Neural Tube Defects

Neural tube defects (NTDs) are serious birth defects (Read about "Birth Defects") with symptoms that range from mild to severe impairment. They are caused by incomplete development of the brain, spinal cord and/or their protective coverings. (Read about "The Brain") This occurs when the fetus' spine fails to close properly during the early stages of pregnancy. (Read about "Stages of Pregnancy") The Spina Bifida Association of America (SBAA) says spina bifida is the most common NTD. Some other types of NTDs include anencephaly and encephaloceles.

While there is no cure for any of these, much research is being done to determine what causes them and how to prevent them. Doctors and scientists are also working to improve surgeries and other treatments for those affected by these disorders. One thing the March of Dimes (MOD), SBAA and other groups agree on is the need for women to take folic acid supplements, even before they are pregnant. SBAA says that some studies have shown that if all women took appropriate folic acid supplements before and during pregnancy, NTDs could be reduced by close to 75 percent. (Read about "Pregnancy and Nutrition") Below you'll find information on some different types of neural tube defects.

Spina Bifida

Spina bifida is the most common neural tube defect. SBAA estimates that more than 70,000 people in the United States are living with spina bifida. However, it also has the best prognosis of the NTDs, as most babies born with spina bifida can now live well into adulthood.

Spina bifida occurs when the spine fails to close properly during the first few weeks of pregnancy, causing damage to the nerves and spinal cord. (Read about "Stages of Pregnancy" "Nervous System") The damage can range from mild to severe. Severe cases can result in full or partial paralysis and other problems such as hydrocephalus (Read about "Hydrocephalus"), bowel and bladder problems and even learning disabilities. MOD says there are three common forms of spina bifida:

• Occulta - the mildest form, in which there is a small gap or malformation in one or more of the vertebrae of the spine. In many cases, there is no nerve damage or symptoms. In other cases, however, even if there are no problems evident early on, subtle, progressive neurologic deterioration may develop in later years.
• Meningocele - the rarest of these three, in which the meninges (the protective membranes covering the spinal cord) protrudes through an opening in the spine. Because it does not involve the spinal cord itself, meningocele can usually be treated surgically and without paralysis, allowing children to develop normally. However, affected children can develop hydrocephalus and bowel or bladder problems.
• Myelomeningocele - the most severe form, in which the spinal cord and meninges protrude from a spinal opening. Surgery (Read about "Neurosurgery") is generally performed within 24 hours after birth to put the exposed nerves and cord back into the spinal canal and prevent further damage, according to NINDS. However, the nerve damage that has occurred is permanent and paralysis and bowel and bladder problems usually remain.

There is no cure for spina bifida because the damaged nerves cannot be replaced or repaired. The prognosis for those with spina bifida depends largely on the number and severity of abnormalities, according to NINDS. The outlook is poorest for those with complete paralysis, hydrocephalus and other problems. However, with today's advanced medical techniques, many children with the more severe forms of spina bifida are living into adulthood.

In cases where spina bifida has caused problems, treatment may include surgery, medication, physical therapy (Read about "Rehabilitation") and other types of care. Many of those affected will need assistive devices such as wheelchairs, crutches or braces. Continual treatment may be necessary throughout an individual's life to manage and prevent complications of the disorder.

One main complication of spina bifida is hydrocephalus, or fluid on the brain. When the fluid that normally surrounds and cushions the brain cannot drain properly - in this case because the spina bifida abnormality blocks the fluid's normal path - the excess builds up putting pressure on the brain. MOD says that about 90 percent of children with severe spina bifida will develop hydrocephalus. This serious condition can usually be treated with surgery to place a special tube called a shunt in the body. The shunt runs under the skin, redirecting the fluid and passing it harmlessly into the chest or abdomen, where it is reabsorbed by the body.

The nerve damage caused by spina bifida leaves most children with weakened muscles and usually some degree of paralysis. Many will require a wheelchair; however, studies show that 70 percent can eventually walk with or without leg braces or crutches, according to the MOD. Affected children may also suffer stiff joints and some are born with abnormalities of the hips, knees and feet. Surgery can correct some of these problems, while physical therapy can help the joints and weak muscles.

Bowel and bladder problems (Read about "The Urinary System") also frequently result from spina bifida. Often the nerves that control these functions are among those damaged. Children may be more likely to develop urinary tract infections, suffer kidney damage (Read about "Urinary Tract Infections" "Kidney Disease") and be unable to have control of their bowels. Special techniques, some medication and dietary management can help manage these problems.

SBAA lists other secondary problems that may result from spina bifida including:

• latex allergy (Read about "Latex Allergy")
• tendinitis (Read about "Tendinitis and Bursitis")
• obesity (Read about "Obesity")
• gastrointestinal disorders (Read about "Digestive System")
• learning disabilities
• social and sexual issues

See risk factors and testing below.

Anencephaly

Anencephaly is the most severe of the neural tube defects. It is rare and it is fatal. Babies with anencephaly have underdeveloped brains (Read about "The Brain") and incomplete skulls and most do not survive more than a few hours after birth. According to the National Institute of Neurological Disorders and Stroke (NINDS), anencephaly occurs when the "cephalic" or head end of the neural tube fails to close, resulting in the absence of a major portion of the brain, skull and scalp. Infants are born without a forebrain and a cerebrum (the thinking part of the brain). A baby born with this disorder is usually blind, deaf, unconscious and unable to feel pain. While some reflex actions, breathing and response to sound or touch, may occur, the lack of a cerebrum means the baby will never gain consciousness. If the infant is not stillborn, then he or she will only live a few hours or days after birth.

The cause of anencephaly is unknown. However, studies have shown that genetics and environment (Read about "Genetics"), along with a mother's diet and vitamin intake may play a role. (Read about "Vitamins & Minerals") In particular, research indicates that adding folic acid to a mother's diet may reduce the chance of neural tube defects. More about the benefits of folic acid will be discussed later.

See risk factors and testing below.

Encephaloceles

Encephaloceles are rare neural tube defects that result in abnormal openings in the skull through which brain tissue protrudes. (Read about "The Brain") Encephaloceles are often accompanied by deformities of the skull or face and/or other brain malformations. Symptoms may include hydrocephalus (fluid on the brain) (Read about "Hydrocephalus"), spastic quadriplegia (paralysis of all four limbs), developmental delay, vision problems, mental and growth retardation and seizures (Read about "Seizures"), according to NINDS.

The prognosis for babies with this disorder varies. It depends on what brain tissue is involved and the accompanying brain malformations and symptoms, according to NINDS. While most babies with encephaloceles do not survive or are severely retarded, early surgery has helped some children. (Read about "Neurosurgery") Generally, surgery is performed during infancy to put the protruding brain tissue back into the skull and correct any craniofacial abnormalities. (Read about "Craniofacial Disorders") Hydrocephalus may require a shunt to drain fluid. Other treatments would depend on additional symptoms.

See risk factors and testing below.

Risk Factors and Testing

While the cause of spina bifida and other NTDs remains unknown, scientists believe that genetic factors may play a part. Those who do have a family history (Read about "Family Health History") are at increased risk of having a child with an NTD. This includes couples that have a child with spina bifida, couples in which one or both parents have spina bifida themselves, or ones who have already had a pregnancy affected by any neural defect. Women with certain chronic health problems, including diabetes (Read about "Diabetes") and seizure disorders (Read about "Seizures"), also have an increased risk of having a baby with an NTD. However, MOD says 90 to 95 percent of babies with NTDs are born to parents with no family history of these disorders.

Another key risk factor for neural tube defects is an insufficient level of folic acid (vitamin B9). According to MOD, studies show that if all women in the U.S. took enough of the B vitamin folic acid every day before and during early pregnancy, up to 70 percent of neural tube defects could be prevented. (Read about "Vitamins & Minerals")

The U.S. Department of Health and Human Services says pregnant women or women who are thinking of getting pregnant should consume 400 micrograms (mcg) per day of synthetic folic acid (from fortified foods and/or supplements) in addition to food forms of folate from a varied diet. Natural folic acid can be found in leafy green vegetables such as broccoli and spinach, orange juice, egg yolks, beans and fortified breakfast cereals. (Read about "Pregnancy and Nutrition")

The Food and Drug Administration recommended that cereal grains be fortified with folic acid starting in 1996 and required it starting in 1998. The National Center for Health Statistics reports that the rate of SB started to decline in 1996 and continued down until leveling off at the turn of the century. The case for folic acid was even more dramatic with anencephalus, with the rate starting to drop in 1998 and continuing downward through the latest surveys.

Women who are at higher risk for having a child with an NTD may need a higher dose of folic acid daily, and can talk to their doctor about a prescription. It also helps to plan a pregnancy ahead of time. This way, a woman can be sure she has enough folic acid in her system before and during the early weeks of pregnancy before the neural tube closes.

If you and your doctor feel you are at risk, there are tests than can detect NTDs before birth. First is a blood test called the maternal serum alpha fetoprotein (MSAFP) test, part of the "triple screen" test. (Read about "Laboratory Testing") If it comes back with a high result, two additional tests can be performed. These are an ultrasound (Read about "Ultrasound Imaging") of the fetal spine and amniocentesis, which measures the levels of alpha fetoprotein in the amniotic fluid. (Read about "Pregnancy Testing")

Diagnosing NTD before birth means that doctors can provide the parents with information and support. They can also plan for delivery in a special medical center so the infant can get immediate treatment after birth. According to MOD, one study found that cesarean delivery prior to labor may reduce the severity of paralysis in babies with spina bifida. If a baby is diagnosed before birth, the parents and doctor could discuss a planned cesarean delivery. (Read about "Childbirth")

Related Information:

    Birth Defects

    Healthy Pregnancy