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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. 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. (From Menkes, Textbook of Child Neurology, 5th ed, p247)

A monster devoid of brain.-Bonetus, G. St. Hilaire. Also, one that has a part only of the brain ;-Paraceph'alus. The condition has been called Anencephal'ia. A weak, silly person.-Hippocrates.

A monstrosity characterized by absence of the brain and spinal cord, the cranium being open throughout its whole extent and the vertebral canal converted into a groove. [Gr.]