Holoprosencephaly (HPE)


Holoprosencephaly (HPE) occurs when an unborn baby's brain does not grow forward and divide properly during early pregnancy. Normally, the brain splits into two halves (called hemispheres) during development. The hemispheres communicate to each other through a band of 200-250 million nerve fibers, called the corpus callosum. In patients with HPE, the hemispheres are not separated properly.
As a result, there are abnormalities in the face and structure and function of the brain.
Common signs and symptoms include a small head (called microcephaly), excessive fluid in the brain (called hydrocephalus), and intellectual disabilities (formerly called mental retardation) of varying degrees.
The severity of HPE ranges from mild to severe. According to studies, in about 97% of cases, the malformations are so severe that the baby dies before birth. In less-severe cases, babies are born with normal or near-normal brain development and facial malformations that may affect the nose, eyes, and upper lip.
According to the National Institute of Neurological Disorders and Stroke (NINDS), there are three classic subtypes of HPE: alobar HPE, semilobar HPE, and lobar HPE.
Researchers estimate that about one baby out of 10,000-20,000 babies born in the United States has HPE. However, because so many mothers of children with HPE have miscarriages, the frequency of HPE among all pregnancies may be as high as one out of 200-250.
There is no cure or specific treatment for HPE. Instead, treatment is aimed at reducing the symptoms.
According to the NINDS, the prognosis for people with HPE is generally poor, but it depends on the severity of the brain and facial malformations and genetic abnormalities. Of the three percent of babies who are born alive, most die before the age of six months. However, patients with mild forms of HPE, such as lobar HPE, may have normal life expectancies if the brain is only mildly affected by the disorder.

Related Terms

Alobar holoprosencephaly, arhinencephaly, brain hemispheres, cebocephaly, congenital brain disorder, cyclopia, demyer sequence, ethmocephaly, familial HPE, familial holoprosencephaly, gastroesophageal reflux disease, GERD, familial alobar holoprosencephaly, holoprosencephaly malformation complex, holoprosencephaly sequence, HPE, hydrocephalus, isolated HPE, isolated holoprosencephaly, karyotype, lobar holoprosencephaly, microcephaly, midline cleft syndrome, sleep apnea, semilobar holoprosencephaly, trisomy 13, trisomy 15, trisomy 18.

types of holoprosencephaly

According to the National Institute of Neurological Disorders and Stroke (NINDS), there are three classic subtypes of HPE: alobar HPE, semilobar HPE, and lobar HPE.
Alobar HPE: Alobar HPE is the most severe type of HPE. This type of HPE occurs when the brain is not divided into hemispheres at all. It is usually associated with severe facial malformations. Almost two-thirds of infants with HPE have alobar HPE. Research has shown that about half of patients with alobar HPE die before the age of 4-5 months, and 20% live past the first year of life.
Semilobar HPE: Semilobar HPE occurs when the brain's two hemispheres have partially divided. Semilobar HPE occurs when the left and right frontal and parietal lobes are fused and the interhemispheric fissure is only present posteriorly. It is considered a moderate form of HPE. About 25% of people with HPE have semilobar HPE.
Lobar HPE: Lobar HPE is the mildest classic form of HPE. It occurs when the brain has almost divided into separate brain hemispheres. In some cases, a patient's brain may be near normal.
Middle interhemispheric fusion variant (MIHV): Middle interhemispheric fusion variant is a very rare and unusual condition that occurs when the anterior parts of the frontal lobes and the occipital lobes are separated. It is unclear if MIHV is a subtype of HPE or a separate medical condition.