Neural tube defects (NTD's) are conditions where an opening in the spinal cord or brain remains from early in human development.
In week 3 gestation, during gastrulation (i.e. phase where the single layered blastula is reorganized into a trilaminar structure called the gastrula), specialized cells on the dorsal/back of the fetus begin to change shape, and form the neural tube
The failure of the neural tube to close completely is called an NTD
Open, which is more common. It occur when the brain or spinal cord are exposed at birth through a defect in the skull or vertebrae (back bones), including: