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Spina Bifida

Definition :
Spina bifida is a serious birth defect that occurs when the tissue surrounding the developing spinal cord of a fetus doesn't close properly. It's part of a group of birth defects called neural tube defects. The neural tube is the embryonic structure that eventually develops into the baby's brain and spinal cord and the tissues that enclose them.

In normal circumstances, the neural tube forms in the developing baby early in the pregnancy and closes by the 26th day after conception. Later, the top of this tube becomes the baby's brain, and the remainder of the tube becomes the baby's spinal cord. In babies with spina bifida, a portion of the neural tube fails to develop or close properly, causing defects in the spinal cord and in the bones that make up the backbone. This can also occur in the middle or upper end of the spine but is most common in the lower spine.

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

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

Risk Factor :
Although doctors and researchers don't know for sure why spina bifida occurs, they have identified a few Risk Factors:
  • Race. Spina bifida is more common among Hispanics and whites of European descent.
  • Family history of neural tube defects. Couples who've had one child with a neural tube defect have a slightly higher chance of having another baby with the same defect. That risk increases if two previous children have been affected by the condition. In addition, a woman who was born with a neural tube defect, or who has a close relative with one, has a greater chance of giving birth to a child with spina bifida. However, most babies with spina bifida are born to parents with no known family history of the condition.
  • Folic acid deficiency. This vitamin is important to the healthy development of a fetus. Lack of folic acid (vitamin B-9) increases the risk of spina bifida and other neural tube defects.
  • Some medications. Anti-seizure medications, such as valproic acid (Depakene), seem to cause neural tube defects when taken during pregnancy, perhaps because they interfere with the body's ability to use folic acid.
  • Diabetes. The risk of spina bifida increases with diabetes, especially when the mother's blood sugar is elevated early in her pregnancy. Much of this risk is preventable by careful blood sugar control and management.
  • Obesity. There's a link between pre-pregnancy obesity and neural tube birth defects, including spina bifida. Obese women may have more babies with spina bifida possibly because of nutritional deficits from poor eating habits or because they may have diabetes — another known risk factor for neural tube defects.
  • Increased body temperature. Some evidence suggests that increased body temperature (hyperthermia) in the early months of pregnancy may increase the risk of spina bifida. Most of the evidence surrounds hyperthermia as a result of a fever. Still, doctors aren't sure whether the increase in risk results from the hyperthermia or the underlying illness causing the fever. On the other hand, the use of saunas, hot tubs and tanning beds, which can raise body temperature, also have been associated with increased risk of spina bifida, suggesting that hyperthermia may indeed play a role.

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

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

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

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

  • Spina bifida occulta. This mildest form of the condition results in a small separation or gap in one or more of the vertebrae of the spine. This can occur in any vertebra but is most common at the base of the back or lower spine. Because the spinal nerves aren't involved, most children with this form of spina bifida have no signs or symptoms and experience no neurological problems. An abnormal tuft of hair, a collection of fat, a small dimple or a birthmark may be seen on the newborn's skin above the spinal defect and may be the only visible indication of the condition. In fact, most people who have spina bifida occulta don't even know it, unless the condition is discovered during an X-ray for unrelated reasons.
  • Meningocele. In this rare form of spina bifida, the protective membranes around the spinal cord (meninges) push out through the opening in the vertebrae. Because the spinal cord develops normally, these membranes can be removed by surgery with little or no damage to nerve pathways.
  • Myelomeningocele. Also known as open spina bifida, myelomeningocele is the most severe form of the condition — and the form people usually mean when they use the term "spina bifida." In myelomeningocele, the baby's spinal canal remains open along several vertebrae in the lower or middle back. Because of this opening, both the membranes and the spinal cord protrude at birth, forming a sac on the baby's back. In some cases, skin covers the sac. But in most cases, tissues and nerves are exposed, making the baby prone to life-threatening infections. Neurological impairment — often including loss of movement (paralysis) — is common. So are bowel and bladder problems, seizures and other medical complications.

Diagnosis:
If you're pregnant, you'll be offered prenatal screening tests to check for spina bifida and other birth defects. These tests may provide reassurance that your fetus doesn't have certain serious birth defects. Or they may detect a birth defect and help you manage your pregnancy more effectively, by planning to deliver in a specially equipped medical center, for example.

The tests aren't perfect. Even if the results are negative, there's still a small chance that spina bifida is present,

and most mothers who have positive blood tests have normal babies. Talk to your doctor about prenatal testing, its risks and how you might handle the results. Prenatal testing is a personal choice.

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

Results are most accurate when the test is performed between 16 and 18 weeks of gestation, but spina bifida can't be diagnosed by blood test alone. Some spina bifida cases don't produce a high level of AFP. On the other hand, when a high level of AFP is found, a neural tube defect is present only a small percentage of the time. [8] Varying levels of AFP can be caused by other factors — including a miscalculation in fetal age or multiple fetuses — so your doctor may order a follow-up blood test for confirmation. If the results are still high, you'll need further evaluation, including an ultrasound examination.

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

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

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

Ultrasound
If blood tests indicate high AFP levels, your doctor will suggest an ultrasound exam to help determine why. The most common ultrasound exams bounce high-frequency sound waves off tissues in your body to form black and white images on a small video monitor. The information these images provide can help establish whether there's more than one fetus and can help confirm gestational age — two factors that can raise AFP levels. An advanced ultrasound can also detect signs of spina bifida, such as an open spine or particular features in your baby's brain that indicate spina bifida. In expert hands, ultrasound today is quite effective in detecting spina bifida and assessing its severity. Ultrasound is safe for both mother and baby.

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

A small amount of AFP is normally found in amniotic fluid. However, when an open neural tube defect is present, the amniotic fluid contains an elevated amount of AFP because the skin surrounding the baby's spine is gone and AFP leaks into the amniotic sac. A second test can be done on the same sample to reliably confirm that a neural tube defect is present. Amniocentesis can't indicate the severity of spina bifida, however. This test does have a risk to the developing fetus. About one in 200 pregnant women miscarries after amniocentesis.

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

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

Children with myelomeningocele may experience physical and neurological problems, including lack of normal bowel and bladder control, and partial or complete paralysis of their legs. Children and adults with this form of spina bifida might need crutches, braces or wheelchairs to help them get around, depending on the size of the opening and the care received after birth.

Babies born with myelomeningocele also commonly experience accumulation of fluid in the brain, a condition known as hydrocephalus. Most babies with myelomeningocele will need a shunt — a surgically placed tube that allows fluid in the brain to drain as needed into the abdomen. This tube might be placed just after birth, during the surgery to close the sac on the lower back, or later as fluid accumulates.

The majority of newborns with myelomeningocele survive. However, some may develop meningitis, an infection in the tissues surrounding the brain. Meningitis may cause brain injury and can be life-threatening.

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

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

Myelomeningocele also requires surgery, usually within several hours to several days after birth. Performing the surgery early can help minimize risk of infection that's associated with the exposed nerves and may also help protect the spinal cord from additional trauma. During the procedure, a neurosurgeon places the spinal cord and exposed tissue inside the body and covers them with muscle and skin. Sometimes a shunt to control hydrocephalus is placed during the operation on the spinal cord. Sometimes the shunt placement isn't needed until weeks or months later.

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

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

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

Prenatal surgery
Researchers are investigating the effectiveness of prenatal surgery for spina bifida. In this experimental and controversial procedure, which is only performed at a handful of hospitals, surgeons lift a pregnant mother's uterus out of her belly and place it on her abdomen, where they are able to cut into the uterus and repair the fetus's spinal cord. The surgery takes place between the 19th and 25th weeks of pregnancy.

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

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

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

The key is having enough folate — the natural form of folic acid — in your system by the early weeks of pregnancy, before the neural tube closes. Because many women don't discover that they're pregnant until this time, the March of Dimes, the Centers for Disease Control and Prevention, and the Institute of Medicine recommend that all women of childbearing age take a daily supplement with 400 micrograms (mcg) of folic acid or consume breakfast cereals fortified with 100 percent (400 mcg) of folic acid per serving (Whole Grain Total, Total Raisin Bran, Smart Start, others). To find out the percentage of daily value supplied by a cereal, check its nutrition label.

The Institute of Medicine advises pregnant women and breast-feeding women to up their daily folic acid intake to 600 mcg and 500 mcg, respectively. These recommendations aren't intended to prevent neural tube defects; the increased amounts are needed because your body uses extra folic acid during pregnancy and lactation.

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

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

It's possible that folic acid will also help reduce the risk of other birth defects, including cleft lip, cleft palate and some congenital heart defects. Folic acid may also help protect against some forms of cancer and heart disease.

When higher doses are needed
If you have spina bifida or if you have a child with spina bifida, you'll need extra folic acid before you become pregnant. If you're taking anti-seizure medications or you have diabetes, you may also benefit from a higher dose of this B vitamin. In these cases, the recommended dose of folic acid may be up to 4,000 mcg (4 milligrams) for up to three months before conception. If you think you might need this increased amount of folic acid, ask your doctor for a prescription dose of the vitamin. Don't simply take extra multivitamins because the additional amounts of other vitamins may be harmful to you and your baby.

 
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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