Prenatal ultrasonographic diagnosis of holoprosencephaly. Two cases of cebocephaly and two of cyclopia.

Four instances of ultrasonographic detection of holoprosencephaly, one during the second and three during the third trimester of gestation, are reported. Horizontal scans of the skull showed absence of midline structures, communication between the lateral ventricles and reduction of the brain mass, particularly anteriorly. Sagittal scans revealed absence of the nose and presence of a proboscis in the fetuses with cyclopia and hypoplasia of the nose in one cebocephalic fetus. Hypotelorism or a single midline orbit are further pathognomonic features detectable by ultrasound, but only the latter was identified in one of the cyclopic fetuses. Facultative findings of holoprosencephaly identifiable by ultrasound, but absent in our cases, are premaxillary agenesis and bilateral cleft lip and maxilla. The characteristic pattern of ultrasonographic findings in holoprosencephaly should allow an unequivocal prenatal diagnosis during the second and third trimester.