Antenatal ultrasonographic findings differentiating complete from partial agenesis of the corpus callosum.

Four cases of complete (three) and partial (one) agenesis were evaluated ultrasonographically. The frontal lobe/biparietal diameter ratio were evaluated in 113 normal fetuses and compared with those ratios in fetuses with corpus callosum agenesis. In the presence of the classic ultrasonographic features of agenesis of the corpus callosum, frontal lobe shortening, along with absence of the cavum septi pellucidi, might contribute to the diagnosis of complete agenesis of the corpus callosum and distinguish it from partial agenesis.