Alobar holoprosencephaly: ultrasonographic prenatal diagnosis.

Abstract

Modern ultrasound imaging devices have increasingly allowed sophisticated prenatal diagnoses of fetal disorders. Embryopathologic and ultrasound findings are reported in five cases of alobar holoprosencephaly that were diagnosed prenatally, two cases as early as 23 menstrual weeks. Specific sonographic findings included a large central cranial fluid collection (a monoventricular cavity lacking ventricular horns and midline structures), a fused thalamus at the floor of this cavity, and characteristic facial features (proboscis, single orbit, single nostril, or severe hypotelorism). Differential diagnosis of the fetus with a large intracranial fluid collection is discussed and illustrated.

Two Cases of Holoprosencephalies

“…There are three main forms of holoprosencephaly, namely, alobar, semilobar and lobar varieties. The alobar holoprosencephaly is the most severe form and shows undifferentiated holosphere of the cerebral parenchyma with a central monoventricle and fused thalami 1,3 . The falx, interhemispheric fissure, corpus callosum, optic tracts, olfactory bulbs, and the septum pellucidum are absent.…”

“…Modern ultrasound imaging devices have increasingly allowed sophisticated prenatal diagnosis of fetal disorders. Embryopathologic and ultrasound findings are reported in five cases of alobar holoprosencephaly that were diagnosed prenatally, two cases as early as 23rd menstrual weeks 3 . Classically three subtypes of…”

Lobar Holoprosencephaly: Cranial Sonography and MRI Imaging Features

“…Holoprosencephaly (HP) results from failure of the prosencephalon to differentiate into the cerebral hemispheres and lateral ventricles between the fourth and eighth week of gestation [1][2][3]. A spectrum of defects of malformations of the brain and face exists, which range from complete to partial failure of cleavage of the prosencephalon.…”

“…It results in a single, amorphous ventricle, fused thalami and absence of the corpus callosum, falx cerebri, optic tracts and olfactory bulbs [3,4]. Semilobar HP, in which the brain's hemispheres have a slight tendency to separate, is an intermediate form of the disease.…”

“…Semilobar HP, in which the brain's hemispheres have a slight tendency to separate, is an intermediate form of the disease. It shares many of these same features but demonstrates partial segmentation of the ventricles and incomplete fusion of the thalami [3,4]. Lobar HP, in which there is considerable evidence of separate brain hemispheres, is the least severe form.…”