Congenital malformations of the brain (anencephaly) or spinal cord (spina bifida) caused by the failure of the closure of the neural tube in early embryonic development.
A congenital anomaly which occurs when the edges of the neural tube do not close up properly while the fetus develops in the uterus, e.g. spina bifida.
Occurs early in embryonic development; can be spina bifida (inadequate closure of the end of the spinal cord) or hydrocephali (infant head enlargement due to fluid accumulation); in some instances may be related to inadequate folate intake prior to and in the early stages of pregnancy. Females contemplating pregnancy should consume 400 μg folate/day.
A birth defect that is the result of the failure of the spinal cord or brain to develop normally in an embryo. In a normal embryo, the neural tube eventually develops into the spinal cord and brain. When neural tube defects occur, the degree of deformity and disability depends on the level of neural involvement. Neural tube defects range from anencephaly (a fatal birth defect in which an infant’s brain and skull fail to develop) to spina bifida (a crippling but not fatal defect in which the backbones, or vertebrae, do not form a complete ring to protect the spinal cord). Adequate folate levels in the first month after conception are important in the prevention of neural tube defects. As a result, doctors advise all women of childbearing age to take a daily multivitamin containing 400 micrograms of folic acid.
A group of congenital abnormalities caused by failure of the neural tube to close. In spina bifida the bony arches of the spine, which protect the spinal cord and its coverings (the meninges), fail to close. More severe defects of fusion of these bones result in increasingly serious neurological conditions. A meningocele is the protrusion of the meninges through the gap in the spine, the skin covering being vestigial. There is a constant risk of damage to the meninges, with resulting infection. Urgent surgical treatment to protect the meninges is required. In a meningomyelocele (myelomeningocele, myelocele) the spinal cord and the nerve roots are exposed, often adhering to the fine membrane that overlies them. There is a constant risk of infection and this condition is accompanied by paralysis and numbness of the legs and urinary incontinence. Hydrocephalus and the Arnold-Chiari malformation are usually present. A failure of fusion at the cranial end of the neural tube (cranium bifidum) gives rise to comparable disorders. The bone defect is most often in the occipital region of the skull but it may occur in the frontal or basal regions. A protrusion of the meninges alone is called a cranial meningocele. The terms meningoencephalocele, encephalocele, and cephalocele are used to indicate the protrusion of brain tissue through the skull defect. This is accompanied by severe mental and physical disorders.
Congenital abnormalities resulting from the failure of the neural tube to form normally. The resulting conditions include spina bifida, meningocele and defects in the bones of the skull.
A group of congenital structural disorders that result from a failure of the embryonic neural tube to close during development. Cranial fusion disorders, including anencephaly and encephalocele or spinal fusion disorders, including spina bifida, lumbar meningomyelocele, and meningocele, may occur as a consequence of this failure. In the U.S. about 3000 children are born each year with neural tube defects. Although there may be a family history of such disorders, roughly 85% of affected infants are born to women who have not been considered at risk. Prenatal folic acid deficiency has been implicated in NTD, but other predisposing factors may be involved as well. To reduce the risk of NTDs, the U.S. Public Health Service recommends a daily folic acid intake of 0.4 mg for all fertile women of childbearing age. Prior supplementation with folic acid prevents damage to the embryonic neural tube during the first 3 to 4 weeks of its development, when many women are unaware that they are pregnant. The importance of an adequate intake before pregnancy is predicated on the fact that damage to the developing embryo often occurs before the woman knows she is pregnant. The neural tube develops from the neural plate at 3 weeks’ gestation. At 4 weeks’ gestation, closure has been achieved except at the cranial and caudal ends; cranial closure occurs at 24 days and caudal closure at 26 days’ gestation.
A group of common, very serious birth defects that involve the failure of an infant’s spinal cord to close properly. When the failure is at the top of the spine, the condition is called anencephaly, a condition that is usually fatal within hours of birth. When the failure is lower on the spinal cord, the condition is called spina bifida.
An impaired neural tube, which is the slender protective covering that fuses to develop the brain and spinal cord in the embryo.
Previously prevalent, a developmental anomaly impacted the spinal cord or brain of the embryo. Around the third week of pregnancy, the neural plate emerges along the embryo’s back, subsequently folding to shape the neural tube, destined to become the brain, spinal cord, and their protective coverings known as the meninges. When the neural tube formation is compromised, it can lead to defects in any of these components.
The gravest form of neural tube defect is anencephaly, characterized by the underdevelopment of the skull and brain, leading to fatality either before birth or shortly after. A more frequent occurrence is spina bifida, where the vertebrae do not fully enclose the spinal cord. While spina bifida can manifest along the spine, it predominantly appears in the lower back.
Various variations of spina bifida exist. In spina bifida occulta, the sole anomaly is the incomplete fusion of the bony arches that surround the spinal cord. Occasionally, this is linked to a patch of hair or a skin dimple in the region. While this may not result in any issues, it could potentially cause the spinal cord to become tethered, necessitating surgical intervention for release.
In cases where the bone defect is more extensive, it can lead to a meningocele (a protrusion of the meningeal membranes) or a myelomeningocele (a condition in which a portion of the spinal cord and its overlaying meninges are fully exposed). Myelomeningocele is likely to result in significant disability, including leg paralysis, diminished sensation in the lower body, and loss of control over the bladder and anus, resulting in incontinence. The severity of the handicap tends to increase the higher up the spine the malformation occurs.
Commonly linked issues involve hydrocephalus, a condition where excessive fluid accumulates in the brain. Often, the pressure must be alleviated by placing a shunt within the first weeks of life. Additionally, some children might experience cerebral palsy, epilepsy, or challenges with learning. Those with neural tube defects face an increased likelihood of developing meningitis—an severe infection affecting the membranes enveloping the brain and spinal cord.
The exact cause of neural tube defects remains incompletely understood; however, their tendency to occur within families suggests a role for genetic factors. Additionally, certain anticonvulsant medications, if taken by women during pregnancy, have been linked to an increased risk of neural tube defects.
Surgery is typically conducted within a few days after birth. For minor instances, the defect can often be fully corrected; however, with myelomeningocele, some level of disability may persist, necessitating ongoing care throughout the affected children’s lives. Physiotherapy and assistive devices might prove beneficial to sustain mobility and enable a significant level of self-sufficiency.
Children who experience significant damage to the brain and/or spinal cord typically have a shorter life expectancy.
The likelihood of a neural tube defect can be significantly decreased if the mother takes folic acid supplements prior to conception and during the initial stages of pregnancy. If a mother has previously had a child with a neural tube defect, she should consult with a specialist before considering another pregnancy. In such situations, a higher dosage of folic acid might be advised to minimize the chances of having another affected child.
During pregnancy, blood tests and ultrasound scans can aid in identifying neural tube defects prior to childbirth. Over the past 25 years, there has been a significant reduction in the occurrences of babies being born with such defects.