Causes and Incidence of Spina Bifida

Spina bifida is the most common neural tube defect. Its incidence varies with population and races, but is estimated at 1-2 in 1000 live births.

There are four types of spina bifida:   occulta, closed neural tube defects, meningocele, and myelomeningocele.

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

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

In the third type, meningocele, the meninges protrude from the spinal opening, and the malformation may or may not be covered by a layer of skin.   Some patients with meningocele may have few or no symptoms while others may experience symptoms similar to closed neural tube defects.

Myelomeningocele, the fourth form, is the most severe and occurs when the spinal cord is exposed through the opening in the spine, resulting in partial or complete paralysis of the parts of the body below the spinal opening.    The paralysis may be so severe that the affected individual is unable to walk and may have urinary and bowel dysfunction.

Spina Bifida Causes

Both genetic factors (heredity) and environmental factors, such as nutrition and exposure to harmful substances, probably contribute to spina bifida. Spina bifida does seem to run in families, although with mixed patterns of inheritance. Having a child with spina bifida increases the chance that another child will also have spina bifida by 8 times. In about 95% of cases of spina bifida, however, there is no family history of neural tube defects.

Research has suggested that many cases of spina bifida can be prevented by adequate intake of folic acid (folate) before and during early pregnancy. However, people with spina bifida appear to have abnormal metabolism of folic acid. This suggests that the underlying problem in spina bifida may be an inborn defect in folic acid metabolism rather than a simple deficiency in this nutrient. However. it is recommended that all women of childbearing age take folic acid supplements to prevent the occurence of spina bifida.

Sources

http://www.emedicinehealth.com/spina_bifida/page2_em.htm#Spina%20Bifida%20Causes

http://www.ninds.nih.gov/disorders/spina_bifida/detail_spina_bifida.htm

By Rachel

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~ by pcl4 on October 14, 2008.

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