is mediated by the cytochrome P450 (CYP) family; some of the CYPs have allelic variants that may affect serum AED concentrations.

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‘Precision medicine’ focuses on the identification of an underlying genetic aetiology allowing personalised therapeutic choices.

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Certain human leukocyte antigen, HLA, alleles are associated with an increased risk of idiosyncratic adverse drug reactions.

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New results are emerging from large-scale multinational efforts, likely imminently to add knowledge of value from a pharmacogenetic perspective.

There is high variability in the response to antiepileptic treatment across people with epilepsy. Genetic factors significantly contribute to such variability. Recent advances in the genetics and neurobiology of the epilepsies are establishing the basis for a new era in the treatment of epilepsy, focused on each individual and their specific epilepsy. Variation in response to antiepileptic drug treatment may arise from genetic variation in a range of gene categories, including genes affecting drug pharmacokinetics, and drug pharmacodynamics, but also genes held to actually cause the epilepsy itself.

From a purely pharmacogenetic perspective, there are few robust genetic findings with established evidence in epilepsy. Many findings are still controversial with anecdotal or less secure evidence and need further validation, e.g. variation in genes for transporter systems and antiepileptic drug targets. The increasing use of genetic sequencing and the results of large-scale collaborative projects may soon expand the established evidence.

Precision medicine treatments represent a growing area of interest, focussing on reversing or circumventing the pathophysiological effects of specific gene mutations. This could lead to a dramatic improvement of the effectiveness and safety of epilepsy treatments, by targeting the biological mechanisms responsible for epilepsy in each specific individual.

Whilst much has been written about epilepsy pharmacogenetics, there does now seem to be building momentum that promises to deliver results of use in clinic.

A Distinctive Ictal Amplitude-Integrated Electroencephalography Pattern in Newborns with Neonatal Epilepsy Associated with KCNQ2 Mutations

BACKGROUND

Recurrent and prolonged seizures are harmful for the developing brain, emphasizing the importance of early seizure recognition and effective therapy. Amplitude-integrated electroencephalography (aEEG) has become a valuable tool to diagnose epileptic seizures, and, in parallel, genetic etiologies are increasingly being recognized, changing the paradigm of the workup and management of neonatal seizures.

OBJECTIVE

To report the ictal aEEG pattern in neonates with KCNQ2-related epilepsy.

SUBJECTS AND METHODS

In this multicenter descriptive study, clinical data and aEEG findings of 9 newborns with KCNQ2 mutations are reported.

RESULTS

Refractory seizures occurred in the early neonatal period with similar seizure type, including tonic features, apnea, and desaturation. A distinct aEEG seizure pattern, consisting of a sudden rise of the lower and upper margin of the aEEG, followed by a marked depression of the aEEG amplitude, was found in 8 of the 9 patients. Prompt recognition of this pattern led to early treatment with carbamazepine in the 2 most recent cases.

CONCLUSION

Early recognition of the electroclinical phenotype by using aEEG may direct genetic testing and a precision medicine approach with sodium channel blockers in neonates with KCNQ2 mutations.