Benign familial neonatal convulsions followed by benign epilepsy with centrotemporal spikes in two siblings

ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions

The International League Against Epilepsy (ILAE) Task Force on Nosology and Definitions proposes a classification and definition of epilepsy syndromes in the neonate and infant with seizure onset up to 2 years of age. The incidence of epilepsy is high in this age group and epilepsy is frequently associated with significant comorbidities and mortality. The licensing of syndrome specific antiseizure medications following randomized controlled trials and the development of precision, gene-related therapies are two of the drivers defining the electroclinical phenotypes of syndromes with onset in infancy. The principal aim of this proposal, consistent with the 2017 ILAE Classification of the Epilepsies, is to support epilepsy diagnosis and emphasize the importance of classifying epilepsy in an individual both by syndrome and etiology. For each syndrome, we report epidemiology, clinical course, seizure types, electroencephalography (EEG), neuroimaging, genetics, and differential diagnosis. Syndromes are separated into self-limited syndromes, where there is likely to be spontaneous remission and developmental and epileptic encephalopathies, diseases where there is developmental impairment related to both the underlying etiology independent of epileptiform activity and the epileptic encephalopathy. The emerging class of etiology-specific epilepsy syndromes, where there is a specific etiology for the epilepsy that is associated with a clearly defined, relatively uniform, and distinct clinical phenotype in most affected individuals as well as consistent EEG, neuroimaging, and/or genetic correlates, is presented. The number of etiology-defined syndromes will continue to increase, and these newly described syndromes will in time be incorporated into this classification. The tables summarize mandatory features, cautionary alerts, and exclusionary features for the common syndromes. Guidance is given on the criteria for syndrome diagnosis in resource-limited regions where laboratory confirmation, including EEG, MRI, and genetic testing, might not be available.

Genetic Etiologies in Developmental and/or Epileptic Encephalopathy With Electrical Status Epilepticus During Sleep: Cohort Study

Background

Recently, the electroencephalogram pattern of electrical status epilepticus during sleep (ESES) had been reported in some genetic disorders, and most of them were noted with developmental and epileptic encephalopathy (DEE) or epileptic encephalopathy (EE). This study aimed to determine the genetic etiologies and clinical characteristics of ESES in DEE/EE.

Methods

We performed a cohort study in cases of DEE or EE with ESES. Tio-based genetic testing was performed in 74 cases and was analyzed to identify underlying variants.

Results

Pathogenic or likely pathogenic variants were identified in 17/74 cases, including KCNQ2 (n = 6), KCNA2 (n = 5), GRIN2A (n = 3), SLC9A6 (n = 1), HIVEP2 (n = 1), and RARS2 (n = 1). Eleven were boys. The median age at seizure onset was 6 months. ESES occurred at the mean age of 2.0 ± 1.2 years, predominant in the Rolandic region in 14 years. Twelve of 17 cases had the first stage of different epilepsy preceding ESES: 2/12 were diagnosed as Ohtahara syndrome, 2/12 were diagnosed as infantile spasms, 3/12 were diagnosed as DEE, and 5/12 were diagnosed as EE without the epileptic syndrome.

Conclusion

Monogenic variants explained over 20% of DEE/EE with ESES. ESES could be an age-related feature in genetic disorders and occurred after the first stage of different epilepsy. Both age-related factors and genetic etiology were suggested to play a role in the occurrence of ESES in genetic DEE/EE.

Progress in unraveling the genetic etiology of rolandic epilepsy

Rolandic epilepsy (RE), or benign epilepsy of childhood with centrotemporal spikes (BECT), is the most frequent idiopathic partial epilepsy syndrome of childhood, where the "idiopathic" implies a genetic predisposition. Although RE has long been presumed to have a genetic component, clinical and genetic studies have shown a complex inheritance pattern. Furthermore, the underlying major genetic influence in RE has been challenged by recent reports of twin studies. Meanwhile, many genes or loci have been shown to be associated the RE/atypical RE (ARE) spectrum, with a higher frequency of causative variants in ARE. However, a full understanding of the genetic basis in the more common forms of the RE spectrum remains elusive.

Familial neonatal seizures in 36 families: Clinical and genetic features correlate with outcome

OBJECTIVE

We evaluated seizure outcome in a large cohort of familial neonatal seizures (FNS), and examined phenotypic overlap with different molecular lesions.

METHODS

Detailed clinical data were collected from 36 families comprising two or more individuals with neonatal seizures. The seizure course and occurrence of seizures later in life were analyzed. Families were screened for KCNQ2, KCNQ3, SCN2A, and PRRT2 mutations, and linkage studies were performed in mutation-negative families to exclude known loci.

RESULTS

Thirty-three families fulfilled clinical criteria for benign familial neonatal epilepsy (BFNE); 27 of these families had KCNQ2 mutations, one had a KCNQ3 mutation, and two had SCN2A mutations. Seizures persisting after age 6 months were reported in 31% of individuals with KCNQ2 mutations; later seizures were associated with frequent neonatal seizures. Linkage mapping in two mutation-negative BFNE families excluded linkage to KCNQ2, KCNQ3, and SCN2A, but linkage to KCNQ2 could not be excluded in the third mutation-negative BFNE family. The three remaining families did not fulfill criteria of BFNE due to developmental delay or intellectual disability; a molecular lesion was identified in two; the other family remains unsolved.

SIGNIFICANCE

Most families in our cohort of familial neonatal seizures fulfill criteria for BFNE; the molecular cause was identified in 91%. Most had KCNQ2 mutations, but two families had SCN2A mutations, which are normally associated with a mixed picture of neonatal and infantile onset seizures. Seizures later in life are more common in BFNE than previously reported and are associated with a greater number of seizures in the neonatal period. Linkage studies in two families excluded known loci, suggesting a further gene is involved in BFNE.

A novel KCNQ3 mutation in familial epilepsy with focal seizures and intellectual disability

Mutations in the KCNQ2 gene encoding for voltage-gated potassium channel subunits have been found in patients affected with early onset epilepsies with wide phenotypic heterogeneity, ranging from benign familial neonatal seizures (BFNS) to epileptic encephalopathy with cognitive impairment, drug resistance, and characteristic electroencephalography (EEG) and neuroradiologic features. By contrast, only few KCNQ3 mutations have been rarely described, mostly in patients with typical BFNS. We report clinical, genetic, and functional data from a family in which early onset epilepsy and neurocognitive deficits segregated with a novel mutation in KCNQ3 (c.989G>T; p.R330L). Electrophysiological studies in mammalian cells revealed that incorporation of KCNQ3 R330L mutant subunits impaired channel function, suggesting a pathogenetic role for such mutation. The degree of functional impairment of channels incorporating KCNQ3 R330L subunits was larger than that of channels carrying another KCNQ3 mutation affecting the same codon but leading to a different amino acid substitution (p.R330C), previously identified in two families with typical BFNS. These data suggest that mutations in KCNQ3, similarly to KCNQ2, can be found in patients with more severe phenotypes including intellectual disability, and that the degree of the functional impairment caused by mutations at position 330 in KCNQ3 may contribute to clinical disease severity.

Neonatal seizures

Epileptic seizures are more frequent in the neonate than at any other time. The incidence of neonatal seizures (NNS) is estimated to be between 1.5 and 5.5/1000 living births, its onset being during the first week in 80% of cases. Mortality rate remains very high (20-45%). Not all paroxysmal manifestations are epileptic, and differential diagnosis remains an important challenge. Neonates may present with different types of seizures: clonic, tonic, myoclonic (axial, focal, erratic), epileptic spasms, and subtle seizures, including autonomic signs or automatisms. The main etiology is hypoxic-ischemic encephalopathy (40-45%) with a very early onset, and variable semiology including all seizure types. An EEG is necessary to recognize the seizures, and interictal tracing may help in assessing prognosis. Ischemic stroke is associated with seizures of early onset, being focal or unilateral. Interictal EEG is asymmetrical, with focal or unilateral patterns. Other etiologies less often linked to epileptic seizures must be looked for such as brain infection, metabolic disorders, chromosomal abnormalities, inborn errors of metabolism, brain malformations, and vitamin B6 dependency. Neonatal epilepsy syndromes may have favorable (benign familial neonatal seizures) or poor (early infantile encephalopathy with epilepsy, early myoclonic encephalopathy, and migrating partial seizures in infancy) prognosis.

KCNQ2 abnormality in BECTS: benign childhood epilepsy with centrotemporal spikes following benign neonatal seizures resulting from a mutation of KCNQ2

The molecular pathogenesis of benign childhood epilepsy with centrotemporal spikes (BECTS) remains unclear whereas mutations of the KCNQ2 and KCNQ3 genes have been identified as causes of benign familial neonatal convulsions. We report here a girl with benign neonatal convulsions followed by BECTS, for whom a mutation of KCNQ2 was identified. This case may provide the clue to the understanding of the molecular pathogenesis of BECTS.

The first Korean case of KCNQ2 mutation in a family with benign familial neonatal convulsions

Neonatal seizures represent a heterogeneous group of disorders with vastly different etiologies and outcomes. Benign familial neonatal convulsions (BFNC) are a distinctive epileptic syndrome of autosomal dominant inheritance with a favorable prognosis, characterized by the occurrence of unprovoked partial or generalized clonic seizures in the neonatal period or early infancy. Recently, mutations in two potassium channel genes, KCNQ2 and KCNQ3, have been described in this disorder. In this report, we describe a family with BFNC due to a KCNQ2 mutation, the first such family to be described in the Korean population. The diagnosis of BFNC can be made based on clinical suspicion and careful history taking with special emphasis on the familial nature of the disorder. KCNQ2 mutations may be associated with BFNC in a number of different races, as has been reported in other ethnic groups.

Early seizures: causal events or predisposition to adult epilepsy?

Past studies have been unable to confirm whether early seizures predispose to epilepsy in adults. Seizures in infancy were classically thought to cause brain lesions that led to epilepsy in adulthood. However, these infants were not thought to have epilepsy, but acute events that included seizures. Accumulating evidence suggests that early seizures may be associated with, or cause, brain damage; or alternatively, they may be the first expression of a genetic or lesional predisposition to epilepsy. The course of early seizures ranges from transient to life-long, depending on epilepsy syndrome, causes, and treatment. The main factors that determine late or persisting epilepsy after the occurrence of early seizures are protracted seizures, tonic seizures, and involvement of mesial temporal structures. A developmental approach to seizure disorders will aid understanding of epilepsy in adults and improve the design of antiepileptic agents for children and adults.

Benign partial epilepsy in infancy long-term outcome and marginal syndromes

Benign partial epilepsy in infancy (BPEI) is an infantile epilepsy with excellent seizure and developmental outcome proposed by Watanabe et al. Our telephone interview survey revealed that the long-term outcome of patients with BPEI was also excellent over 8 years of age. Six of 39 patients did not fulfill the criteria of BPEI by the last follow-up. Two patients had a recurrence of unprovoked seizure beyond 2 years of age, three had cognitive problems (mild mental retardation in two and Asperger syndrome in one) and the other had both a recurrence of seizure and mild mental retardation. These results indicates that a large majority of patients diagnosed as possible BPEI at 2 years of age did not have a recurrence of unprovoked seizures and mental problems beyond 8 years of age. Our study also suggested a presence of some marginal syndromes of BPEI. An association of paroxysmal kinesigenic choreoathetosis was observed in three patients. Another three patients had experienced seizures with mild gastroenteritis. The seizure outcome of three patients with mild cognitive problems was quite excellent. These patients can be grouped as a marginal syndrome of BPEI.

A novel splicing mutation in KCNQ2 in a multigenerational family with BFNC followed for 25 years

PURPOSE

A large multigenerational family with benign familial neonatal convulsions (BFNC) was revisited to identify the disease-causing mutation and to assess long-term outcome.

METHODS

We supplemented the original data with recent clinical and neurophysiologic data on patients and first-degree relatives, including information on seizure recurrence. We conducted linkage analysis at the EBN1 and EBN2 loci, followed by mutation analysis of KCNQ2. We evaluated the qualitative effect of the KCNQ2 mutation at the messenger RNA (mRNA) level by using reverse-transcribed total RNA isolated from leukocytes.

RESULTS

Thirteen relatives had a history of neonatal convulsions, 11 of whom showed remission within 2 months. One patient showed an atypical course of neonatal convulsions, developing photosensitive myoclonic epilepsy at age 13 years. We found suggestive linkage of the BFNC phenotype to the 20q13-EBN1 locus (lod score, 2.03) and an intronic mutation IVS14-6 C>A in KCNQ2 segregating with the trait in all affected members, but absent in 100 unrelated control subjects. This mutation creates a new, preferentially used, splice site. Alternative splicing adds 4 nt containing a premature stop codon to the transcript, resulting in a truncated protein after position R588.

CONCLUSIONS

We detected and characterized a novel splicing mutation in the brain-specific KCNQ2 gene by using easily accessible blood leukocytes. Aberrant splicing cosegregates with BFNC but not with photosensitivity.

Long-term Follow-up of Patients with Benign Partial Epilepsy in Infancy

PURPOSE

The aim of this study was to investigate the long-term outcome of children with benign partial epilepsy in infancy (BPEI).

METHODS

A telephone-interview survey using a structured questionnaire was conducted with patients who were diagnosed as having possible BPEI at age 2 years and who were 8 years or older at the time of the survey. The data from 39 of 48 patients were available. The median age at the time of the survey was 11.3 years; 18 boys and 21 girls were included.

RESULTS

Three patients had a recurrence of unprovoked seizure beyond age 2 years. Four patients had cognitive problems (mild mental retardation in three and Asperger syndrome in one). An association of paroxysmal kinesigenic choreoathetosis was observed in three patients, and another three had experienced seizures associated with mild gastroenteritis. Major behavioral problems were not recognized in any patients. Four patients were excluded from having definite BPEI at age 5 years, and another two were excluded for having definite BPEI at the last follow-up. Eventually, 33 of 39 patients were categorized as having definite BPEI beyond 8 years of age.

CONCLUSIONS

A large majority of patients diagnosed as possibly having BPEI at age 2 years did not have a recurrence of unprovoked seizures and cognitive problems beyond 8 years of age.

Neonatal seizures with tonic clonic sequences and poor developmental outcome

Seizures consisting of a tonic followed by a clonic phase have rarely been described in neonates and are not included in the current classifications of neonatal seizures. Our video archive of 105 neonates with seizures or suspected seizures revealed six neonates with such tonic clonic or tonic myoclonic sequences. Two of those neonates had pyridoxine dependent seizures. The other four neonates had drug refractory seizures and demonstrated similarities in electro-clinical pattern, clinical course and outcome. Their seizures started with tonic posturing and after 10-20s tonic posturing was superimposed by focal or multifocal cloni or myocloni. Ictal EEG started with voltage attenuation followed by bilateral or alternating focal epileptic discharges. The interictal EEG was abnormal. One child died, while the other three children became seizure free but had severe motor delay and mental retardation. In one of those three children, a de novo missense mutation was detected in the voltage gated potassium channel gene KCNQ2, indicating a genetic relationship between drug refractory neonatal seizures of unknown etiology with tonic clonic or myoclonic sequences and the well-known syndrome of benign familial neonatal convulsions (BFNC).

Occipital sharp waves in idiopathic partial epilepsies--clinical and genetic aspects

In order to gain new insight into the pathogenesis and nosography of benign partial epilepsy with occipital paroxysms (BEOP) we retrospectively analysed cases with benign focal sharp waves (SHW) of different localisations, in which analogous EEG changes had been found in at least one first degree relative. Fifty-six families were evaluated. Nineteen cases with occipital SHW (group A) were compared with 37 cases without (group B). There was a broad spectrum of symptomatology with large overlaps between the two groups. However, a number of striking differences, yielding a characteristic picture of early childhood epilepsy with occipital foci were identified: (1) Age of onset under 5 years; (2) a larger proportion of febrile convulsions (FC 47 vs. 19%); (3) a trend towards a higher rate of typical early childhood occipital seizures (26 vs. 5%); (4) a higher rate of frontal and generalizing SHW foci (32 vs. 5%; 37 vs. 11%); (5) a higher rate of generalized spikes and waves (SW) (46 vs. 14%); (6) a trend towards a higher rate of photoparoxysmal response (PPR) (57 vs. 32%). The high prevalence of independent genetic traits favours a multifactorial pathogenesis. The predisposition to FC with characteristic early seizure onset and varying patterns of generalized genetic EEG traits plays a crucial role within the complex pathogenetic network. The early-onset benign childhood occipital seizure susceptibility syndrome of Panayiotopoulos (Benign Childhood Partial Seizures and Related Epileptic Syndromes, John Libbey & Company Ltd., London (1999)) cannot be regarded as the sole representative of occipital spikes in early childhood but as an important even though rare form of occipital epilepsy.

Benign familial neonatal epilepsy with mutations in two potassium channel genes

The significant progress made over the past year in understanding the basis for a form of neonatal seizures can be attributed to the successful positional cloning of two new voltage-gated potassium channel genes. Expression studies have increased our understanding of the biology of these channels and their role in epilepsy.