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Summary: Objective: We aimed to characterize epilepsy of infancy with migrating focal seizures (EIMFS), a rare, severe early onset developmental epilepsy related to KCNT1 mutation, and to define specific electroencephalography (EEG) markers using EEG quantitative analysis. The ultimate goal would be to improve early diagnosis and to better understand seizure onset and propagation of EIMFS as compared to other early onset developmental epilepsy. Methods: EEG of 7 EIMFS patients with KCNT1 mutations (115 seizures) and 17 patients with other early onset epilepsies (30 seizures) was included in this study. After detection of seizure onset and termination, spatiotemporal characteristics were quantified. Seizure propagation dynamics were analyzed using chronograms and phase coherence. Results: In patients with EIMFS, seizures started and were localized predominantly in temporal and occipital areas, and evolved with a stable frequency (4‐10 Hz). Inter‐ and intrahemispheric migrations were present in 60% of EIMFS seizures with high intraindividual reproducibility of temporospatial dynamics. Interhemispheric migrating seizures spread in 71% from temporal or occipital channels to the homologous contralateral ones, whereas intrahemispheric seizures involved mainly frontotemporal, temporal, and occipital channels. Causality links were present between ictal activities detected under different channels during migrating seizures. Finally, time delay index (based on delays between the different ictal onsets) and phase correlation index (based on coherence of ictal activities) allowed discrimination of EIMFS and non‐EIMFS seizures with a specificity of 91.2% and a sensitivity of 84.4%. Significance: We showed that the migrating pattern in EIMFS is not a random process, as suggested previously, and that it is a particular propagation pattern that follows the classical propagation pathways. It is notable that this study reveals specific EEG markers (time delay and phase correlation) accessible to visual evaluation, which will improve EIMFS diagnosis. [ABSTRACT FROM AUTHOR]

Objective Mutations in the syntaxin binding protein 1 gene ( STXBP1) have been associated mostly with early onset epileptic encephalopathies ( EOEEs) and Ohtahara syndrome, with a mutation detection rate of approximately 10%, depending on the criteria of selection of patients. The aim of this study was to retrospectively describe clinical and electroencephalography ( EEG) features associated with STXBP1-related epilepsies to orient molecular screening. Methods We screened STXBP1 in a cohort of 284 patients with epilepsy associated with a developmental delay/intellectual disability and brain magnetic resonance imaging ( MRI) without any obvious structural abnormality. We reported on patients with a mutation and a microdeletion involving STXBP1 found using array comparative genomic hybridization ( CGH). Results We found a mutation of STXBP1 in 22 patients and included 2 additional patients with a deletion including STXBP1. In 22 of them, epilepsy onset was before 3 months of age. EEG at onset was abnormal in all patients, suppression-burst and multifocal abnormalities being the most common patterns. The rate of patients carrying a mutation ranged from 25% in Ohtahara syndrome to <5% in patients with an epilepsy beginning after 3 months of age. Epilepsy improved over time for most patients, with an evolution to West syndrome in half. Patients had moderate to severe developmental delay with normal head growth. Cerebellar syndrome with ataxic gait and/or tremor was present in 60%. Significance Our data confirm that STXBP1 mutations are associated with neonatal-infantile epileptic encephalopathies. The initial key features highlighted in the cohort of early epileptic patients are motor seizures either focal or generalized, abnormal initial interictal EEG, and normal head growth. In addition, we constantly found an ongoing moderate to severe developmental delay with normal head growth. Patients often had ongoing ataxic gait with trembling gestures. Altogether these features should help the clinician to consider STXBP1 molecular screening. [ABSTRACT FROM AUTHOR]

Summary Purpose: STXBP1 (MUNC18-1) mutations have been associated with various types of epilepsies, mostly beginning early in life. To refine the phenotype associated with STXBP1 aberrations in early onset epileptic syndromes, we studied this gene in a cohort of patients with early onset epileptic encephalopathy. Methods: STXBP1 was screened in a multicenter cohort of 52 patients with early onset epilepsy (first seizure observed before the age of 3 months), no cortical malformation on brain magnetic resonance imaging (MRI), and negative metabolic screening. Three groups of patients could be distinguished in this cohort: (1) Ohtahara syndromes (n = 38); (2) early myoclonic encephalopathies (n = 7); and (3) early onset epileptic encephalopathies that did not match any familiar syndrome (n = 7). None of the patients displayed any cortical malformation on brain MRI and all were screened through multiple video-electroencephalography (EEG) recordings for a time period spanning from birth to their sixth postnatal month. Subsequently, patients had standard EEG or video-EEG recordings. Key Findings: We found five novel STXBP1 mutations in patients for whom video-EEG recordings could be sampled from the beginning of the disease. All patients with a mutation displayed Ohtahara syndrome, since most early seizures could be classified as epileptic spasms and since the silent EEG periods were on average shorter than bursts. However, each patient in addition displayed a particular clinical and EEG feature: In two patients, early seizures were clonic, with very early EEG studies exhibiting relatively low amplitude bursts of activity before progressing into a typical suppression-burst pattern, whereas the three other patients displayed epileptic spasms associated with typical suppression-burst patterns starting from the early recordings. Epilepsy dramatically improved after 6 months and finally disappeared before the end of the first year of life for four patients; the remaining one patient had few seizures until 18 months of age. In parallel, EEG paroxysmal abnormalities disappeared in three patients and decreased in two, giving place to continuous activity with fast rhythms. Each patient displayed frequent nonepileptic movement disorders that could easily be mistaken for epileptic seizures. These movements could be observed as early as the neonatal period and, unlike seizures, persisted during all the follow-up period. Significance: We confirm that STXBP1 is a major gene to screen in cases of Ohtahara syndrome, since it is mutated in >10% of the Ohtahara patients within our cohort. This gene should particularly be tested in the case of a surprising evolution of the patient condition if epileptic seizures and EEG paroxysmal activity disappear and are replaced by fast rhythms after the end of the first postnatal year. [ABSTRACT FROM AUTHOR]