الفهرس 
Development of nervous systemOnly 14 pages are availabe for public view
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Abstract
Understanding development of the nervous system is essential for understanding of neonatal neurology. Neural development is one of the earliest to begin and the last to be complete, generating the most complex structure within the embryo. This long time period of development also means insult during pregnancy may have consequences to development of the nervous system. The major developmental events have peak times of occurrence, but the time periods are overlapping with each other.
Primary neurulation refers to formation of the neural tube, exclusive of the most caudal aspects. The time period involved is the third and fourth weeks of gestation while secondary neurulation occur later than those of primary neurulation and result in the development of the remainder of the neural tube. Growth of the cerebral hemispheres is continuous throughout embryonic and fetal development and continues after birth.
Following telencephalic cleavage there are starting of neuronal proliferation, differentiation and migration. Some of the postnatal growth of the brain is due to increase in the size of neural cell bodies and to proliferation of neuronal processes. Most of this growth however, results from the myelination of nerve fibers.
It is very importance to performing a neonatal neurological examination. The combination of clinical and neuroimaging techniques not only improves our understanding of the severity of clinical signs in relation to brain lesions and outcome but can also strengthen the diagnostic value of neuroimaging. This appears to be important in all the disorders in which both central and peripheral nervous systems are involved, such as metabolic disorders or muscle diseases with central nervous system involvement. In these cases, signs of CNS involvement often predominate and neuroimaging often provides evidence of structural brain lesions.
Detailed clinical examination will reveal signs of peripheral involvement and help to select the most appropriate investigations to reach a diagnosis. Several examinations have been used. The patterns of specific aspects of neurological function in normal infants and in those with brain lesions are very important. Conventional neurological examination and general movements in predicting abnormal outcome in both preterm and full-term infants with brain lesions is of value.
Increasing strength and complexity are seen, as gestational age advances, in the moro reflex, palmar and planter grasp, head control in traction, straightening reactions of the lower limbs and trunk, placing reactions of the feet and rooting reactions. There is importance to know when these reflexes disappear and observation of the spontaneous and provoked behaviour of the newborn infant with exploitation of these primitive responses have been described will give much information about the functioning state of his nervous system.
During nervous system development, neonatal malformations can result from ‘an intrinsically abnormal developmental process’ within CNS or extrinsic factors such as teratogens & infections. The etiology of these malformations is unknown in more than 60% of patients, While hereditary factors including autosomal and x-linked conditions account for (7.5%) and chromosomal abnormalities (6%).
Perinatal HIE is an important cause of brain injury in the newborn. And can result in complications including periventricular intraventricular hemorrhage, Periventricular leucomalacia, seizures, mental retardation, and/or cerebral palsy. The best method of treatment of HIE & IVH is prevention.
Patterns of cerebral injury vary according to gestational age at insult and the nature of insult. This will impact on the methods of diagnosis and the likely long term consequences of the lesion: Malformations of the nervous system are unique. No two individual cases are identical, even if both are categorized as the same anatomical malformation
a. Term infants with hypoxic—ischemic injury will suffer more neuronal injury with resulting seizures and combined cognitive and motor deficits.
b. Preterm infants with hypoxic—ischemic and/ or inflammatory insults will suffer more primary cerebral white matter injury with secondary impact on the developing grey matter.
c. Investigation and definition of these cerebral lesions is optimized with magnetic resonance imaging.
The most prominent feature of neurological dysfunction in the neonatal period is seizures. Most neonatal seizures occur over only a few days of conception, and fewer than half of affected infants develop seizures later in life. Such neonatal seizures could be considered acute reactive (acute symptomatic), with variable clinical manifestations. Their presence is often the first sign of neurological dysfunction.
Bacterial meningitis is the most common cause of neonatal infection in newborn & more common in premature than in full term infants and generally has a two fold pattern of illness; early onset disease within the first days of life caused by group B streptococcus, Escherichia coli, and listeria mono cytogenes acquired from an infected birth canal and late onset disease after several days, may be caused by staphylococcus or pseudomonas aeroginosa. Early diagnosis and treatment are critical to prevent morbidity & mortality.
TORCH infections occur in the newborn. The acronym TORCH is used as a reminder of the major nonbacterial neonatal infections: Toxoplasmosis, Others (such as syphilis), Rubella, Cytomegalovirus (CMV), and Herpes simplex. All of TORCH infections occur during pregnancy by transplacental inoculation, except for herpes simplex, which usually is transmitted by passage of the fetus through an infected birth canal.
The most common neurologic degenerative diseases encountered in pediatric neurology, presented in a manner in which we use an anatomopathologic classification. In which progressive neurodegenerative illnesses are organized into five subtypes according to clinical phenomena and pathologic features that are most characteristic for a group of illnesses. In polioencephalopathies, the clinical & pathologic features are Maximum in the cerebral cortex. In leukoencephalopathies, there is a prominent involvement of subcortical & or periventricular white Matter. In corencephalopathies, there is more obvious involvement of subcortical grey matter (basal ganglia, Thalamus & midbrain. In spinocerebellopathies, the clinical & pathologic features are maximum in the cerebellum, spinal Cord & sometimes medulla& pons. In diffuse encephalopathies, clinical and pathologic studies fail to characterize a maximum CNS involvement.
The CMDs are the single most common neuromuscular disorders present at birth. They are group of genetic disorders in which weakness and abnormal muscle histologic features are present at birth. Muscle weakness tends to be more stable overall, depending on the individual disease, but complications of the dystrophy can become more prominent over time. To establish a diagnosis of CMD, a muscle biopsy is required. For a useful clinical approach, CMD can be segregated in subgroups with normal mental development or mental retardation. Magnetic resonance imaging of the brain is indispensable in the clinical approach to CMD, as it may show abnormalities of brain formation and neuronal migration or changes in the white matter, or it may be completely normal.
The most common diagnosis in this group is germ cell tumors (GCT) which constituted 60% of all tumors. The second most common was neuroblastoma (NB) 22%, central nervous system tumors (CNS), retinoblastoma (RB) and immature teratoma. Neuroblastoma is a malignant tumor of primitive neuroblasts that is the most common malignant tumor in neonates
Neurocutaneous syndrome is a term for a group of rare neurological (brain, spine, and peripheral nerve) disorders. These diseases are life-long conditions that can cause tumors to grow inside the brain, spinal cord, organs, skin, and skeletal bones.
There is increase incidence of congenital malformations in infants exposed to some of drugs prenatally like :Antibiotics including (Tetracyclines, chloramphenicol, quinolones, doxycycline, tetracycline and tobramycin), Analgesics including (Aspirin, nonsteroidal anti-inflammatory (ibuprofen, naproxen), Anticonvulsants including (Carbamazepine, phenobarbital, phenytoin, primidone, secobarbital, and valproate), Hypnotics and Tranquillizers including Barbiturates (butobarbital, aminophenazone, hexobarbital, butobarbital, butobarbital & hyoscyamine), Benzodiazepines including (Alprazolam, chlordiazepoxide, clonazepam, diazepam, lorazepam, oxazepam and temazepam), Psychiatric medications including Imipramine, lithium, and nortriptyline.
The neuroactive drugs taken by pregnant women have two principals’ side effects: a teratogenic effects and a postnatal withdrawal effect.