Can anyone tell me what....?

Holoprosencephaly is a brain malformation that is caused by a primary defect in patterning and induction of the basal forebrain during embryogenesis, causing the brain to develop improperly and resulting in incomplete division of the cerebral hemispheres (Stashinko 2004). The level of non-separation of the cerebral hemispheres indicates the severity of this defect. From most severe to least, the types of holoprosencephaly include alobar, semilobar, and lobar. In alobar holoprosencephaly, there is a single, small ventricular cerebrum without division into hemispheres, a single ventricle, and absent olfactory bulbs and optic tracts. In semilobar holoprosencephaly, there are rudimentary cerebral lobes with partially separated hemispheres. In lobar holoprosencephaly, the central lobes are well developed and the fissure between the hemispheres is distinct, but there is still some fusion of brain structures. Facial anomalies are frequently present, ranging in severity from a flattened nose and closely spaced eyes through a cleft or split lip and a single nostril to cyclopia, where a nose-like proboscis is present over a single eye in the middle of the face. Hydrocephaly or microcephaly is sometimes present. Recently, a fourth type of holoprosencephaly has been described. Middle interhemispheric variant of holoprosencephaly occurs when the rear portion of the brain (posterior frontal and parietal areas) do not separate but the frontal portion of the brain is preserved (Stashinko 2004).

What is Holoprosencephaly?

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.

Is there any treatment?

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

What is the prognosis?

The prognosis for individuals with the disorder depends on the severity of the brain and facial deformities.

What research is being done?

The NINDS supports and conducts a wide range of studies that focus on identifying and learning more about the factors involved in normal brain development. Recent research has identified specific genes that cause holoprosencephaly. The knowledge gained from these fundamental studies provides the foundation for understanding how to develop new ways to treat, and potentially prevent, this disorder.

Holoprosencephaly is a type of cephalic disorder. This is a disorder characterized by the failure of the prosencephalon (the forebrain of the embryo) to develop. During normal development the forebrain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy, though the condition also occurs in other species (as with Cy, the Cyclops Kitty). Holoprosencephaly is caused by a failure of the embryo's forebrain to divide to form bilateral cerebral hemispheres (the left and right halves of the brain), causing defects in the development of the face and in brain structure and function.

Symptoms

There are three classifications of holoprosencephaly. Alobar holoprosencephaly, the most serious form in which the brain fails to separate, is usually associated with severe facial anomalies. Semilobar holoprosencephaly, in which the brain's hemispheres have a slight tendency to separate, is an intermediate form of the disease. Lobar holoprosencephaly, 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.

Holoprosencephaly, once called arhinencephaly, consists of a spectrum of defects or malformations of the brain and face. At the most severe end of this spectrum are cases involving serious malformations of the brain, malformations so severe that they 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 defects (or anomalies) is cyclopia, an abnormality characterized by the development of 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. The condition is also referred to as cyclocephaly or synophthalmia.

In his book Mutants: On the Form, Varieties and Errors of the Human Body [1], Armand Marie Leroi describes the cause of cyclopia as a genetic malfunctioning during the process by which the embryonic brain is divided into two. Only later does the visual cortex take recognisable form, and at this point an individual with a single forebrain region will be likely to have a single, possibly rather large, eye (at such a time, individuals with separate cerebral hemispheres would form two eyes).

Leroi goes on to state that:

[Holoprosencephaly] is, in all its manifestations, the most common brain deformity in humans, afflicting 1 in 16,000 live-born children and 1 in 200 miscarried foetuses.

The regular appearance in Western society of such deformed human babies seems to have ceased or been withheld from the public view, probably in part due to the contemporary Western practice of hospitalisation at birth.

Holoprosencephaly is a type of cephalic disorder. This is a disorder characterized by the failure of the prosencephalon (the forebrain of the embryo) to develop. During normal development the forebrain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy, though the condition also occurs in other species (as with Cy, the Cyclops Kitty). Holoprosencephaly is caused by a failure of the embryo's forebrain to divide to form bilateral cerebral hemispheres (the left and right halves of the brain), causing defects in the development of the face and in brain structure and function.

ever heard of google, these answers are a great thing but so is reading a little bit, this isn't a smarta'ss answer , it a realistic one. it's where the brain doesn't develop normally when babies are still unborn.