Spina bifida

Definition

Spina bifida belongs to a group of disorders known as neural tube defects (NTDs). These all involve problems in the development and closure of the neural tube, a structure in the human fetus that begins forming very early in a pregnancy. The neural tube eventually becomes the spinal column. When the neural tube does not close properly, it can lead to spina bifida, a disruption in the spinal column. Spina bifida occurs to varying degrees of severity, and in various forms.

Description

Spina bifida is also known by the name spinal dysraphism. It generally occurs in two major types. One types is spina bifida cystica or spina bifida aperta, which involves a sac filled with spinal contents along the spine. The other type is spina bifida occulta, in which the spinal cord stays inside the spinal canal and there is no sac.

Spina bifida ranges from having no or mild effects, to having severe effects and a significant impact upon a person's life. Physical symptoms can include weakness of limbs, paralysis, lack of bowel or bladder control, learning problems, hydrocephalus , seizures , central apnea, club-feet, impaired vision, and latex sensitivity.

Depending upon the involvement of the spinal problem, spina bifida can also have psychological and emotional impacts upon the affected person and his or her family.

Demographics

Spina bifida is fairly common; it is thought to occur in about one in 2,000 live births in the United States. NTDs in general occur in about one in 1,000 live births in the United States. Many areas have an even higher prevalence, for somewhat unknown reasons. A population with a higher prevalence for NTDs is the United Kingdom, with an estimated rate of 2.8 per 1,000 live births in the 1970s. A similar study in Ireland at that time estimated the rate to be about 7.1 per 1,000 live births. Through the advent of prenatal screening, prenatal diagnosis, pregnancy management options, and unknown factors the prevalence in the British Isles has fallen somewhat in recent years.

Higher rates of NTDs have been reported in the northwest British Isles, with lower rates in the southeast. In Canada, higher prevalence rates for NTDs have been reported in the eastern region of the country, as compared to the western region. A higher prevalence of NTDs has been seen in China in the provinces north of the Yangtze River, and these may be as much as six times higher than in the southern provinces. Pockets of higher prevalence have also been seen in India, but these do not fit any clear geographic areas or regions.

In the United States, people of Hispanic ancestry have a higher chance for NTDs than other ethnic groups. Conversely, African Americans and some Asians have a lower risk than other ethnic groups. When those with high NTD risks immigrate to other countries, they do not keep their high risk for NTDs. When those with low NTD risks migrate, they tend to maintain their low risk status, as a group.

Spina bifida has been reported in males and females roughly equally.

Causes and symptoms

Spina bifida occurs because the neural tube, around the area of the spine, fails to close during fetal development. A multifactorial cause for this has been assumed, because multiple factors seem to be involved. It may best be described as an interaction between multiple genes and the environment. Many aspects of this interaction are still not well understood. As well, an exact neurological cause for spina bifida has not been identified.

Spina bifida can run in families. Multiple genes may be involved because identical twins, those with the exact same genetics, have been studied at length. Spina bifida also occurs as part of genetic syndromes and chromosome disorders.

Numerous families with NTDs have been studied to help identify recurrence risks. Generally, the risk is 3–5% for a couple to have another child with an NTD if they already have one. If a parent has an NTD, they have a 3–5% chance to have a child with one. If two or more children

already have NTDs, the risk is 6–9% for another one. If an NTD is in other more distant family members, the risk is somewhat higher than the average population, but probably not higher than 0.5%.

Environmental factors are also important in spina bifida. For example, taking the B vitamin folic acid before pregnancy conception has been shown to significantly reduce a woman's risk of having a child with the condition. Additionally, some medications can increase a woman's risk for spina bifida; these include some anti-seizures medications. As it turns out, many of these medications naturally reduce the levels of folic acid in one's body.

Neurological symptoms of spina bifida are varied. Many of them relate back to the early embryo's development, and how spina bifida occurs at this time. Three cell layers develop in the very early embryo; these are the ectoderm, mesoderm, and endoderm. The mesoderm normally sends signals to a region of the ectoderm to make it develop into neural tissue. Eventually, the neural ectoderm folds to form a tube, which runs for most of the length of the embryo. The top of the neural tube eventually forms the brain and top of the spinal column. The bottom of the neural tube eventually forms the lower back and bottom of the spinal column. This happens through very careful and controlled cell movements. The neural tube is usually completed forming by about 18 to 26 days after ovulation.

Failure of the neural tube to close causes spina bifida, and this disrupts the spinal column's structure and functioning. This disruption can be mild, as in spina bifida occulta. It may also be more severe with a large sac or cyst present, as in spina bifida cystica.

In about 80–90% of spina bifida cases, there is a cyst with parts of the spinal cord and spinal wall present. This is called a myelomeningocele (or meningomyelocele). This type of spina bifida can happen in a relatively high or low position on one's back. It often causes problems with bladder and bowel functioning, and sometimes paralysis or limb weaknesses. A neuropathic bladder can sometimes affect kidney functioning as well.

When a developing baby cannot move their limbs well in utero, this sometimes leads to feet and legs that turn inward, or clubfoot. As a result, some children with spina bifida are born with clubfoot.

Myelomeningoceles often cause spinal fluid to not flow properly through the system, and hydrocephalus may be a result. Head ultrasound scans may show hydrocephalus in about 90% of newborns with spina bifida. It is often associated with an Arnold-Chiari malformation , Type II. This occurs when the medulla pushes downward below the foramen magnum, and overlaps the spinal cord. This malformation is present in about 70% of people who have a meningomyelocele; it can cause distortion of the medulla and midbrain, as well as central apnea.

Hydrocephalus can eventually cause increased pressure to develop in the brain. This may ultimately lead to one's brain not being able to grow properly, and cause learning problems. Seizures may also be present. Learning problems are not a certainty with spina bifida, but when present they vary greatly. Their severity is impossible to predict. However, hydrocephalus and seizures put one at a higher risk for learning problems. Surveys on intellectual development have shown that children with hydrocephalus have lower IQs than their siblings without the condition.

In about 5% of spina bifida cases, there is no spinal tissue in the cyst wall; these are called meningoceles. Hydrocephalus is not usually present in this type of spina bifida, and a neurological examination may even be perfectly normal.

Optic atrophy and squinting may occur in people who have spina bifida, and a result of these may be poorer vision.

There is an association between spina bifida and latex sensitivity. Many have attributed this to the fact that people with the condition have a higher exposure to latex, since they may be in hospitals more often. Interestingly, a study in 2000 showed that 22% of children with spina bifida still had latex sensitivity, despite efforts to maintain latex-free environments for them.

Spina bifida occulta may cause mild symptoms, or none at all. Sometimes the only signs of it may in the lower spine area as a dimple, a small tuft of hair, or a small growth. If one has an imaging scan and a tethered spinal cord is noted, this can sometimes be a sign of spina bifida occulta as well.

Diagnosis

A early time to find spina bifida is during a detailed prenatal ultrasound scan, especially between 16 and 20 weeks gestation (from the last menstrual period). Ultrasounds cannot identify every structural problem in a developing baby, so some cases of spina bifida (especially mild forms) may be missed. However, it is a risk-free method to use that gives immediate results.

Prenatal blood screening is often offered to women between 15 and 21 weeks in a pregnancy. This screening measures the levels of various chemicals naturally found in a mother's blood, including alpha-fetoprotein (AFP). For this reason, the screening is often called AFP screening. AFP is a protein normally made by a developing fetus, so it is naturally present in maternal serum and called MSAFP. When a fetus has spina bifida, the levels of MS-AFP may be higher than usual because it leaks out of the hole in the spine. If a woman's AFP screen comes back abnormal with a high MS-AFP value, she often is at a higher risk for having a baby with spina bifida. This may prompt her physician to offer her a detailed ultrasound, as well as other medical options that might give her more information about the baby.

One option to find spina bifida is a procedure called amniocentesis. Amniocentesis involves removing a small amount of fluid from around the baby, using a fine needle. This fluid naturally contains AFP, which may also be elevated if the baby has spina bifida. There is a small risk of miscarriage, about one in 200, with this procedure. As such, every women usually receives proper counseling through their doctor or a genetic counselor before having the test done.

Sometimes, spina bifida can only be seen at birth. A physical examination usually identifies spina bifida cystica fairly easily, especially if the sac is large. Spina bifida occulta can be more difficult to find, but clues can be a dimple in the lower back, a tuft of hair, or a small growth.

Once spina bifida is seen outwardly, imaging scans like x rays, ultrasound, magnetic resonance imaging (MRI) , or computed tomography (CT ) can be helpful to see the extent of it. It is also a good way to identify whether someone has associated neurological complications like hydrocephalus.

Since spina bifida may occur as part of some genetic conditions, a medical geneticist should be involved to thoroughly examine a child with spina bifida. Identifying a particular syndrome in a child can help them receive more personalized medical care, and can help families identify a cause for why the spina bifida happened. It can also help to give families specific information about the chance of it happening again, for them or for other family members.

Some genetic testing, like chromosome studies, may identify a diagnosis or cause for the spina bifida. Abnormal genetic test results cannot be changed or reversed, but may provide answers about why the spina bifida occurred.

Treatment team

Treatment for people with spina bifida is highly dependent upon their symptoms. A multi-disciplinary team and approach is extremely helpful. Some hospitals offer day-long clinics devoted to people with spina bifida, which makes things much easier for families in terms of coordinating multiple appointments.

A treatment team for someone with spina bifida may include a neurologist , neurosurgeon, surgeon, neuropsychologist , medical geneticist, genetic counselor, orthopedic surgeon, physiatrist, physical therapist, occupational therapist, speech therapist, registered dietitian, social worker, nephrologist, ophthalmologist, audiologist, and a primary care provider. A neonatologist and pediatric specialists in those fields may be available to aid in the care for children. Those specializing in early childhood and development are particularly helpful, especially for issues related to attending school. Above all, good communication between the various specialists to coordinate care is essential.

Treatment

There is no known cure for spina bifida. Treatment primarily focuses on dealing with symptoms as they arise, since they vary so greatly from person to person.

Surgery to correct the spinal problem in spina bifida cystica is often done. This involves carefully tucking the spinal contents back into the spinal column, and closing the covering back up. This often happens shortly following birth to reduce the risk of developing an infection, and requires some time to heal afterward. Surgery has not been known to allow someone to regain functions they would not have had otherwise like movement, bowel, or bladder control.

A child with spina bifida is often carefully watched for signs of hydrocephalus. This may be done by measuring head circumference (which may enlarge) or with periodic head ultrasound or CT scans. If hydrocephalus is found, a procedure to put in a ventriculoperitoneal (VP) or ventriculoatrial (VA) shunt may be done. If a shunt is placed, it must be continually monitored and may need to be adjusted. Some people have their shunts removed later if the hydrocephalus never returns, and some people have a shunt for their entire lives.

Medications are widely available to treat those who develop seizures, and these may need periodic adjustments. Those who have problems with bowel or bladder control may require surgery, medications, or may never fully have these functions.

Babies and children with clubfoot often need to see an orthopedic surgeon and physiatrist, both of whom can recommend ways to correct them. Wearing braces on the legs can turn the feet back to their usual position, and this may be the only thing required. Sometimes surgery is necessary.

Surgery to correct the spinal problem during a pregnancy is experimental and not widely available. Since 1997, about 200 fetuses have had closure of myelomeningoceles during pregnancy. Since the surgery is so new, exact success rates, safety and long-term effects of the procedure are still not known as of early 2004.

Recovery and rehabilitation

Therapies and rehabilitation may be quite involved or relatively brief for people with spina bifida, depending on the severity of symptoms. Physical therapy is extremely important and can be ongoing. Speech and occupational therapies may be helpful if learning problems or delayed development are noted.

For those with wheelchairs, ramps and other assistive devices are helpful in their homes and places they frequent.

Clinical trials

As of early 2004, two clinical trials are under way in the United States to study spina bifida. National Institute of Child Health and Human Development (NICHD) sponsors both of these studies. One study is devoted to the genetics of spina bifida, recruiting many family members of an affected person to analyze and compare selected genes. The other study is attempting to identify the effectiveness and safety of spina bifida surgery during pregnancies. More information can be found at <http://www.clinicaltrials.gov>.

Prognosis

Prognosis in spina bifida is extremely varied and unpredictable. Years ago with far less intervention and fewer treatments available, someone with severe spina bifida had a high chance to die from complications. Mortality may still be high in complex cases even today. Conversely, those with a mild form of spina bifida may never even know they have it unless they have an internal imaging scan for an unrelated reason. As such, they may never have complications related to spina bifida and would have an average life span.

Today, there are far more options for helping those with spina bifida. Information can be learned during a pregnancy, allowing parents to make decisions and potentially prepare before birth. These treatments and therapies help maintain a better quality of life for those with spina bifida, and continue to offer hope.

Special concerns

Many couples who find their child has spina bifida during a pregnancy experience an array of emotional and psychological issues. They may be wondering how and why this happened, and may want some immediate answers. They also may be feeling guilt or wondering whether they could have caused it to happen. Issues related to these pregnancies, such as continuation or interrupting a pregnancy, can be complex and should be treated with sensitivity and care.

An important aspect of good prenatal care is regular folic acid supplementation, because this is known to reduce the risk for NTDs significantly. This can be gained through a prenatal vitamin, a separate supplement, or a healthy diet. Many breakfast cereals, breads, and other foods are now being supplemented with folic acid.

The current recommendation is for all women in their reproductive years to take 0.4 milligrams of folic acid daily, especially from about three to four months before conception. A woman with an affected child should take 4 milligrams of folic acid daily, beginning at least three to four months prior to conception. The reason for taking folic acid before conception is because the fetal spine forms very early, sometimes before a woman even knows she is pregnant.

Another tricky issue is managing the pregnancy of a woman with epilepsy or a seizure disorder. Many antiseizure medications, like Depakote, cause an increased risk for NTDs and spina bifida. However, the risk of a woman having a seizure during pregnancy is also significant. The art is to find a balance between these two risks, in a way that makes everyone feel the most comfortable.

Resources

BOOKS

Lutkenhoff, Marlene. Spinabilities: A Young Person's Guide to Spina Bifida. Woodbine House, 1997.

Lutkenhoff, Marlene. Children with Spina Bifida: A Parent's Guide, 1st ed. Woodbine House, 2003.

Sandler, Adrian. Living with Spina Bifida: A Guide for Families and Professionals. University of North Carolina Press, 2004.

PERIODICALS

Frey, Lauren, and W. Allen Hauser. "Epidemiology of Neural Tube Defects." Epilepsia 44, Suppl. 3 (2003): 4–13.

Zipitis, Christos S., and Constantinos Paschalides. "Caring for a child with spina bifida: understanding the child and carer." Journal of Child Health Care 7, no. 2 (2003): 101–112.

WEBSITES

Children with Spina Bifida: A Resource Page for Parents. <www.waisman.wisc.edu/~rowley/sb-kids/index.html>.

March of Dimes. <www.modimes.org>.

National Institute of Neurological Disorders and Stroke. <www.ninds.nih.gov/index.htm>.

ORGANIZATIONS

Association for Spina Bifida & Hydrocephalus (U.K.). ASBAH House, 42 Park Road, Peterborough, United Kingdom PE1 2UQ. (01733) 555988. (01733) 555985. [email protected]. <http://www.asbah.org>.

Spina Bifida and Hydrocephalus Association of Canada. 977-167 Lombard Avenue, Winnipeg, Manitoba, Canada R3B 0V3. 204-925-3650 or 800-565-9488; Fax: 204-925-3654. [email protected]. <http://www.sbhac.ca/index.php?page=main>.

Spina Bifida Association of America. 4590 MacArthur Boulevard N.W., Suite 250, Washington, DC 20007-4226. 202-944-3285 or 800-621-3141; Fax: 202-944-3295. [email protected]. <http://www.sbaa.org>.

Deepti Babu, MS, CGC

Spina bifida

Definition

Spina bifida is a serious birth abnormality, termed a neural tube defect, in which the spinal cord is malformed and lacks its usual protective skeletal and soft tissue coverings.

Description

Spina bifida is a lesion that may appear in the midline of the body anywhere from the neck to the buttocks. It is caused by the failure of the vertebrae to form properly in fetal development, leaving the spinal cord some degree of vulnerability or exposure to the environment. Spina bifida occurs in multiple forms of varying exposure of the spinal cord.

Spina bifida occulta

This form of spina bifida usually involves the deformation of a single vertebra in the cervical, lumbar, or sacral regions. The spinal cord and nerves are usually normal with no neurological symptoms. There is usually skin covering the vertebral abnormality, which is typically indicated visually by a dimple with a tuft of hair. Clinical symptoms are absent in the majority of cases.

Spina bifida cystica

Spina bifida cystica is a term used to describe several severe forms of spina bifida. The spinal cord protrudes outward through an open defect in the vertebrae, forming a cyst-like sac on the outside of the body filled with cerebrospinal fluid. When the sac includes the meninges, a protective three-layered membrane that covers the spinal cord, the condition is said to involve a meningocele. When the actual spinal cord or nerve roots are included in the sac, the condition is described as involving a meningomyelocele. This is a more common form of spina bifida cystica. Neurological deficits occur because nervous tissue is integrated in the wall of the sac, disrupting their function. Both types of spina bifida cystica are most common in the lumbar and sacral regions.

Rachischisis and spina bifida with myeloschisis

The most severe type of spina bifida is caused by the failure of the neural folds to fuse. The entire spinal canal is open, exposing the spinal nerves completely. The spinal cord is only developed into a flattened mass of nervous tissue.

Spina bifida is usually readily apparent at birth because of the malformation of the back and clinical symptoms associated with most forms of the abnormality. There are varying degrees of neurological deficit present, depending on the position and degree of the abnormality. There is usually a loss of sensation to the skin, with varying skeletal muscle paralysis in the region below the lesion. Paralysis of the urinary bladder or anal sphincters is also common.

Genetic profile

Spina bifida may occur as an isolated defect or associated with other malformations, such as partial absence of the brain. As an isolated abnormality, spina bifida is caused by a combination of genetic factors and environmental influences. The most important factor that causes neural tube defects such as spina bifida is a maternal folic acid deficiency during early pregnancy. Folic acid levels are dependent on dietary intake. During pregnancy, the requirement for folic acid is increased, and is difficult to meet with an average contemporary diet. Mothers of children with neural tube defects may have reduced blood folate levels, along with a defect in the recycling pathway for digested folic acid. This defect can be caused by a genetic mutation in the enzyme 5,10-methylenetetrahy-drofolate reductase (MTHFR). The mutation in the gene for MTHFR causes an unstable enzyme that cannot function properly in the metabolism of folic acid. The mutant allele for unstable MTHFR is very common in many populations. Between 5–15% of the population may have both alleles for MTHFR in a mutated form. Research has demonstrated that mothers of infants with neural tube defects are twice as likely to have all mutant alleles of the gene for MTHFR. A folic acid deficiency may be caused by other genetic defects or by dietary deprivation alone. A small percentage of neural tube defects such as spina bifida can be narrowed down to other specific causes, such as the early rupture of the amnion-forming fibrous amniotic bands that disrupt vertebral development. Exposure to some teratogens, chemicals that produce abnormal fetal development, may cause spina bifida. Other causes may include separate single gene mutations , chromosomal abnormalities , environmental insults such as maternal diabetes mellitus, or prenatal exposure to certain anticonvulsant drugs. The recurrence risk varies with each of these specific causes.

Demographics

Spina bifida occurs worldwide, but there has been a steady decrease in occurrence rates over the past 50–70 years, due to dietary supplementation with folic acid. Before folic acid fortification, approximately 2,500–3,000 births in the United States were affected annually by some form of neural tube defect. In 2001, there was a 24% decline in spina bifida in the United States from folic acid fortification of enriched grain products and other folic acid initiatives. The highest prevalence rates, about one in 200 pregnancies, have been reported from northern provinces in China. High prevalence rates of approximately one in 1,000 pregnancies have also been found in Central and South America. The lowest prevalence rates, less than one in 2,000 pregnancies, have been found in the European countries. Regionally, the highest prevalence in the United States occurs in the southeast, in approximately one in 500 pregnancies. A study performed by the CDC in North Carolina between 1995 and 1999 demonstrated a 32% decline in the incidence of spina bifida. The decline in incidence was not uniform across the population, but was dependent on geographic region as correlated with maternal sociodemographic characteristics. Populations with higher income and education have afforded the greatest decline in spina bifida. Although the use of multivitamins has played a role in this population, much of the recent decline in neural tube defects in the United States has been a result of the mandatory government fortification program of enriched grain products.

Signs and symptoms

In most cases, spina bifida is obvious at birth because of the malformation of the spinal column and associated neurological deficits. The spinal cord may be completely exposed, appearing as a mass on the back covered by the meningeal membranes or skin. Although spina bifida may occur anywhere from the base of the skull to the buttocks, about 75% of cases occur in the lumbar region. When the defect is covered by skin, it may include a dimple or depression, a port wine-colored birthmark, or a bulge with a tuft ofhair.

Along with the malformations, the neurological deficit is also obvious. The level of anesthesia of the skin depends on which dermatomes are affected. Dermatomes are patches of skin innervated by specific spinal nerves. The spinal nerves leave the spinal cord to innervate structures in descending order. The higher the lesion of spina bifida is located on the vertebral column, the more spinal nerves may be affected. Skeletal muscle may also be paralyzed in the same fashion, over the entire pelvic area and lower extremity. Saddle anesthesia is the term used to refer to the entire loss of sensation to the area of the body that touches the saddle during horseback riding. Saddle anesthesia is a symptom often seen when paralysis of urinary bladder and anal sphincters is present. A lack of response to touch, lack of leg movement or resistance to passive-elicited movement, severe flaccidity, and lack of anal reflex (reflex of musculature in response to touch) in an infant are signs that neurological deficits in the lower region are present.

There are other complications that sometimes develop in association with spina bifida. Some infants develop hydrocephaly, an accumulation of excess fluid in the four cavities of the brain. At least one of every seven cases develops findings of Chiari II malformation, a condition in which the lower part of the brain is crowded and may be forced into the upper part of the spinal cavity. A lipomeningocele or lipomyelomeningocele may occur in the lumbar or sacral back area. In these conditions, a tumor of fatty tissue becomes isolated among the nerves below the spinal cord, which may result in tethering of the spinal cord and complications similar to those with open spina bifida.

Diagnosis

A mother carrying a fetus with spina bifida will not experience any unusual signs or symptoms in early pregnancy. Spina bifida is often discovered prenatally by initial signs and symptoms in the maternal amniotic fluid. During amniocentesis obstetricians may screen for high levels of a protein called alphafetoprotein (AFP). High AFP is a general indicator that the fetus may have a defect. The AFP test is not indicative of spina bifida specifically, but alerts the obstetrician that a detailed ultrasonogram (use of ultrasound) may be necessary. Spina bifida may cause elevated levels of AFP because it is an open fetal defect that allows high levels of the AFP of the fetus to travel into

maternal amniotic fluid and smaller amounts to enter maternal blood serum. A prenatal diagnosis of spina bifida may be made with ultrasonograpic examination. Malformations may be detected via ultrasonogram as early as 12–14 weeks of pregnancy. Postnatally, the diagnosis is usually obvious, based on external lesions. In addition to the characteristic malformations, paralysis below the level of the lesion may be part of the diagnosis. In cases in which there are no external indicators, the diagnosis may not become evident until neurological abnormalities develop weeks, months, or years following birth.

Treatment and management

Prevention of spina bifida and other neural tube defects is improved with the use of folic acid vitamin supplements for several months prior to and following conception. The Centers for Disease Control and Prevention (CDC) recommend an intake of 400 mcg of synthetic folic acid per day for all women of childbearing years to prevent neural tube defects.

Open fetal surgery has been performed for spina bifida during the several months of pregnancy. After direct closure of the spine malformation, the fetus is returned to the womb. By preventing chronic intrauterine exposure to mechanical and chemical trauma, prenatal surgery improves neurological function and leads to fewer complications after birth. Fetal surgery is considered experimental, and results have been mixed.

Postnatally, aggressive surgical and medical management have improved the survival and function of infants with spina bifida. Initial surgery on the spinal column defect may be performed in the first days of life, providing protection against injury and infection. Subsequent surgery is often necessary to protect against excessive curvature of the spine. When spina bifida occurs in conjunction with hydrocephaly, surgery is performed to implant a mechanical shunt to decrease the pressure and amount of cerebrospinal fluid in the cavities of the brain. Because of weakness or paralysis below the level of the spinal defect, most children will require physical therapy, bracing, and other orthopedic assistance to enable them to walk. A variety of approaches, including periodic bladder catheterization, surgical diversion of urine, and antibiotics, is used to protect urinary function.

Although most individuals with spina bifida have normal intellectual function, learning disabilities or mental impairment may occur. This may result, in part, from hydrocephaly and/or infections of the nervous system. Children so affected may benefit from early educational intervention, physical therapy, and occupational therapy. Counseling to improve self-image and lessen barriers to socialization becomes important in late childhood and adolescence.

Prognosis

More than 80% of infants born with spina bifida survive with surgical and medical management. Although complications from paralysis, hydrocephaly, Chiari II malformation, and urinary tract deterioration threaten the well-being of the survivors, the outlook for normal intellectual function is good.

Resources

BOOKS

Moore, Keith L., and T. V. N. Persaud. The Developing Human, Clinically Oriented Embryology, Seventh Edition. St. Louis, MO: Elsevier Science, 2003.

Thompson & Thompson Genetics in Medicine, Sixth Edition. St. Louis, MO: Elsevier Science, 2004.

PERIODICALS

Sells, C. J., and J. G. Hall, guest eds. "Neural Tube Defects." Mental Retardation and Developmental Disabilities Research Reviews. Volume 4, Number 4. New York: Wiley-Liss, 1998.

ORGANIZATIONS

March of Dimes Birth Defects Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. (888) 663-4637. [email protected]. (April 7, 2005.) <http://www.modimes.org>.

National Birth Defects Prevention Network. Atlanta, GA (770) 488-3550. (April 7, 2005.) <http://www.nbdpn.org/NBDPN>.

Shriners Hospitals for Children. International Shrine Headquarters, 2900 Rocky Point Dr., Tampa, FL 33607-1460. (813) 281-0300. (April 7, 2005.) <http://www.shrinershq.org>.

Spina Bifida Association of America. 4590 MacArthur Blvd. NW, Suite 250, Washington, DC 20007-4226. (800) 621-3141 or (202) 944-3285. Fax: (202) 944-3295. <http://www.sbaa.org>.

WEBSITES

Medline. (April 7, 2005.) <http://medlineplus.gov/>.

NINDS Spina Bifida Information Page. (April 7, 2005.) <http://www.ninds.nih.gov/disorders/spina_bifida/spina_bifida.htm>.

Prevalence of Spina Bifida at Birth—United States, 1983–1990: A Comparison of Two Surveillance Systems. CDC Surveillance Summaries. (April 7, 2005.) <http://www.cdc.gov/mmwr/preview/mmwrhtml/00040954.htm>.

Sociodemographic Patterns in Spina Bifida Birth Prevalence Trends—North Carolina, 1995–1999. CDC Recommendations and Reports. (April 7, 2005.) <http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5113a4.htm>.

Spina Bifida and Anencephaly Prevalence—United States, 1991–2001. CDC Recommendations and Reports. (April 7, 2005.) <http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5113a3.htm>.

Surveillance for Anencephaly and Spina Bifida and the Impact of Prenatal Diagnosis—United States, 1985–1994. (April 7, 2005.) <http://www.cdc.gov/mmwr/preview/mmwrhtml/00038567.htm>.

Maria Basile, PhD

Spina bifida

Definition

Spina bifida is a birth abnormality in which the spine is malformed and lacks its usual protective skeletal and soft tissue coverings.

Description

Spina bifida may appear in the body midline anywhere from the neck to the buttocks. In its most severe form, termed spinal rachischisis, the entire spinal canal is open, exposing the spinal cord and nerves. More commonly, the abnormality appears as a localized mass on the back that is covered by skin or by the meninges, the three-layered membrane that envelops the spinal cord. Spina bifida is usually readily apparent at birth because of the malformation of the back and paralysis below the level of the abnormality.

Various forms of spina bifida are known as meningomyelocele, myelomeningocele, spina bifida aperta, open spina bifida, myelodysplasia, spinal dysraphism, spinal rachischisis, myelocele, and meningocele. The term meningocele is used when the spine malformation contains only the protective covering (meninges) of the spinal cord. The other terms indicate involvement of the spinal cord and nerves in the malformation. A related term, spina bifida occulta, indicates that one or more of the bony bodies in the spine are incompletely hardened, but that there is no abnormality of the spinal cord itself.

Demographics

Spina bifida occurs worldwide, but there has been a steady downward trend in occurrence rates since about 1940, particularly in regions of high prevalence. The highest prevalence rates, about one in 200 pregnancies, have been reported from certain northern provinces in China. Intermediate prevalence rates, about one in 1000 pregnancies, have been found in Central and South America. The lowest prevalence rates, less than one in 2,000 pregnancies, have been found in European countries. The highest regional prevalence in the United States of about one in 500 pregnancies has occurred in the Southeast.

Causes and symptoms

Spina bifida may occur as an isolated abnormality or in the company of other malformations. As an isolated abnormality, spina bifida is caused by the combination of genetic factors and environmental influences that bring about malformation of the spine and spinal column. The specific genes and environmental influences that contribute to the many-factored causes of spina bifida were not as of 2004 completely known. An insufficiency of folic acid is known to be one influential nutritional factor. Changes (mutations) in genes involving the metabolism of folic acid are believed to be significant genetic risk factors. The recurrence risk after the birth of an infant with isolated spina bifida is 3 to 5 percent. Recurrence may be for spina bifida or another type of spinal abnormality.

Spina bifida may arise because of chromosome abnormalities, single gene mutations, or specific environmental insults such as maternal diabetes mellitus or prenatal exposure to certain anticonvulsant drugs. The recurrence risk varies with each of these specific causes.

In most cases, spina bifida is obvious at birth because of malformation of the spine. The spine may be completely open, exposing the spinal cord and nerves. More commonly, the spine abnormality appears as a mass on the back covered by membrane (meninges) or skin. Spina bifida may occur any where from the base of the skull to the buttocks. About 75 percent of abnormalities occur in the lower back (lumbar) region. In rare instances, the spinal cord malformation may occur internally, sometimes with a connection to the gastrointestinal tract.

In spina bifida, many complications arise, dependent in part on the level and severity of the spine malformation. As a rule, the nerves below the level of the abnormality develop in a faulty manner and fail to function, resulting in paralysis and loss of sensation below the level of the spine malformation. Since most abnormalities occur in the lumbar region, the lower limbs are paralyzed and lack sensation. Furthermore, the bowel and bladder have inadequate nerve connections, causing an inability to control bowel and bladder function. Most infants also develop hydrocephaly, an accumulation of excess fluid in the four cavities of the brain. At least one of every seven cases develops findings of Chiari II malformation, a condition in which the lower part of the brain is crowded and may be forced into the upper part of the spinal cavity.

There are a number of mild variant forms of spina bifida, including multiple vertebral abnormalities, skin dimples, tufts of hair, and localized areas of skin deficiency over the spine. Two variants, lipomeningocele and lipomyelomeningocele, typically occur in the lower back area (lumbar or sacral) of the spine. In these conditions, a tumor of fatty tissue becomes isolated among the nerves below the spinal cord, which may result in tethering of the spinal cord and complications similar to those with open spina bifida.

Diagnosis

Few disorders are to be confused with open spina bifida. The diagnosis is usually obvious based on the external findings at birth. Paralysis below the level of the abnormality and fluid on the brain (hydrocephaly) may contribute to the diagnosis. Other spine abnormalities such as congenital scoliosis and kyphosis, or soft tissue tumors overlying the spine, are not likely to have these accompanying findings. In cases in which there are no external findings, the diagnosis is more difficult and may not become evident until neurological abnormalities or hydrocephaly develop weeks, months, or years following birth.

Prenatal diagnosis may be made in most cases with ultrasound examination after 12 to 14 weeks of pregnancy. Many cases are also detected by the testing of the mother's blood for the level of alpha-fetoprotein at about 16 weeks of pregnancy. If the spine malformation is not skin covered, alpha-fetoprotein from the fetus's circulation may leak into the surrounding amniotic fluid, a small portion of which is absorbed into the mother's blood.

Treatment

Aggressive surgical and medical management have improved the survival and function of infants with spina bifida. Initial surgery may be carried out during the first days of life, in the hope of providing protection against injury and infection. Subsequent surgery is often necessary to protect against excessive curvature of the spine, and in the presence of hydrocephaly, to place an echanical shunt to decrease the pressure and amount of cerebrospinal fluid in the cavities of the brain. Because of weakness or paralysis below the level of the spine abnormality, most children require physical therapy, bracing, and other orthopedic assistance in order to be able to walk. A variety of approaches including periodic bladder catheterization, surgical diversion of urine, and antibiotics are used to protect urinary function.

Although most individuals with spina bifida have normal intellectual function, learning disabilities or mental retardation occur in a minority. This deficit may result, in part, from hydrocephaly and/or infections of the nervous system. Children so affected may benefit from early educational intervention, physical therapy, and occupational therapy. Counseling to improve self-image and lessen barriers to socialization becomes important in late childhood and adolescence .

Open fetal surgery has been performed for spina bifida during the last half of pregnancy. After direct closure of the spine malformation, the fetus is returned to the womb. By preventing chronic intrauterine exposure to mechanical and chemical trauma, prenatal surgery improves neurological function and leads to fewer complications after birth. Fetal surgery is considered experimental, and results have been mixed.

Prognosis

More than 80 percent of infants born with spina bifida survive with surgical and medical management. Although complications from paralysis, hydrocephaly, Chiari II malformation, and urinary tract deterioration threaten the well-being of the survivors, the outlook for normal intellectual function is good.

Prevention

Prevention of isolated spina bifida and other spinal abnormalities became possible in the 1980s and 1990s. The major prevention is through the use of folic acid, one of the B vitamins , for several months prior to and following conception. The Centers for Disease Control and Prevention (CDC) recommend the intake of 400 micrograms of synthetic folic acid every day for all women of childbearing years. For women who have had a previous child with spina bifida, the CDC recommends a daily intake of 4 milligrams of synthetic folic acid to help prevent a recurrence of spina bifida in future pregnancies.

Parental concerns

Caring for a child with spina bifida can be a daunting endeavor. Initially, parents may be overwhelmed with the medical decisions to be made and with the grief experienced after the birth of a special needs child. Many parents benefit from early and continuing involvement of an experienced social worker. There will be a multitude of medical decisions to be made. Children with spina bifida require a multidisciplinary team of healthcare providers, including surgeons, physicians, and therapists. Parents may find it helpful to designate a physician, usually the primary pediatrician, or an experienced rehabilitation counselor to act as an advocate for their child and to aid them in coordinating their child's treatment program.

Parental concerns may be two-fold, medical and emotional. Medical concerns include monitoring their child's condition after surgery. Children with spina bifida may have many surgical procedures throughout their lives. Post surgical complications are common but may often be avoided. Parents will be given care instructions after each surgery. Children with spina bifida face a multitude of heath issues such as monitoring bladder and bowel function, maintaining proper nutrition , preventing broken bones, promoting healthy growth and development, and encouraging activity and mobility. Many children with spina bifida have non-surgical treatments as well, such as positional aides to help the child sit and stand, physical therapy, and bracing and splints usually of the lower extremities.

Parents of children with spina bifida experience an array of emotions, including grief, fear , anxiety , and stress. Spina bifida impacts not only the affected child but the entire family . Groups and networks of other families affected by spina bifida can provide valuable support. Parents may need to be active in ensuring that their child receives the early intervention and educational services available in their community. Each state has programs to encourage healthy development in children with special needs.

Finally, parents should remember that most children with spina bifida live productive and happy lives. For the most part, children with spina bifida have average or above-average intelligence . Many of these children can go on to higher education, have active careers, and live self-sufficiently. It is important for parents to encourage strong self esteem in their child and to foster independent living skills.

KEY TERMS

Bracing —Using orthopedic devices to hold joints or limbs in place.

Chiari II anomaly —A structural abnormality of the lower portion of the brain (cerebellum and brainstem) associated with spina bifida. The lower structures of the brain are crowded and may be forced into the foramen magnum, the opening through which the brain and spinal cord are connected.

Fetus —In humans, the developing organism from the end of the eighth week to the moment of birth. Until the end of the eighth week the developing organism is called an embryo.

Hydrocephalus —An abnormal accumulation of cerebrospinal fluid within the brain. This accumulation can be harmful by pressing on brain structures, and damaging them.

Splint —A thin piece of rigid or flexible material that is used to restrain, support, or immobilize a part of the body while healing takes place.

Resources

BOOKS

Behrman, Richard E., Robert M. Kliegman, and Hal B. Jenson, eds. Nelson Textbook of Pediatrics, 16th ed. Philadelphia: W. B. Saunders, 2000.

Sutton, Amy L. Back and Neck Sourcebook: Basic Consumer Health Information. Detroit, MI: Omnigraphics, 2004.

ORGANIZATIONS

March of Dimes Birth Defects Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. Web site: <www.modimes.org>.

National Birth Defects Prevention Network. Web site: <www.nbdpn.org>.

Shriners Hospitals for Children. International Shrine Headquarters, 2900 Rocky Point Dr., Tampa, FL 33607–1460. Web site: <www.shrinershq.org>.

Spina Bifida Association of America. 4590 MacArthur Blvd. NW, Suite 250, Washington, DC 20007–4226. Web site: <www.sbaa.org>.

Roger E. Stevenson Deborah L. Nurmi, MS

Spina Bifida

Brian Teaches Class

What Is Spina Bifida?

Prenatal Testing for Spina Bifida

Is Spina Bifida Always Serious?

What Causes Spina Bifida?

Living with Spina Bifida

Resources

Spina bifida (SPY-na BI-fi-da) is a birth defect in which the spinal column does not form properly, leaving a gap or opening in the spine.

KEYWORDS

for searching the Internet and other reference sources

Meningocele

Myelomeningocele

Neural tube defects

Neurology

Orthopedics

Brian Teaches Class

As part of a sixth grade science project, Brian chose to report on a condition called spina bifida. He showed a picture of the ring-shaped bones, or vertebrae, of the spine and demonstrated how the vertebrae protect the spinal cord and anchor muscles. He explained that in people with spina bifida, some of the bony plates that should cover the spine do not close, leaving an unprotected opening at the back of the spine.

No one in Brian’s class had ever heard of spina bifida, and they all were surprised to learn that Brian had been born with it. He had a mild form of the condition that was corrected surgically when he was an infant. He ended his presentation by showing the small scar on his lower back.

What Is Spina Bifida?

Spina bifida is a Latin term meaning “split spine” or “open spine.” It is the most common of several birth defects called neural tube defects. The neural tube contains the cells that ultimately make the spinal cord and the brain, and it develops during the first three to four weeks of pregnancy (often before a woman even knows that she is pregnant).

Spina bifida results when the sides of the neural tube fail to join together properly, leaving an open area. Often the gap occurs in the lower back at the base of the spine. The spinal cord is part of the central nervous system, which allows a person to move and sense the world around them. Thus, because spina bifida involves the central nervous system, it can cause a range of physical and mental problems.

Prenatal Testing for Spina Bifida

Sometimes parents can find out whether their baby has spina bifida before the baby is born. There are several commonly used tests.

The maternal-serum alfa-fetoprotein (AFP) test is performed between the sixteenth and eighteenth weeks of pregnancy. Alfa-fetoprotein is a substance made by the developing fetus. Because the mother and fetus are connected via their circulatory systems, AFP from the fetus gets into the mother’s bloodstream. By measuring the amount of AFP in the mother’s blood, doctors get an indication of the likelihood that the fetus has certain birth defects. This test does not give a definite answer, and high levels of AFP only suggest that the fetus might have spina bifida. If AFP levels are high, the test is repeated. If still high, other tests are needed to confirm that the fetus has spina bifida. Many times, high AFP readings are false alarms and the baby is just fine.

Ultrasound can be used to confirm or rule out spina bifida. An ultrasound works by bouncing sound waves off of internal structures. A computer converts the returning sound waves into an image of the fetus inside the uterus. Sometimes the defect in the developing spine is visible on the ultrasound image.

Amniocentesis is a procedure performed between the sixteenth and eighteenth week of pregnancy. In this procedure, a needle is passed through the mother’s belly into her uterus to collect some of the fluid in which the fetus lives. This fluid, called amniotic fluid, contains cells and chemicals from the fetus. Levels of AFP can be measured to determine whether the fetus has spina bifida.

Is Spina Bifida Always Serious?

Spina bifida is a common birth defect, but it does not always cause serious problems. At birth, the gap may be so slight that it is invisible and harmless. On the other hand, sometimes the spinal cord bulges out through the malformed vertebrae and there are serious neurological (nerve) problems.

Spina bifida occulta

Brian was born with spina bifida occulta, the mildest form of spina bifida. “Occulta’ means hidden, and in many cases, the gap in the spine is never detected. Often there is an opening in one or two of the vertebrae but the spinal cord is not affected. A dimple, a birthmark, or a patch of hair may be visible on the skin overlying the site of the gap. Scientists estimate that about 40 percent of all Americans have this form of spina bifida, but not many ever know they have it. Most people with spina bifida occulta never need treatment. Brian was an exception. He needed surgery because as he grew, the lower end of his spinal cord got caught against his vertebrae, causing him to have problems controlling his bladder. The doctors “unhooked” the spinal cord and closed the gap surgically.

Spina bifida manifesta

Spina bifida manifesta includes two forms of spina bifida that together represent one of the most common disabling birth defects. On average, 1 out of 1,000 babies in the United States is born with either meningocele (me-NING-go-seel) or myelomeningocele (MY-e-lo-me-NING-go-seel).

Meningocele

Of babies born with spina bifida manifesta, about 4 percent have the meningocele form. The meninges (me-NIN-jez) consist of three layers of tough membranes that cover and protect the brain and spinal cord. The brain and spinal cord also are bathed in a fluid called cerebro-spinal fluid (CSF). A meningocele is a CSF-filled sac formed when the meninges balloon through the gap in the vertebrae. It looks like a large blister covered by a thin layer of skin. The sac can range in size from as small as a grape to as large as a grapefruit.

A meningocele is harmless if the sac contains only CSF. However, if nerves are caught in the sac, the affected baby can have problems controlling muscles and the bladder. Babies with this form of spina bifida usually have surgery during infancy to put the meninges back inside the vertebrae and to close the gap in the vertebrae.

Myelomeningocele

When most people think of spina bifida, they think of the myelomeningocele form. Approximately 96 percent of babies born with spina bifida manifesta have myelomeningocele, and it is the most serious type of spina bifida. As in meningocele, the meninges bulge out through the gap in the spine, but in myelomeningocele, part of the spinal cord bulges out as well. The sac can be covered with skin or the nerves can actually be exposed.

Preventing Spina Bifida: The Role of Folic Acid

Scientists estimate that the incidence of spina bifida can be decreased by as much as 75 percent if all women of child-bearing age consume 0.4 mg of folic acid each day.

Spina bifida has been linked to a deficiency of folic acid during the first weeks of pregnancy. Folic acid is one of the B vitamins and it is essential for proper functioning of the human body. When the body is growing quickly, such as during pregnancy and during fetal development, the body needs more folic acid than usual.

Good sources offolic acid include dark green leafy vegetables (like spinach and broccoli), eggs, and orange juice. In addition, the U.S. Food and Drug Administration requires breads and enriched grains and cereals to have folic acid added to them. Even with folic acid supplements added to common foods, the average American diet does not contain 0.4 mg of folic acid per day. Most multivitamins, however, now contain the recommended dose offolic acid.

People with myelomeningocele have a variety of physical and mental problems, the severity of which depends on where the defect in the spine occurs. A gap high up on the spinal column will create more problems than a gap at the lower back. People with this condition usually experience loss of movement and feeling (paralysis) below the abnormal vertebrae. The most severely impaired children cannot walk or control their bowel or bladder. Most babies born with myelomeningocele also have hydrocephalus, which means that they have too much fluid inside and surrounding their brain. If hydrocephalus is not treated, the excess pressure in the skull can cause blindness and permanent brain damage.

Myelomeningocele requires surgery within 24 to 48 hours of birth. Surgeons must close the gap in the vertebrae to protect the spinal cord and prevent infection. They also must treat hydrocephalus, if present. They do this by placing a device called a shunt into the brain to drain excess fluid and relieve pressure on the brain.

What Causes Spina Bifida?

Spina bifida sometimes runs in families, which suggests that genes may play a role in some cases, but 90 to 95 percent of babies with spina bifida are born to families that have never before had a child with the condition. Mothers who have diabetes, a high fever during pregnancy, or who have taken a drug called valproic acid to treat epilepsy seem to have a greater chance of having a baby with spina bifida than mothers without these conditions. There also appears to be a link between a deficiency of folic acid (a B vitamin) in the mother’s diet and having a baby with spina bifida. Adding folic acid to the diet significantly reduces the chance that a baby will be born with spina bifida.

Living with Spina Bifida

Most children with spina bifida occulta, and many with meningocele, live normal lives without any impairment. Children born with myelomeningocele, however, often have multiple problems resulting from damage to their spinal cord. Surgery to repair the gap in the vertebrae and to place a shunt in the brain can prevent further damage to the nervous system. However, it cannot reverse the nerve problems that already are present at birth.

The severity of symptoms caused by myelomeningocele varies from child to child. Common problems, however, include the inability to control the bowel and bladder. Catheters*, diapers, and attentive caregivers can help alleviate embarrassment caused by these problems.

* catheters

(KATH-e-terz) are tubes inserted into parts of the body to allow fluids to flow in and out. Catheters into the bladder through the urethra (the last part of the urinary tract) allow urine to flow into an outside container.

Many affected children cannot walk without crutches or leg braces, and many need a wheelchair. In addition, some children have learning problems, particularly with reading and math. For children with these problems, special education classes can help to prepare them for school.

Children with spina bifida often develop sensitivity or an allergy to latex (natural rubber), which is used in such healthcare products as gloves and catheter tubes, probably because they come into contact with latex so often and from such a young age.

Even with the disabilities caused by spina bifida, children with the disease often live well into adulthood. With the help of early and continuing medical, psychological, and educational treatment, children with spina bifida can lead full and productive lives.

See also

Birth Defects

Hydrocephalus

Incontinence

Paralysis

Resources

Books

Sandler, Adrian. Living with Spina Bifida: A Guide for Families and Professionals. Chapel Hill: University of North Carolina Press, 1997.

Lutkenhoff, Marlene. Spinabilities: A Young Persons Guide to Spina Bifida. Bethesda: Woodbine House, 1997.

Organizations

Spina Bifida Association of America, 4590 MacArthur Boulevard, Suite 250, Washington, DC 20007. Telephone 800-621-3141 http://www.sbaa.org

Association for Spina Bifida and Hydrocephalus, 42 Park Road, Peterborough, PEI 2UQ, England. Telephone 01733-555988 http://www.asbah.demon.co.uk

March of Dimes Foundation, 1275 Mamaroneck Avenue, White Plains, NY 10605. Telephone 888-663-4637 http://www.modimes.org/

Spina Bifida

Definition

Spina bifida is a serious birth abnormality in which the spinal cord is malformed and lacks its usual protective skeletal and soft tissue coverings.

Description

Spina bifida may appear in the body midline anywhere from the neck to the buttocks. In its most severe form, termed spinal rachischisis, the entire spinal canal is open, exposing the spinal cord and nerves. More commonly, the abnormality appears as a localized mass on the back that is covered by skin or by the meninges, the three-layered membrane that envelopes the spina cord. Spina bifida is usually readily apparent at birth because of the malformation of the back and paralysis below the level of the abnormality.

Various forms of spina bifida are known as meningomyelocele, myelomeningocele, spina bifida aperta, open spina bifida, myelodysplasia, spinal dysraphism, spinal rachischisis, myelocele, and meningocele. The term meningocele is used when the spine malformation contains only the protective covering (meninges) of the spinal cord. The other terms indicate involvement of the spinal cord and nerves in the malformation. A related term, spina bifida occulta, indicates that one or more of the bony bodies in the spine are incompletely hardened, but that there is no abnormality of the spinal cord itself.

Spina bifida occurs worldwide, but there has been a steady downward trend in occurrence rates over the past 50-70 years, particularly in regions of high prevalence. The highest prevalence rates, about one in 200 pregnancies, have been reported from certain northern provinces in China. Intermediate prevalence rates, about one in 1,000 pregnancies, have been found in Central and South America. The lowest prevalence rates, less than one in 2,000 pregnancies, have been found in the European countries. The highest regional prevalence in the United States of about one in 500 pregnancies has occurred in the Southeast.

Causes and symptoms

Spina bifida may occur as an isolated abnormality or in the company of other malformations. As an isolated abnormality, spina bifida is caused by the combination of genetic factors and environmental influences that bring about malformation of the spine and spinal column. The specific genes and environmental influences that contribute to the many-factored causes of spina bifida are not completely known. An insufficiency of folic acid is known to be one influential nutritional factor. Changes (mutations) in genes involving the metabolism of folic acid are believed to be significant genetic risk factors. The recurrence risk after the birth of an infant with isolated spina bifida is 3-5%. Recurrence may be for spina bifida or another type of spinal abnormality.

Spina bifida may arise because of chromosome abnormalities, single gene mutations, or specific environmental insults such as maternal diabetes mellitus or prenatal exposure to certain anticonvulsant drugs. The recurrence risk varies with each of these specific causes.

In most cases, spina bifida is obvious at birth because of malformation of the spine. The spine may be completely open, exposing the spinal cord and nerves. More commonly, the spine abnormality appears as a mass on the back covered by membrane (meninges) or skin. Spina bifida may occur anywhere from the base of the skull to the buttocks. About 75% of abnormalities occur in the lower back (lumbar) region. In rare instances, the spinal cord malformation may occur internally, sometimes with a connection to the gastrointestinal tract.

In spina bifida, many complications arise, dependent in part on the level and severity of the spine malformation. As a rule, the nerves below the level of the abnormality develop in a faulty manner and fail to function, resulting in paralysis and loss of sensation below the level of the spine malformation. Since most abnormalities occur in the lumbar region, the lower limbs are paralyzed and lack sensation. Furthermore, the bowel and bladder have inadequate nerve connections, causing an inability to control bowel and bladder function. Most infants also develop hydrocephaly, an accumulation of excess fluid in the four cavities of the brain. At least one of every seven cases develop findings of Chiari II malformation, a condition in which the lower part of the brain is crowded and may be forced into the upper part of the spinal cavity.

There are a number of mild variant forms of spina bifida, including multiple vertebral abnormalities, skin dimples, tufts of hair, and localized areas of skin deficiency over the spine. Two variants, lipomeningocele and lipomyelomeningocele, typically occur in the lower back area (lumbar or sacral) of the spine. In these conditions, a tumor of fatty tissue becomes isolated among the nerves below the spinal cord, which may result in tethering of the spinal cord and complications similar to those with open spina bifida.

Diagnosis

Few disorders are to be confused with open spina bifida. The diagnosis is usually obvious based on the external findings at birth. Paralysis below the level of the abnormality and fluid on the brain (hydrocephaly) may contribute to the diagnosis. Other spine abnormalities such as congenital scoliosis and kyphosis, or soft tissue tumors overlying the spine, are not likely to have these accompanying findings. In cases in which there are no external findings, the diagnosis is more difficult and may not become evident until neurological abnormalities or hydrocephaly develop weeks, months, or years following birth.

Prenatal diagnosis may be made in most cases with ultrasound examination after 12-14 weeks of pregnancy. Many cases are also detected by the testing of the mother's blood for the level of alpha-fetoprotein at about 16 weeks of pregnancy. If the spine malformation is not skin covered, alpha-fetoprotein from the fetus' circulation may leak into the surrounding amniotic fluid, a small portion of which is absorbed into the mother's blood.

Treatment

Aggressive surgical and medical management have improved the survival and function of infants with spina bifida. Initial surgery may be carried out during the first days of life, providing protection against injury and infection. Subsequent surgery is often necessary to protect against excessive curvature of the spine, and in the presence of hydrocephaly, to place a mechanical shunt to decrease the pressure and amount of cerebrospinal fluid in the cavities of the brain. Because of weakness or paralysis below the level of the spine abnormality, most children will require physical therapy, bracing, and other orthopedic assistance to enable them to walk. A variety of approaches including periodic bladder catheterization, surgical diversion of urine, and antibiotics are used to protect urinary function.

Although most individuals with spina bifida have normal intellectual function, learning disabilities or mental retardation occur in a minority. This may result, in part, from hydrocephaly and/or infections of the nervous system. Children so affected may benefit from early educational intervention, physical therapy, and occupational therapy. Counseling to improve self-image and lessen barriers to socialization becomes important in late childhood and adolescence.

Open fetal surgery has been performed for spina bifida during the last half of pregnancy. After direct closure of the spine malformation, the fetus is returned to the womb. By preventing chronic intrauterine exposure to mechanical and chemical trauma, prenatal surgery improves neurological function and leads to fewer complications after birth. Fetal surgery is considered experimental, and results have been mixed.

KEY TERMS

Chiari II anomaly— A structural abnormality of the lower portion of the brain (cerebellum and brain stem) associated with spina bifida. The lower structures of the brain are crowded and may be forced into the foramen magnum, the opening through which the brain and spinal cord are connected.

Fetus— The term used to describe a developing human infant from approximately the third month of pregnancy until delivery. The term embryo is used prior to the third month.

Hydrocephalus— The excess accumulation of cerebrospinal fluid around the brain, often causing enlargement of the head.

Prevention of isolated spina bifida and other spinal abnormalities has become possible during recent decades. The major prevention is through the use of a B vitamin, folic acid, for several months prior to and following conception. The Centers for Disease Control and Prevention recommend the intake of 400 micrograms of synthetic folic acid every day for all women of childbearing years.

Prognosis

More than 80% of infants born with spina bifida survive with surgical and medical management. Although complications from paralysis, hydrocephaly, Chiari II malformation, and urinary tract deterioration threaten the well-being of the survivors, the outlook for normal intellectual function is good.

Resources

ORGANIZATIONS

March of Dimes Birth Defects Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. (888) 663-4637. 〈http://www.modimes.org〉.

National Birth Defects Prevention Network. Atlanta, GA (770) 488-3550. 〈http://www.nbdpn.org〉.

Shriners Hospitals for Children. International Shrine Headquarters, 2900 Rocky Point Dr., Tampa, FL 33607-1460. (813) 281-0300. 〈http://www.shrinershq.org〉.

Spina Bifida Association of America. 4590 MacArthur Blvd. NW, Suite 250, Washington, DC 20007-4226. (800) 621-3141 or (202) 944-3285. Fax: (202) 944-3295.