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.
(See also Overview of Brain and Spinal Cord Birth Defects Overview of Brain and Spinal Cord Birth Defects Birth defects of the brain and spinal cord can occur in early or late fetal development. Typical symptoms include intellectual disability, paralysis, incontinence, or loss of sensation in some... 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.
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 (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 a dilation of the normally small fluid-filled central canal of the spinal cord, cord may be present.
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 occult spinal dysraphism, a more severe form of spina bifida, newborns are born with visible abnormalities on their lower back. These include birthmarks, overly pigmented areas (hemangiomas Hemangiomas of infancy (also called strawberry 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 be abnormal such as having 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 other problems that can lead to nerve damage.
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.
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.
Brain damage can cause problems, 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 is 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. Incontinence may be present During the day (daytime or diurnal... 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 (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.
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 2nd 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 may also be 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.
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 needed to treat hydrocephalus, may occur and sometimes cause death in older children.
Prevention of Neural Tube Defects
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...
Treatment of Neural Tube Defects
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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