neural /neu·ral/ (noor´al)
neural
neural [noor´al]
1. pertaining to a nerve or to the nerves.
2. situated in the region of the spinal axis, as the neural arch.
neu·ral (n r  l)adj. 1. Of or relating to a nerve or the nervous system. 2. Of, relating to, or located on the same side of the body as the spinal cord; dorsal. |
neural
[noo͡r′əl]
Etymology: Gk, neuron, nerve
pertaining to nerve cells and their processes.
neural [noor´al]
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.
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.
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.
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
pertaining to a nerve or to the nerves.
neural crest cells
a group of neuroepithelial cells which condenses dorsal to the neural tube in the embryo; they subsequently migrate and set up dorsal root ganglia, the ganglia of the autonomic nervous system, and the pigment cells of the integument (melanocytes).
neural folds
in the embryo, the sides of the invaginated neural plate that meet and fuse over the neural groove to form the neural tube.
neural groove
the longitudinal furrow in the neural plate of the embryo.
neural lymphomatosis
see marek's disease.
neural plate
the thickened ectoderm dorsal to the notochord in the embryo that gives rise to the neural tube.
neural retina
separated from the outer layer of the optic retina by the intraretinal space; constitutes the pars optica retinae, with its neuroepithelial layer (contains rods and cones—the receptor cells), bipolar ganglion layer, multipolar ganglion layer, and a layer of axons of the latter layer. Light must pass through the latter three layers before reaching the receptor cells.
neural substrates
functional units of the central nervous system, often composed of a series of structural units which may be widely separated anatomically but which interact to support or drive complex nervous system functions, such as hunger and sleepiness. They are the counterparts of simple centers, e.g. the respiratory center, which control simple physiological mechanisms.
neural tropic influence
the tropic influence of nerves on, for example, muscle, demonstrated by the atrophy of muscle when it is denervated.
neural tube
the precursor of the central nervous system in the embryo, formed by invagination and fusion of the neural plate.
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