Acephaly (medicine)

Overview
Acephaly is a type of cephalic disorder. This literally means absence of the head. It is a much rarer condition than anencephaly. The acephalic fetus is a parasitic twin attached to an otherwise intact fetus. The acephalic fetus has a body but lacks a head and heart; the fetus's neck is attached to the normal twin. The blood circulation of the acephalic fetus is provided by the heart of the twin. The acephalic fetus can not exist independently of the fetus to which it is attached. Similarly, acardiac fetuses lack everything from the heart upwards, including head and arms, and behave similarly to acephalic fetuses.