الفهرس 
Neural Tube FormationOnly 14 pages are availabe for public view
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Abstract
Myelomeningocele is the most common significant birth defect involving the spine. The incidence of the condition ranges from less than one case per 1000 live birth in the United States to almost nine cases per 1000 in areas of Ireland.
The etiology is unknown, but evidence exists for both environmental and genetic influences. A role for genetic risk factors is supported by numerous studies documenting familial aggregation of this condition. In addition, several lines of evidence point to the potential importance of maternal nutritional status as a determinant of the risk of having a child with myelomeningocele.
Embryologically, the abnormality manifests between 3 & 4 weeks of gestation. At this point of development, the neural plate folds into the neural tube (neurulation). The last portion of the tube to close is the posterior end (neuropore) at 28 days. Myelomeningocele presumably occurs when the posterior neuropore falls to close, or if it reopens as a result of distension of the spinal cord’s central canal with Cerebrospinal Fluid (CSF). The spinal abnormality is only a part of a more widespread complex of central nervous system abnormalities e.g. hydrocephalus are Chiari II malformation of hindbrain.
Recent developments in the prenatal diagnosis of fetal anomalies have made antenatal recognition of myelomeningocele a common place. Families at risk are routinely offered amniocentesis for amniotic alpha fetoprotein and acetylcholine esterase.