Spina Bifida

Spina bifida, like all neural tube defects, is a disorder involving incomplete development of the brain, spinal cord, and/or their protective coverings. It is caused by the failure of the fetus's spine to close properly during the first month of spinal cord. Spina bifida, which literally means “cleft spine,” is the most common neural tube defect in the United States—affecting 1,500 to 2,000 of the more than 4 million babies born in the country each year.

Drawing of a child with spina bifida. Source: Wikimedia Commons.

Types

Spina bifida has four types: occulta, meningocele, and myelomeningocele are the closed neural tube defects, while rachischisis is an open neural tube defect.

Closed neural tube defects are characterized by a diverse group of spinal defects in which the spinal cord is marked by a malformation of fat, bone, or membranes. In some patients, there are few or no symptoms; in others, the malformation causes incomplete paralysis with urinary and bowel dysfunction.

Occulta is the mildest and most common form in which one or more vertebrae are malformed. The name “occulta,” which means “hidden,” indicates that the malformation, or opening in the spine, is covered by a layer of skin. This form of spina bifida rarely causes disability or symptoms.

With the meningocele, the meninges protrude from the spinal opening but the spinal cord remains in the vertebral canal, which is the opening in the spinal column holding the spinal cord, and the malformation may or may not be covered by a layer of skin. Some patients with meningocele may have few or no symptoms, whereas others may experience a more severe set of symptoms.

Myelomeningocele is the most severe of the closed neural tube defects. It occurs when the spinal cord covered in the meninges is outside the vertebral canal and results in partial or complete paralysis of the parts of the body below the spinal opening. The paralysis may be so severe that the affected individual is unable to walk and may have urinary and bowel dysfunction.

The most severe form of spina bifida is Rachischisis, which is an open neural tube defect. This condition occurs because the neural tube does not close and is open to the skin. It is quite commonly associated with craniorachischisis or total dysraphism, which is a complete open neural tube from the head to the pelvis, and anencephaly. This form is usually not compatible with life.

Symptoms

Infants born with spina bifida sometimes have an open lesion on their spine where significant damage to the nerves and spinal cord has occurred. Although the spinal opening can be surgically repaired shortly after birth, the nerve damage is permanent, resulting in varying degrees of paralysis of the lower limbs. Even when there is no lesion present, there may be improperly formed or missing vertebrae and accompanying nerve damage. In addition to physical and mobility difficulties, many individuals have some form of learning disability. Spina bifida may also cause bowel and bladder complications, and many children with spina bifida have hydrocephalus (excessive accumulation of cerebrospinal fluid in the brain).

The symptoms of spina bifida vary from person to person, depending on the type. Often, individuals with occulta have no outward signs of the disorder. Closed neural tube defects are often recognized early in life due to an abnormal tuft or clump of hair or a small dimple or birthmark on the skin at the site of the spinal malformation.

Meningocele and myelomeningocele are generally characterized by a fluid-filled sac—visible on the back—protruding from the spinal cord. In meningocele, the sac may be covered by a thin layer of skin, whereas in most cases of myelomeningocele, there is no layer of skin covering the sac and a section of spinal cord tissue is usually exposed.

Causes

Schematic of neural tube closure. Source: Wikimedia Commons.

The human nervous system develops from a small, specialized plate of cells along the back of an embryo. Early in development, the edges of this plate begin to curl up toward each other, creating the neural tube—a narrow sheath that closes to form the brain and spinal cord of the embryo. As development progresses, the top of the tube becomes the brain and the remainder becomes the spinal cord. This process is usually complete by the 28th day of pregnancy. Spina bifida, and other neural tube defects, result from problems during this process.

The exact cause of spina bifida still under investigation. At this time, scientists are beginning to understand how the closure of the neural tube is induced and completed by the various signaling molecules. Scientists suspect a number of genetic, nutritional, and environmental factors play a role. Research studies indicate that insufficient intake of folic acid—a common B vitamin—in the mother’s diet is a key factor in causing spina bifida and other neural tube defects. Prenatal vitamins that are prescribed for the pregnant mother typically contain folic acid as well as other vitamins.

Diagnosis

In most cases, spina bifida is diagnosed prenatally, or before birth. However, some mild cases may go unnoticed until after birth, or postnatally. Very mild cases, in which there are no symptoms, may never be detected.

Prenatal diagnosis

The most common screening methods used to look for spina bifida during pregnancy are second trimester maternal serum alpha-fetoprotein (MSAFP) screening and fetal ultrasound. The MSAFP screen measures the level of a protein called alpha-fetoprotein (AFP), which is made naturally by the fetus and placenta. During pregnancy, a small amount of AFP normally crosses the placenta and enters the mother’s bloodstream. But if abnormally high levels of this protein appear in the mother’s bloodstream, it may indicate that the fetus has a neural tube defect. The MSAFP test, however, is not specific for spina bifida, and the test cannot definitively determine that there is a problem with the fetus. If a high level of AFP is detected, additional tests may be performed, such as an ultrasound or amniocentesis.

The second trimester MSAFP screen may be performed alone or as part of a larger, multiple-marker screen. Multiple-marker screens look not only for neural tube defects, but also for other birth defects, including Down syndrome and other chromosomal abnormalities. First trimester screens for chromosomal abnormalities also exist, but signs of spina bifida are not evident until the second trimester when the MSAFP screening is performed.

Amniocentesis—an exam in which the doctor removes samples of fluid from the amniotic sac that surrounds the fetus—may also be used to diagnose spina bifida. Although amniocentesis cannot reveal the severity of spina bifida, finding high levels of AFP may indicate that the disorder is present.

Postnatal diagnosis

Mild cases of spina bifida not diagnosed during prenatal testing may be detected postnatally by X-ray during a routine examination. Doctors may use magnetic resonance imaging (MRI) or a computed tomography (CT) scan to get a clearer view of the spine and vertebrae. Individuals with the more severe forms of spina bifida often have muscleweakness in their feet, hips, and legs. If hydrocephalus is suspected, the doctor may request a CT scan and/or X-ray of the skull to look for extra fluid inside the brain.

Treatment

Treatments of spina bifida include surgery, medication, and physical therapy (physiotherapy). Many individuals with spina bifida need assistive devices such as braces, crutches, or wheelchairs. Ongoing therapy, medical care, and/or surgical treatments may be necessary to prevent and manage complications throughout the individual's life. Surgery to close the newborn's spinal opening is generally performed within 24 hours after birth to minimize the risk of infection and to preserve existing function in the spinal cord.

Treatment depends on the type and severity of the disorder. Generally, children with the mild form need no treatment, although some may require surgery as they grow.

Surgery

The priorities for treating myelomeningocele are to prevent infection from developing through the exposed nerves and tissue of the defect on the spine, and to protect the exposed nerves and structures from additional trauma. Typically, a child born with spina bifida has surgery to close the defect and prevent infection or further trauma within the first few days of life.

Some children need subsequent surgeries to manage problems with the feet, hips, or spine. Individuals with hydrocephalus generally require additional surgeries to replace the shunt, which can be outgrown or become clogged.

Experimental surgery

Doctors are beginning to perform fetal surgery as treatment of myelomeningocele. Fetal surgery is performed in utero (within the uterus). It involves opening the mother’s abdomen and uterus in order to close the opening over the developing baby’s spinal cord. Some doctors believe the earlier the defect is corrected, the better the outcome is for the baby. Although the procedure cannot restore lost neurological function, it may prevent additional loss from occurring. However, the surgery is considered experimental and risks to both the mother and fetus still exist.

The major risks to the fetus of this experimental surgery are complications from premature birth. These complications include organ immaturity, brain hemorrhage, and death. Risks to the mother include infection, blood loss with the need for blood transfusion, gestational diabetes, and weight gain due to bed rest.

Still, fetal surgery is promising. One benefit is that the vulnerable spinal nerve tissue and bones of the developing fetus are not exposed to the toxic amniotic fluid. As an added benefit, doctors have discovered that the procedure allows certain complications, such as Chiari II malformation with associated hydrocephalus, to correct themselves. This can reduce or even eliminate the need to implant a shunt.

Therapies

Some individuals with spina bifida require assistive devices such as braces, crutches, or wheelchairs. The location of the malformation on the spine often indicates the type of assistive devices needed. Children with a defect high on the spine and more extensive paralysis often require a wheelchair, while those with a defect lower on the spine may be able to use crutches, bladder catheterizations, leg braces, or walkers.

Treatment for paralysis and bladder and bowel problems typically begins soon after birth, and may include special exercises for the legs and feet to help prepare the child for walking with braces or crutches when he or she is older.

Cures

Spina bifida has no cure. The nerve tissue that is damaged or lost cannot be repaired or replaced, nor can function be restored to the damaged nerves.

Prevention

Folic acid, also called folate, is a vitamin that contributes to the healthy development of the fetus. Studies have shown that folic acid supplementation to women of child bearing age reduces the risk of having a child with spina bifida. Therefore, it is recommended that all women of childbearing age consume 400 micrograms of folic acid daily. Foods high in folic acid include dark green vegetables, egg yolks, and some fruits. Many foods—such as some breakfast cereals, enriched breads, flours, pastas, rice, and other grain products—are now fortified with folic acid. A lot of multivitamins contain the recommended dosage of folic acid as well.

Women, who know they are pregnant, should be taking 4000 micrograms of folic acid daily and maintain this level until the neural tube closes 28 days after fertilization.

Women who have a child with spina bifida, have spina bifida themselves, or have already had a pregnancy affected by any neural tube defect, are at greater risk of having a child with a neural tube defect. These women may require more folic acid before they become pregnant.

Living with Spina Bifida

Spina bifida is a lifelong disease that requires lifestyle modifications. The person with spina bifida can learn to cope with the disease with help from family and friends.

Lifestyle changes

Depending on the nature of the condition, a variety of lifestyle changes need to be made. This may include using assistive devices like wheelchairs or walkers, using catheters to empty the bladder, or other adjustments. People with spina bifida need to avoid latex, because of the frequency of allergies seen in this population. The Spina Bifida Association provides more information on living with spina bifida.

Caring for someone with spina bifida

Children with spina bifida often require support from a caregiver for assistance with multiple activities. Caregivers may need to learn how to catheterize the child.

Long-term care

People with spina bifida generally need lifelong medical care to help avoid and treat complications that can develop. The Spina Bifida Association publishes guidelines for young people and guidelines for adults with spina bifida.

Chances of Developing Spina Bifida

According to the Centers for Disease Control and Prevention (CDC), spina bifida affects about 1,300 babies per year.^[1]

Risk factors

According to the American College of Obstetrics and Gynecology, 95% of babies born with spina bifida are born to families without a history of these disorders.^[2] Risk factors for spina bifida include having previously had a child with a neural tube defect^[1] Women who are obese, have diabetes, or who use certain anti-seizure medications are at increased risk of having a child with spina bifida.^[1]

Genetics

Statistics show that a couple with one child with spina bifida has about a 4 percent chance of having another affected child. A couple with two affected children has about a 10 percent chance. When one parent has spina bifida, there is about a 4 percent chance of having a baby with spina bifida.^[1]

Hispanics and Caucasians are more likely to have a child with spina bifida than African Americans, Ashkenazi Jews, or most Asian ethnic groups.^[1]

Related Problems

Complications of spina bifida can range from minor physical problems to severe physical and mental disabilities. It is important to note, however, that most people with spina bifida are of normal intelligence. Severity is determined by the size and location of the malformation, whether or not skin covers it, whether or not spinal nerves protrude from it, and which spinal nerves are involved. Generally all nerves located below the malformation are affected. Therefore, the higher the malformation occurs on the back, the greater the amount of nerve damage and loss of muscle function and sensation.

In addition to loss of sensation and paralysis, another neurological complication associated with spina bifida is Chiari II Malformation|Chiari II malformation—a rare condition (but common in children with myelomeningocele) in which the brainstem and the cerebellum, or rear portion of the brain, protrude downward into the spinal canal or neck area. This condition can lead to compression of the spinal cord and cause a variety of symptoms, including choking, arm stiffness, and difficulties with feeding, swallowing, and breathing.

Chiari II malformation may also result in a blockage of cerebrospinal fluid, causing a condition called hydrocephalus, which is an abnormal buildup of cerebrospinal fluid in the brain. Cerebrospinal fluid is a clear liquid that surrounds the brain and spinal cord. The buildup of fluid puts damaging pressure on the brain. Hydrocephalus is commonly treated by surgically implanting a shunt—a hollow tube—in the brain to drain the excess fluid into the abdomen.

Some newborns with myelomeningocele may develop meningitis, an infection in the meninges. Meningitis may cause brain injury and can be life-threatening.

Children with both myelomeningocele and hydrocephalus may have learning disabilities, including difficulty paying attention, problems with language and reading comprehension, and trouble learning math.

Many children with myelomeningocele develop a condition called progressive tethering, or tethered cord syndrome, in which their spinal cords become fastened to an immovable structure, such as overlying membranes and vertebrae, causing the spinal cord to become abnormally stretched and the vertebrae elongated with growth and movement. This condition can cause loss of muscle function to the legs, bowel, and bladder. Early surgery on the spinal cord may allow the child to regain a normal level of functioning and prevent further neurological deterioration.

Additional problems such as latex allergies, skin problems, gastrointestinal conditions, and depression may occur as children with spina bifida get older.

Clinical Trials

ClinicalTrials.gov lists government-sponsored clinical trials on spina bifida here.

Research

Within the Federal Government, the National Institute of Neurological Disorders and Stroke (NINDS), a component of the National Institutes of Health (NIH), supports and conducts research on brain and nervous system disorders, including spina bifida. NINDS conducts research in its laboratories at the NIH in Bethesda, Maryland, and supports research through grants to major medical institutions across the country.

In one study supported by NINDS, scientists are looking at the hereditary basis of neural tube defects. The goal of this research is to find the genetic factors that increase susceptibility. Lessons learned from this research will fill in gaps of knowledge about the causes of neural tube defects and may lead to ways to prevent these disorders. These researchers are also studying gene expression during the process of neural tube closure, which will provide information on the developing nervous system.

In addition, NINDS-supported scientists are working to identify, characterize, and evaluate genes for neural tube defects. The goal is to understand the genetics of neural tube closure, and to develop information that will translate into improved clinical care, treatment, and genetic counseling.

Other scientists are studying genetic risk factors for spina bifida, especially those that diminish or lessen the function of folic acid in the mother during pregnancy. This research will shed light on how folic acid prevents spina bifida and may lead to improved forms of folate supplements.

Genetic research has already found associations between several genes and spina bifida. A study published in 2008 described the association between spina bifida and genes for glucose (a form of sugar) metabolism. The study stresses the importance of glucose and weight control during pregnancy in reducing the risk of having a child with spina bifida.^[3]

NINDS also supports and conducts a wide range of basic research studies to understand how the brain and nervous system develop. These studies contribute to a greater understanding of neural tube defects, and offer hope for new avenues of treatment for and prevention of these disorders.

Management of myelomeningocele study (MOMS)

Another component of the NIH, the National Institute of Child Health and Human Development (NICHD), is conducting a large 5-year study to determine if fetal surgery to correct spina bifida in the womb is safer and more effective than the traditional surgery. Researchers hope this study, called the Management of Myelomeningocele Study, or MOMS, will better establish which procedure, prenatal or postnatal, is best for the baby.

Expected Outcome

Children with spina bifida can lead relatively active lives. Prognosis depends on the number and severity of abnormalities and associated complications. Most children with the disorder have normal intelligence and can walk, usually with assistive devices. If learning problems develop, early educational intervention is helpful.

Prognosis is poorest for those with complete paralysis, hydrocephalus, and other congenital defects. With proper care, most children with SB live well into adulthood.

Survival rates

Most children with spina bifida have normal life spans.^[1]

Epidemiology

Incidence

According to the CDC, the rate of spina bifida in 2005, 17.96 per 100,000 live births, was the lowest ever reported.^[4]

Interesting Facts

A list of famous people with spina bifida is published on the Children and Adults with Spina Bifida Web site.

Social Issues

Controversy exists over prenatal diagnosis of conditions such as spina bifida, because many chose pregnancy termination.^[5] Ethical arguments have been made over the validity of using prenatal diagnosis to terminate a pregnancy because the fetus is thought to have a disability.^[6][7]

Public Health

In 1992, the U.S. Public Health Service recommended that women of childbearing age increase consumption of folic acid to 400 micrograms to reduce spina bifida and anencephalus. This recommendation occurred after previous research suggested women with high risk factors (i.e. a previous pregnancy with a neural tube defect) should take 4000 micrograms folic acid. In 1996, the U.S. Food and Drug Administration authorized that all enriched cereal grain products be fortified with folic acid. Optional fortification started in March 1996 and mandatory fortification in January 1998.

References

1. ↑ ^{1.0 1.1 1.2 1.3 1.4 1.5} March of Dimes Foundation Web site. Quick References and Fact Sheets: Spina Bifida
2. ↑ American College of Obstetrics and Gynecology Neural Tube Defects
3. ↑ Davidson CM, Northrup H, King TM, et al. Genes in glucose metabolism and association with spina bifida. Reprod Sci. 2008 Jan;15(1):51-8. Abstract | Press Release
4. ↑ Mathews TJ. Centers for Disease Control and Prevention Web site. Trends in Spina Bifida and Anencephalus in the United States, 1991-2005
5. ↑ Mansfield C, Hopfer S, Marteau TM. Termination rates after prenatal diagnosis of Down syndrome, spina bifida, anencephaly, and Turner and Klinefelter syndromes: a systematic literature review. European Concerted Action: DADA (Decision-making After the Diagnosis of a fetal Abnormality). Prenat Diagn. 1999 Sep;19(9):808-12. Abstract
6. ↑ McMahan J. Is Prenatal Genetic Screening Unjustly Discriminatory? Virtual Mentor. January 2006, Volume 8, Number 1: 50-52. Full Text
7. ↑ Wasserman D and Asch A. The Uncertain Rationale for Prenatal Disability Screening. Virtual Mentor. January 2006, Volume 8, Number 1: 53-56. Full Text

External Links

National Institute of Neurological Disorders and Stroke: Spina Bifida Fact Sheet

March of Dimes Foundation: Quick References and Fact Sheets: Spina Bifida

Spina Bifida Association

National Dissemination Center for Children with Disabilities

Disabled Sports USA

National Organization for Rare Disorders

eMedicine Spina Bifida

U.S. Public Health Service and Centers for Disease Control Folic Acid and Prevention of Spina Bifida and Anencephaly