A congenital a neural tube defect in which the spinal canal does not close before birth and part of the meninges (Meningocele) and sometimes part of the spinal cord itself (Myelomeningocele) creates a sac-like herniation in the back. Additionally, a hidden form (Spina Bifida Occulta) is now known to exist, where little/none of the meninges or spinal cord protrude through the back.