Spina bifida

Spina bifida is the common name for a range of birth defects caused by problems with the early development of the spine. The main defect of spina bifida is an abnormal opening in the spinal column through which the spinal cord passes. This leaves the spinal cord unprotected and vulnerable to either injury or infection.

Spina bifida occurs in one of every 700 births to whites in North America, but only one in every 3,000 births to blacks. In some areas of Great Britain, the occurrence of spina bifida is as high as one in every 100 births, leadingto the hypothesis that some environmental factors must be at work.

The classic defect of spina bifida is an opening in the spine, obvious at birth, out of which protrudes a fluid-filled sac. This sac may include either just the membranes which cover the spinal cord or the membranes plus some partof the actual spinal cord. Often, the spinal cord itself has not developed properly. In spina bifida occulta, there may be some opening in the vertebrae,but no protruding sac. The entire defect may be covered with skin. The most severe form is called rachischisis, in which the entire length of the spine may be open.

The problems caused by spina bifida depend on a number of factors, includingwhere along the spine the defect occurs and what other defects there are. Themost severe types of spina bifida (raschischisis) is often fatal, either dueto infection of the exposed tissues, or because of severe loss of function.

Spina bifida is one of a number of "neural tube" defects. The neural tube isthe name for the very primitive structure which forms during fetal development, and which ultimately becomes the spinal cord and the brain. In spina bifida, the spinal column fails to wrap completely around the developing spinal cord. The abnormal development which causes in neural tube defects occurs veryearly in pregnancy, within the first three to four weeks.

Because different levels of the spinal cord are responsible for different functions, the location and the size of the defect in spina bifida will affect what kind of disabilities an individual will experience. Most patients with spina bifida have some degree of weakness in the legs ranging from slight to total paralysis, depending on the spinal cord condition. The higher up in the spine the defect occurs, the more severe the disabilities.

People with spina bifida frequently face severe problems with both bladder and bowel function, because complete emptying of both bladder and bowels requires an intact spinal cord. Difficulty in completely emptying the bladder can result in severe, repeated infections, ultimately causing kidney damage, whichcan be life threatening.

There are several types of defects which frequently accompany spina bifida. Arnold-Chiari malformations are changes in the brain structures that contribute to a condition called water on the brain (called hydrocephalus). Hydrocephalus is a condition in which there is too much cerebrospinal fluid (which protects the brain and spinal cord). If left to accumulate, this fluid puts damaging pressure on the brain.

Many children with spina bifida have other complications, including clubfeetand hip dislocations, as well as abnormal curves and bends in their spine causing a hunchbacked or twisted appearance.

Intelligence in children with spina bifida varies widely, and depends on theseverity of the spinal defect and the presence of other conditions. Some children have normal intellectual potential, while others may operate at a slightly lower than normal capacity. Extreme intellectual deficits may occur in children with very severe spinal defects with associated Arnold-Chiari malformations and water on the brain.

It has recently been noted that children with spina bifida have a much higherrisk of allergic sensitivity to latex causing anything from a minor skin rash to a more life-threatening reaction. This latex sensitivity is an importantissue for these children, who have a much higher likelihood of coming into contact with latex surgical or exam gloves, as well as other medical supplies.

The protruding sac of severe spina bifida is quite apparent at birth, but other forms of spina bifida may be so subtle as to cause just the slightest dimple at the base of the spine. Clues that a baby has mild spina bifida includebirthmarks located on the back along the area of the spine or areas of hair growth in the same general location. Other symptoms include muscle weakness and poor reflexes, as well as poor muscle tone of the ring of muscles that makeup the anal opening (sphincter).

When spina bifida is suspected, spinal x rays, computed tomography scans (CTscans) of the spine, and ultrasound examinations of the area may help in diagnosis. Myelography is a procedure in which dye is injected into the area surrounding the spinal cord, followed by either x ray or CT scan. This allows thespinal cord to be examined more accurately. X ray, CT, and magnetic resonance imaging (MRI) exams are also needed in order to search for those problems which frequently accompany spina bifida, including hydrocephalus, Arnold-Chiari malformations, hip problems, and kidney damage.

Diagnosis prior to birth is an important area of concern. A particular substance, known as alpha-fetoprotein (AFP), is present at higher-than-normal levels in the blood of mothers who are carrying a fetus with a neural tube defect.AFP levels are tested during the 16 to 18 weeks of pregnancy. Abnormally high levels of AFP indicate that other tests should be done. These tests includewithdrawing a sample of the fluid around the fetus (amniocentesis) to test for higher levels of AFP, and sophisticated ultrasound examination of the fetus. Results of amniocentesis, together with the results of careful ultrasoundexamination can diagnose more than 90% of all neural tube defects. Parents must then decide whether to terminate the pregnancy, or to use this informationto prepare themselves to care for a child who will have significant medicalneeds.

Treatment of spina bifida is aimed first at closing the spinal defect in order to avoid complications which could be brought on by infection. Further operations are often necessary in order to repair the hip dislocations, clubfeetand spinal distortions which often go along with a spinal defect. Children with hydrocephalus will need drainage tubes to prevent brain damage. Many children who are able to learn to walk will require braces.

Many children with severe spina bifida are unable to completely empty their bladders, and can only do so with the insertion of a catheter tube. Such catheterization may be necessary at regular points throughout every day, in orderto avoid the accumulation of urine which could back up, become infected, anddamage the kidneys.

Children with significant bowel impairment may have severe constipation, which requires a high-fiber diet, laxative medications, enemas, or even removal of stool by hand to avoid bowel blockage.

Prognosis for a child with spina bifida has certainly improved, yet it stilldepends on the severity of the original spinal defect, as well as on other associated problems. The worst prognosis exists for those who are completely paralyzed, have a serious infection, or have hydrocephalus or other birth defects. Current care for children with spina bifida usually enables them to liveinto adulthood.

While doctors don't yet know how to prevent spina bifida or other neural tubedefects, women who supplement their diets with folic acid prior to pregnancyand during the early weeks of pregnancy have a much lower risk of producinga baby with a neural tube defect. In fact, some studies indicate that taking0.4 mg of folic acid decreases the risk of spina bifida by up to 75%. Becausethe defect which causes spina bifida occurs within the first 3 to 4 weeks ofpregnancy, usually before a woman even realizes that she is pregnant, current recommendations state that any woman who is considering getting pregnant should immediately begin taking a folic acid supplement. Medications such as valproic acid, which increase the risk of neural tube defects if taken during pregnacy, should be avoided.

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