Congenital defects of closure of one or more vertebral arches, which may be associated with malformations of the spinal cord, nerve roots, congenital fibrous bands, lipomas, and congenital cysts; spinal dysraphism includes all forms of spina bifida; the open form is called spina bifida cystica and the closed form is spina bifida occulta (based on MeSH-2007)