新生儿惊厥的原因及机制.doc

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新生儿惊厥的原因及机制

对于新生儿惊厥这种疾病，我们千万不能忽略，因为这种疾病如果不能治疗好，会给宝宝的将来造成一定的营养，那么到底什么是新生儿惊厥呢？新生儿惊厥的发病原因和发病机制是什么呢？我们先来看看吧！

　　一、发病原因

　　(1)惊厥可仅由于中枢神经系统的异常放电引起，但这种异常放电可由许多原发性颅内病变(脑膜炎，脑血管意外，脑炎，颅内出血，肿瘤)引起，或继发于全身性或代谢性(如缺血缺氧，低血糖，低血钙，低血钠)疾病。

　　(2)缺血缺氧引起的惊厥常发生在分娩前，分娩时和分娩后，并常在伴有呼吸窘迫综合征的早产儿中发生。

　　(3)低血糖在糖尿病母亲的新生儿，小于胎龄儿和有缺血缺氧及其他应激的新生儿中常见。足月儿血糖<40mg/dl(2.2mmol/L)， 低出生体重儿<30mg/dl(1.7mmol/L)为低血糖;并不是这种血糖水平的新生儿都有症状，长期或反复发作低血糖可造成中枢神经系统的永 久性损害。

　　(4)感染可引起惊厥

　　脑膜炎常有惊厥，败血症也可发生，但一般不出现此征。革兰氏阴性菌常引起新生儿颅内和全身性感染，巨细胞病毒，单纯疱疹病毒，风疹病毒，梅毒螺旋体和弓形虫造成的中枢神经系统感染常引起惊厥。

　　(5)低血镁不常见

　　但当血清镁<1.4mEq/L时能引起惊厥。低血镁常与低血钙有关，低血钙婴儿用足量钙剂治疗后惊厥仍持续存在时，应考虑低血镁。

　　(6)低血钙

　　定义为血清钙水平<7.5mg/dl(<1.87mmol/L)常伴血清磷>3mg/dl(>0.95mmol/L)，和低血糖一样，可以无症状，低血钙常和早产及难产有关。

　　(7)高钠血症或低钠血症可引起惊厥，口服和静脉输注氯化钠负荷过量可造成高钠血症，过多的经口或静脉输注水分，或粪便或尿液中失钠后可引起低钠血症。

　　(8)先天性代谢性疾病，如氨基酸或有机酸尿症可出现新生儿惊厥，维生素B6缺乏或维生素B6依赖是引起惊厥的罕见病因，但易于治疗。

　　(9)围生期并发症，新生儿缺氧缺血脑病(HIE)、颅内出血、脑损伤等疾病的并发症;

　　(10)先天性酶缺陷

　　枫糖尿病、尿素循环障碍、高甘氨酸血症、丙酸血症、甲基丙二酸血症、异戊酸血症、半乳糖血症。

　　(11)家族遗传

　　家族性良性家族性癫痫、肾上腺白质萎缩、神经皮肤综合征、Zellwegen综合征、Smith-Lemli-Opitz综合征。

　　(12)药物影响

　　兴奋剂、异烟肼、氨茶碱、局麻药、有机磷、撤药综合征。母亲滥用药物(如可卡因，海洛因和地西泮)也可能诱发该病，婴儿生后因发生急性撤药综合征而惊厥。

　　二、发病机制

　　新生儿惊厥表现形式和脑电图方面也与成人和儿童有很大不同，与新生儿中枢神经系统发育尚不成熟，易受各种病理因素的刺激有关。所以会产生异常放电。 同时，新生儿大脑皮质的分层及神经元的胞膜、胞浆分化不全，树突、突触、髓鞘的形成亦不完善，神经元与神经胶质之间的正常联系尚未建立，当皮质局部出现异 常放电时，不易向邻近部位传导和扩散，更不易扩散至对侧半球引起同步放电，故新生儿惊厥时全身强直性的抽搐很少见。

皮质下惊厥的发作机制，可能源于皮质下灰质的异常放电，这种深部的异常放电，脑电图的头皮电极不能发现;或源于大脑受损处于高度抑制状态时的脑干释放现象。临床上60%～90%的惊厥患儿无皮质的异常放电，故脑电图的阳性发现有助确诊，未见异常放电不能否定惊厥。

For neonatal convulsions of this disease, we must not ignore, because if you can't cure the disease, can cause certain nutrition for your baby's future, so what is neonatal convulsion? What is the etiology and pathogenesis of neonatal convulsion? We first and see it!
First, causes
(1) the convulsions may be caused by abnormal discharge of the central nervous system only, but the abnormal discharge can be made of many primary intracranial lesions (meningitis, cerebrovascular accident, encephalitis, intracranial hemorrhage, tumor), or secondary to systemic or metabolic (such as ischemia hypoxia, hypoglycemia, low blood calcium, low serum sodium) disease.
(2) of ischemia hypoxia caused by seizures often occur before birth, birth and after birth, and often occur in the for premature infants with respiratory distress syndrome.
(3) low blood sugar in diabetic mothers of newborns, less than the gestational age and ischemia newborns hypoxia and other stress in common. Full term blood sugar < 40 mg/dl (tendency for 2.2 L), low birth weight < 30 mg/dl tendency (1.7 L) for hypoglycemia; Not the blood sugar level of neonatal have symptoms of prolonged or recurrent hypoglycemia may cause permanent damage of central nervous system.
(4) infection can cause seizures
Meningitis often convulsions, sepsis can also occur, but this is generally not has. Gram-negative bacteria often cause neonatal intracranial and systemic infections, cytomegalovirus, herpes simplex virus, rubella virus, treponema pallidum, and central nervous system caused toxoplasma infection often cause convulsions.
(5) low blood magnesium is not common
But when the serum magnesium < 1.4 mEq/L can cause seizures. Low blood magnesium is often associated with low blood calcium, low blood calcium baby after treatment with adequate calcium convulsion continues to exist, should consider to low blood magnesium.
(6) low blood calcium
Defined as serum calcium level of < 7.5 mg/dl (< 1.87 tendency/L) is often associated with serum phosphorus > 3 mg/dl (> 0.95 tendency/L), and low blood sugar, can be asymptomatic, low blood calcium is often related to premature birth and during childbirth.
(7) high natremia or hyponatremia can cause convulsions, oral and intravenous sodium chloride load excessive can cause high blood sodium, too much water, through the mouth or intravenous or feces or urine after the loss of sodium can lead to hyponatremia.
(8) congenital metabolic diseases, such as amino acid or organic acid urine disease can appear neonatal convulsion, and a lack of vitamin B6 or vitamin B6 relies on is a rare cause of eclampsia etiology, but easy to treat.
(9) complications in the perinatal period and neonatal hypoxic ischemic encephalopathy (HIE), intracranial hemorrhage, the complications of the disease such as brain damage;
Congenital enzyme (10)
Maple diabetes, urea cycle disorder, high glycine blood disease, propionic acid, methyl malonic acid hematic disease, isovaleric acidemia, galactosemia.
(11) family
Familial benign familial epilepsy, adrenal gland atrophy, neurocutaneous syndrome, white matter Zellwegen syndrome, Smith Lemli Opitz syndrome.
(12) drugs affect
Doping, isoniazid, aminophylline, local anesthetics, organophosphorus, withdrawal syndrome. Mother abused drugs like cocaine, heroin and diazepam) may also induce the disease, due to acute withdrawal syndrome after baby born convulsions.
Second, the pathogenesis
Neonatal seizures manifestation and eeg also is different with adults and children with the newborn central nervous system development is not yet mature, vulnerable to a variety of pathological factors related to the stimulus. So can produce abnormal discharge. Layered and at the same time, the neonatal brain cortex neuron's cell membrane, cytoplasm differentiation is not complete, dendrites and synapses, the formation of the myelin sheath is not perfect, the normal relationship between neurons and glia have not been established, when there is discharge cortex local, not easy to adjacent parts transmission and diffusion, are less likely to spread to the contralateral hemisphere cause synchronous discharge, so the neonatal convulsions with whole body tonic seizure are rare.
Subcortical eclampsia attack mechanism, probably comes from the abnormal discharge of subcortical gray matter, the deep abnormal discharge, electroencephalogram (eeg) of scalp electrodes cannot be found; Or is the result of brain damage in high inhibition in the brain stem release phenomenon. 60% ~ 90% of clinical seizures in children with abnormal discharge without cortex, so the electroencephalogram (eeg) positive findings help to confirmed, no abnormal discharge cannot deny convulsions.

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