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Neural Tube Defects and Spina Bifida

By

Stephen J. Falchek

, MD, Nemours/Alfred I. duPont Hospital for Children

Last full review/revision Apr 2019| Content last modified Apr 2019
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Neural tube defects are a certain type of birth defect of the brain, spine, and/or spinal cord.

  • Neural tube defects can result in nerve damage, learning disabilities, paralysis, and death.

  • The diagnosis can be made before birth and is based on a blood test, an amniotic fluid test, or an ultrasound.

  • After birth, doctors do a physical examination and may do additional imaging tests.

  • Folate (folic acid) taken by the mother before conception and during the first trimester can help prevent these defects.

  • Surgery is needed to close neural tube defects.

Anencephaly is the most severe form of neural tube defect. In anencephaly, the brain tissue fails to develop. This defect is always fatal.

Chiari malformation may be present. In this abnormality, the cerebellum (the part of the brain that controls balance) protrudes through the opening in the bottom of the skull. The protruding cerebellum may put pressure on the brain stem or spinal cord. Children may develop hydrocephalus Hydrocephalus Hydrocephalus is an accumulation of extra fluid in the normal spaces within the brain (ventricles) and/or between the inner and middle layers of tissues that cover the brain (the subarachnoid... read more Hydrocephalus (water on the brain).

Spina bifida

Spina bifida results when the neural tube fails to close completely and remains an open channel. In spina bifida, the bones of the spine (vertebrae) do not close over the spinal cord. It most commonly affects the spine in the lower back. One or more of the vertebrae may be involved.

Spina bifida occulta is the mildest form of spina bifida. Only the bone is affected and the spinal cord and meninges are unaffected. This common defect is called occulta because it is hidden (covered) by a layer of skin that typically appears normal except sometimes there may be a small tuft of hair or different color of the skin overlying the defect. It usually causes no symptoms, but children who have a larger defect may have symptoms such as leg weakness or bladder dysfunction.

In spina bifida cystica, the most serious form of spina bifida, tissues of the meninges and/or spinal cord protrude through the opening in the vertebrae, causing the following defects:

  • A meningocele: Only the meninges protrude

  • A meningoencephalocele: The meninges and brain tissue protrude

  • A meningomyelocele: The meninges and spinal cord tissue protrude

  • An encephalocele: Only brain tissue protrudes

  • A myelocele: Only spinal cord tissue protrudes

Damage to brain or spinal cord tissue is much more likely when the tissue protrudes than when it does not. Also, when spinal cord tissue or meninges are exposed, they may become infected by bacteria, causing meningitis Meningitis in Children Bacterial meningitis is a serious infection of the layers of tissue covering the brain and spinal cord (meninges). Bacterial meningitis in older infants and children usually results from bacteria... read more .

Spina Bifida: A Defect of the Spine

In spina bifida, the bones of the spine (vertebrae) do not form normally. Spina bifida can vary in severity.

In occult spinal dysraphism, one or more vertebrae do not form normally, and the spinal cord and the layers of tissues (meninges) surrounding it may also be affected. The only symptom may be a tuft of hair, a dimpling, or a pigmented area on the skin over the defect.

In a meningocele, the meninges protrude through the incompletely formed vertebrae, resulting in a fluid-filled bulge under the skin. The spinal cord is in its normal location.

The most severe type is a meningomyelocele, in which the meninges and spinal cord protrude. The affected area appears raw and red, and the infant is likely to be severely impaired.

Spina Bifida: A Defect of the Spine

Causes of Neural Tube Defects

There are many causes of neural tube defects. Deficiency of a B vitamin, folate Folate Deficiency Folate deficiency is common. Because the body stores only a small amount of folate, a diet lacking in folate leads to a deficiency within a few months. Not eating enough raw leafy vegetables... read more , during pregnancy is a significant factor. Genetic factors and use of certain drugs during pregnancy (such as valproate) can make neural tube defects more likely. The defect often develops before the mother knows she is pregnant.

Symptoms of Neural Tube Defects

Many children who have minor neural tube defects have no symptoms.

Most symptoms caused by neural tube defects result from brain or spinal cord damage.

Spinal cord damage can cause severe problems, typically involving the bowels, bladder, and legs. Problems include

Diagnosis of Neural Tube Defects

  • Before birth, blood tests or amniocentesis to measure alpha-fetoprotein levels or prenatal ultrasonography

  • After birth, physical examination and additional imaging tests

Prognosis of Neural Tube Defects

With appropriate care, most children do well. However, complications, such as loss of kidney function and problems with shunts Treatment Hydrocephalus is an accumulation of extra fluid in the normal spaces within the brain (ventricles) and/or between the inner and middle layers of tissues that cover the brain (the subarachnoid... read more Treatment needed to treat hydrocephalus, may occur and sometimes cause death in older children.

Prevention of Neural Tube Defects

  • Folate

All women of childbearing age who have not had an infant with a neural tube defect should consume folate Folate Deficiency Folate deficiency is common. Because the body stores only a small amount of folate, a diet lacking in folate leads to a deficiency within a few months. Not eating enough raw leafy vegetables... read more (folic acid) through diet or by taking a supplement and continue doing so through the first 3 months of pregnancy.

Women who have had an infant with a neural tube defect are at high risk of having another affected infant and should take high-dose folate supplements beginning 3 months before getting pregnant and continuing through the first 3 months of pregnancy. Folate can reduce the risk of neural tube defects by as much as 75%.

Did You Know...

  • Taking folate before and during pregnancy can decrease the risk of neural tube defects.

Treatment of Neural Tube Defects

  • Surgery

Health care practitioners, usually a team of specialists (including a neurosurgeon, a urologist, a pediatrician, a pediatric rehabilitation medicine specialist, an orthopedic surgeon, a physical therapist, a nurse practitioner, and a social worker), evaluate the type and severity of the defect and talk to the family about how treatment and care can be implemented.

Neural tube defects are usually closed surgically. Certain defects, such as a myelomeningocele, are typically repaired soon after birth.

Problems with the bladder, bones, or muscles and other problems are treated as needed.

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