Can clinical signs identify newborns with neuromuscular disorders?

OBJECTIVE: To evaluate retrospectively the prevalence of neuromuscular disorders in 83 newborns referred to a tertiary care center because of hypotonia and weakness and/or contractures, with a possible diagnosis of neuromuscular disorder. We also aimed to establish whether clinical signs could help to identify infants with neuromuscular disorders. STUDY DESIGN: Sixty-six of the 83 infants who fulfilled the inclusion criteria (79.5%) had an identifiable disorder, which was a neuromuscular disorder in 39 (46.9%). RESULTS: Absent or extremely reduced antigravity movements were mainly found in infants with neuromuscular disorders (sensitivity and specificity 97.4% and 75%), whereas partial range antigravity movements were more frequent in infants with other diagnosis. Contractures were mainly found in infants with peripheral nerve or muscle involvement but also were relatively frequent in infants with genetic or metabolic syndromes (sensitivity 69.2%, specificity 61.3%). Reduced fetal movements and abnormal liquor were frequent but not present consistently in infants with neuromuscular disorders (sensitivity 46.1% and 38.4%) and were found rarely in infants with other disorders (specificity 88.6% and 75.0%). CONCLUSIONS: Severe muscle weakness and contractures are the most reliable indicators of a neuromuscular disorder and should be carefully assessed in an infant with neonatal hypotonia.     

Survey of severe respiratory syncytial virus infection in Kyoto Prefecture from 2003 to 2007

Background: Respiratory syncytial virus (RSV) infection in infants can develop into a severe condition. Methods: A survey of patients with severe RSV infection in hospitals in Kyoto Prefecture was performed from 2003 to 2007. Patients requiring intubation and those with cardiopulmonary arrest on arrival (CPAOA) were considered to have severe RSV infection. Results: Twenty‐five patients with severe infection were identified and detailed data were available for 21 patients, of whom 18 required intubation and three had CPAOA. The male/female ratio was 12/9 and age ranged from 8 days to 19 years (average, 5.2 months; median: 2 months). At admission white blood cell count, lactate dehydrogenase (P < 0.05), and blood glucose (P < 0.01) were higher and Na was lower (P < 0.01) in the 18 patients with severe infection (excluding the CPAOA cases) compared to 18 sex‐ and age‐matched patients with mild RSV infection. The incidence of bacterial infection was also higher in severe cases (P < 0.05). The outcome was death in four patients (19.0%, including two sudden deaths), aftereffects in two (9.5%), hospital discharge with improvement in 14 (66.7%), and an unclear outcome in one patient. Excluding the two sudden death cases, 14 of 19 patients (73.7%) were extubated within 2 weeks. The period of intubation was longer in older patients (P < 0.05). Conclusion: Because severe RSV infection led to sudden death in two cases, detection of RSV is important at admission for an infant with CPAOA. Fourteen patients (66.7%), however, had good outcomes and most patients were extubated within 2 weeks.     

Inherited neuromuscular disorders: pathway to diagnosis

Muscle weakness in childhood can be caused by a lesion at any point extending from the motor cortex, brainstem and spinal cord to the anterior horn cell, peripheral nerve, neuromuscular junction and muscle. A comprehensive history and physical examination is essential to aid classification of the neuromuscular disorder and direct gene testing. The more common disorders such as spinal muscular atrophy, Duchenne muscular dystrophy, myotonic dystrophy and facioscapulohumeral dystrophy may be diagnosed on direct gene testing based on the history and clinical examination. The congenital myopathies are classified based on structural abnormalities on muscle biopsy, while protein abnormalities on immunohistochemistry and immunoblotting aid classification of the muscular dystrophies. In this review, we provide an approach to diagnosis of a child with weakness, with a focus on the inherited neuromuscular disorders, and the features on history, examination and investigation that help to distinguish between them.     

Neonatal long QT syndrome and sudden cardiac death

Neonatal sudden cardiac death most often results from cardiac electrical diseases, cardiomyopathies, or sudden infant death syndrome. In infants without a known premortem diagnosis or abnormalities identified at autopsy, sudden infant death syndrome accounts for the vast majority of sudden deaths. Potential cardiac causes of some sudden infant death syndrome cases may include malignant brady- or tachyarrhythmias and congenital long QT syndrome. The possible mechanisms include abnormal brain stem respiratory control of arousal, dysautonomia and malignant cardiac bradyarrhythmias or tachyarrhythmias. Screening for neonatal sudden cardiac death may not be feasible, but hopefully through careful review of history, physical examination, and family health history, and judicious diagnostic testing, can the risk of cardiac sudden death be reduced. Further comprehension of the genetic basis of inherited arrhythmia disorders may help elucidate the mechanisms of arrhythmogenesis and etiologies of sudden infant death. Prevention and treatment of these disorders may also be improved through more detailed understanding of the molecular basis of cardiac electrical pathophysiology.     

The sudden infant death syndrome gene: does it exist?

BACKGROUND: Sudden infant death syndrome (SIDS) is in a difficult position between the legal and medical systems. In the United Kingdom, prosecutors have for years applied the simple rule that 1 unexpected death in a family is a tragedy, 2 are suspicious, and 3 are murder. However, it seems that the pendulum has now swung to the opposite extreme; mutations or polymorphisms with unclear biological significance are accepted in court as possible causes of death. This development makes research on genetic predisposing factors for SIDS increasingly important, from the standpoint of the legal protection of infants. The genetic component of sudden infant death can be divided into 2 categories, ie (1) mutations that give rise to genetic disorders that constitute the cause of death by themselves and (2) polymorphisms that might predispose infants to death in critical situations. Distinguishing between these 2 categories is essential, and cases in which a mutation causing a lethal genetic disorder is identified should be diagnosed not as SIDS but as explained death. GENETIC ALTERATIONS THAT MAY CAUSE SUDDEN INFANT DEATH: Deficiencies in fatty acid metabolism have been extensively studied in cases of SIDS, and by far the most well-investigated mutation is the A985G mutation in the medium-chain acyl-CoA dehydrogenase (MCAD) gene, which is the most prevalent mutation causing MCAD deficiency. However, <1% of sudden infant death cases investigated have this mutation, and findings of biochemical profiles seen in specific fatty acid oxidation disorders in a number of such cases emphasize the importance of investigating fatty acid oxidation disorders other than MCAD deficiency. Severe acute hypoglycemia may cause sudden death among infants, but only rare novel polymorphisms have been found when key proteins involved in the regulation of blood glucose levels are investigated in cases of SIDS. The long QT syndrome (LQTS) is another inherited condition proposed as the cause of death in some cases of sudden infant death. The LQTS is caused by mutations in genes encoding cardiac ion channels, and mutations in the genes KVLQT1 and SCNA5 have been identified in cases initially diagnosed as SIDS, in addition to several polymorphisms in these 2 genes and in the HERG gene. In addition, genetic risk factors for thrombosis were investigated in a small number of SIDS cases; the study concluded that venous thrombosis is not a major cause of sudden infant death. GENE POLYMORPHISMS THAT MAY PREDISPOSE INFANTS TO SUDDEN INFANT DEATH UNDER CERTAIN CIRCUMSTANCES: Many SIDS victims have an activated immune system, which may indicate that they are vulnerable to simple infections. One reason for such vulnerability may be partial deletions of the complement component 4 gene. In cases of SIDS, an association between slight infections before death and partial deletions of the complement component 4 gene has been identified, which may indicate that this combination represents increased risk of sudden infant death. There have been a few studies investigating HLA-DR genotypes and SIDS, but no association has been demonstrated. The most common polymorphisms in the interleukin-10 (IL-10) gene promoter have been investigated in SIDS cases, and the ATA/ATA genotype has been reported to be associated with both SIDS and infectious death. The findings may indicate that, in a given situation, an infant with an unfavorable IL-10 genotype may exhibit aberrant IL-10 production, and they confirm the assumption that genes involved in the immune system are of importance with respect to sudden unexpected infant death. Another gene that has been investigated is the serotonin transporter gene, and an association between the long alleles of this gene and SIDS has been demonstrated. Serotonin influences a broad range of physiologic systems, as well as the interactions between the immune and nervous systems, and findings of decreased serotonergic binding in parts of the brainstem, together with the findings in the serotonin transporter gene, may indicate that serotonin plays a regulatory role in SIDS. It has also been speculated that inadequate thermal regulation is involved in SIDS, but investigations of genes encoding heat-shock proteins and genes encoding proteins involved in lipolysis from brown adipose tissue have not found evidence of linkages between common polymorphisms in these genes and SIDS. A number of human diseases are attributable to mutations in mitochondrial DNA (mtDNA), and there are several reasons to think that mtDNA mutations also are involved in SIDS. Both a higher substitution frequency and a different substitution pattern in the HVR-I region of mtDNA have been reported in SIDS cases, compared with control cases. A number of coding region mtDNA mutations have also been reported, but many are found only in 1 or a few SIDS cases, and, to date, no predominant mtDNA mutation has been found to be associated with SIDS. CONCLUSIONS: All mutations giving rise to metabolic disorders known to be associated with life-threatening events are possible candidates for genes involved in cases of sudden infant death, either as a cause of death or as a predisposing factor. It is necessary to distinguish between lethal mutations leading to diseases such as MCAD and LQTS, and polymorphisms (for instance, in the IL-10 gene and mtDNA) that are normal gene variants but might be suboptimal in critical situations and thus predispose infants to sudden infant death. It is unlikely that one mutation or polymorphism is the predisposing factor in all SIDS cases. However, it is likely that there are "SIDS genes" operating as a polygenic inheritance predisposing infants to sudden infant death, in combination with environmental risk factors. For genetically predisposed infants, a combination of, for instance, a slight infection, a prone sleeping position, and a warm environment may trigger a vicious circle with a death mechanism, including hyperthermia, irregular breathing, hypoxemia, and defective autoresuscitation, eventually leading to severe hypoxia, coma, and death.     

Diaphragmatic paralysis due to spinal muscular atrophy. An unrecognised cause of respiratory failure in infancy?

An unusual form of spinal muscular atrophy presenting with respiratory failure was observed in four infants from two families. In one, whose death was attributed to pneumonia, the diagnosis was inferred retrospectively after two siblings died from an identical illness and were shown to have diaphragmatic paralysis and the typical electrophysiological and histological features of spinal muscular atrophy. Other signs of skeletal muscular weakness were absent or inconspicuous. The fourth, unrelated infant presented in an identical way but has survived for over a year on a ventilator. Two months after the onset of respiratory paralysis, more extensive skeletal muscular weakness was seen. Other infants, dying of unexplained respiratory illness, may have this disorder and some may be included in the miscellany of disorders that constitute the sudden infant death syndrome.     

Infant botulism and sudden infant death syndrome

Infant botulism represents a distinct entity of botulism. Ingestion of the ubiquitously present spores of Clostridium botulinum leads to germination of the organism and neurotoxin production in the infant intestine. Symptoms typically develop gradually in contrast to classical food botulism in which an acute onset of symptoms shortly after the ingestion of preformed toxin in a food is characteristic. Microbiologically, the diagnosis is established by identification of Clostridium botulinum organism and toxin in stool specimen. However, positive results in these tests provide only indirect evidence for the clinical relevance of the neurotoxin since asymptomatic carriers have been found. The toxin irreversibly blocks the release of acetylcholin from the motoric end plate which results in muscle weakness and paralysis. Depending on the amount of toxin produced, infant botulism exhibits a broad clinical spectrum ranging from oligosymptomatic forms to a fulminant course with acute respiratory failure within hours leading to sudden death. Unrecognized mild forms or beginning muscle weakness can be a co-factor for other risk factors of sudden infant death (SIDS). In studies analyzing infants who died from SIDS, botulism bacteria or toxin were found in up to 20 % of cases. Infant botulism therefore represents an important differential diagnosis of unexplained and inconclusive muscular hypotonia in the first year of life.     

Needle muscle biopsy in infants and children

Percutaneous muscle biopsies were performed in 77 infants and children using the Bergstrom muscle biopsy needle and local anesthesia. Satisfactory specimens for histochemistry and electron microscopy were obtained in all but one case, and the procedure was well tolerated by all patients. No complications were observed. The percutaneous biopsy is a useful technique for the diagnosis of neuromuscular disorders in children.     

Congenital muscular dystrophy with laminin-a2 deficiency in early infancy: diagnosis and long-term follow-up

Congenital muscular dystrophy (CMD) is a heterogeneous group of neuromuscular disorders characterized by muscle weakness and hypotonia at birth or within the first few months of life. It is inherited in an autosomal recessive pattern. About half of the patients have a deficiency of the alpha-2-chain of laminin (merosin). We describe a case of congenital muscular dystrophy in an infant with laminin-a2-chain deficiency, which appeared hypotonia in early infancy. Diagnosis was made by clinical features and the histological and immunohistochemical studies on muscle biopsy.     

Merosin-deficient congenital muscular dystrophy and cortical dysplasia.

Congenital muscular dystrophy (CMD) encompasses a heterogenous group of muscle disorders with autosomal recessive inheritance, characterized by muscular weakness and hypotonia at birth or within the first few months of life and developmental delay. Merosin-deficient CMD is a clinically distinct form which may be associated with significant abnormalities of the brain detectable by neuroimaging. We report two siblings of consanguineous parents with merosin-deficient CMD in an Irish family who in addition to the characteristic white matter abnormalities on neuroimaging, had occipital dysplasia. Clinical, electrophysiological muscle biopsy findings and neuroimaging were very similar in both cases. Although merosin-deficient CMD with white matter abnormalities on neuroimaging is well documented in the literature, the association with occipital dysplasia has only rarely been reported. The appearance of an identical cortical defect in these siblings suggests an underlying genetic mechanism.     

重视导致危重症及猝死的潜在遗传代谢病及内分泌疾病

不明原因猝死综合征是高收入国家儿童死亡的主要原因。猝死可发生在新生儿期至成人,貌似健康的人在日常活动、睡眠或运动中意外死亡,潜在的遗传病是导致心脏性猝死和脑死亡的病因。1977年美国首先关注到不明原因猝死综合征,美国、英国、泰国、日本等国家通过对猝死者的病因研究,证实多种遗传病导致的心脏病、脑病是猝死的两组主要疾病。其中心脏性猝死占一半以上,猝死或猝死样发作也常常是潜在遗传病的首发表现。已知多种遗传代谢病及内分泌疾病可导致猝死,如：原发性肉碱缺乏症、长QT综合征、心律失常、低镁血症、低钾血症、高钾血症、低钙血症、低血糖、线粒体病等。遗传代谢病及内分泌疾病包括氨基酸、有机酸、糖、脂肪等近千种先天性代谢缺陷,其中许多疾患可导致急性危重症甚至猝死。运用生化、电生理、影像、病理和基因诊断等技术,一些疾病可通过新生儿筛查及高危筛查获得早期诊断,通过饮食及药物干预,有望减少意外死亡,降低残障的发生。     

What's new in neuromuscular disorders? The congenital myopathies.

The congenital myopathies are a heterogeneous group of early-onset neuromuscular conditions with characteristic findings on muscle biopsy, comprising central core disease, minicore myopathy (multi-minicore disease), nemaline myopathy and myotubular myopathy. Recent years have seen genetic resolution of a proportion of these conditions. The following review summarizes recent genetic findings in the congenital myopathies and outlines implications for our understanding of their pathophysiological basis and their relation to other neuromuscular disorders.     

先天性肌营养不良的诊断及层黏连蛋白表达的意义

目的 探讨先天性肌营养不良（CMD）的临床诊断、肌肉免疫组织化学特点及随访情况。方法 对8例CMD患儿的病例资料进行综合分析,并进行肌肉活检,利用抗层黏连蛋白以（laminin α2,又称merosin）、α抗肌萎缩相关糖蛋白（α-dystroglycan,α-DG）和β抗肌萎缩相关糖蛋白（β-dystroglycan,β-DG）抗体行肌肉活检组织免疫组织化学染色。结果 8例均于出生时或生后半年之内出现肌无力、肌张力低下,有的合并关节挛缩、喂养困难或呼吸功能不全。肌肉病理检查均发现肌营养不良改变特点。其中merosin染色阴性者4例,头颅MRI示脑白质髓鞘化不良;4例为merosin染色阳性,呈散发或常染色体隐性遗传,2例合并有智力低下,抗α-DG（1IH6）抗体染色显示α-DG糖基化低下,其中1例伴视神经萎缩,头颅MRI提示脑结构异常。结论 本组CMD中merosin染色既有阴性,也有阳性,merosin缺乏症（先天性肌营养不良1A型）更为常见,伴随脑白质病变。merosin染色阳性者中存在抗肌萎缩相关糖蛋白糖基化低下病例。     

Severe neonatal centronuclear (myotubular) myopathy: an X-linked recessive disorder

Prenatal onset and rapidly fatal course of centronuclear myopathy are described in four male newborns including two brothers. Diagnosis was established by muscle biopsy within the first week of life in two and at autopsy in the two other patients: Central nuclei, central aggregation of oxydative enzyme activity in the majority of muscle fibers and type 1 fibre hypotrophy were demonstrated. Prenatal manifestation included polyhydramnios, reduced fetal movements and breech presentation. All four newborns developed respiratory insufficiency requiring artificial ventilation immediately after birth. Severe muscular weakness and hypotonia as well as hardly elicitable grasping, deep tendon reflexes and Moro response were noticed. Additional findings included high arched palate, joint contractures, thin ribs, lung hypoplasia, abundant skin and cryptorchidism. In two families, the pedigree contains other affected males, suggesting X-linked inheritance. Seven female carriers were clinically healthy and one of them showed normal muscle histology. Fourteen previously published neonatal cases of centronuclear myopathy are reviewed and compared with our findings. This severe perinatal form of centronuclear myopathy has to be considered in male fetuses and newborns with polyhydramnios and respiratory failure due to muscular weakness or in infants who died of unexplained postnatal asphyxia. Diagnosis should be established by muscle biopsy.     

Routine microbiological testing in sudden and unexpected infant death

Objective : To evaluate the significance of microbiological test results in a series of infants who had died suddenly and unexpectedly.
Methodology : Following a review of all cases of sudden natural death in infants presenting to the Adelaide Children's Hospital (ACH) division of the Women's and Children's Hospital (WCH) over the 10 year period between 1983 and 1992, specific evaluation of microbiological test results was undertaken.
Results : There were 329 cases of sudden infant death syndrome (SIDS) and 23 cases in which sudden infant death was either attributed to other conditions or was unclassifiable. Positive microbiological results were recorded in the majority of cases, most being considered to be due to postmortem overgrowth or to contamination at autopsy. Of the remaining cases, microbiological results were essential to the establishment of the diagnosis in three cases, and were a useful adjunct to the diagnosis in a further six cases.
Conclusions : Routine microbiological testing in cases presenting as SIDS did not reveal occult sepsis in most instances. Such testing did, however, add support to the diagnosis of SIDS where no pathogens were isolated and, if not undertaken, would have resulted in a small percentage of cases of sudden infant death due to infections remaining undiagnosed.     

V-shaped pillows and unsafe infant sleeping

To investigate the possibility that adult size V-shaped pillows may be associated with accidental asphyxial deaths in infants.

Methodology:

Review was undertaken of all cases of sudden infant death presenting to the Women's and Children's Hospital in Adelaide involving infants who had been found on adult size V-shaped pillows.

Results:

Four cases of sudden infant death were found in which infants were found sleeping on V-shaped pillows. All of the deaths had occurred in 1995. In two of the cases the pillows were considered to be implicated in the cause of death as the potential for obstruction of the infants' airways could be demonstrated on death scene reconstruction.

Conclusion:

Adult size V-shaped pillows may be unsafe for use in small infants who may accidentally suffocate if trapped between the two arms, or under, the pillow. The use of such pillows to maintain the body position of sleeping infants should be discouraged.     

Diagnose und Therapie der Muskeldystrophie Duchenne

Duchenne muscular dystrophy (DMD) is not only the most frequent but also one of the most severe neuromuscular disorders in childhood. The natural course of the disease is characterized by progressive muscle weakness with loss of ambulation around the age of 10 years. In the second decade life-shortening respiratory insufficiency and cardiomyopathy emerge, leading to an early death in the second decade if untreated. Even if DMD can still not be cured, with a proactive, multidisciplinary, symptomatic treatment, the quality of life can be improved and life expectancy into the fourth decade is possible. The main therapeutic elements comprise physiotherapy, orthopedic and rehabilitative interventions as well as a long-term treatment with corticosteroids, non-invasive ventilation in cases of respiratory insufficiency and an early medicinal treatment of heart failure.     

Nemaline myopathy in the neonate: two case reports

Nemaline myopathy, one of the most benign myopathies in older children and adults, may be rarely associated with early death in the neonate. The authors report two cases, describing the ante-and postnatal clinical courses. Family history may help in establishing the diagnosis, but this was not the case in the two infants described. Above all, the diagnosis is based on the results of muscle biopsy.Conclusion Nemaline myopathy may lead to early death in the neonate.     

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??Abstract??Hereditary neuromuscular disease is a group of diseases clinically manifested as motor function disorders and hereditary myopathies??peripheral neuropathies??motor neuropathies as well as neuromuscular junction diseases are mainly included.With the rapid development of genetic testing technology??genes related to hereditary neuromuscular diseases and novel mutations are continued to discover?? providing a reliable basis for genetic diagnosis??genetic counseling and prenatal diagnosis.Taking medical history in detail and doing physical examination completely as well as laboratory examinations??such as serum chemical analysis??muscle imaging studies??neuroelectrophysiology studies and muscle biopsy??provide important clues to detecting the virulence genes.     

Apnoea and seizures.

We report two infants with near miss sudden infant death syndrome events exhibiting seizure disorders after caffeine treatment, suggesting there is an infant subgroup diagnosed as near miss sudden infant death syndrome who have apnoea possibly with seizures whose seizure threshold may be lowered by central nervous system stimulants like caffeine.