neural tube defect

defect

[de´fekt] an imperfection, failure, or absence.congenital heart defect see congenital heart defect.aortic septal defect see aortic septal defect.atrial septal defect see atrial septal defect.filling defect an interruption in the contour of the inner surface of stomach or intestine revealed by radiography, indicating excess tissue or substance on or in the wall of the organ.neural tube defect see neural tube defect.septal defect a defect in the cardiac septum resulting in an abnormal communication between opposite chambers of the heart. Common types are aortic septal defect, atrial septal defect, and ventricular septal defect. See also congenital heart defect.

neural

[noor´al] pertaining to a nerve" >nerve or to the nerves; called also nervous.neural tube defect a congenital defect in closure of the bony encasement of the spinal cord or of the skull. The most severe defects are a fissure along the entire length of the spinal column that leaves the meninges and spinal cord exposed (rachischisis), or herniation through the skull of a saclike structure containing brain tissue and meninges (encephalocele). anencephaly is a major defect in which the brain is absent and there is only an exposed vascular mass with no bony covering.
Classification and nomenclature of spinal column defects are based on the extent to which the meninges and spinal cord are involved. spina bifida refers to abnormal closure with or without visible protrusion of the meninges and spinal cord through the cleft in the spinal column. If there is no visible protrusion, the condition is called spina bifida occulta. An external protrusion consisting of a saclike structure is called spina bifida cystica. Two subtypes of spina bifida cystica are meningocele, which involves the meninges surrounded by spinal fluid, and myelomeningocele (or meningomyelocele), in which the sac contains meninges, spinal fluid, and a portion of the spinal cord with its nerves.
Developmental defects of the neural tube tend to run in families and are believed by most authorities to occur during early development of the embryo. Prenatal detection of some major open neural tube defects is possible through ultrasonic scanning of the uterus and laboratory evaluation of the amniotic fluid. In the presence of anencephaly and meningomyelocele there are elevated concentrations of alpha-fetoprotein in the amniotic fluid.
Genetic predisposition to neural tube defects is inheritable; thus family history is significant in predicting the risk of recurrence. For example, a couple who has had one child with such a defect has a one in twenty (5 per cent) probability of having a second child with the disorder. The risk is doubled to one in ten (10 per cent) if two of their children are so affected. Siblings of an affected child who are themselves normal are at greater than average risk of producing a child with a similar problem.Treatment. Immediate care of the neonate with a neural tube defect includes prevention of infection and assessment of neurological involvement. Later, an orthopedic assessment is done to identify problems related to locomotion. Corrective procedures such as casting, bracing, and traction are indicated if there is hope for some functioning of the lower extremities. Associated anomalies of the hip, knee, and foot may require correction by orthopedic surgery.
Meningoceles usually are repaired to prevent infection, especially if there is danger of rupture of the sac. Most authorities recommend closure within the first 24 to 48 hours after birth. However, authorities do not agree on whether an attempt should be made to perform skin closure over a myelomeningocele. If hydrocephalus develops, the treatment of choice is a ventriculoperitoneal shunt or some other procedure to drain spinal fluid and decompress the fluid-filled ventricles.
Bowel and bladder dysfunction usually occur as a result of myelomeningocele. Management of neurogenic bladder and incontinence includes preventing urinary stasis and infection and providing some means for collecting urine. Fecal incontinence may be amenable to bowel training and modification of the diet. In some children a colostomy is the most desirable way to handle the problem.Patient Care. Immediate concerns in the care of the newborn with a neural tube defect center on protection of the fragile sac from trauma and infection, observation for complications, and support and guidance for parents and family members. Positioning before and after surgery is critical. Preoperatively, the goal is to minimize tension on and trauma to the sac. The baby may be placed in a prone position with head slightly lower than body to reduce spinal fluid pressure in the sac. The hips are slightly flexed to relieve tension on the spine. After surgery, it may be desirable to elevate the head because of increased intracranial pressure and impending hydrocephalus. Many surgeons allow a side-lying position postoperatively because of diapering and feeding problems associated with the prone position. The variety of allowable positions permits frequent position changes to avoid pressure sores. As soon as the operative site is sufficiently healed, the baby can be held for feeding and receiving the body contact every neonate needs. If a baby with inoperable myelomeningocele cannot be held and cuddled, stroking, fondling, and other comfort measures can be used to meet the need for tactile stimulation.
Long-term care will depend on the specific orthopedic, urologic, and neurologic problems each child has. Patients will require continued guidance and support. Comprehensive care for the patient and family can only be provided by a coordinated team of health care providers, including physicians, nurses, physical therapists, rehabilitation specialists, and social workers. The familial tendency toward neural tube defects demands that genetic counseling be available to the family.

neural tube defect

n. Any of various congenital defects of the brain and spinal cord, such as spina bifida, resulting from incomplete closing of the neural tube in an embryo.

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

neu·ral tube de·fect

(nūr'ăl tūb dē'fekt) A birth defect that may be caused by a deficiency of folate early in pregnancy, characterized by incomplete midline fusion of the developing central nervous system.

单词	neural tube defect
释义	neural tube defect neural tube defect n. Any of various congenital defects of the brain and spinal cord, such as spina bifida, resulting from incomplete closing of the neural tube in an embryo. neural tube defect defect [de´fekt] an imperfection, failure, or absence.congenital heart defect see congenital heart defect.aortic septal defect see aortic septal defect.atrial septal defect see atrial septal defect.filling defect an interruption in the contour of the inner surface of stomach or intestine revealed by radiography, indicating excess tissue or substance on or in the wall of the organ.neural tube defect see neural tube defect.septal defect a defect in the cardiac septum resulting in an abnormal communication between opposite chambers of the heart. Common types are aortic septal defect, atrial septal defect, and ventricular septal defect. See also congenital heart defect. neural [noor´al] pertaining to a nerve" >nerve or to the nerves; called also nervous.neural tube defect a congenital defect in closure of the bony encasement of the spinal cord or of the skull. The most severe defects are a fissure along the entire length of the spinal column that leaves the meninges and spinal cord exposed (rachischisis), or herniation through the skull of a saclike structure containing brain tissue and meninges (encephalocele). anencephaly is a major defect in which the brain is absent and there is only an exposed vascular mass with no bony covering. Classification and nomenclature of spinal column defects are based on the extent to which the meninges and spinal cord are involved. spina bifida refers to abnormal closure with or without visible protrusion of the meninges and spinal cord through the cleft in the spinal column. If there is no visible protrusion, the condition is called spina bifida occulta. An external protrusion consisting of a saclike structure is called spina bifida cystica. Two subtypes of spina bifida cystica are meningocele, which involves the meninges surrounded by spinal fluid, and myelomeningocele (or meningomyelocele), in which the sac contains meninges, spinal fluid, and a portion of the spinal cord with its nerves. Developmental defects of the neural tube tend to run in families and are believed by most authorities to occur during early development of the embryo. Prenatal detection of some major open neural tube defects is possible through ultrasonic scanning of the uterus and laboratory evaluation of the amniotic fluid. In the presence of anencephaly and meningomyelocele there are elevated concentrations of alpha-fetoprotein in the amniotic fluid. Genetic predisposition to neural tube defects is inheritable; thus family history is significant in predicting the risk of recurrence. For example, a couple who has had one child with such a defect has a one in twenty (5 per cent) probability of having a second child with the disorder. The risk is doubled to one in ten (10 per cent) if two of their children are so affected. Siblings of an affected child who are themselves normal are at greater than average risk of producing a child with a similar problem.Treatment. Immediate care of the neonate with a neural tube defect includes prevention of infection and assessment of neurological involvement. Later, an orthopedic assessment is done to identify problems related to locomotion. Corrective procedures such as casting, bracing, and traction are indicated if there is hope for some functioning of the lower extremities. Associated anomalies of the hip, knee, and foot may require correction by orthopedic surgery. Meningoceles usually are repaired to prevent infection, especially if there is danger of rupture of the sac. Most authorities recommend closure within the first 24 to 48 hours after birth. However, authorities do not agree on whether an attempt should be made to perform skin closure over a myelomeningocele. If hydrocephalus develops, the treatment of choice is a ventriculoperitoneal shunt or some other procedure to drain spinal fluid and decompress the fluid-filled ventricles. Bowel and bladder dysfunction usually occur as a result of myelomeningocele. Management of neurogenic bladder and incontinence includes preventing urinary stasis and infection and providing some means for collecting urine. Fecal incontinence may be amenable to bowel training and modification of the diet. In some children a colostomy is the most desirable way to handle the problem.Patient Care. Immediate concerns in the care of the newborn with a neural tube defect center on protection of the fragile sac from trauma and infection, observation for complications, and support and guidance for parents and family members. Positioning before and after surgery is critical. Preoperatively, the goal is to minimize tension on and trauma to the sac. The baby may be placed in a prone position with head slightly lower than body to reduce spinal fluid pressure in the sac. The hips are slightly flexed to relieve tension on the spine. After surgery, it may be desirable to elevate the head because of increased intracranial pressure and impending hydrocephalus. Many surgeons allow a side-lying position postoperatively because of diapering and feeding problems associated with the prone position. The variety of allowable positions permits frequent position changes to avoid pressure sores. As soon as the operative site is sufficiently healed, the baby can be held for feeding and receiving the body contact every neonate needs. If a baby with inoperable myelomeningocele cannot be held and cuddled, stroking, fondling, and other comfort measures can be used to meet the need for tactile stimulation. Long-term care will depend on the specific orthopedic, urologic, and neurologic problems each child has. Patients will require continued guidance and support. Comprehensive care for the patient and family can only be provided by a coordinated team of health care providers, including physicians, nurses, physical therapists, rehabilitation specialists, and social workers. The familial tendency toward neural tube defects demands that genetic counseling be available to the family. neural tube defect n. Any of various congenital defects of the brain and spinal cord, such as spina bifida, resulting from incomplete closing of the neural tube in an embryo. 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 neu·ral tube de·fect (nūr'ăl tūb dē'fekt) A birth defect that may be caused by a deficiency of folate early in pregnancy, characterized by incomplete midline fusion of the developing central nervous system. 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