Neural Tube Defects

Abstract Neural tube defects (NTDs) and hemivertebra represent major congenital abnormalities of the cranial vault and the fetal spine. NTDs are the consequence of a failed closure of the cranial and/or the caudal neural tube. Their pathogenesis is unknown; however, an association with folic acid deficiency and a variable incidence of structural abnormalities and karyotype/genetic defects have been reported. NTDs include the spectrum of acrania-exencephaly-anencephaly, encephaloceles, spinal defects (“spina bifida” or myelomeningocele), and combined cranial and spinal defects such as craniorachischisis. Prognosis is strongly dependent on the type of the NTD and the presence or absence of additional structural or genetic findings. Spina bifida, either open or covered by skin, represents a common malformation of the central nervous system. Closed defects generally have a good prognosis, whereas open defects are associated with high rates of mortality and handicap. Acrania-exencephaly-anencephaly sequence and craniorachischisis represent invariably lethal defects. On the other hand, treatment options do exist for encephaloceles and spina bifida. In these latter, prognosis is dependent on the extent of the defect, its location in the skull or in the spine, and the amount of herniated neural tissue. Among NTDs, encephalocele carries the higher chance of associated extracranial abnormalities and chromosomal or genetic defects. Hemivertebra is among the causes of congenital scoliosis and is caused by the failed development of one half of the vertebral body. Hemivertebra is commonly associated with other skeletal, cardiac, and genitourinary tract anomalies; however, when isolated, it usually carries a good prognosis.