[The exencephaly-anencephaly sequence. Ultrasound diagnosis in early pregnancy]

Abstract

Aim: In animal studies exencephaly is well described as a precursor of anencephaly. We have evidence that also in the human fetus the transition from exencephaly to anencephaly is possible.

Method: We diagnosed either exencephaly or anencephaly by high-frequency vaginal ultrasound in 14 human fetuses at gestational ages varying between 9 + 4 and 22 + 3 weeks.

Results: In the first trimester exencephaly was the predominant finding, while in the second trimester the classic appearance of anencephaly was seen more often. In one fetus with exencephaly diagnosed at a gestational age of 12 + 2 weeks, where the parents decided not to intervene, the transition to anencephaly was documented by serial ultrasound examinations.

Conclusions: Our findings support an exencephaly-anencephaly sequence also in humans. The cephalic changes resulting in the classic anencephalic appearance are of importance for the first trimester diagnosis with high resolution vaginal probe ultrasound.