Neural Tube Defect (NTD) is a birth defect that results from incomplete closure of the neural tube during embryonic development. Some of the manifestations of it are:

ANENCEPHALY: a universally fatal deformity, where the brain is partially formed. It comprises between 50 per cent and 80 per cent of all NTDs.

ENCEPHALOCELE: a defect in the skull that results in protrusion of the meninges