Clinical features and genetic analysis of the early-onset epileptic encephalopathy caused by sodium channel mutations / 中华实用儿科临床杂志

ABSTRACT

Objective:To explore the clinical phenotype characteristics of early-onset epileptic encephalopathy (EOEE) caused by sodium channel mutations.Methods:A retrospective study was used.A total of 52 EOEE patients treated in the Department of Neurology, Children′s Hospital of Fudan University and Department of Neurology, Wuhan Children′s Hospital, Tongji Medical College, Huazhong University of Science & Technology from June 2016 to June 2019 were recruited.Peripheral blood samples of 52 patients and their parents were collected for analyzing pathogenic mutations by the next generation sequencing and copy number variations of whole exons in family. Chi- square test was used to compare seizure control data among different voltage-gated sodium channel α1 subunit ( SCN1A) mutation types. Results:A total of 35/52 cases (67.3%) were diagnosed as Dravet syndrome, 3/52 cases (5.8%) were West syndrome, and 14/52 cases (26.9%) were non-symptomatic EOEE.The electroencephalogram (EEG) findings showed a large number of multifocal spikes, spike-slow waves, sharp waves, and sharp-slow waves.A total of 45/52 cases (86.5%) showed normal brain magnetic resonance imaging(MRI), 1 case had slightly widened bilateral frontal sulcus, 1 case had widened bilateral temporal pole and frontal top subarachnoid space, and the remaining 5 cases had widened extracerebral space and slightly larger ventricles.Thirteen cases were re-examined with brain MRI, and 3 cases had mild brain atrophy.A total of 43/52 cases (82.7%) were examined with SCN1A gene mutations, of which 28/52 cases (53.8%) were missense mutations, 5/52 cases (9.6%) were nonsense mutations, 7/52 cases (13.5%) were frameshift mutations and 3/52 cases (5.8%) were splice site mutations.A total of 3/52 cases (5.8%) had SCN2A mutations, of which 2/52 cases (3.8%) were missense mutations, and 1/52 case (1.9%) was a frameshift mutation, 1/52 cases (1.9%) carrying the missense mutation of the SCN3A gene.A total of 5/52 cases (9.6%) had missense mutations of the SCN8A gene.After an average of 1-year follow-up, a total of 13/52 cases (25.0%) had more than 1-year control of seizure, of which 6/52 cases (11.5%) with seizure control for more than 2 years, and 4/52 cases (7.7%) with more than 3-year control.Children carrying SCN1A missense mutations were relatively easier to be controlled for seizures than those carrying SCN1A truncation mutations (nonsense mutations+ frameshift mutations) ( P<0.05). In 5 children carrying SCN8A mutations, 2 cases of them had seizures control for more than 1 year after adding Oxcarbazepine, but the improvement of mental motor function was not obvious. Conclusions:In children with EOEE associated with sodium channel gene mutations, SCN1A, SCN2A, SCN3A, and SCN8A mutations were pathogenic factors.Among them, SCN1A was the most common pathogenic gene for EOEE, with the mutation rate of 82.7%.Dravet syndrome was the most common clinical phenotype of EOEE associated with sodium channel gene mutations.Epileptic seizures in children carrying SCN1A missense mutations were easier to be controlled than those with truncated mutation (nonsense mutations + frameshift mutations), suggesting that the gene mutation type was related to the degree of seizures control.Oxcarbazepine was effective in the treatment of EOEE with SCN8A gene mutations, indicating that the combination therapy using anti-epilepsy drugs can be applied to EOEE patients according to the type of gene function.