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 usually is needed to close neural tube defects.
(See also Overview of Brain and Spinal Cord Birth Defects Overview of Brain and Spinal Cord Birth Defects Birth defects of the brain or spinal cord cause a spectrum of neurologic problems; some may be barely noticeable, others may be fatal. Birth defects of the brain and spinal cord can occur in... read more .)
In the fetus, the brain Brain The brain’s functions are both mysterious and remarkable, relying on billions of nerve cells and the internal communication between them. All thoughts, beliefs, memories, behaviors, and moods... read more and spinal cord Spinal Cord The spinal cord is a long, fragile tubelike structure that begins at the end of the brain stem and continues down almost to the bottom of the spine. The spinal cord consists of bundles of nerve... read more develop as a groove that folds over to become a tube called the neural tube. Layers of tissue that come from this tube normally become the brain and spinal cord and the tissues that cover them, including part of the spine and the meninges Meninges The brain’s functions are both mysterious and remarkable, relying on billions of nerve cells and the internal communication between them. All thoughts, beliefs, memories, behaviors, and moods... read more . Sometimes the neural tube does not develop normally, which may affect the brain, spinal cord, and meninges.
Spina bifida is a neural tube defect. Although spina bifida can be serious, people who have it may live a long life.
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. Typically, only the bone at the back of the vertebra (one of the bones that make up the backbone) 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. This skin layer typically appears normal, but sometimes it is a different color than the surrounding skin, or there may be a small tuft of hair overlying the defect.
Spina bifida occulta usually causes no symptoms but can be associated with other birth defects or with abnormalities of the spinal cord (occult spinal dysraphism).
Occult spinal dysraphism is a form of spina bifida in which the spinal cord is affected. In occult spinal dysraphism, newborns may have visible abnormalities on their lower back. These include birthmarks, overly pigmented areas (hemangiomas Hemangiomas of infancy (also called strawberry or infantile hemangiomas) Hemangiomas are abnormal overgrowths of blood vessels that can appear as red or purple lumps in the skin and on other parts of the body. (See also Overview of Skin Growths and Overview of Growths... read more and flame nevus [ stork bite Port-Wine Stains Port-wine stains are flat pink, red, or purplish discolorations present at birth due to malformed blood vessels. (See also Overview of Skin Growths and Overview of Growths and Malformations... read more ]), tufts of hair, openings in the skin (dermal sinus), or small lumps (masses). The underlying spinal cord may have a defect, such as a fatty tumor (lipoma Lipomas Lipomas are soft deposits of body fat that grow under the skin, causing round or oval lumps. (See also Overview of Skin Growths.) Lipomas are very common. They appear as smooth, soft bumps under... read more ), or the band that anchors the spinal cord (filum terminale) may be thickened and short, causing the cord to be stretched and unable to move normally within the spinal canal. As the child grows, the spinal cord must be able to move freely inside the spinal canal. If not treated, this problem with the cord can lead to nerve damage that results in a loss of bladder and bowel control, leg weakness, and spasm of leg muscles, which can eventually lead to an inability to walk.
Spina bifida cystica is the most serious form of spina bifida. In spina bifida cystica, tissues of the meninges, spinal cord, or both protrude through the opening in the vertebrae. A thin membrane of skin may cover the tissues, or they may not be covered by skin.
Spina bifida cystica has the following categories:
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 tissue protrudes outside the normal contour of the back, especially if there is no normal skin covering the protruding tissue. Also, when spinal cord tissue or meninges are fully 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. There are several types with differing neurologic severities. The diagnosis is sometimes suggested by symptoms in the lower back, such as 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.
Other neural tube and associated defects
Anencephaly is the most severe neural tube defect. In anencephaly, the brain tissue fails to develop. This defect is always fatal.
Chiari malformation may occur with spina bifida. 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 (water on the brain).
Syringomyelia Syrinx of the Spinal Cord or Brain Stem A syrinx is a fluid-filled cavity that develops in the spinal cord (called syringomyelia), in the brain stem (called syringobulbia), or in both. Syrinxes may be present at birth or develop later... read more occurs when the normally small fluid-filled central canal within the spinal cord widens and fills with a larger amount of fluid. Syringomyelia can occur with spina bifida or with Chiari malformations.
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 medications 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.
Neural tube defects can cause brain damage, including water on the brain (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 ), learning disabilities Learning Disorders Learning disorders involve an inability to acquire, retain, or broadly use specific skills or information, resulting from deficiencies in attention, memory, or reasoning and affecting academic... read more , and difficulty swallowing Difficulty Swallowing Some people have difficulty swallowing (dysphagia). In dysphagia, foods and/or liquids do not move normally from the throat (pharynx) to the stomach. People feel as though food or liquids become... read more .
Spinal cord damage can cause severe problems, typically involving the bowels, bladder, and legs. Problems include
Weakness and paralysis: Walking can be difficult or impossible, unused muscles shrink and stiffen up
Decreased sensation of the skin
Urinary problems: Inability to pass urine (urine retention Urinary Retention Urinary retention is inability to urinate or incomplete emptying of the bladder. People who have incomplete emptying of the bladder may have urinary frequency or urinary incontinence. If the... read more ) or urinary incontinence Urinary Incontinence in Children Urinary incontinence is defined as the involuntary release of urine occurring two or more times per month after toilet training has been completed. Incontinence may be present During the day... read more and frequent urinary tract infections Urinary Tract Infection (UTI) in Children A urinary tract infection is a bacterial infection of the urinary bladder ( cystitis), the kidneys ( pyelonephritis), or both. Urinary tract infections are caused by bacteria. Infants and younger... read more (severe urinary problems sometimes lead to kidney failure)
Bowel problems: Loss of control over bowel movements Stool Incontinence in Children Stool incontinence is the inappropriate passing of bowel movements that is not caused by illness or physical abnormality. Stool incontinence can be voluntary or involuntary. It occurs in about... read more or constipation Constipation in Children Constipation refers to delay or difficulty in passing stool for a period of at least 1 month in infants and toddlers and a period of 2 months in older children (see also Constipation in adults)... read more
Other problems, such as clubfoot Clubfoot and Other Foot Defects Clubfoot (talipes equinovarus) is a birth defect in which the foot and ankle are twisted out of shape or position. Birth defects, also called congenital anomalies, are physical abnormalities... read more , arthrogryposis Arthrogryposis Multiplex Congenita Arthrogryposis multiplex congenita refers to a group of rare disorders that develop in the womb and cause many joints to become "frozen" in position. Birth defects, also called congenital anomalies... read more (joints, usually ankles, that become frozen and cannot bend), a dislocated hip Developmental Dysplasia of the Hip Developmental dysplasia of the hip is a birth defect in which the bones in the hip are incorrectly developed. Birth defects, also called congenital anomalies, are physical abnormalities that... read more , or an abnormally curved spine that causes a humpback (kyphosis Kyphosis Kyphosis is an abnormal curving of the spine that causes a humpback. (See also Overview of Bone Disorders in Children.) The upper back normally curves forward somewhat. Some children have a... read more ), may also be present at birth. Scoliosis may develop later in some children.
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
Many neural tube defects can be detected before birth with prenatal screening tests Screening of the Pregnant Woman Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more .
A high level of alpha-fetoprotein in a pregnant woman's blood or in amniotic fluid may indicate a neural tube defect in the fetus. So during the second trimester, blood tests Second-Trimester Screening Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more or amniocentesis Amniocentesis Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more (removing a sample of fluid from around the fetus) may be done to measure these levels.
Prenatal ultrasonography Ultrasonography Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more may show the defect or characteristic abnormalities.
After birth, some defects are obvious during the physical examination. If newborns have abnormalities that suggest occult spinal dysraphism, ultrasonography Ultrasonography Ultrasonography uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. A device called a transducer converts electrical current into sound waves... read more or magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (MRI) is done to check for defects in the spine. X-rays Plain X-Rays X-rays are high-energy radiation waves that can penetrate most substances (to varying degrees). In very low doses, x-rays are used to produce images that help doctors diagnose disease. In high... read more of the spine, hips, and sometimes the legs are done.
After spina bifida is diagnosed, tests to evaluate bladder function are done. They include urinalysis Urinalysis and Urine Culture Urinalysis, the testing of urine, may be necessary in the evaluation of kidney and urinary tract disorders and can also help evaluate bodywide disorders such as diabetes or liver problems. A... read more , urine culture Urinalysis and Urine Culture Urinalysis, the testing of urine, may be necessary in the evaluation of kidney and urinary tract disorders and can also help evaluate bodywide disorders such as diabetes or liver problems. A... read more , blood tests, and ultrasonography.
Treatment of Neural Tube Defects
Health care professionals, 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. A shunt (a plastic tube that creates a permanent alternate drainage path for cerebrospinal fluid) may be placed to treat hydrocephalus 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 .
Problems with the bladder, bones, or muscles and other problems are treated as needed.
Prognosis for 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 needed to treat hydrocephalus, may occur and sometimes cause death in older children.
Prevention of Neural Tube Defects
Folate reduces the risk of neural tube defects.
All women of childbearing age who have not had an infant with a neural tube defect should take a vitamin supplement with folic acid (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 ) beginning 3 months before getting pregnant and continuing 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 doses of folate supplements beginning 3 months before getting pregnant again and continuing through the first 3 months of pregnancy. Folate supplements may not prevent all cases of neural tube defects but can reduce the risk of neural tube defects substantially.
Did You Know...
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
Spina Bifida Association: An organization providing support, education, and research resources and information about how to live with or care for someone who has spina bifida
March of Dimes: An organization for pregnant people and babies that provides support and information about how to prevent maternal health risks, premature birth, and mother and infant deaths
Drugs Mentioned In This Article
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