Spina Bifida

Spina bifida is the most common of a group of birth defects called neural tube defects (NTDs). The neural tube is the embryonic structure that develops into the brain and spinal cord. Often called open spine, spina bifida affects the backbone and, sometimes, the spinal cord. It is one of the most common severe birth defects in the United States, affecting about 1,300 babies each year (1).

How does spina bifida affect a child?
In the embryo, there is a tiny ribbon of tissue that folds inward to form a tube. This structure, called the neural tube, forms by the 28th day after conception. When this process goes awry and the neural tube does not close completely, defects in the spinal cord and in the vertebrae (small bones of the spine) can result. There are three forms of spina bifida:

• Occulta. In this mildest form, there are usually no symptoms. Affected individuals have a small defect or gap in one or more of the vertebrae of the spine. A few have a dimple, hairy patch, dark spot or swelling over the affected area. The spinal cord and nerves usually are normal, and most affected individuals need no treatment.
• Meningocele. In this rarest form, a cyst or fluid-filled sac pokes through the open part of the spine. The sac contains the membranes that protect the spinal cord, but not the spinal nerves. The cyst is removed by surgery, usually allowing for normal development.
• Myelomeningocele. In this most severe form, the cyst holds both the membranes and nerve roots of the spinal cord and, often, the cord itself. Or there may be no cyst, but only a fully exposed section of the spinal cord and nerves. Affected babies are at high risk of infection until the back is closed surgically, although antibiotic treatment may offer temporary protection. In spite of surgery, affected babies have some degree of leg paralysis and bladder and bowel control problems. In general, the higher the cyst on the back, the more severe the paralysis.

What causes spina bifida?
The causes of spina bifida are not completely understood. Scientists believe that both genetic and environmental factors act together to cause this and other NTDs. However, 95 percent of babies with spina bifida and other NTDs are born to parents with no family history of these disorders (2).

Who is at risk of having a baby with spina bifida?
Anyone can have a baby with spina bifida. However, couples who have already had a baby with spina bifida or another NTD have an increased risk of having another affected baby. A couple with one child with spina bifida usually has about a 4 percent chance, and a couple with two affected children has about a 10 percent chance, of having another affected baby (2). Similarly, when one parent has spina bifida, there is about a 4 percent chance of passing the disorder on to the baby (2). Couples who have had an affected baby or have a family history of NTDs should consult a genetic counselor to discuss risks to their future children.

In most cases, spina bifida occurs by itself. However, sometimes spina bifida occurs as part of a syndrome with other birth defects. In these cases, recurrence risks in another pregnancy may vary widely.

Women with certain health conditions also are at increased risk of having a baby with spina bifida. These include women who are obese, have poorly controlled diabetes or who are treated with certain anti-seizure medications (2, 3). Women with these conditions should consult their health care providers before pregnancy about steps they can take to reduce their risk of having a baby with spina bifida. For example, they may be able to control their diabetes or change anti-seizure medications.

Spina bifida and other NTDs occur more commonly in some ethnic groups than others. For example, NTDs are more common in Hispanics and Caucasians, and less common among Ashkenazi Jews, most Asian ethnic groups and African-Americans (4).

How is spina bifida treated?
Spina bifida occulta usually requires no treatment. Most individuals don't know they are affected, unless the defect is diagnosed during an X-ray for some other reason. Occasionally newborns are diagnosed with this form of spina bifida if they have a dimple or other marking on their back. In some cases, these babies may need to be evaluated for signs of complications that may require treatment.

Meningocele is repaired surgically, and affected babies usually have no paralysis. However, a small number of affected children develop hydrocephalus (fluid on the brain) and bladder problems. Doctors monitor affected children carefully, so that they can treat any complications promptly.

A baby with myelomeningocele usually requires surgery within 24 to 48 hours after birth (2). Doctors surgically tuck exposed nerves and spinal cord back inside the spinal canal and cover them with muscle and skin. Prompt surgery helps prevent additional nerve damage. However, nerve damage that already has occurred cannot be reversed. As soon after surgery as possible, a physical therapist teaches parents how to exercise their baby's legs and feet to prepare for walking with leg braces and crutches. Studies show that about 60 percent of affected children can walk with or without these devices, although many children will require a wheelchair (5). 

What medical problems occur with spina bifida?
Common medical problems include:

• Hydrocephalus. About 70 to 90 percent of children with myelomeningocele develop hydrocephalus (6). When cerebrospinal fluid, which cushions and protects the brain and spinal cord, is unable to circulate normally, fluid collects in and around the brain, causing the head to be enlarged. Without treatment, hydrocephalus can result in brain damage and mental retardation. Doctors usually treat hydrocephalus by surgically inserting a tube called a shunt that drains the excess fluid. The shunt runs under the skin into the chest or abdomen, and the fluid passes harmlessly into the child's body. A newer surgical procedure called endoscopic third ventriculostomy, which creates a new pathway for draining cerebrospinal fluid, may be recommended for some children who are over 6 months of age, including some who experience shunt malfunctions (7). 

• Chiari II malformation. Nearly all children with myelomeningocele have this change in the position of the brain. The lower part of the brain is located further down than normal and is partly displaced into the upper part of the spinal canal. This can block the flow of cerebrospinal fluid and contribute to hydrocephalus. In most cases, affected children have no other symptoms. But a small number develop serious problems, such as breathing and swallowing difficulties and upper body weakness. In these cases, doctors may recommend surgery to relieve pressure on the brain.

• Tethered spinal cord. Most children with myelomeningocele, and a small number with meningocele or spina bifida occulta, have a tethered spinal cord. This means that the spinal cord does not slide up and down with movement as it should, because it is held in place by surrounding tissue. Some children have no symptoms, but others develop leg weakness, worsening leg function, scoliosis (curvature of the spine), pain in the back or legs and changes in bladder function. Doctors usually recommend surgery to release the spinal cord from surrounding tissue. After surgery, a child should return to his or her usual level of functioning.

• Urinary tract disorders. Individuals with myelomeningocele often have problems emptying the bladder completely. This can lead to urinary tract infections and kidney damage. A technique called intermittent catheterization, in which the parent or child inserts a plastic tube into the bladder several times a day, is often helpful. Children with spina bifida should have regular care by a urologist (a doctor who specializes in urinary tract problems) to help prevent urinary tract problems.

• Latex allergy. According to the Spina Bifida Association of America (SBAA), up to 73 percent of children with myelomeningocele are allergic to latex (natural rubber), possibly due to repeated exposures during surgeries and medical procedures (6). Symptoms may include watery eyes, wheezing, hives, rash and even life-threatening anaphylactic reactions. Doctors should use only nonlatex gloves and equipment during any procedures on individuals with spina bifida. Affected individuals and their families should avoid latex items often found in the home and community, such as most baby bottle nipples, pacifiers and balloons. A list of safe and unsafe items is available from the SBAA.

• Learning disabilities. At least 80 percent of children with myelomeningocele have normal intelligence (6). However, some have learning problems.

• Other conditions associated with severe spina bifida include obesity, digestive tract disorders and psychological and sexual issues.

With treatment, children with spina bifida usually can become active individuals. Most live normal or near-normal life spans (8). 

Can spina bifida be prevented?
A B-vitamin called folic acid can help prevent spina bifida and other NTDs. Studies show that if all women in the United States took the recommended amount of folic acid every day before and during early pregnancy, up to 70 percent of NTDs could be prevented (3, 4). The key is having enough folic acid in the system before pregnancy and during the early weeks of pregnancy, before the neural tube closes. The March of Dimes recommends that all women who can become pregnant take a multivitamin containing 400 micrograms of folic acid every day starting before pregnancy, as part of a healthy diet. However, a woman should not take more than 1,000 micrograms (or 1 milligram) without her provider's advice.

A healthy diet should include foods that are fortified with folic acid and foods that contain folate, the natural form of folic acid that is found in foods. Many grain products are fortified with folic acid. This means that a synthetic (manufactured) form of folic acid is added to them. Enriched flour, rice, pasta, bread and cereals are examples of fortified gain products. (Check the label to see if a product is enriched.) Folate-rich foods include leafy green vegetables, dried beans and other legumes, oranges and orange juice.

Women who already have had a baby with spina bifida or another NTD, as well as women who have spina bifida, diabetes or seizure disorders, should consult their health care providers before another pregnancy about the amount of folic acid to take. Studies have shown that taking a ten-fold larger dose of folic acid daily (4 milligrams), beginning at least one month before pregnancy and in the first trimester of pregnancy, reduces the risk of having another affected pregnancy by about 70 percent (2).

Can spina bifida be detected prenatally?
Pregnant women are routinely offered screening tests to help identify fetuses at increased risk of spina bifida. These screening tests include an ultrasound examination and a blood test called the quad screen. The blood test measures the levels of four substances in the mother's blood to identify pregnancies at higher-than-average risk of spina bifida and other NTDs, as well as Down syndrome and certain related birth defects.

If the screening test suggests an increased risk of spina bifida, the health care provider may recommend additional tests that are accurate in detecting severe spina bifida. The tests are a detailed ultrasound examination of the fetal spine and amniocentesis. A detailed ultrasound exam can help determine the seriousness of spina bifida and whether certain complications are present (3). In amniocentesis, the doctor inserts a needle into the woman's uterus to take a small sample of amniotic fluid. The fluid is sent to the lab to measure levels of alpha-fetoprotein (AFP) in the fluid.

What are the benefits of detecting spina bifida before birth?
When spina bifida is diagnosed before birth, health care professionals can provide parents with information and support. They can plan for delivery in a specially equipped medical center so that the baby can have any necessary surgery or treatment soon after birth.

Parents and doctors also can discuss whether a vaginal or cesarean delivery would be best for their baby. Fetuses with myelomeningocele are more likely than other babies to be in a breech (feet-first) position. A cesarean delivery is generally recommended for these babies (2). Some doctors also recommend a cesarean delivery for babies with myelomeningocle who are in a normal head-first position because one study that found that a planned cesarean delivery can reduce the severity of paralysis in affected babies (9). However, several newer studies have not found any reduction in paralysis in babies delivered by cesarean (2).

More than 300 babies have undergone experimental prenatal surgery to repair myelomeningocele before birth (10). This approach is based on the idea that early repair (between the 19th and 25th weeks of pregnancy) may help prevent damage to exposed spinal nerve tissue in the womb and reduce paralysis and other complications. Preliminary results suggest that children who have prenatal surgery may need a shunt less frequently, but their walking ability and bladder and bowel function do not appear to be improved (2, 10). This procedure poses surgery-related risks to mother and baby and puts the baby at high risk of premature delivery. Prematurity increases the risk of health problems during the newborn period and lasting disabilities. Doctors do not yet know whether the benefits of prenatal surgery outweigh these risks.

To try to find out whether prenatal or postnatal surgery is more effective, the National Institute of Child Health and Human Development (NICHD), a part of the National Institutes of Health (NIH), is conducting a study to compare the results of both types of surgery in 200 babies with myelomeningocele (8). Half of the babies will undergo surgery before birth, while the other half will do so shortly after birth. The surgery is being carried out at three major medical centers: Children's Hospital of Philadelphia, the University of California at San Francisco, and Vanderbilt University Medical Center in Nashville, Tenn. More about this study is available at www.spinabifidamoms.com or (866) ASK-MOMS (866-275-6667).

Is the March of Dimes conducting research on spina bifida?
Several March of Dimes grantees are searching for genes that may contribute to spina bifida and other NTDs to develop new ways to prevent these disorders. Others are seeking a better understanding of how folic acid prevents NTDs, to make this treatment even more effective. One grantee is developing programs to prevent behavior and adjustment problems in children and adolescents with spina bifida.

The March of Dimes is a member of the National Council on Folic Acid, an alliance of organizations working to promote the benefits and consumption of folic acid.

Where can families find additional information on spina bifida?
More information is available from: 
Spina Bifida Association of America
4590 MacArthur Boulevard, NW, Suite 250
Washington, DC  20007-4226
(202) 944-3285
(800) 621-3141

References

1. Centers for Disease Control and Prevention. Spina Bifida and Anencephaly Before and After Folic Acid Mandate—United States, 1995-1996 and 199-2000. Morbidity and Mortality Weekly Report, volume 53, number 17, May 7, 2004, pages 362-365.

2. American College of Obstetricians and Gynecologists (ACOG). Neural Tube Defects. ACOG Practice Bulletin, number 44, July 2003.

3. Mitchell, L.E., et al. Spina Bifida. The Lancet, volume 364, November 20, 2004, pages 1885-1895.

4. Centers for Disease Control and Prevention (CDC). Folic Acid Now. Updated 11/05.

5. Mendoza, S.A., and Weinstein, S.L. Physical Examination of the Spine, in Wyszynski (ed.): Neural Tube Defects: From Origin to Treatment, New York City, Oxford University Press, 2006, pages 55-65.

6. Spina Bifida Association of America. About Spina Bifida, accessed 2/28/06.

7. Jallo, G.I., et al. Endoscopic Third Ventriculostomy. Neurosurg Focus, volume 19, number 6, E11, December 2005.

8. Management of Myelomeningocele Study. About Spina Bifida, accessed 2/28/06.

9. Luthy, D.A., et al. Cesarean Section Before the Onset of Labor and Subsequent Motor Function in Infants with Meningomyelocele Diagnosed Antenatally. New England Journal of Medicine, volume 324, 1991, pages 662-666.

10. Bennett, K.A., et al. Fetal Surgery for Myelomeningocele, in Wyszynski, D. (ed.): Neural Tube Defects: From Origin to Treatment. New York City, Oxford University Press, 2006, pages 217-230.

April 2006