What is Spina Bifida?

Taken from the National Institute of Neurological Disorders and Stroke web page:

"Spina bifida, which literally means “cleft spine,” is characterized by the incomplete development of the brain, spinal cord, and/or meninges (the protective covering around the brain and spinal cord).   It is the most common neural tube defect in the United States—affecting 1,500 to 2,000 of the more than 4 million babies born in the country each year.

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. 
The exact cause of spina bifida remains a mystery.   No one knows what disrupts complete closure of the neural tube, causing a malformation to develop.  Scientists suspect genetic, nutritional, and environmental factors play a role.  Research studies indicate that insufficient intake of folic acid—a common B vitamin—in the mother’s diet is a key factor in causing spina bifida and other neural tube defects.   Prenatal vitamins that are prescribed for the pregnant mother typically contain folic acid as well as other vitamins."