钠离子通道基因突变相关早发性癫痫脑病患儿临床特征及分子遗传学研究

Clinical features and genetic analysis of the early-onset epileptic encephalopathy caused by sodium channel mutations

目的探讨不同类型的钠离子通道基因突变相关早发性癫痫脑病(EOEE)患儿的临床表型特点。方法采用回顾性研究。选取2016年6月至2019年6月复旦大学附属儿科医院神经内科和华中科技大学同济医学院附属武汉儿童医院神经内科收治的52例患儿,采集患儿及其父母外周血,应用疾病基因家系全外显子二代测序及拷贝数变异技术进行测序分析,寻找致病突变。不同电压门控钠通道α1亚基(SCN1A)突变类型间癫痫发作控制数据比较采用χ^(2)检验。结果52例患儿中35例(35/52例,67.3%)诊断为Dravet综合征、3例(3/52例,5.8%)婴儿痉挛症、14例(14/52例,26.9%)非综合征类EOEE。脑电图提示多量多灶性棘波、棘慢波、尖波、尖慢波发放。45例(45/52例,86.5%)头颅磁共振成像(MRI)提示正常,1例双侧额叶脑沟稍增宽,1例双侧颞极、额顶部蛛网膜下腔增宽,余5例脑外间隙增宽、脑室稍大。后期13例患儿复查头颅MRI,其中3例患儿轻度脑萎缩。52例患儿中SCN1A突变43例(43/52例,82.7%),其中28例(28/52例,53.8%)为错义突变、5例(5/52例,9.6%)无义突变、7例移码突变(7/52例,13.5%)、3例(3/52例,5.8%)剪切位点突变。SCN2A突变3例(3/52例,5.8%),其中2例(2/52例,3.8%)错义突变,1例(1/52例,1.9%)移码突变。SCN3A突变1例(1/52例,1.9%),为错义突变。SCN8A突变5例(5/52例,9.6%),均为错义突变。治疗后平均随访1年,发作控制1年以上者13例(13/52例,25.0%),其中发作控制2年以上者6例(6/52例,11.5%),3年以上者4例(4/52例,7.7%)。分析SCN1A突变类型与癫痫发作控制程度,发现SCN1A错义突变较SCN1A截断突变(无义突变+移码突变)患儿癫痫发作相对易控制(P<0.05)。5例SCN8A突变患儿中,2例添加奥卡西平后,发作控制1年以上,智力运动功能改善不明显。结论钠离子通道基因突变相关EOEE患儿中,SCN1A、SCN2A、SCN3A、SCN8A的遗传变异是EOEE遗传学病因的重要因素,以SCN1A最为多见,突变率高达82.7%。Dravet综合征是钠离子通道基因突变相关EOEE最常见临床表型。SCN1A错义突变患儿较截断突变患儿癫痫发作相对容易控制,提示基因突变类型与发作控制程度相关。奥卡西平添加治疗SCN8A脑病患儿有效,提示EOEE依然可根据基因功能类型选择联合用药。

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 channelα1 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.