HYDRANENCEPHALY is a congenital anomaly of the head that consists of complete or nearly complete absence of the cerebral hemispheres together with intact meninges and skull. It is associated with a normal-sized head when the condition is encountered early in infancy. Babies who have this anomaly present normal appearances and reactions during the first few weeks of life. Retardation of neuromuscular development and excessive enlargement of the head usually are not obvious until the child is several months old.
This anomaly was first described by Cruveilhier in 1835 and was named "l'anencephalie hydrocephalique" (hydrocephalic anencephaly).1 This term later was consolidated into one word by Spielmeyer2 in 1905, and hydranencephaly has been the accepted designation for this condition, although Yakovlev and Wadsworth3 suggested the name "schizencephalies" after detailed histologic study of two cases. The latter authors considered the defect to be a true cerebral agenesia, with congenital clefts