neural tube defect

defect /de·fect/ (de´fekt) an imperfection, failure, or absence.defec´tive

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acquired defect  a non-genetic imperfection arising secondarily, after birth.

aortic septal defect  a congenital anomaly in which there is abnormal communication between the ascending aorta and pulmonary artery just above the semilunar valves.

atrial septal defects , atrioseptal defects congenital anomalies in which there is persistent patency of the atrial septum, owing to failure of the ostium primum or ostium secundum.

Atrial septal defects; cutaway composite view showing possible locations of ostium primum and secundum defects in the right atrium.

birth defect  one present at birth, whether a morphological defect (dysmorphism) or an inborn error of metabolism.

congenital defect  birth d.

congenital ectodermal defect  anhidrotic ectodermal dysplasia.

cortical defect  a benign, symptomless, circumscribed rarefaction of cortical bone, detected radiographically.

endocardial cushion defects  a spectrum of septal defects resulting from imperfect fusion of the endocardial cushions, and ranging from persistent ostium primum to persistent common atrioventricular canal; see atrial septal d. and atrioventricularis communis.

fibrous cortical defect  a small, asymptomatic, osteolytic, fibrous lesion occurring within the bone cortex, particularly in the metaphyseal region of long bones in childhood.

filling defect  any localized defect in the contour of the stomach, duodenum, or intestine, as seen in the radiograph after a barium enema.

genetic defect  see under disease.

luteal phase defect  inadequate secretory transformation of the endometrium during the luteal phase of the menstrual cycle; it can cause habitual abortion.

metaphyseal fibrous defect 

1. fibrous cortical d.

2. nonossifying fibroma.

neural tube defect  a developmental anomaly of failure of closure of the neural tube, resulting in conditions such as anencephaly or spina bifida.

retention defect  a defect in the power of recalling or remembering names, numbers, or events.

septal defect  a defect in a cardiac septum resulting in an abnormal communication between the opposite chambers of the heart.

ventricular septal defect  a congenital cardiac anomaly in which there is persistent patency of the ventricular septum in either the muscular or fibrous portions, most often due to failure of the bulbar septum to completely close the interventricular foramen.

Abnormal communication between the ventricles in ventricular septal defect.

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neural tube defect (NTD),

any of a group of congenital malformations involving defects in the skull and spinal column that are caused primarily by the failure of the neural tube to close during embryonic development. In some instances the cleft results from an abnormal increase in cerebrospinal fluid pressure on the closed neural tube during the first trimester of development. The defect may occur at any point along the neural axis or extend the entire length of the spinal column, as in holorachischisis. The amount of deformity and disability depends on the degree of neural involvement, the most severe defect being complete cranioschisis, or the total absence of the skull and defective brain development. Other cerebral dysplasias resulting from the failure of the cranial end of the neural tube to fuse are meningoencephalocele and cranial meningocele. These defects, usually accompanied by severe mental and physical disorders, occur most often in the occipital region of the skull but may also occur in the frontal or basal regions. Most neural tube malformations are caused by incomplete fusion of one or more laminae of the vertebral column, with varying degrees of tissue protrusion and neural involvement. The two most common NTDs are spina bifida and anencephaly. Other NTDs include rachischisis, myelocele, myelomeningocele, and meningocele. In all of these conditions there is constant risk of rupture of the saclike protrusion and danger of meningeal infection. Often immediate surgical repair is necessary. Adequate folate levels during the first month after conception are important in preventing neural tube defects; the U.S. Public Health Service recommends that all women of childbearing age increase their folate intake to 400 mg per day. Many of the major neural tube defects can be determined prenatally by ultrasonic scanning of the uterus and by tests for the presence of elevated concentrations of alpha-fetoprotein levels in the amniotic fluid. Such diagnostic tests are preferably performed during the 14th to 16th week of gestation so that termination of the pregnancy is possible. See also anencephaly, Arnold-Chiari malformation, spina bifida cystica.

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neural tube defect

Neurology Any of the congenital developmental defects of the CNS characterized by defective closure of the neural tube at one or more segments; NTDs range from asymptomatic to extreme–anencephaly with absent cranial vault and most or all of the cerebral hemispheres and spina bifida cystica attributable to multifactorial events and noxious environmental agents; NTDs occur in 1:1000-5000 live births, ♂:♀ ratio 2-3:1, with regional differences–eg, higher in Ireland–2-7% recurrence rate Clinical Cinercephaly, cephalocele, spina bifida, and myelodysplasia; failure to close neural tube at 4^th-5^th fetal wk Lab ↑ α-fetoprotein, detected in antenatal screening of maternal serum or amniotic fluid Prevention Multivitamins in early pregnancy ↓ risk of NTDs