Migrating partial seizures in infancy: two new cases

KCNT1 epilepsy with migrating focal seizures shows a temporal sequence with poor outcome, high mortality and SUDEP

Data on KCNT1 epilepsy of infancy with migrating focal seizures are heterogeneous and incomplete. Kuchenbuch et al. refine the syndrome phenotype, showing a three-step temporal sequence, poor prognosis with acquired microcephaly, high prevalence of extra-neurological manifestations and early mortality, particularly due to SUDEP. Refining the electro-clinical spectrum should facilitate early diagnosis.

Ion Channels in Genetic Epilepsy: From Genes and Mechanisms to Disease-Targeted Therapies

Epilepsy is a common and serious neurologic disease with a strong genetic component. Genetic studies have identified an increasing collection of disease-causing genes. The impact of these genetic discoveries is wide reaching-from precise diagnosis and classification of syndromes to the discovery and validation of new drug targets and the development of disease-targeted therapeutic strategies. About 25% of genes identified in epilepsy encode ion channels. Much of our understanding of disease mechanisms comes from work focused on this class of protein. In this study, we review the genetic, molecular, and physiologic evidence supporting the pathogenic role of a number of different voltage- and ligand-activated ion channels in genetic epilepsy. We also review proposed disease mechanisms for each ion channel and highlight targeted therapeutic strategies.

Migrating partial seizures in infancy and 47XYY syndrome: Cause or coincidence?

Migrating partial seizures in infancy (MPSI) is a rare epilepsy syndrome with poor prognosis. The exact etiology of MPSI is still not known. We report a 14-month-old baby with 47XYY karyotype who presented with developmental delay and drug-refractory seizures satisfying the diagnostic criteria for MPSI and discuss the possible association between the 47XYY karyotype and this syndrome. The excess of genes due to an additional Y chromosome could cause disturbance in various stages of formation, migration, or differentiation of neurons. Depending on the degree of disturbance and the resultant cortical excitability, this could result in various epilepsy syndromes. We feel that this association is more likely causal than coincidental. Chromosome studies need to be performed in more individuals with atypical and uncommon epilepsies. Multicenter studies are required to establish the association between epilepsy syndrome and these rare chromosome disorders.

Migrating partial seizures of infancy: expansion of the electroclinical, radiological and pathological disease spectrum

Migrating partial seizures of infancy, also known as epilepsy of infancy with migrating focal seizures, is a rare early infantile epileptic encephalopathy with poor prognosis, presenting with focal seizures in the first year of life. A national surveillance study was undertaken in conjunction with the British Paediatric Neurology Surveillance Unit to further define the clinical, pathological and molecular genetic features of this disorder. Fourteen children with migrating partial seizures of infancy were reported during the 2 year study period (estimated prevalence 0.11 per 100,000 children). The study has revealed that migrating partial seizures of infancy is associated with an expanded spectrum of clinical features (including severe gut dysmotility and a movement disorder) and electrographic features including hypsarrhythmia (associated with infantile spasms) and burst suppression. We also report novel brain imaging findings including delayed myelination with white matter hyperintensity on brain magnetic resonance imaging in one-third of the cohort, and decreased N-acetyl aspartate on magnetic resonance spectroscopy. Putaminal atrophy (on both magnetic resonance imaging and at post-mortem) was evident in one patient. Additional neuropathological findings included bilateral hippocampal gliosis and neuronal loss in two patients who had post-mortem examinations. Within this cohort, we identified two patients with mutations in the newly discovered KCNT1 gene. Comparative genomic hybridization array, SCN1A testing and genetic testing for other currently known early infantile epileptic encephalopathy genes (including PLCB1 and SLC25A22) was non-informative for the rest of the cohort.

De novo gain-of-function KCNT1 channel mutations cause malignant migrating partial seizures of infancy

Malignant migrating partial seizures of infancy (MMPSI) is a rare epileptic encephalopathy of infancy that combines pharmacoresistant seizures with developmental delay. We performed exome sequencing in three probands with MMPSI and identified de novo gain-of-function mutations affecting the C-terminal domain of the KCNT1 potassium channel. We sequenced KCNT1 in 9 additional individuals with MMPSI and identified mutations in 4 of them, in total identifying mutations in 6 out of 12 unrelated affected individuals. Functional studies showed that the mutations led to constitutive activation of the channel, mimicking the effects of phosphorylation of the C-terminal domain by protein kinase C. In addition to regulating ion flux, KCNT1 has a non-conducting function, as its C terminus interacts with cytoplasmic proteins involved in developmental signaling pathways. These results provide a focus for future diagnostic approaches and research for this devastating condition.

A case of malignant migrating partial seizures in infancy as a continuum of infantile epileptic encephalopathy

The syndrome of malignant migrating partial seizures in infancy (MMPSI) is characterized by onset before the age of 6 months, nearly continuous electrographic seizures involving multiple independent areas of onset in both hemispheres, and poor developmental outcome. This report presents a case involving a patient with MMPSI, who later developed West syndrome. At the age of 2 months old, he showed multifocal partial seizures, which were refractory to antiepileptic drugs. His electroencephalogram (EEG) revealed characteristic migrating multifocal epileptiform activities and neuroimaging finding was normal. The focal seizures were refractory to antiepileptic drugs and ketogenic diet. When he was 9 months old, epilepic spasms were observed with hypsarrhythmia on EEG. He also showed severe developmental delay. MMPSI may be a continuum of infantile epileptic encephalpathy and could evolve to West syndrome.

Migrating focal seizures during infancy: a case report and pathologic study

Migrating focal seizures in infancy are an unusual and often overlooked epilepsy syndrome, with onset before age 6 months, in which nearly continuous seizures involve multiple, independent areas of both hemispheres with an arrest of psychomotor development. We describe a patient with migrating focal seizures in infancy whose seizures began at age 45 days. The seizures were refractory to common antiepileptic drugs. At age 6 months, the infant received potassium bromide and became almost seizure-free. The infant developed severe neurologic impairment, with marked axial hypotonia and an absence of visual contact and head control. At age 8 months, the child suddenly died. Pathologic findings included multiple malformations of cortical development, polymicrogyria, and focal cortical dysplasia associated with hippocampal sclerosis.

Novel SCN1A mutation in a proband with malignant migrating partial seizures of infancy

OBJECTIVE

To characterize a novel SCN1A mutation in a proband with malignant migrating partial seizures of infancy.

DESIGN

Genomic DNA was isolated from blood and submitted for commercial testing. The identified missense mutation was confirmed in brain DNA obtained at autopsy. Genomic DNA from the brain of the proband was analyzed by comparative genome hybridization, and the coding exons of SCN9A were amplified. Quantitation studies of the mutant transcript were performed.

SETTING

Children's National Medical Center and Yale University School of Medicine. PROBAND: A full-term female infant who experienced seizure onset at age 10 weeks, with progression of hemiclonic, apneic, and multifocal migrating partial seizures leading to recurrent status epilepticus and death at age 9 months.

MAIN OUTCOME MEASURES

Electroencephalographic and magnetic resonance imaging results, quantitative RNA expression, and secondary mutation test results.

RESULTS

The heterozygous missense mutation c.C5006C>A was identified by sequencing genomic DNA from blood and was confirmed in brain DNA. The resulting amino acid substitution p.A1669E alters an evolutionarily conserved residue in an intracellular linker of domain 4 of the SCN1A sodium channel protein Na(v)1.1. The mutant transcript is found to be expressed at levels comparable to the wild-type allele in brain RNA. No variation in copy number was detected in the chromosome region 2q24 containing SCN1A or elsewhere in the genome. No mutations were detected in the linked sodium channel gene SCN9A, which has been reported to act as a modifier of SCN1A mutations.

CONCLUSION

This report expands the spectrum of SCN1A epileptic channelopathies to include malignant migrating partial seizures of infancy.

Malignant migrating partial seizures in Aicardi syndrome

This article reports on a female infant with Aicardi syndrome presenting with malignant migrating partial seizures from her first day of life. Initially, unilateral tonic seizures were seen with contralateral ictal electroencephalogram findings. Typically, these tonic seizures were accompanied by head and eye deviation and were followed by a tonic seizure on the other side of the body. At 6 months of age she developed epileptic spasms. She showed no motor development, did not respond to eye contact, and was nasogastric tube-fed. The epilepsy syndrome in this child is refractory to antiepileptic treatment and there is no psychomotor development. This case expands the phenotype of this catastrophic epileptic encephalopathy and suggests that the corpus callosum is not necessary for the 'migration' of partial seizures in this syndrome.

Migrating focal seizures in infancy: analysis of the electroclinical patterns in 17 patients

We describe the electroclinical features, therapy, and long-term evolution of 17 patients with migrating focal seizures in infancy, and analyzed the charts of these patients seen between February 1985 and July 2005. Three different electroclinical patterns were recognized: (1) 8 cases with alternating simple focal motor seizures at onset. The ictal electroencephalography (EEG) pattern was characterized by recurrence of rhythmic focal spikes or rhythmic sharp activity in the Rolandic region; (2) 5 cases with complex focal seizures and progressive appearance of polymorphic delta- activity in 1 temporo-occipital region recurring independently; (3) 4 cases with focal complex seizures with motor manifestations. Ictal EEG showed flattening or fast activity in 1 frontotemporal region followed by unilateral fast poly-spikes in alternating clusters in both hemispheres. The focal seizures were refractory to antiepileptic drugs, and all patients except 3 had severe developmental delay. Migrating focal seizures in infancy is a newly defined and rare, but underrecognized, epileptic encephalopathy.

The clinical-electrographic expression of infantile seizures

PURPOSE

To describe the electro-clinical expression of seizures in infants (1-24 months).

METHODS

We reviewed the video and EEG files of all infantile seizures recorded at Children's Memorial Hospital, Chicago, IL, from 2000 to 2005. Electrographic and clinical features were entered into separate databases. The electrographic component of the database analyzed the predominant location and pattern at onset, the evolution, the termination and the duration of each seizure. The clinical data sheet included 25 items. Each seizure was assigned to a specific category according to its most prominent clinical feature, according to the opinion of both observers.

RESULTS

Thirteen seizure types were identified. In a significant number of cases, the EEG correlate could not be predicted on the basis of clinical observations only. Generalized seizures were observed, on average, at a later age than focal seizures. Excluding spasms, the mean duration of seizures was short (36 s).

CONCLUSIONS

The results of this study are useful in describing the clinical and electrographic repertoire of infantile seizures. The findings show that video-EEG recordings in infants with frequent, recurrent seizures are useful by fully allowing complete recognition of subtle events, and in fully categorizing the true nature of the ictus. Video-EEG findings and accurate seizure classification may add fundamental information with regards to epilepsy syndrome diagnosis and specific treatment options, including surgery.

Benign Partial Epilepsy in Infancy: Myth or Reality?

PURPOSE

Benign partial epilepsy in infancy (BPEI) was first described by Watanabe in 1987. The aim of this study is to describe a series of infants from the United States to characterize this entity further.

METHODS

Among patients with the diagnosis of epilepsy followed up at our institution between 2002 and 2004, those satisfying the criteria for BPEI were included in a retrospective study.

RESULTS

Sixteen (10.2%) of 150 patients with new onset of epilepsy younger than 2 years were identified. The mean age at seizure onset was 8 months. Four (25%) infants had a family history of benign seizures. All infants were neurologically and developmentally normal at the onset of seizures. The seizures occurred in clusters in 75% of patients, predominantly in wakefulness. The initial manifestation was behavioral arrest with staring (69%) and apnea with cyanosis or pallor (37.5%). These symptoms were followed by deviation of eyes or head or both (56%), mild clonic movements (31%), or increased limb tone (35%). Secondary generalization was noticed in 37.5% of patients. All infants had normal interictal EEGs and brain MRIs. Ictal EEGs disclosed electrographic seizures in 50% of patients (temporal origin in 62% and central in 38%). Fifteen (94%) patients were treated with AEDs with good response. The mean duration of treatment was 12.4 months. The final developmental assessment of all patients was normal.

CONCLUSIONS

We believe that BPEI exists as a unique entity and should be included in the differential diagnosis of epilepsies in infancy with partial origin.

Mutational scanning of potassium, sodium and chloride ion channels in malignant migrating partial seizures in infancy

The mutational analysis of potassium (KCNQ2, KCNQ3), sodium (SCN1A, SCN2A), and chloride (CLCN2) ion channels was performed in three children with typical features of the recently described syndrome of migrating partial seizures in infancy. Mutational analysis was performed by PCR and automatic sequencing. The coding regions, including the exon-intron boundaries, were amplified in the patients using appropriate primers sets. No mutations associated to migrating partial seizures have been found. Mutational screening of CLCN2 gene, revealed a homozygous mutation G2003C (exon 17), leading to a Ser/Thr substitution at the codon 668, in two of the three patients. The same variation has been found in 38 out of 100 control alleles. The identification of the genetic basis of this new epileptic encephalopathy requires further studies that might be enforced by familial cases.

Levetiracetam in a neonate with malignant migrating partial seizures

This report describes the first neonatal case of "malignant migrating partial seizures in infancy" with a positive therapeutic response to levetiracetam. This patient is the youngest reported infant with this rare syndrome, and the report provides the first documentation on levetiracetam treatment in a neonatal patient. Treatment with levetiracetam improved both ictal and interictal status. This observation also highlights the need to consider and include malignant migrating partial seizures in the differential diagnosis of early neonatal seizure disorders, even during the first hours of life.

Migrating partial seizures in infancy: expanding the phenotype of a rare seizure syndrome

PURPOSE

The constellation of early-onset, unprovoked, alternating electroclinical seizures and neurodevelopmental devastation was first described by Coppola et al. We report six new patients and the prospect of a more optimistic developmental outcome.

METHODS

Retrospective chart reviews were performed on six infants evaluated at the Children's Hospital of Philadelphia (five patients) and at Hershey Medical Center (one patient) who had electroclinically alternating seizures before age 6 months of age. Electroclinical characteristics and long-term follow-up were recorded.

RESULTS

All had unprovoked, early-onset (range, 1 day to 3 months; mean, 25 days) intractable electroclinical seizures that alternated between the two hemispheres. Each patient underwent comprehensive brain imaging and neurometabolic workups, which were unrevealing. In all patients, subsequently intractable partial seizures developed and often a progressive decline of head circumference percentile occurred with age. Three demonstrated severe developmental delay and hypotonia. All survived, and 7-year follow-up on one patient was quite favorable.

CONCLUSIONS

Our patients satisfied the seven major diagnostic criteria first described by Coppola et al. The prognosis of this rare neonatal-onset epilepsy syndrome from the original description and subsequent case reports was very poor, with 28% mortality, and the majority of survivors were profoundly retarded and nonambulatory. Our patient data validate the diagnostic criteria of this syndrome and further quantify a previously described observation of progressive decline of head circumference percentiles with age. Our data also suggest that the prognosis of this syndrome, although poor, is not as uniformly grim as the cases reported previously in the literature.

Malignant migrating partial seizures in infancy

Malignant migrating partial seizures in infancy is a rare, age-specific epileptic encephalopathy. It is characterized by onset before age 6 months, virtually continuous multifocal seizures with ictal electrical encephalographic activity shifting from one hemisphere to the other, no identifiable immediate or remote causes, intractability to antiepileptic drugs, and developmental arrest. This report adds two patients to the 21 previously described in the literature. One infant, microcephalic at birth, developed at age 4 months clusters of nearly continuous multifocal seizures with secondary generalization, refractory to antiepileptic drugs. By age 4.5 years she was seizure-free but remains without any cognitive or motor function. Patient 2, born with a normal head circumference, began seizures at age 3 months, never became seizure-free, and died at age 18 months. Electroencephalograms of both children were characteristic, and the neuroimaging finding was one of progressive cortical and subcortical atrophy. It has been hypothesized that neurotransmitter dysfunction with persistent, pronounced excitatory or cytotoxic mechanisms may explain the continuous, erratic epileptic activity. Awareness of malignant migrating partial seizures in infancy and research focused on its pathophysiologic mechanisms may reveal innovative treatments of this devastating, age-specific disorder.

Clinical study of catastrophic infantile epilepsy with focal seizures

This study investigated clinico-electrical and etiologic characteristics of catastrophic infantile epilepsy with focal seizures developed in early infancy. The patients included 15 children who fulfilled the following criteria: seizure onset before 12 months of age, presence of daily focal or secondarily generalized seizures resistant to antiepileptic drugs for at least 3 months, and exclusion of Ohtahara and West syndromes. Patients were classified into three subgroups. Three patients demonstrated progressively deteriorating neurologic symptoms associated with progressive cerebral atrophy and multifocal seizure onset. Three other children were characterized by hemiparesis and exclusively lateralized seizure onset because of focal cortical dysplasia in the contralateral hemisphere. The remaining nine children did not demonstrate any rapidly progressive neurologic deterioration or increasing cerebral atrophy and exhibited multifocal seizure onset. At the last examinations, all except one patient demonstrated moderate to severe psychomotor retardation. Catastrophic infantile epilepsy with focal seizures tended to demonstrate multifocal seizure onset and a deleterious clinical course with numerous focal seizures regardless of etiology. Because migratory focal seizures appear to be common in these infants, we have to search for the underlying etiopathogenesis of these patients, including not only metabolic errors but also localized or lateralized structural abnormality.