Holoprosencephaly is a disorder caused by the failure of the prosencephalon (the embryonic forebrain) to sufficiently divide into the double lobes of the cerebral hemispheres. The result is a single-lobed brain structure and severe skull and facial defects. In most cases of holoprosencephaly, the malformations are so severe that babies die before birth. In less severe cases, babies are born with normal or near-normal brain development and facial deformities that may affect the eyes, nose, and upper lip. For more complete information, please follow the link below.+ Associated link: http://www.ninds.nih.gov/health_and_medical/disorders/holoprosencephaly.htm

serious brain abnormality where the developing forebrain fails to undergo normal division into 2 lobes. Facial development is often altered—there may be a single eye, closely spaced eyes with a single nostril, a midline cleft lip or a single central front incisor tooth. Holoprosencephaly often causes mental retardation and/or death.

A birth defect where the forebrain does not separate properly into two halves during early fetal life. The disorder results in mild to severe brain malformation and is sometimes fatal. It may be caused by environmental or genetic factors. Holoprosencephaly affects between 1 in 5,000 and 1 in 10,000 live births.