Holoprosencephaly (HPE)

Published on July 2, 2016

History: 2-month-old girl with a craniofacial abnormality

Findings: Three-dimensional CT with soft tissue algorithm shows a cleft lip, abnormal nares, and hypotelorism (eyes close together).
Axial CT images demonstrate fusion of the thalami and a large monoventricle.

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Hypotelorism is a medical condition pertaining to eyes that have an abnormally small distance between them.
It is often a result of fetal alcohol syndrome (FAS) caused by large alcohol intake in the first month of pregnancy.
It can be associated with trisomy 13 which is also known as Patau syndrome, as well as hereditary neuralgic amyotrophy.

It can also be associated with fragile X syndrome and Prader-Willi syndrome.
Metopic synostosis, the early closure of metopic suture during skull development in children, can also cause hypotelorism.

Discussion: Holoprosencephaly refers to a continuum of congenital malformations occurring from failure of induction of the  prosencephalon and absent or incomplete clevage of the brain into distinct hemispheres. Three subtypes have been proposed according to the severity of cerebral and facial anomalies. These include alobar, semilobar, and lobar holoprosencephaly. In the most severe subtype, alobar holoprosencephaly, there is complete or near complete lack of hemispheric cleavage. A primitive midline monoventricle, fused thalami, and absence of the falx cerebri and interhemispheric fissure are the typical imaging features. Midline facial anomalies ranging from hypotelorism to cyclopia (one eye) are usually present. A multitude of extracranial and chromosomal abnormalities may occur in association with alobar holosencephay, frequently resulting in a stillborn infant or death in the neonatal period.

Aunt Minnie’s Pearls: Midline monoventricle with a fused thalami = alobar holoprocencephaly.

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