Anencephaly is a malformation of the nervous system caused by failure of the anterior neuropore to close. Infants are born with intact spinal cords, cerebellums, and brainstems, but lack formation of neural structures above this level. All structures associated with sensation and consciousness are missing.
The skull is only partially formed but the eyes are usually normal. This condition may be associated with folate deficiency. Affected infants are only capable of primitive (brain stem) reflexes and usually do not survive for more than two weeks.  The condition is often cited as a case in which active treatment would be futile care, since there is no possibility of interaction with the world, and no way to restore the missing brain functions, although others believe that an anencephalic infant is fully human and deserves aggressive care.
- Menkes, Textbook of Child Neurology, 5th ed, p247, quoted in Medical Subject Headings