Spina bifida is the most common disabling birth defect in the United States. It is a type of neural tube defect, which is a problem with the spinal cord or its coverings. It happens if the fetal spinal column doesn't close completely during the first month of pregnancy. There is usually nerve damage that causes at least some paralysis of the legs. Many people with spina bifida will need assistive devices such as braces, crutches or wheelchairs. They may have learning difficulties, urinary and bowel problems or hydrocephalus, a buildup of fluid in the brain.
MedlinePlus - Spina Bifida