Intraventricular fused fornices: a specific sign of fetal lobar holoprosencephaly

Abstract

Lobar holoprosencephaly can be recognized in utero with sonography. However, a specific diagnosis is difficult and thus far has relied upon a qualitative evaluation of the morphology of the cerebral ventricles. In infants with this condition, magnetic resonance imaging demonstrates at times an abnormal appearance of the fornices, which are rudimentary and fused in to a single fascicle running within the third ventricle. In a 30-weeks' fetus affected by lobar holoprosencephaly, this finding could be well demonstrated by sonography and was confirmed after birth by both transfontanellar ultrasound and magnetic resonance imaging. It is proposed that the antenatal demonstration of an echogenic linear structure running within the third ventricle is a specific sign of lobar holoprosencephaly, and can assist this difficult diagnosis.