Holoprosencephaly

Holoprosencephaly is a disorder caused by the failure of the prosencephalon (the forebrain of the embryo) to divide to form bilateral cerebral hemispheres, causing defects in the development of the face and in brain structure and function.

Once called arhinencephaly, the disorder consists of a spectrum of defects or malformations of the brain and face. Most cases are associated with severe malformations of the brain which are incompatible with life and often cause spontaneous intrauterine death. At the other end of the spectrum are individuals with facial defects which may affect the eyes, nose, and upper lip and normal or near-normal brain development. Seizures and mental retardation may occur. The most severe of the facial anomalies 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 nose in the form of a proboscis (a tubular appendage), located above the eye.

Ethmocephaly is the least common facial anomaly. It consists of a proboscis separating narrow-set eyes with an absent nose and microphthalmia (abnormal smallness of one or both eyes). Cebocephaly, another facial anomaly, is characterized by a small, flattened nose with a single nostril situated below incomplete or underdeveloped closely set eyes. The least severe in the spectrum of facial anomalies is the median cleft lip also called premaxillary agenesis.

There are three classifications of holoprosencephaly. Alobar, the most serious form in which the brain has no tendency to separate, is usually associated with severe facial anomalies. Semilobar, in which the brain's hemispheres have a slight tendency to separate, is an intermediate form of the disease. Lobar, in which there is considerable evidence of separate brain hemispheres, is the least severe form. In some cases of lobar holoprosencephaly the patient's brain may be nearly normal.

There is no standard course of treatment for holoprosencephaly. Treatment is symptomatic and supportive.

The prognosis for individuals with the disorder is poor. Most of those who survive show no significant developmental gains.

Information provided by the
National Institute of Neurological Disorders and Stroke,
National Institutes of Health

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.