Unknown: Spina Bifida

Definition
Description
Demographics
Causes and Symptoms
Diagnosis
Treatment
Prognosis
Prevention
The Future
For more information

Definition

Spina bifida (pronounced SPEYE-na BIFF-ih-da) is a birth defect in which the tissues and vertebrae that normally cover the spinal cord fail to close completely during the baby's development before birth. The words spina bifida mean “split spine” in Latin. Spina bifida is also known as a neural tube defect (NTD). Neural tube is the medical term for the folds of tissue in a human embryo that eventually give rise to the brain and spinal cord.

Description

Spina bifida is a birth defect that occurs during the first few weeks of pregnancy, before the mother knows she is pregnant. As the fertilized egg develops into the embryo, it forms three layers of tissue, one of which contains cells along the back of the embryo that eventually form the central nervous system. As this group of cells grows, it folds inward to form a sheath that eventually closes to form the brain and spinal cord. This closure usually takes place around the twenty-eighth day of pregnancy. If a portion of the neural tube fails to close properly, the baby's spine may be weakened, or portions of the spinal cord and meninges (the membranes that cover the brain and spinal cord) may push through the opening in the vertebrae.

The severity of spina bifida varies from a mild form that may be discovered only by accident to a severe form that can lead to premature death if untreated. There are three main types:

• Spina bifida occulta. This is the mildest form. Occulta means “hidden,” because the condition is not noticeable at birth. In this form, there is a small space or gap in one or several of the vertebrae in the spinal column. Because there is no damage to the spinal cord or other nerves, children with spina bifida occulta do not usually have symptoms. In many cases the gap in the vertebrae is discovered only during a routine x ray study in later life. Doctors estimate that between 5 and 30 percent of cases may fall into this group.
• Meningocele. This is a relatively rare form. The meninges that cover the spinal cord may push outward through the gap in the vertebrae to form a lump or cyst. The spinal cord itself is not affected, and in most cases the cyst can be removed surgically without damage.
• Myelomeningocele. This is the most severe form, also known as open spina bifida, which usually involves some type of permanent disability. A section of the spinal cord and the nerves leading outward from it protrude through the gap in the vertebrae and are exposed on the outside of the body.

Demographics

Spina bifida is the most common permanently disabling birth defect worldwide. It is estimated to affect one to two of every 1,000 newborns in the United States. In some parts of the world, the rates are higher: in Ireland and Wales, for example, there are three to four cases of myelomeningocele per 1,000 births.

There are some variations in frequency among different ethnic groups in the United States, with Hispanics having the highest rate of spina bifida, followed by Caucasians, Native Americans, African Americans, and Asian Americans. The total number of Americans with severe spina bifida was estimated to be around 70,000 in the early 2000s.

Spina bifida is slightly more common in girls than in boys, although the reason for this difference is not known.

Causes and Symptoms

The exact cause of NTD is not known, but is thought to be the result of interactions between genetic factors and the mother's diet. The fact that the rates of NTD vary from country to country and among different races suggests that genes are involved in the disorder. In addition, researchers have found that a woman who has one child with NTD has a greater chance of having a second child with NTD. Diabetes and seizure disorders also increase a woman's risk of having a baby with spina bifida.

Spina Bifida and Euthanasia

In 2004 a group of doctors in the Netherlands made headlines around the world with their publication of the Groningen Protocol, a document justifying the euthanasia, or mercy killing, of infants that the doctors regarded as involving “unbearable and hopeless suffering.” The doctors then published an article in the New England Journal of Medicine in 2005 defending their position and discussing the euthanasia of twenty-two newborns between 1997 and 2004 on the grounds that their cases were hopeless. All had spina bifida.

The article disturbed many people because even severe spina bifida is not considered a fatal disability. None of the twenty-two infants died simply from allowing their birth defect to take its course; they were killed by administering an overdose of a sleeping medication. Another Dutch doctor openly questioned the Groningen Protocol's reference to “unbearable suffering,” noting that the majority of patients with myelomeningocele can be treated surgically and have good prospects of a productive adult life. He concludes, “There is no reason whatsoever for active life-termination of these newborns.” An ongoing question remains: if spina bifida is considered a reason for ending a newborn's life, might other diseases come to be regarded in the same way?

With regard to diet, it is known that adequate amounts of folic acid (a form of vitamin B₉) in the mother's food during pregnancy can help to prevent spina bifida, though scientists are not yet certain why the vitamin has this beneficial effect. Folic acid is found in green leafy vegetables, egg yolks, dried peas and beans, brewer's yeast, fortified cereal products, and certain other fruits and vegetables. It can also be taken by itself as a dietary

supplement. Since January 1998, following recommendations from the Food and Drug Administration (FDA), folic acid has been added to breads, breakfast cereals, and other grain products sold in the United States.

The symptoms of spina bifida vary considerably according to the severity of the defect:

• Spina bifida occulta: There are usually no symptoms of damage to the nervous system; sometimes a small birthmark or tuft of hair on the skin over the small opening in the affected vertebrae is visible.
• Meningocele. A small fluid-filled sac, usually covered by a thin layer of skin, protrudes from the baby's back.
• Myelomeningocele. There may be a sac on the baby's back at birth, but in most cases the nerves and other tissues are exposed, leaving them extremely vulnerable to infection.

Open spina bifida is associated with a number of health problems and physical disabilities, depending on the location of the exposed part of the spinal cord.

• There is usually some degree of paralysis below the level of the defect in the spinal cord. The closer the defect lies to the head and neck, the more difficulties the person will have with walking, coordination, deformities of the hips and knees, and loss of muscle tone.
• A defect close to the lower back may lead to intense pain in the lower back, upper leg, and knee.
• Defects occurring toward the base of the spinal cord often result in loss of bowel and bladder control.
• About 90 percent of patients with open spina bifida develop hydrocephalus, or a buildup of fluid inside the skull caused by interference with the normal flow of cerebrospinal fluid, potentially lead to learning difficulties and problems with concentration as the child grows older.
• Babies with open spina bifida are at increased risk of meningitis, an infection of the meninges that can be life-threatening.
• Tethering of the spinal cord. With this complication, the spinal cord cannot move freely inside the vertebrae but is attached (tethered) to nearby tissues, which can lead to scoliosis (curvature of the spine), dislocation of the hip, and other deformities.
• Latex allergies, depression, obesity, and stomach disorders. These complications occur as children with spina bifida grow older.

Diagnosis

Spina bifida can be diagnosed during pregnancy by testing the mother's blood for a protein called alpha-fetoprotein, which is produced by the fetus and the placenta during pregnancy and enters the mother's bloodstream in small amounts. Unusually high levels of this protein may indicate a neural tube defect. The doctor can order additional tests, including taking a sample of the amniotic fluid surrounding the baby and performing an ultrasound imaging study.

Mild cases of spina bifida can be detected after the baby is born by an x-ray study, computed tomography (CT) scan, or magnetic resonance imaging (MRI). A CT scan may be ordered to check for fluid inside the skull if the doctor thinks that the baby may have hydrocephalus.

Treatment

There is no cure for spina bifida. Treatment depends on the location and severity of the defect in the spine. Babies with spina bifida occulta may not need any treatment, and those with meningocele are usually treated by having the cyst on the back removed by surgery. They usually have no complications.

Treatment of myelomeningocele is complex, as children with this severe form of spina bifida usually need extensive physical therapy and sometimes special education following surgery. In most cases newborns with open spina bifida are operated on as soon as possible after birth. They are given antibiotics to prevent infection of the exposed part of the spinal cord. The opening of the spinal cord is closed, and covered with skin and muscles taken from either side of the back. If the baby has hydrocephalus, a shunt system may be inserted to redirect excess fluid away from the brain to other parts of the body.

As the child grows older, additional operations are usually needed to correct a tethered spinal cord or scoliosis or to replace the shunt for hydrocephalus. Physical therapy usually includes range-of-motion exercises as well as strength exercises to prepare the child for walking with braces or crutches.

Prognosis

The prognosis for patients with spina bifida occulta and meningocele is good. The prognosis for patients with myelomeningocele depends on the location of the defect in the spinal column and the amount of spinal cord

that was exposed. Advances in prenatal diagnosis and surgery mean that most patients survive; and early treatment of hydrocephalus prevents mental retardation in most cases. With appropriate follow-up surgery and physical therapy, most patients with open spina bifida can complete their education and live independently; many marry and have families of their own.

Prevention

Although the genetic factors that may be involved in spina bifida have not been identified, adding folic acid to a mother's diet has been found to reduce a the baby's risk of spina bifida by 70 percent.

The Future

New approaches to surgical treatment of spina bifida include fetal surgery or operating on the baby before delivery. This technique involves opening the mother's abdomen and uterus and closing the opening over the baby's spinal cord. Fetal surgery is usually performed between the nineteenth and twenty-fifth weeks of pregnancy. Some researchers think that this early surgery improves the baby's chances of normal brain development as well as lowering the risk that the spinal cord may become infected; however, it also increases the risk of premature birth and the baby's death.

Other areas of research include the search for specific genes associated with spina bifida and studies that may shed light on why folic acid helps to prevent it.

WORDS TO KNOW

Euthanasia: Sometimes called mercy killing; the act of killing a hopelessly ill human or pet in a painless way.

Folic acid: A form of vitamin B₉ that helps to prevent spina bifida.

Meninges (singular, meninx): The three layers of protective tissue that cover the central nervous system.

Neural tube: The medical term for the folds of tissue in the human embryo that eventually form the brain and spinal cord.

Shunt: A flexible plastic tube inserted by a surgeon to drain cerebrospinal fluid from the brain and redirect it to another part of the body.

SEE ALSO Hydrocephalus; Meningitis; Scoliosis

For more information

BOOKS

Lutkenhoff, Marlene, ed. Children with Spina Bifida: A Parents' Guide, 2nd ed. Bethesda, MD: Woodbine House, 2008.

Watson, Stephanie. Spina Bifida. New York: Rosen Publishing Group, 2008.

PERIODICALS

Verhagen, Eduard, and Pieter J. J. Sauer. “The Groningen Protocol—Euthanasia in Severely Ill Newborns.” New England Journal of Medicine 352 (March 10, 2005): 959–962. Available online at http://content.nejm.org/cgi/content/full/352/10/959 (accessed July 26, 2008). This is the article that touched off a major controversy about intentionally ending the lives of newborns with spina bifida.

WEB SITES

Centers for Disease Control and Prevention (CDC). The Basics about Spina Bifida. Available online at http://www.cdc.gov/ncbddd/folicacid/spinabifidabasics.htm (updated October 16, 2007; acccessed July 27, 2008).

Mayo Clinic. Spina Bifida. Available online at http://www.mayoclinic.com/health/spina-bifida/DS00417 (updated October 4, 2007; accessed July 26, 2008).

National Institute of Neurological Disorders and Stroke (NINDS). Spina Bifida Fact Sheet. Available online at http://www.ninds.nih.gov/disorders/spina_bifida/detail_spina_bifida.htm (updated December 11, 2007; accessed July 26, 2008).

Spina Bifida Association (SBA). FAQs about Spina Bifida. Available online at http://www.spinabifidaassociation.org/site/c.liKWL7PLLrF/b.2642327/k.5899/FAQ_About_Spina_Bifida.htm (accessed July 26, 2008).