PRRT2 benign familial infantile seizures (BFIS) with atypical evolution to encephalopathy related to status epilepticus during sleep (ESES).

PURPOSE: Heterozygous variants in PRRT2 are mostly associated with benign phenotypes, being the major genetic cause of benign familial infantile seizures (BFIS), as well as in paroxysmal disorders. We report two children from unrelated families with BFIS that evolved to encephalopathy related to status epilepticus during sleep (ESES). METHODS AND RESULTS: Two probands presented with focal motor seizures at 3 months of age, with a limited course. Both children presented, at around 5 years of age, with centro-temporal interictal epileptiform discharges with a source in the frontal operculum, markedly activated by sleep, and associated with stagnation on neuropsychological development. Whole-exome sequencing and co-segregation analysis revealed a frameshift mutation c.649dupC in the proline-rich transmembrane protein 2 (PRRT2) in both probands and all affected family members. CONCLUSION: The mechanism leading to epilepsy and the phenotypic variability of PRRT2 variants remain poorly understood. However, its wide cortical and subcortical expression, in particular in the thalamus, could partially explain both the focal EEG pattern and the evolution to ESES. No variants in the PRRT2 gene have been previously reported in patients with ESES. Due to the rarity of this phenotype, other possible causative cofactors are likely contributing to the more severe course of BFIS in our probands.

Single nucleotide variations in CLCN6 identified in patients with benign partial epilepsies in infancy and/or febrile seizures.

Nucleotide alterations in the gene encoding proline-rich transmembrane protein 2 (PRRT2) have been identified in most patients with benign partial epilepsies in infancy (BPEI)/benign familial infantile epilepsy (BFIE). However, not all patients harbor these PRRT2 mutations, indicating the involvement of genes other than PRRT2. In this study, we performed whole exome sequencing analysis for a large family affected with PRRT2-unrelated BPEI. We identified a non-synonymous single nucleotide variation (SNV) in the voltage-sensitive chloride channel 6 gene (CLCN6). A cohort study of 48 BPEI patients without PRRT2 mutations revealed a different CLCN6 SNV in a patient, his sibling and his father who had a history of febrile seizures (FS) but not BPEI. Another study of 48 patients with FS identified an additional SNV in CLCN6. Chloride channels (CLCs) are involved in a multitude of physiologic processes and some members of the CLC family have been linked to inherited diseases. However, a phenotypic correlation has not been confirmed for CLCN6. Although we could not detect significant biological effects linked to the identified CLCN6 SNVs, further studies should investigate potential CLCN6 variants that may underlie the genetic susceptibility to convulsive disorders.

Unusual variability of PRRT2 linked phenotypes within a family.

BACKGROUND: Mutations in the proline-rich transmembrane protein 2 (PRRT2) gene on chromosome 16p11.2 have recently been identified as a cause of paroxysmal kinesigenic dyskinesias (PKD), infantile convulsions and choreoathetosis (ICCA) syndrome or infantile convulsions (IC). AIMS: Here, we describe a family with four affected members. They all suffer from different diseases: febrile convulsion, epileptic seizures, PKD or headache. METHODS: The whole coding region of PRRT2 gene has been analyzed. RESULTS: Molecular testing revealed the PRRT2 gene mutation c649.delC in exon 2 for all three sibs as well as for the mother. CONCLUSION: Our presented family case shows the great variability within PRRT2 linked phenotypes even within the same family. Further and more detailed studies will be needed before genetic findings enter into the daily diagnostic and the daily genetic counseling with all its consequences.

KCNQ2 encephalopathy: delineation of the electroclinical phenotype and treatment response.

Neonatal-onset epilepsies are rare conditions, mostly genetically determined, that can have a benign or severe phenotype.(1,2) There is recent recognition of de novo KCNQ2 mutations in patients with severe neonatal-onset epilepsy with intractable seizures and severe psychomotor impairment, termed KCNQ2 encephalopathy.(3,4) This is a rare condition and all patients reported so far were diagnosed well after the neonatal period.(3,4) We report on 3 new cases of KCNQ2 encephalopathy diagnosed in the neonatal period and studied with continuous video-EEG recording. We describe a distinct electroclinical phenotype and report on efficacy of antiepileptic drug (AED) therapies.

PRRT2-related disorders: further PKD and ICCA cases and review of the literature.

Recent studies reported mutations in the gene encoding the proline-rich transmembrane protein 2 (PRRT2) to be causative for paroxysmal kinesigenic dyskinesia (PKD), PKD combined with infantile seizures (ICCA), and benign familial infantile seizures (BFIS). PRRT2 is a presynaptic protein which seems to play an important role in exocytosis and neurotransmitter release. PKD is the most common form of paroxysmal movement disorder characterized by recurrent brief involuntary hyperkinesias triggered by sudden movements. Here, we sequenced PRRT2 in 14 sporadic and 8 familial PKD and ICCA cases of Caucasian origin and identified three novel mutations (c.919C>T/p.Gln307, c.388delG/p.Ala130Profs 46, c.884G>A/p.Arg295Gln) predicting two truncated proteins and one probably damaging point mutation. A review of all published cases is also included. PRRT2 mutations occur more frequently in familial forms of PRRT2-related syndromes (80-100 %) than in sporadic cases (33-46 %) suggesting further heterogeneity in the latter. PRRT2 mutations were rarely described in other forms of paroxysmal dyskinesias deviating from classical PKD, as we report here in one ICCA family without kinesigenic triggers. Mutations are exclusively found in two exons of the PRRT2 gene at a high rate across all syndromes and with one major mutation (c.649dupC) in a mutational hotspot of nine cytosines, which is responsible for 57 % of all cases in all phenotypes. We therefore propose that genetic analysis rapidly performed in early stages of the disease is highly cost-effective and can help to avoid further unnecessary diagnostic and therapeutic interventions.

Mutations in PRRT2 result in familial infantile seizures with heterogeneous phenotypes including febrile convulsions and probable SUDEP.

Mutations of PRRT2, which encodes proline-rich transmembrane protein 2, are associated with heterogeneous phenotypes including benign familial infantile seizures (BFIS) and/or familial paroxysmal kinesigenic dystonia (PKD). Here, we performed mutation screening of PRRT2 in six Italian families with BFIS/PKD phenotypes. The mutation, c.649dupC (p.Arg217ProfsX8), was found in two families with BFIS phenotype. In a third BFIS family, a missense mutation, c.718C/T (R240X), was identified. All these mutations co-segregated with the disease and were not observed in 100 controls of matched ancestry. In one BFIS family that carried the c.649dupC mutation, one affected member developed afebrile focal seizures and died at age of 14 years of probable sudden unexpected death in epilepsy, while his brother also had simple febrile convulsions (FC) and performed poorly on complex psychomotor functioning. In another family carrying the c.718C/T mutation, two of three affected members also had simple FC. This study enlarges the clinical spectrum related to PPRT2 mutations and underscores the complexity of the phenotypic consequences of mutations in this gene.

Genetic analysis of PRRT2 for benign infantile epilepsy, infantile convulsions with choreoathetosis syndrome, and benign convulsions with mild gastroenteritis.

PURPOSE: PRRT2 mutations were recently identified in benign familial infantile epilepsy (BFIE) and infantile convulsions with paroxysmal choreoathetosis (ICCA) but no abnormalities have so far been identified in their phenotypically similar seizure disorder of benign convulsions with mild gastroenteritis (CwG), while mutations in KCNQ2 and KCNQ3 have been recognized in benign familial neonatal epilepsy (BFNE). The aim of this study was to identify PRRT2 mutations in infantile convulsions in Asian families with BFIE and ICCA, CwG and BFNE. METHODS: We recruited 26 unrelated Japanese affected with either BFIE or non-familial benign infantile seizures and their families, including three families with ICCA. A total of 17 Japanese and Taiwanese with CwG, 50 Japanese with BFNE and 96 healthy volunteers were also recruited. Mutations of PRRT2 were sought using direct sequencing. RESULTS: Heterozygous truncation mutation (c.649dupC) was identified in 15 of 26 individuals with benign infantile epilepsy (52.1%). All three families of ICCA harbored the same mutation (100%). Another novel mutation (c.1012+2dupT) was found in the proband of a family with BFIE. However, no PRRT2 mutation was found in either CwG or BFNE. CONCLUSIONS: The results confirm that c.649dupC, a truncating mutation of PRRT2, is a hotspot mutation resulting in BFIE or ICCA regardless of the ethnic background. In contrast, PRRT2 mutations do not seem to be associated with CwG or BFNE. Screening for PRRT2 mutation might be useful in early-stage differentiation of BFIE from CwG.

Homozygous c.649dupC mutation in PRRT2 worsens the BFIS/PKD phenotype with mental retardation, episodic ataxia, and absences.

Heterozygous mutations of PRRT2, which encodes proline-rich transmembrane protein 2, are associated with heterogeneous phenotypes including benign familial infantile seizures (BFIS), or familial paroxysmal kinesigenic dystonia (PKD). We report a consanguineous Italian family with BFIS/PKD phenotype that contained 14 living members with 6 affected individuals (four men, ranging in age from 6-44 years). We identified the reported c.649dupC (p.Arg217ProfsX8) mutation of PRRT2 gene that cosegregated with the disease and was not observed in 100 controls of matched ancestry. Four patients with BFIS phenotype were heterozygous for this mutation, including the consanguineous parents of the two affected brothers with more severe phenotypes of BFIS/PKD--mental retardation, episodic ataxia, and absences--who were the only individuals to carry a homozygous c.649dupC mutation. This family provides strong evidence that homozygous PRRT2 mutations give rise to more severe clinical disease of mental retardation, episodic ataxia, and absences, and, thus, enlarges the clinical spectrum related to PRRT2 mutations. Moreover, it suggests an additive effect of double dose of the genetic mutation and underscores the complexity of the phenotypic consequences of mutations in this gene.

PRRT2 phenotypes and penetrance of paroxysmal kinesigenic dyskinesia and infantile convulsions.

OBJECTIVE: To describe the phenotypes and penetrance of paroxysmal kinesigenic dyskinesia (PKD), a movement disorder characterized by attacks of involuntary movements occurring after sudden movements, infantile convulsion and choreoathetosis (ICCA) syndrome, and benign familial infantile convulsions (BFIC), caused by PRRT2 mutations. METHODS: We performed clinical and genetic studies in 3 large families with ICCA, 2 smaller families with PKD, and 4 individuals with sporadic PKD. Migraine was also present in several individuals. RESULTS: We detected 3 different PRRT2 heterozygous mutations: the recurrent p.Arg217Profs*8 mutation, previously reported, was identified in 2 families with ICCA, 2 families with PKD, and one individual with sporadic PKD; one novel missense mutation (p.Ser275Phe) was detected in the remaining family with ICCA; and one novel truncating mutation (p.Arg217*) was found in one individual with sporadic PKD. In the 2 remaining individuals with sporadic PKD, PRRT2 mutations were not detected. Importantly, PRRT2 mutations did not cosegregate with febrile convulsions or with migraine. The estimated penetrance of PRRT2 mutations was 61%, if only the PKD phenotype was considered; however, if infantile convulsions were also taken into account, the penetrance was nearly complete. Considering our findings and those reported in literature, 23 PRRT2 mutations explain ∼56% of the families analyzed. CONCLUSIONS: PRRT2 mutations are the major cause of PKD or ICCA, but they do not seem to be involved in the etiology of febrile convulsions and migraine. The identification of PRRT2 as a major gene for the PKD-ICCA-BFIC spectrum allows better disease classification, molecular confirmation of the clinical diagnosis, and genetic testing and counseling.

Paroxysmal kinesigenic dyskinesia: cortical or non-cortical origin.

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by involuntary dystonia and/or chorea triggered by a sudden movement. Cases are usually familial with an autosomal dominant inheritance. Hypotheses regarding the pathogenesis of PKD focus on the controversy whether PKD has a cortical or non-cortical origin. A combined familial trait of PKD and benign familial infantile seizures has been reported as the infantile convulsions and paroxysmal choreoathetosis (ICCA) syndrome. Here, we report a family diagnosed with ICCA syndrome with an Arg217STOP mutation. The index patient showed interictal EEG focal changes compatible with paroxysmal dystonic movements of his contralateral leg. This might support cortical involvement in PKD.

Epilepsias benignas de la infancia: dificultades académicas y alteraciones comportamentales / Benign childhood epilepsies: academic difficulties and behavioural disorder

Introducción. Se han publicado artículos en los que se muestra que los pacientes pueden presentar trastornos del comportamiento y dificultad para el aprendizaje en las epilepsias benignas de la infancia (EBI). Objetivos. Hacer una revisión de los pacientes con diagnóstico de EBI en nuestro hospital e identificar si presentan dichas alteraciones. Pacientes y métodos. Revisión retrospectiva de las historias clínicas de los pacientes con diagnóstico de EBI. Se realizó electroencefalograma (EEG) o video-EEG-poligrafía de sueño a todos los pacientes. Para la valoración intelectual se utilizaron los tests de inteligencia para niños de Wechsler. Resultados. Se recogieron 102 pacientes con diagnóstico de EBI. El 51,6% de los pacientes con epilepsia rolándica mostraba una atención dispersa y el 16,2% evidenciaba un temperamento impulsivo. En el grupo con síndrome de Panayiotopoulos, un 30,3% mostraba una atención dispersa y un 27,3% presentaba un temperamento impulsivo. Se llevó a cabo una valoración psicométrica en 43 pacientes. El valor del cociente intelectual total medio fue de 95 (rango: 55-126). En los tres grupos el rendimiento escolar fue bueno en aproximadamente la mitad, regular en cerca del 30% y malo en alrededor del 15%. En el grupo con epilepsia rolándica se encontró relación entre paroxismos frontales (p = 0,039) y occipitales (p = 0,004) en el EEG y un peor rendimiento escolar. En este grupo, los niños con conductas calificadas como dispersa, impulsiva o hiperactiva mostraban con más frecuencia paroxismos izquierdos (p = 0,030). Conclusiones. Las EBI son entidades con buen pronóstico, pero parecen asociar trastornos del aprendizaje y conductuales. Sería conveniente realizar estudios neuropsicológicos a estos pacientes para detectar tales alteracione (AU)

Introduction. Some papers published in the literature have shown that patients can present behavioural disorders and learning difficulties in benign childhood epilepsies (BCE). Aims. To review the patients diagnosed with BCE in our hospital and to determine whether they present such disorders. Patients and methods. The study consisted in a retrospective review of the medical records of patients diagnosed with BCE. An electroencephalogram (EEG) or video-EEG-polygraph recordings were performed on all patients during sleep. The Wechsler Intelligence Scale for Children was used to evaluate intelligence. Results. Data were collected for 102 patients diagnosed with BCE. Dispersed attention was observed in 51.6% of the patients with rolandic epilepsy and 16.2% displayed an impulsive temperament. In the group of patients with Panayiotopoulos syndrome, 30.3% displayed dispersed attention and 27.3% presented an impulsive temperament. A psychometric evaluation was carried out in 43 patients. The overall mean intelligence quotient was 95 (range: 55-126). In the three groups, academic achievement was good in approximately half the sample, regular in about 30% and poor in around 15%. In the group with rolandic epilepsy, the EEG showed a relation between frontal (p = 0.039) and occipital paroxysms (p = 0.004) and poorer academic achievement. In this group, the children with behaviours classed as dispersed, impulsive or hyperactive showed left-side paroxysms more frequently (p = 0.030). Conclusions. BCE are conditions with a good prognosis, but seem to be associated to learning and behavioural disorders. Neuropsychological studies should be conducted on these patients to detect these disorders (AU)

Neonatal seizures associated with a severe neonatal myoclonus like dyskinesia due to a familial KCNQ2 gene mutation.

UNLABELLED: Mutations in the potassium channel gene KCNQ2, usually cause benign familial neonatal epilepsy. This is an autosomal dominant disorder characterized by clusters of seizures occurring in the first days of life. Most patients have normal psychomotor development and spontaneous remission of seizures by 12 months of age. Since Rett and Teubel reported the first family in 1964 and the identification of KCNQ2 gene mutations in this family by Zimprich et al. in 2006, phenotypic variability has been recognized including: later onset of seizures, myokymia in isolation or accompanied by seizures, neurological deficit and mental retardation. We report a mother and son with an atypical presentation of familial neonatal epilepsy. The mother has persistent epilepsy and subnormal intelligence. The son developed a severe dyskinesia clinically compatible with multifocal myoclonus in the neonatal period that only responded to carbamazepine. He also has ataxia and delayed psychomotor development. EMG revealed a spontaneous occurrence of repetitive normal motor potentials in different muscle groups. Genetic analysis identified a heterozygous missense mutation in KCNQ2 in the child and his mother. CONCLUSION: KCNQ2 mutations can present with a neonatal onset multifocal myoclonus-like dyskinesia.

Cardiovascular and neuroendocrine features of Panayiotopoulos syndrome in three siblings.

OBJECTIVE: Panayiotopoulos syndrome is a benign idiopathic childhood epilepsy characterized by altered autonomic activity at seizure onset. METHODS: Three siblings with Panayiotopoulos syndrome underwent 24-hour EEG recording and head-up tilt testing with continuous blood pressure and RR interval monitoring. Plasma catecholamines and vasopressin were measured while supine, upright, and during a typical seizure. RESULTS: Patient 1, a 12-year-old girl, had a history of involuntary lacrimation, abdominal pain, and recurrent episodes of loss of muscle tone and unresponsiveness followed by somnolence. Her EEG revealed bilateral frontotemporal spikes. Patient 2, a 10-year-old boy, had episodic headaches with pinpoint pupils, skin flushing of the face, trunk, and extremities, purple discoloration of hands and feet, diaphoresis, nausea, and vomiting. Tilt testing triggered a typical seizure after 9 minutes; there was a small increase in blood pressure (+5/4 mm Hg, systolic/diastolic) and pronounced increases in heart rate (+59 bpm) and norepinephrine (+242 pg/mL), epinephrine (+175 pg/mL), and vasopressin (+22.1 pg/mL) plasma concentrations. Serum glucose was elevated (206 mg/dL). His EEG revealed right temporal and parietal spikes. Patient 3, an 8-year-old boy, had a history of restless legs at night, enuresis, night terrors, visual hallucinations, cyclic abdominal pain, and nausea. His EEG showed bitemporal spikes. CONCLUSION: Hypertension, tachycardia, and the release of vasopressin suggest activation of the central autonomic network during seizures in familial Panayiotopoulos syndrome. These autonomic and neuroendocrine features may be useful in the diagnosis and may have therapeutic implications.

Benign epilepsy in children.

The diagnosis of benign epilepsy syndrome should meet the following criteria: age-related and self-limited; good response to medication; and no obvious neurological sequelae after seizure. However, the current concept of benign epilepsy syndrome has been challenged because of the advancements in genetic studies, neuroimaging, and molecular techniques. Many studies have revealed that the prevalence of behavioral problems and learning difficulties as well as subtle cognitive deficits is higher among patients with benign epilepsy, compared with the normal population. Here, we review updated results of these studies to show the latest and broad comprehensive knowledge of benign epilepsy in children.

Genetics of infantile seizures with paroxysmal dyskinesia: the infantile convulsions and choreoathetosis (ICCA) and ICCA-related syndromes.

The relationship between paroxysmal movement disorders (PD: paroxysmal dyskinesia) and epilepsy continues to present a challenging problem. Attacks of PD and epileptic seizures have several characteristics in common: both are paroxysmal in nature with a tendency to spontaneous remission, and a subset of PD responds well to anticonvulsants. In 1997, description of the ICCA (infantile convulsions and choreoathetosis) syndrome and linkage to chromosome 16p12-q12 provided the first genetic evidence for common mechanisms shared by benign infantile seizures and PD. The chromosome 16 ICCA locus is by far the most frequently involved in such associations as well as in pure forms of benign infantile seizures. The ICCA region at the pericentromeric area of chromosome 16 shows complicated genomic architecture and the ICCA gene still remains unknown. Genetic studies focusing on PD with or without epilepsy have led to the identification of other genes linked to chromosomes 2q35 and 10q22. Alterations of ion channel and ion pump subunits could provide a simple, albeit probably non-unique, explanation for the pathophysiology of the link between epilepsy and PD. The aim of this review is to update genetic aspects of infantile epileptic seizures and PD and their association in the context of ICCA and ICCA related syndromes.

A BFIS-like syndrome with late onset and febrile seizures: suggestive linkage to chromosome 16p11.2-16q12.1.

Benign familial infantile seizures (BFIS) is a dominant idiopathic epilepsy with partial and secondarily generalized seizures with age of onsetr between 3 and 12 months. Here we describe a four-generation family with some characteristic features of BFIS but with unusual clinical signs, in eight affected members with an unusual clinical phenotype. Onset was consistently between 14 and 20 months of age with clusters of complex-partial or generalized tonic-clonic seizures and a high rate of febrile seizures, which have not been described for BFIS previously. All affected members showed multifocal interictal epileptiform discharges in the EEG. The known loci for benign familial neonatal/infantile seizures (BFNS/BFNIS), generalized epilepsy with febrile seizures plus (GEFS+) and the BFIS locus on chromosome 19q were excluded. Further genetic analysis showed suggestive linkage to the major BFIS locus on chromosome 16 between markers D16S690 and D16S3136. This ;;BFIS-like'' syndrome may enlarge the phenotypic spectrum of diseases linked to the chromosome 16 region.

Seizure recurrence and developmental disabilities after neonatal seizures: outcomes are unrelated to use of phenobarbital prophylaxis.

This study investigated treatment patterns at discharge in infants with neonatal seizures and evaluated the impact of outpatient phenobarbital prophylaxis on the frequency of seizure recurrence and the long-term neurodevelopmental outcome at 1 to 11 years. Infants with neonatal seizures during a 12-year period were identified retrospectively (n = 146), and data were obtained by medical chart review. Outcomes were ascertained by standardized telephone survey. Thirty-three infants (23%) were taking phenobarbital, and 99 infants (68%) were taking no anticonvulsants at discharge. Comparisons were made between these 2 groups. Phenobarbital prophylaxis did not improve neurologic outcomes, either with respect to seizure recurrence or neurologic development. These data have important implications at a time when many are questioning the practice of prophylaxis after neonatal seizures and when newer anticonvulsants are being recommended for treatment of acute neonatal seizures.

[The effect of neonatal convulsions and antiepileptic drugs on the developing brain: controversial aspects and therapeutic implications]. / Efecto de las convulsiones neonatales y de los fármacos antiepilépticos sobre el cerebro en desarrollo: aspectos controvertidos e implicaciones terapéuticas.

INTRODUCTION: Neonatal seizures are the clinical or subclinical manifestations of epileptic nature during the first 28 days of life. Their pathophysiological basis depends on the anatomic and biochemical characteristics of the developing brain. The question whether neonatal seizures cause brain damage, even today, has not a clear answer. DEVELOPMENT: Data from clinical cases suggest that neonatal seizures may increase the cerebral blood flow and augment the energy requirements of the developing brain. Clinical research studies also suggest that neonatal seizures, even when they are only electrographic, may cause brain lesion independently from their cause. Multiple experimental investigations using mostly rat models of isolated or repeated induced seizures, have demonstrated that neonatal seizures may alter brain metabolic content, maturation of glutamatergic and GABAergic receptors, future cognitive development and epileptogenic risk, neuroneogenesis, intranuclear penetration of calcium, and neuronal apoptotic activation. On the other hand, some experimental studies suggest that phenobarbital, phenytoin and benzodiazepines may have a negative effect on brain development. CONCLUSIONS: In my opinion, the ideal short-term goal of treating neonatal seizures should be stopping not only the clinical but also the subclinical epileptic activity. If prolonged treatment is necessary, one should consider to stop it as soon as the clinical and EEG course allows it. There is a need for future randomized, controlled trials of sufficient statistical power to assess the efficacy and tolerability of classic and new antiepileptic drugs in the treatment of neonatal seizures.