Spina bifida

Definition

Spina bifida is a serious birth defect that occurs when the tissue surrounding the developing spinal cord of a fetus doesn't close properly.

Spina bifida is part of a group of birth defects called neural tube defects. The neural tube is the embryonic structure that eventually develops into the baby's brain and spinal cord and the tissues that enclose them. In babies with spina bifida, a portion of the neural tube fails to develop or close properly, causing defects in the spinal cord and in the bones of the backbone.

Spina bifida is one of the more common birth defects in the United States. When treatment for spina bifida is necessary, it's done through surgery, although such treatment doesn't always completely resolve the problem.

Symptoms

Spina bifida occurs in three forms, each varying in severity:

• Spina bifida occulta. This mildest form results in a small separation or gap in one or more of the vertebrae of the spine. Because the spinal nerves usually aren't involved, most children with this form of spina bifida have no signs or symptoms and experience no neurological problems.

  An abnormal tuft of hair, a collection of fat, a small dimple or a birthmark on the newborn's skin above the spinal defect may be the only visible indication of the condition. In fact, most people who have spina bifida occulta don't even know it, unless the condition is discovered during an X-ray for unrelated reasons.

• Meningocele. In this rare form, the protective membranes around the spinal cord (meninges) push out through the opening in the vertebrae. Because the spinal cord develops normally, these membranes can be removed by surgery with little or no damage to nerve pathways.

• Myelomeningocele. Also known as open spina bifida, myelomeningocele is the most severe form — and the form people usually mean when they use the term "spina bifida."

  In myelomeningocele, the baby's spinal canal remains open along several vertebrae in the lower or middle back. Because of this opening, both the membranes and the spinal cord protrude at birth, forming a sac on the baby's back. In some cases, skin covers the sac. Usually, however, tissues and nerves are exposed, making the baby prone to life-threatening infections.

  Neurological impairment — often including loss of movement (paralysis) — is common. So are bowel and bladder problems, seizures and other medical complications.

Myelomeningocele is a severe form of spina bifida, in which the membranes and the spinal cord protrude at birth, forming a sac on the baby's back. Exposed nerves and muscles may become infected, so prompt surgery is needed after birth.

Causes

The neural tube is the embryonic structure that eventually develops into the baby's brain and spinal cord and the tissues that enclose them. In normal circumstances, the neural tube forms in the developing baby early in the pregnancy and closes by the 28th day after conception. Later, the top of this tube becomes the baby's brain, and the remainder of the tube becomes the baby's spinal cord.

Doctors aren't certain why neural tubes don't develop or close properly in some babies. As with many other problems, it appears to result from a combination of genetic and environmental risk factors, such as a family history of neural tube defects, folic acid deficiency, and medical conditions such as diabetes and obesity.

At 21 days after conception (left drawing), folds of tissue on the back of a developing embryo are rapidly growing together (see arrows) to form the neural tube. Just a day later (center drawing), the growth is almost complete. If the tissue fails to close completely (right drawing), development of the spine, muscle and skin in this region is affected and the baby will be born with spina bifida.

Risk factors

Although doctors and researchers don't know for sure why spina bifida occurs, they have identified a few risk factors:

• Race. Spina bifida is more common among Hispanics and whites of Northern European descent.
• Sex. More female babies are born with spina bifida.
• Family history of neural tube defects. Couples who've had one child with a neural tube defect have a slightly higher chance of having another baby with the same defect. That risk increases if two previous children have been affected by the condition. In addition, a woman who was born with a neural tube defect, or who has a close relative with one, has a greater chance of giving birth to a child with spina bifida. However, most babies with spina bifida are born to parents with no known family history of the condition.
• Folic acid deficiency. This vitamin is important to the healthy development of a fetus. Lack of folic acid (vitamin B-9) increases the risk of spina bifida and other neural tube defects.
• Some medications. Anti-seizure medications, such as valproic acid (Depakene), seem to cause neural tube defects when taken during pregnancy, perhaps because they interfere with the body's ability to use folic acid.
• Diabetes. The risk of spina bifida increases with diabetes, especially when the mother's blood sugar is elevated early in her pregnancy. Careful blood sugar control and management can decrease this risk.
• Obesity. There's a link between pre-pregnancy obesity and neural tube birth defects, including spina bifida. Exactly why obese women have an increased risk of having a baby with spina bifida isn't known, but is possibly because of nutritional deficits from poor eating habits or because they may have diabetes — another known risk factor for neural tube defects.
• Increased body temperature. Some evidence suggests that increased body temperature (hyperthermia) in the early months of pregnancy may increase the risk of spina bifida. Elevating your core body temperature by about 2 degrees Celsius — about 3 to 4 degrees Fahrenheit above normal — due to fever or the use of saunas and hot tubs, which can raise body temperature, have been associated with increased risk of spina bifida.

When to seek medical advice

Before or during pregnancy
If you're a woman planning to start a family, talk to your doctor about taking a daily prenatal multivitamin containing 1 milligram (mg) of the B vitamin folic acid. Because folic acid plays a vital role in fetal development, the majority of cases of spina bifida could be prevented if all women took enough folic acid every day before and during early pregnancy.

If you have known risk factors for spina bifida, talk with your doctor to determine if you should take a larger dose of prescription folic acid, even before a pregnancy begins. If you take medications, tell your doctor. Some medications can be adjusted to diminish the potential risk of spina bifida, if plans are made ahead of time.

After your child is born
If your baby is born with myelomeningocele, you'll likely need to consult with a multidisciplinary team of physicians, surgeons and therapists at a center that specializes in spina bifida treatment. Children with myelomeningocele require ongoing medical attention throughout their lives to monitor their condition and treat complications.

Tests and diagnosis

If you're pregnant, you'll be offered prenatal screening tests to check for spina bifida and other birth defects. The tests aren't perfect. Even if the results are negative, there's still a small chance that spina bifida is present, and most mothers who have positive blood tests have normal babies. Talk to your doctor about prenatal testing, its risks and how you might handle the results. Prenatal testing is a personal choice.

Blood tests
The primary test used to check for myelomeningocele is the maternal serum alpha-fetoprotein (MSAFP) test. To perform this test, your doctor draws a blood sample to be sent to a laboratory, where it's tested for alpha fetoprotein (AFP) — a protein that's produced by the fetus. It's normal for a small amount of AFP to cross the placenta and enter the mother's bloodstream, but abnormally high levels of AFP may indicate that the fetus has a neural tube defect, most commonly spina bifida or anencephaly, a condition characterized by an underdeveloped brain and an incomplete skull.

Some spina bifida cases don't produce a high level of AFP. On the other hand, when a high level of AFP is found, a neural tube defect is present only a small percentage of the time. Varying levels of AFP can be caused by other factors — including a miscalculation in fetal age or multiple fetuses — so your doctor may order a follow-up blood test for confirmation. If the results are still high, you'll need further evaluation, including an ultrasound examination.

Screening for neural tube defects can be combined with screening for chromosomal abnormalities, but the increasing use of first trimester screening for Down syndrome has diminished the use of this testing strategy. That's because first trimester screening is not a reliable screening test for spina bifida.

Your doctor may pair the MSAFP test with two or three other blood tests, which look for:

• Human chorionic gonadotropin (HCG), a hormone produced in the placenta
• Inhibin A, another hormone produced in the placenta
• Estriol, an estrogen produced by both the fetus and the placenta

Depending on the number of tests, the combination is called a triple or quadruple screen. In addition to checking for neural tube defects, looking at these additional substances can help doctors determine whether chromosome abnormalities are present.

But, the AFP test alone can detect about 80 percent of babies with spina bifida. The test has a false-positive rate of about 5 percent.

Ultrasound
Many obstetricians rely on ultrasonography to screen for spina bifida. If blood tests indicate high AFP levels, your doctor will suggest an ultrasound exam to help determine why. The most common ultrasound exams bounce high-frequency sound waves off tissues in your body to form black and white images on a small video monitor.

The information these images provide can help establish whether there's more than one fetus and can help confirm gestational age — two factors that can alter AFP levels. An advanced ultrasound can also detect signs of spina bifida, such as an open spine or particular features in your baby's brain that indicate spina bifida.

In expert hands, ultrasound today is quite effective in detecting spina bifida and assessing its severity. Ultrasound is safe for both mother and baby.

Amniocentesis
If a blood test shows high levels of AFP in your blood and the ultrasound is normal, your doctor may offer amniocentesis in addition to ultrasound. During amniocentesis, your doctor uses a needle to remove samples of fluid from the amniotic sac that surrounds the fetus. An analysis indicates the level of AFP present in the amniotic fluid.

A small amount of AFP is normally found in amniotic fluid. However, when an open neural tube defect is present, the amniotic fluid contains an elevated amount of AFP because the skin surrounding the baby's spine is gone and AFP leaks into the amniotic sac. A second test can be done on the same sample to reliably confirm that a neural tube defect is present. Amniocentesis can't indicate the severity of spina bifida, however.

This test does have a risk to the developing fetus. About one in 200 to one in 500 pregnant women miscarries after amniocentesis.

During amniocentesis, samples of amniotic fluid are removed using a needle and then tested for genetic abnormalities in the laboratory.

Complications

Spina bifida may occasionally cause only minor physical disabilities. More frequently, it leads to severe physical and mental disabilities. Factors that affect the severity of complications include:

• The size and location of the neural tube defect
• Whether skin covers the affected area
• Whether spinal nerves come out of the affected area of the spinal cord

Complications may include:

• Physical and neurological problems. This may include lack of normal bowel and bladder control, and partial or complete paralysis of the legs.Children and adults with this form of spina bifida might need crutches, braces or wheelchairs to help them get around, depending on the size of the opening and the care received after birth.
• Hydrocephalus. Babies born with myelomeningocele also commonly experience accumulation of fluid in the brain, a condition known as hydrocephalus. Most babies with myelomeningocele will need a shunt — a surgically placed tube that allows fluid in the brain to drain as needed into the abdomen. This tube might be placed just after birth, during the surgery to close the sac on the lower back or later as fluid accumulates.
• Meningitis. Some babies with myelomeningocele may develop meningitis, an infection in the tissues surrounding the brain. Meningitis may cause brain injury and can be life-threatening.

Other complications
Additional problems may arise as children with spina bifida get older. Children with myelomeningocele may develop learning disabilities, including difficulty paying attention, problems with language and reading comprehension, and trouble learning math. Children with spina bifida may also suffer from latex allergies, skin problems, urinary tract infections, gastrointestinal disorders, depression, and social and emotional problems.

Treatments and drugs

Spina bifida treatment depends on the severity of the condition. Spina bifida occulta doesn't require treatment at all, while meningocele involves surgery to put the meninges back in place and close the opening in the vertebrae. This surgery usually occurs soon after birth.

Myelomeningocele also requires surgery, usually within several hours to several days after birth. Performing the surgery early can help minimize risk of infection that's associated with the exposed nerves and may also help protect the spinal cord from additional trauma. During the procedure, a neurosurgeon places the spinal cord and exposed tissue inside the body and covers them with muscle and skin. Sometimes a shunt to control hydrocephalus in the brain is placed during the operation on the spinal cord.

Ongoing care
Treatment doesn't end with the initial surgery, though. In babies with myelomeningocele, irreparable nerve damage has already occurred, and ongoing care from a multidisciplinary team of surgeons, physicians and therapists is usually needed. Paralysis and bladder and bowel problems often remain, and treatment for these conditions typically begins soon after birth. Babies with myelomeningocele may also start exercises that will prepare their legs for walking with braces or crutches when they're older.

In addition, babies with myelomeningocele may require further operations for a variety of complications. Many suffer from a tethered spinal cord — a condition in which the spinal cord is bound to the scar of the closure and is less able to properly grow in length as the child grows. This progressive "tethering" can cause loss of muscle function to the legs, bowel or bladder. Surgery can limit the degree of disability and may also restore some function.

Caesarean birth
Caesarean birth also may be part of the treatment for spina bifida. Many babies with spina bifida are detected before birth, and Caesarean birth is the safest way to deliver these babies. Delivery before labor begins may diminish the degree of damage to the baby's exposed nerves, so most specialists now recommend a Caesarean section. This planned birth has another advantage — it allows a pediatric neurosurgical team to be ready for intervention soon after birth.

Prenatal surgery
Researchers are investigating the effectiveness of prenatal surgery for spina bifida. In this experimental and controversial procedure, which isn't widely available, surgeons expose a pregnant mother's uterus surgically, open the uterus and repair the fetus' spinal cord. The surgery takes place between the 19th and 25th weeks of pregnancy.

Proponents of fetal surgery believe that nerve function in babies with spina bifida seems to worsen rapidly after birth, so it may be better to repair spina bifida defects in utero. So far, children who received the fetal surgery seem to have better brain functioning and fewer shunts, but their bowel and bladder functioning don't seem to be improved. And the operation poses a substantial risk of death to the fetus from an extremely premature delivery.

So, the question remains: Is there a real benefit to repairing myelomeningocele in utero? The National Institute of Child Health & Human Development is conducting a large, long-term clinical trial called the Management of Myelomeningocele Study to try to answer that question. For now, it's unclear whether this risky technique is more effective than is traditional surgery to close the spinal column after birth.

Prevention

Folic acid plays an essential role in a baby's development. When taken in supplement form at least one month before conception and during the first trimester of pregnancy, folic acid greatly reduces the risk of spina bifida and other neural tube defects.

How much folic acid to take
It's critical to have enough folic acid in your system by the early weeks of pregnancy, before the neural tube closes to prevent spina bifida. Because many women don't discover that they're pregnant until this time, the March of Dimes, the Centers for Disease Control and Prevention, and the Institute of Medicine recommend that all women of childbearing age take a daily supplement with 400 micrograms (mcg) of folic acid or consume breakfast cereals fortified with 100 percent (400 mcg) of folic acid per serving. To find out the percentage of Daily Value supplied by a cereal, check its nutrition label. Folic acid may be listed as folate, which is the natural form of folic acid found in food.

Most pregnancy experts believe supplementation of folic acid at a level of 1 milligram (mg) a day — the usual dose in prescription prenatal vitamins — is the best approach for women planning pregnancy. Because high levels of folate can potentially mask a deficiency of vitamin B-12 — which can cause a condition called pernicious anemia, particularly in older adults — supplementation of dietary folic acid for the general population has been kept to a lower dose. But this risk is minimal when folic acid is used specifically while seeking pregnancy.

In addition, eat a healthy diet, including foods rich in folate. This vitamin is present in many foods, including dried beans, citrus fruits, whole-grain products, and dark green vegetables such as broccoli and spinach. However, your body doesn't absorb folate as easily as it absorbs synthetic folic acid, and most people don't get the recommended amount of folate through diet alone, so vitamin supplements are necessary to prevent spina bifida.

It's possible that folic acid will also help reduce the risk of other birth defects, including cleft lip, cleft palate and some congenital heart defects.

When higher doses are needed
If you have spina bifida or if you have a child with spina bifida, you'll need extra folic acid before you become pregnant. If you're taking anti-seizure medications or you have diabetes, you may also benefit from a higher dose of this B vitamin. In these cases, the recommended dose of folic acid may be up to 4,000 mcg (4 mg) beginning one month prior to conception and during the first few months of pregnancy.

If you think you might need this increased amount of folic acid, ask your doctor for a prescription dose of the vitamin. Don't simply take extra multivitamins because the additional amounts of other vitamins may be harmful to you and your baby.

Coping and support

News that a newborn child has a devastating condition such as spina bifida can naturally cause parents to feel grief, anger, frustration, fear and sadness. There's good reason to hope, however, because most people with spina bifida live active and productive lives.

Most children with spina bifida can walk for at least short distances, usually with the assistance of braces, canes or crutches, although they may require wheelchairs for longer distances. Using these devices can help a child compensate for his or her condition and gain more independence.

Many children with spina bifida have normal intelligence. But they may need early educational intervention for learning problems, and they may need extra help from teachers and counselors to adapt to school. A physical disability like spina bifida can also cause emotional and social problems. Children with spina bifida need encouragement to participate in activities with their peers and to lead independent lives, within their physical limitations and capabilities. It may be helpful to remember that these children have never known what's accepted as normal function and often adapt to their condition in remarkable ways.

Support groups
If your child has spina bifida, you may benefit from finding a support group of other parents who are dealing with the condition. Talking with others who understand the challenges — and rewards — of living with spina bifida can be helpful.