Pediatric Neurology, Part III


Book Description

The child is neither an adult miniature nor an immature human being: at each age, it expresses specific abilities that optimize adaptation to its environment and development of new acquisitions. Diseases in children cover all specialties encountered in adulthood, and neurology involves a particularly large area, ranging from the brain to the striated muscle, the generation and functioning of which require half the genes of the whole genome and a majority of mitochondrial ones. Human being nervous system is sensitive to prenatal aggression, is particularly immature at birth and development may be affected by a whole range of age-dependent disorders distinct from those that occur in adults. Even diseases more often encountered in adulthood than childhood may have specific expression in the developing nervous system. The course of chronic neurological diseases beginning before adolescence remains distinct from that of adult pathology – not only from the cognitive but also motor perspective, right into adulthood, and a whole area is developing for adult neurologists to care for these children with persisting neurological diseases when they become adults. Just as pediatric neurology evolved as an identified specialty as the volume and complexity of data became too much for the general pediatician or the adult neurologist to master, the discipline has now continued to evolve into so many subspecialties, such as epilepsy, neuromuscular disease, stroke, malformations, neonatal neurology, metabolic diseases, etc., that the general pediatric neurologist no longer can reasonably possess in-depth expertise in all areas, particularly in dealing with complex cases. Subspecialty expertise thus is provided to some trainees through fellowship programmes following a general pediatric neurology residency and many of these fellowships include training in research. Since the infectious context, the genetic background and medical practice vary throughout the world, this diversity needs to be represented in a pediatric neurology textbook. Taken together, and although brain malformations (H. Sarnat & P. Curatolo, 2007) and oncology (W. Grisold & R. Soffietti) are covered in detail in other volumes of the same series and therefore only briefly addressed here, these considerations justify the number of volumes, and the number of authors who contributed from all over the world. Experts in the different subspecialties also contributed to design the general framework and contents of the book. Special emphasis is given to the developmental aspect, and normal development is reminded whenever needed – brain, muscle and the immune system. The course of chronic diseases into adulthood and ethical issues specific to the developing nervous system are also addressed. - A volume in the Handbook of Clinical Neurology series, which has an unparalleled reputation as the world's most comprehensive source of information in neurology - International list of contributors including the leading workers in the field - Describes the advances which have occurred in clinical neurology and the neurosciences, their impact on the understanding of neurological disorders and on patient care




Pediatric Neurology Part III


Book Description

The Neuroaxonal Dystrophies (NADs) are a group of clinically and genetically heterogeneous neurodegenerative conditions. These disorders show the unique pathological feature of neuroaxonal dystrophy (NAD): axonal swelling (spheroids) localized throughout the central nervous and peripheral nervous systems. NADs are also morphologically characterized by iron accumulation in the basal ganglia; and are now included in the group of diseases called neurodegeneration with brain iron accumulation (NBIA). NADs comprise two main diseases: pantothenate-kinase associated neurodegeneration (PKAN) and infantile neuroaxonal dystrophy (INAD). PKAN in caused by mutation in the PANK-2 gene. In classic PKAN onset of disease is in the first decade and patients show dystonia, rigidity and dysarthria; course is progressive leading to loss of autonomous gait within 15 years. In atypical PKAN age at onset is later and progression slower. Psychiatric symptoms, obsessive-compulsive disorder, and tourettism may be prominent. In classic INAD patients present with psychomotor regression between 6 months-3 years, followed by neurological deterioration leading to tetraparesis, optic atrophy, and dementia. Atypical NAD refers to all patients who differ from the classical phenotype in term of age at onset and disease progression. Mutations in PLA2G6 gene are found both in classic and atypical INAD patients.




Pediatric Neurology Part III


Book Description

The lack of creatine in the central nervous system causes a severe but treatable neurological disease. Three inherited defects, AGAT, GAMT, and CrT deficiency, compromising synthesis and transport of creatine have been discovered recently. Together these so-called creatine deficiency syndromes (CDS) might represent the most frequent metabolic disorders with a primarily neurological phenotype. Patients with CDS present with global developmental delays, mental retardation, speech impairment especially affecting active language, seizures, extrapyramidal movement disorder, and autism spectrum disorder. The two defects in the creatine synthesis, AGAT and GAMT, are autosomal recessive disorders. They can be diagnosed by analysis of the creatine, guanidinoacetate, and creatinine in body fluids. Treatment is available and, especially when introduced in infancy, has a good outcome. The defect of creatine transport, CrT, is an X-linked condition and perhaps the most frequent reasons for X-linked mental retardation. Diagnosis is made by an increased ratio of creatine to creatinine in urine, but successful treatment still needs to be explored. CDS are under-diagnosed because easy to miss in standard diagnostic workup. Because CDS represent a frequent cause of cognitive and neurological impairment that is treatable they warrant consideration in the workup for genetic mental retardation syndromes, for intractable seizure disorders, and for neurological diseases with a predominant lack of active speech.




Pediatric Neurology Part III


Book Description

The catalytic properties of many enzymes depend on the participation of vitamins as obligatory cofactors. Vitamin B12 (cobalamin) and folic acid (folate) deficiencies in infants and children classically present with megaloblastic anemia and are often accompanied by neurological signs. A number of rare inborn errors of cobalamin and folate absorption, transport, cellular uptake, and intracellular metabolism have been delineated and identification of disease-causing mutations has improved our ability to diagnose and treat many of these conditions. Two inherited defects in biotin metabolism are known, holocarboxylase synthetase and biotinidase deficiency. Both lead to multiple carboxylase deficiency manifesting with metabolic acidosis, neurological abnormalities, and skin rash. Thiamine-responsive megaloblastic anemia is characterized by megaloblastic anemia, non-type I diabetes, and sensorineural deafness that responds to pharmacological doses of thiamine (vitamin B1). Individuals affected with inherited vitamin E deficiencies including ataxia with isolated vitamin E deficiency and abetalipoproteinemia present with a spinocerebellar syndrome similar to patients with Friedreich's ataxia. If started early, treatment of these defects by oral or parenteral administration of the relevant vitamin often results in correction of the metabolic defect and reversal of the signs of disease, stressing the importance of early and correct diagnosis in these treatable conditions.




Pediatric Neurology Part III


Book Description

We review the supranuclear control centers and pathways leading to individual cranial nerve nuclei in the brainstem. We discuss horizontal and vertical gaze and their abnormalities, and review the cranial nerves which subserve eye movements, III, IV, VI, including their clinical testing. We highlight the sites at which these nerves are clinically affected, which often result in characteristic associated features with neurological localizing value. Differential diagnoses of cranial nerve palsies including Duane and Möbius syndromes are also described. Lastly, we discuss the nature of childhood neuromuscular junction disorders such as myasthenia gravis, as well as disorders of the muscle itself (chronic progressive external ophthalmoplegia (CPEO), thyroid orbitopathy).




Pediatric Neurology Part III


Book Description

Symptoms in patients with defects in amino acid catabolism and the urea cycle usually develop because of intoxication of accumulating metabolites. The cumulative prevalence of these disorders is considerable (at least>1:2000 newborns). Timely and correct intervention during the initial presentation and during later episodes is most important. Evaluation of metabolic parameters should be performed on an emergency basis in every patient with symptoms of unexplained metabolic crisis, intoxication, and/or unexplained encephalopathy. A substantial number of patients develop acute encephalopathy or chronic and fluctuating progressive neurological disease. The so-called cerebral organic acid disorders present with (progressive) neurological symptoms: ataxia, myoclonus, extrapyramidal symptoms, and “metabolic stroke.” Important diagnostic clues, such as white matter abnormalities, cortical or cerebellar atrophy, and injury of the basal ganglia can be derived from cranial magnetic resonance imaging (MRI). Long-term neurological disease is common, particularly in untreated patients, and the manifestations are varied, the most frequent being (1) mental defect, (2) epilepsy, and (3) movement disorders. Successful treatment strategies are becoming increasingly available. They mostly require an experienced interdisciplinary team including a neuropediatrician and/or later on a neurologist.




Pediatric Neurology Part III


Book Description

Deficient repair of ubiquitous errors in the genome risks faulty transcription or replication. Its direct and indirect phenotypic consequences are rare, complex, dementing, lethal disorders of children with inadequately understood overlapping genotypes and variable severity. Mutations of CSA or CSB responsible for impaired transcription-coupled repair cause Cockayne syndrome (CS). Its characteristics are (1) profound growth deficiency affecting all tissues, including the brain, (2) premature aging marked by cachexia, vascular disease, exocrine deficiency, and osteopenia, but not cancer, and (3) a selective degenerative disorder of central and peripheral myelin and by neuronal loss in the retina and inner ear, and in the cerebellum and basal ganglia where it is associated with calcification. Xeroderma pigmentosum (XP) can arise from mutations of at least eight genes involved in global genomic repair. Severe XPA and XPC cause innumerable carcinomas and melanomas in light-exposed eyes and skin, and enhanced risk of visceral cancers. XPA and XPD and others can cause childhood XP neurological disease with widespread neuronal loss, axonal sensorimotor neuropathy, and dwarfing. Four genes, including XPD, can cause trichothiodystrophy (TTD) with sulfur-deficient, brittle, tiger-tail hair, and growth and developmental inadequacy. CSB or XPD can cause the severe congenital cerebro-oculofacioskeletal (COFS) CS-like syndrome with joint contractures, cataracts, and early death. Three XP genes can also cause XP/CS complex. Much more needs to be learned about these and other disorders of DNA repair to enable prevention and treatment.




Pediatric Neurology Part III


Book Description

Although poorly recognized and studied, congenital sucking, swallowing, and/or feeding disorders are common. They can be the symptoms that reveal a neuromuscular disease, or that complicate a neuromuscular disease. It is essential to know feeding physiology during fetal and infant development in order to understand the variety of its disorders and to direct correctly diagnostic and therapeutic processes. A good semiological analysis will identify the symptoms. Several investigations help to determine the mechanism of the trouble (fiber endoscopy, videofluoroscopy, facial and swallowing electromyography, esophageal manometry, etc.). Other investigations, in addition to clinical assessments, help to identify the cause of the whole picture (peripheral electromyography, brain MRI, genetic or metabolic investigations, etc.). The main causes of sucking, swallowing, and feeding disorders are lesions of the brainstem (malformations of the posterior fossa, neonatal brainstem tumors, agenesis of cranial nerves, clastic lesion of the posterior brain, craniovertebral anomalies, syndromes that involve the rhombencephalic development such as Pierre Robin sequence, CHARGE syndrome, etc.). Suprabulbar lesions, neuromuscular disorders, peripheral esophageal, digestive, and laryngeal anomalies and dysfunctions can also be involved. The main principles of the management of congenital sucking, swallowing, and feeding disorders are the following: cure the cause if possible, facilitate the sucking reflex, preventing deleterious consequences of aspiration, preventing malnutrition, and preventing posttraumatic anorexia. Advice can be given to caregivers and physiotherapists who take charge of these children.




Pediatric Neurology Part III


Book Description

Cerebrovascular accidents were until recently responsible for much mortality and morbidity in children with sickle cell disease; the likelihood of a child with HbSS having a stroke was 11% before age 20 years, with a peak incidence of ischemic stroke between 2 and 5 years of age, and of hemorrhagic strokes between 20 and 29 years of age. Vessels occlusion is likely initiated by intimal proliferation and amplified by inflammation, excessive adhesion of cells to activated endothelium, hypercoagulable state, and vascular tone dysregulation. Silent infarcts may occur and are associated with decreased cognitive functions. Transcranial Doppler ultrasonography (TCD) was more recently demonstrated able to achieve early detection of the children at high risk for clinical strokes. A randomized study demonstrated that a first stroke may be prevented by monthly transfusion in children with abnormal TCD, leading to a recommendation for annual TCD screening of children aged between 2 and 16 years and monthly transfusion for those with abnormal results. In children who have had a first stroke, the risk of recurrence is more than 50% and is greatly reduced by chronic transfusion, although not completely abolished. Hematopoietic stem cell transplant is indicated in children with cerebral vasculopathy who have an HLA-identical sibling.




Pediatric Neurology Part III


Book Description

Two copper-transporting ATPases are essential for mammalian copper homeostasis: ATP7A, which mediates copper uptake in the gastrointestinal tract and copper delivery to the brain, and ATP7B, which mediates copper excretion by the liver into bile. Mutations in ATP7A may cause three distinct X-linked conditions in infants, children, or adolescents: Menkes disease, occipital horn syndrome (OHS), and a newly identified allelic variant restricted to motor neurons called X-linked distal hereditary motor neuropathy. These three disorders show variable neurological findings and ages of onset. Menkes disease presents in the first several months of life with failure to thrive, developmental delay, and seizures. OHS features more subtle developmental delays, dysautonomia, and connective tissue abnormalities beginning in early childhood. ATP7A-related distal motor neuropathy presents even later, often not until adolescence or early adulthood, and involves a neurological phenotype that resembles Charcot–Marie–Tooth disease, type 2. These disorders may be treatable through copper replacement or ATP7A gene therapy. In contrast, mutations in ATP7B cause a single known phenotype, Wilson disease, an autosomal recessive trait that results from copper overload rather than deficiency. Dysarthria, dystonia, tremor, gait abnormalities, and psychiatric problems may be presenting symptoms, at ages from 10 to 40 years. Excellent treatment options exist for Wilson disease, based on copper chelation. In the past 2 years (2012–2013), three new autosomal recessive copper metabolism conditions have been recognized: 1) Huppke–Brendel syndrome caused by mutations in an acetyl CoA transporter needed for acetylation of one or more copper proteins, 2) CCS deficiency caused by mutations in the copper chaperone to SODI, and 3) MEDNIK syndrome, which revealed that mutations in the σ1A subunit of adaptor protein complex 1 (AP-1) have detrimental effects on trafficking of ATP7A and ATP7B.