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.
There are three classifications of holoprosencephaly. Alobar, in which the brain has not divided at all, is usually associated with severe facial deformities. Semilobar, in which the brain's hemispheres have somewhat divided, causes an intermediate form of the disorder. Lobar, in which there is considerable evidence of separate brain hemispheres, is the least severe form. In some cases of lobar holoprosencephaly the baby's brain may be nearly normal.
The least severe of the facial anomalies is the median cleft lip (premaxillary agenesis). The most severe is cyclopia, an abnormality characterized by a single eye located in the area normally occupied by the root of the nose, and a missing nose or a proboscis (a tubular-shaped nose) located above the eye. The least common facial anomaly is ethmocephaly, in which a proboscis separates closely-set eyes. Cebocephaly, another facial anomaly, is characterized by a small, flattened nose with a single nostril situated below incomplete or underdeveloped closely-set eyes.
|Carter Centers for Brain Research in Holoprosencephaly
c/o Texas Scottish Rite Hospital P.O. Box 190567
2222 Welborn Street
Dallas, TX 75219-9982
|National Organization for Rare Disorders (NORD)
55 Kenosia Avenue
Danbury, CT 06810
Tel: 203-744-0100 Voice Mail 800-999-NORD (6673)
|The Arc of the United States
1825 K Street, NW
Washington, DC 20006
Tel: 202-534-3700 800-433-5255
|March of Dimes
1275 Mamaroneck Avenue
White Plains, NY 10605
Tel: 914-997-4488 888-MODIMES (663-4637)
Office of Communications and Public Liaison
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892
NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.
All NINDS-prepared information is in the public domain and may be freely copied. Credit to the NINDS or the NIH is appreciated.
Last updated February 13, 2007