Anencephaly is a neural tube defect (a disorder involving incomplete development of the brain, spinal cord, and/or their protective coverings). The neural tube is a narrow sheath that folds and closes between the 3rd and 4th weeks of pregnancy to form the brain and spinal cord of the embryo. Anencephaly occurs when the "cephalic" or head end of the neural tube fails to close, resulting in the absence of a major portion of the brain, skull, and scalp. Infants with this disorder are born without both a forebrain (the front part of the brain) and a cerebrum (the thinking and coordinating area of the brain). The remaining brain tissue is often exposed--not covered by bone or skin. The infant is usually blind, deaf, unconscious, and unable to feel pain. Although some individuals with anencephaly may be born with a rudimentary brain stem, the lack of a functioning cerebrum permanently rules out the possibility of ever gaining consciousness. Reflex actions such as respiration (breathing) and responses to sound or touch may occur. The cause of anencephaly is unknown. There is no cure or standard treatment for anencephaly. The prognosis for individuals with anencephaly is extremely poor. If the infant is not stillborn, then he or she will usually die within a few hours or days after birth.