All of the following are neural tube defects except:

Ans. D. HoloprosencephalyNeural tube defects (NTDs) are a group of birth defects in which an opening in the spinal cord or brain remains from early in human development. In the 3rd week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo begin to change shape and form the neural tube. When the neural tube does not close completely, an NTD develops. There are 2 types of NTD: open and closed. Open NTDs occur when the brain and/or spinal cord are exposed at birth through a defect in the skull or vertebrae (back bones).Examples of open NTDs are anencephaly, encephaloceles, hydranencephaly, iniencephaly, schizencephaly, and spina bifida. Rarer types of NTDs are called closed NTDs. Closed NTDs occur when the spinal defect is covered by skin. Common examples of closed NTDs are lipomyelomeningocele, lipomeningocele, and tethered cord.