Benign Neonatal Epilepsy Research Articles

SCN2A-Related Epilepsy: The Phenotypic Spectrum, Treatment and Prognosis.

ObjectiveThe aim of this study was to analyze the phenotypic spectrum, treatment, and prognosis of 72 Chinese children with SCN2A variants.MethodsThe SCN2A variants were detected by next-generation sequencing. All patients were followed up at a pediatric neurology clinic in our hospital or by telephone.ResultsIn 72 patients with SCN2A variants, the seizure onset age ranged from the first day of life to 2 years and 6 months. The epilepsy phenotypes included febrile seizures (plus) (n = 2), benign (familial) infantile epilepsy (n = 9), benign familial neonatal-infantile epilepsy (n = 3), benign neonatal epilepsy (n = 1), West syndrome (n = 16), Ohtahara syndrome (n = 15), epilepsy of infancy with migrating focal seizures (n = 2), Dravet syndrome (n = 1), early infantile epileptic encephalopathy (n = 15), and unclassifiable developmental and epileptic encephalopathy (n = 8). Approximately 79.2% (57/72) patients had varying degrees of developmental delay. All patients had abnormal MRI findings with developmental delay. 91.7% (55/60) patients with de novo SCN2A variants had development delay, while only 16.7% (2/12) patients with inherited SCN2A variants had abnormal development. 83.9% (26/31) SCN2A variants that were located in transmembrane regions of the protein were detected in patients with development delay. Approximately 69.2% (9/13) SCN2A variants detected in patients with normal development were located in the non-transmembrane regions. Approximately 54.2% (39/72) patients were seizure-free at a median age of 8 months. Oxcarbazepine has been used by 38 patients, and seizure-free was observed in 11 of them (11/38, 28.9%), while 6 patients had seizure worsening by oxcarbazepine. All 3 patients used oxcarbazepine and with seizure onset age > 1 year presented seizure exacerbation after taking oxcarbazepine. Valproate has been used by 53 patients, seizure-free was observed in 22.6% (12/53) of them.ConclusionThe phenotypic spectrum of SCN2A-related epilepsy was broad, ranging from benign epilepsy in neonate and infancy to severe epileptic encephalopathy. Oxcarbazepine and valproate were the most effective drugs in epilepsy patients with SCN2A variants. Sodium channel blockers often worsen seizures in patients with seizure onset beyond 1 year of age. Abnormal brain MRI findings and de novo variations were often related to poor prognosis. Most SCN2A variants located in transmembrane regions were related to patients with developmental delay.

Genotypes and clinical features of neonatal-onset genetic epilepsy in 141 patients

Objective: To summarize the genotypes and clinical features of neonatal-onset genetic epilepsy. Methods: Patients (114 cases) with identified gene variants were collected from May 2013 to May 2019 in Peking University First Hospital, retrospectively. The genotype, clinical, electroencephalographic and neuroimaging characteristics were analyzed. Results: A total of 141 neonatal-onset epilepsy patients with identified gene variants were enrolled, including 76 males and 65 females and involving 33 epilepsy genes. Top five genes were KCNQ2 (56 cases), SCN2A (25 cases), STXBP1 (9 cases), CDKL5 (8 cases) and KCNT1 (6 cases), accounting for 73.8% (104/141). The age of seizure onset was 3(1-28) days of age, 71.6% (101/141) were within 1 week of age. The age of genetic diagnosis was 4 months (1 month to 13 years) of age. A total of 130 patients presented focal seizures; 47 patients presented epileptic spasms. Other seizure types included generalized tonic-clonic seizures, clonic seizures, myoclonic seizures, tonic seizures and absence seizures. Fifty-eight patients experienced multiple seizure types. The results of video-electroencephlogram (VEEG) were abnormal in 127 patients and in 62 patients clinical seizures were captured. Global developmental delay was presented in 122 patients. Epilepsy syndromes were diagnosed in 59 patients. Thirteen patients were diagnosed as Ohtahara syndrome (OS), 9 as epilepsy of infancy with migrating focal seizures (EIMFS), 17 as West syndrome (WS), 4 as OS developed to WS, 9 as benign neonatal epilepsy (BNE), 2 as benign familiar neonatal-infantile epilepsy (BFNIE), 2 as benign infantile epilepsy (BIE) and 3 as benign familial infantile epilepsy (BFIE). Sixty-seven patients were diagnosed as unclassified early infantile epileptic encephalopathy (EIEE), 13 patients could not be diagnosed as any epilepsy syndrome, and 2 patients were diagnosed as pyridoxine-dependent epilepsy. Forty-six patients had abnormal neuroimaging including cortical atrophy, corpus callosum dysplasia and cerebellar atrophy, involving 19 genes. Conclusions: Neonatal-onset epilepsy is related to many different genes. Seizure onset age of most patients is within one week after birth. Focal seizures and epileptic spasms are more common. Some patients show abnormal neuroimaging.

A Novel Kv7.3 Variant in the Voltage-Sensing S4 Segment in a Family With Benign Neonatal Epilepsy: Functional Characterization and in vitro Rescue by β-Hydroxybutyrate.

Pathogenic variants in KCNQ2 and KCNQ3, paralogous genes encoding Kv7.2 and Kv7.3 voltage-gated K+ channel subunits, are responsible for early−onset developmental/epileptic disorders characterized by heterogeneous clinical phenotypes ranging from benign familial neonatal epilepsy (BFNE) to early−onset developmental and epileptic encephalopathy (DEE). KCNQ2 variants account for the majority of pedigrees with BFNE and KCNQ3 variants are responsible for a much smaller subgroup, but the reasons for this imbalance remain unclear. Analysis of additional pedigrees is needed to further clarify the nature of this genetic heterogeneity and to improve prediction of pathogenicity for novel variants. We identified a BFNE family with two siblings and a parent affected. Exome sequencing on samples from both parents and siblings revealed a novel KCNQ3 variant (c.719T>G; p.M240R), segregating in the three affected individuals. The M240 residue is conserved among human Kv7.2-5 and lies between the two arginines (R5 and R6) closest to the intracellular side of the voltage-sensing S4 transmembrane segment. Whole cell patch-clamp recordings in Chinese hamster ovary (CHO) cells revealed that homomeric Kv7.3 M240R channels were not functional, whereas heteromeric channels incorporating Kv7.3 M240R mutant subunits with Kv7.2 and Kv7.3 displayed a depolarizing shift of about 10 mV in activation gating. Molecular modeling results suggested that the M240R substitution preferentially stabilized the resting state and possibly destabilized the activated state of the Kv7.3 subunits, a result consistent with functional data. Exposure to β-hydroxybutyrate (BHB), a ketone body generated during the ketogenic diet (KD), reversed channel dysfunction induced by the M240R variant. In conclusion, we describe the first missense loss-of-function (LoF) pathogenic variant within the S4 segment of Kv7.3 identified in patients with BFNE. Studied under conditions mimicking heterozygosity, the M240R variant mainly affects the voltage sensitivity, in contrast to previously analyzed BFNE Kv7.3 variants that reduce current density. Our pharmacological results provide a rationale for the use of KD in patients carrying LoF variants in Kv7.2 or Kv7.3 subunits.

Duplication within the KCNQ2 Gene in a Child with Benign Early-Onset Epileptic Encephalopathy

Introduction: Mutations in the KCNQ2 gene lead to autosomal dominant benign neonatal seizures or early-onset epileptic encephalopathy. We describe here a female patient with focal epileptic seizures starting from four months of age, carrying a heterozygous duplication of exons 9 – 17 of the KCNQ2 gene. Case Presentation: It is the second child of German non-consanguineous parents without any family history for seizures or epilepsy. After uneventful pregnancy, delivery and neonatal period, the patient developed focal seizures with impairment of awareness several times per week. Cranial MRI, screening for inborn disorders of metabolism or prenatal infections (TORCH) did not show pathogenic results. A panel analysis for epileptic encephalopathies (CeGaT) revealed a heterozygous duplication of exons 9 to 17 of the KCNQ2 gene which was classified as variant of unknown significance. With application of Levetiraetam (at least 40 mg/kg daily, blood level of ~10 μg/mL) absence of seizures except for febrile situations was achieved. After the 7th month, no more seizures were observed, even during infections, and Levetiraetam therapy could be gradually reduced and finally stopped. Psychomotor development of the patient is almost normal. Due to muscular hypotonia, she received physiotherapy, but the developmental milestones were all reached age-appropriately. Conclusion: The clinical interpretation of variants of unknown significance revealed through a panel analysis is often difficult, even with incorporation of data from large databases. So far, a partial KCNQ2 duplication, of exons 3 to 12, has been described only once in the literature in a patient with benign neonatal epilepsy. The reported disease course in our patient carrying another partial duplication of KCNQ2 suggests a benign outcome in this family as well.

NovelKCNQ2andKCNQ3Mutations in a Large Cohort of Families with Benign Neonatal Epilepsy: First Evidence for an Altered Channel Regulation by Syntaxin-1A

Mutations in the KCNQ2 and KCNQ3 genes encoding for Kv 7.2 (KCNQ2; Q2) and Kv 7.3 (KCNQ3; Q3) voltage-dependent K(+) channel subunits, respectively, cause neonatal epilepsies with wide phenotypic heterogeneity. In addition to benign familial neonatal epilepsy (BFNE), KCNQ2 mutations have been recently found in families with one or more family members with a severe outcome, including drug-resistant seizures with psychomotor retardation, electroencephalogram (EEG) suppression-burst pattern (Ohtahara syndrome), and distinct neuroradiological features, a condition that was named "KCNQ2 encephalopathy." In the present article, we describe clinical, genetic, and functional data from 17 patients/families whose electroclinical presentation was consistent with the diagnosis of BFNE. Sixteen different heterozygous mutations were found in KCNQ2, including 10 substitutions, three insertions/deletions and three large deletions. One substitution was found in KCNQ3. Most of these mutations were novel, except for four KCNQ2 substitutions that were shown to be recurrent. Electrophysiological studies in mammalian cells revealed that homomeric or heteromeric KCNQ2 and/or KCNQ3 channels carrying mutant subunits with newly found substitutions displayed reduced current densities. In addition, we describe, for the first time, that some mutations impair channel regulation by syntaxin-1A, highlighting a novel pathogenetic mechanism for KCNQ2-related epilepsies.

Ion Channels and Epilepsy

The role of voltage-gated and ligand-gated ion channels in epileptogenesis of both genetic and acquired epilepsies, and as targets in the development of new antiepileptic drugs (AEDs) is reviewed. Voltage-gated Na+ channels are essential for action potentials, and their mutations are the substrate for generalised epilepsy with febrile seizures plus and benign familial neonatal infantile seizures; Na+ channel inhibition is the primary mechanism of carbamazepine, phenytoin and lamotrigine, and is a probable mechanism for many other classic and novel AEDs. Voltage-gated K+ channels are essential in the repolarisation and hyperpolarisation that follows paroxysmal depolarisation shifts (PDSs), and their mutations are the substrate for the benign neonatal epilepsy and episodic ataxia type 1; they are new targets for AEDs such as retigabine. Voltage-gated Ca2+ channels are involved in neurotransmitter release, in the sustained depolarisation-phase of PDSs, and in the generation of absence seizures; their mutations are a substrate for juvenile myoclonic epilepsy and the absence-like pattern seen in some mice; the antiabsence effect of ethosuximide is due to the inhibition of thalamic T-type Ca2+ channels. Voltage-gated Cl- channels are implicated in GABA(A) transmission, and mutations in these channels have been described in some families with juvenile myoclonic epilepsies, epilepsy with grand mal seizures on awakening or juvenile absence epilepsy. Hyperpolarisation-activated cation channels have been implicated in spike-wave seizures and in hippocampal epileptiform discharges. The Cl- ionophore of the GABA(A) receptor is responsible for the rapid post-PDS hyperpolarisation, it has been involved in epileptogenesis both in animals and humans, and mutations in these receptors have been found in families with juvenile myoclonic epilepsy or generalised epilepsy with febrile seizures plus; enhancement of GABA(A) inhibitory transmission is the primary mechanism of benzodiazepines and phenobarbital and is a mechanistic approach to the development of novel AEDs such as tiagabine or vigabatrin. Altered GABA(B)-receptor function is implicated in spike-wave seizures. Ionotropic glutamate receptors are implicated in the sustained depolarisation phase of PDS and in epileptogenesis both in animals and humans; felbamate, phenobarbital and topiramate block these receptors, and attenuation of glutamatergic excitatory transmission is another new mechanistic approach. Mutations in the nicotinic acetylcholine receptor are the substrates for the nocturnal frontal lobe epilepsy. The knowledge of the role of the ion channels in the epilepsies is allowing the design of new and more specific therapeutic strategies.

Mapping of the ACTH, MSH, and neural (MC3 and MC4) melanocortin receptors in the mouse and human

The melanocortin peptides regulate a wide variety of physiological processes, including pigmentation and glucocorticoid production, and also have several activities in the central and peripheral nervous systems. The melanocortin receptor family includes the melanocyte-stimulating hormone receptor (MSH-R), adrenocorticotropic hormone receptor (ACTH-R), and two neural receptors, MC3-R and MC4-R. In the human these receptors map to 16q24 (MSH-R), 18p11.2 (ACTH-R), 20q13.2 (MC3-R), and 18q22 (MC4-R). The corresponding locations in the mouse are 8, 18, and 2; a variant for mapping MC4-R has not yet been identified. The data reported here also show that the neural MC3 receptor maps close to a disease locus for benign neonatal epilepsy in human and near the E1-2 epilepsy susceptibility locus in the mouse.