[...]... Abnormality The essential defect of anencephaly is failure of anterior neural tube closure Thus, in the most severe cases, the abnormality extends from the level of the lamina terminalis, the site of final closure at the most rostral portion of the neural tube, to the foramen magnum, the approximate site of onset of anterior neural tube closure.2,36 When the defect in the skull extends through the level of the. .. neurulation refers to formation of the neural tube, exclusive of the most caudal aspects (see later) The time period involved is the third and fourth weeks of gestation (Table 1-2) The nervous system begins on the dorsal aspect of the embryo as a plate of tissue differentiating in the middle of the ectoderm (Fig 1-1) The underlying notochord and chordal mesoderm induce formation of the neural plate, which... the eastern United States.46 Renewed investigation of the neurological function and survival of anencephalic infants was provoked by interest in the 1990s in the use of organs of such infants for transplantation.49-53 Because lack of function of the entire brain, including the brain stem, is obligatory for the diagnosis of brain death in the United States, the finding of persistent clinical signs of. .. death after the first year of life The management of these groups of complications is a major problem after the newborn period and is best discussed in another context.177-182 However, urodynamic evaluation in the newborn with myelomeningocele is of major predictive value concerning the risk of subsequent decompensation of the urinary tract.182,183 Indeed, in a study of 36 infants, 13 of 16 who had... growth of the vertebral column and the neural tissue) This concept of differential growth as the sole cause of the injury is contradicted by the finding that differential growth is slight between approximately the 26th week of gestation, when the cord is at the level of the third lumbar segment, and maturity, when the cord is at the level of the first or second lumbar segment.82,300 Nevertheless, contributory... development: formation of the neural tube and the subsequent formation of the prosencephalon These early processes are discussed separately from later events because, together, the early processes result in the essential form of the central nervous system (CNS) and can be considered the neural components of embryogenesis The later developmental events, relating largely to the intrinsic structure of the CNS, can... covering is present The defects of the spinal column were studied in detail by Barson82 and consist of a lack of fusion or an absence of the vertebral arches, resulting in bilateral broadening of the vertebrae, lateral displacement of pedicles, and a widened spinal canal The caudal extent of the vertebral changes is usually considerably greater than the extent of the neural lesion Timing Onset of myelomeningocele... variety of cellular and molecular mechanisms.7-9,12-34 The most important cellular mechanisms involve the function of the cytoskeletal network of microtubules and microfilaments Under the influence of vertically oriented microtubules, cells of the developing neural plate elongate, and their basal portions widen Under the influence of microfilaments oriented parallel to the apical surface, the apical... determinants of patient and family perceptions of quality of life in adolescence.184 Results of Therapy Conservative therapy (i.e., no early surgery), the standard of care in the 1950s, provides an approximate measure of the natural history of the disorder (Table 1-14).185 Approximately 50% of patients managed conservatively were dead by 2 months of age, 80% by 1 year, and 85% to 90% by 10 years Of the survivors,... mg/day for women from the time they plan to become pregnant through the first 3 months of pregnancy.284 The folate was not recommended to be administered as a multivitamin preparation because of the potential danger for toxicity from excessive amounts of other vitamins in the multivitamin preparation Because of the uncertainty of the degree of risk from the folate supplementation, the initial recommendations