Presentation
Pregnant woman came for a routine obstetric ultrasound to investigate a possible malformation in the central nervous system of the fetus.
Patient Data
Absence of brain and calvaria superior to the orbits on coronal views of the fetal head.
"Frog eye" appearance due to absent cranial bone/brain and bulging eyes. Sagital plane showing the fetal profile with no skull cap.
Case Discussion
Anencephaly is a defect of the development of the central nervous system, and its condition is incompatible with survival. Prenatal detection of anencephaly by ultrasound is accurate and reliable at 10-14 weeks scan, in some cases earlier, but diagnosis at a very early pregnancy is still unreliable because calcification of skull is complete by 10 weeks.
Ultrasound features of anencephaly are different in the first and second trimesters. In the first-trimester "mickey-mouse" bi-lobar face are viewed and typically represents this pathology, besides, other features can be present such as an increase of amniotic fluid echogenicity, irregular head morphology, and crown-rump length significantly reduced.
In the second trimester, the typical appearance of anencephaly is the "frog eye" sign, as shown in our ultrasound images due to absent cranial bone/brain and bulging eyes. In addition, polyhydramnios may be present due to a decrease in fetal swallowing.
Start folic acid supplementation before conception and throughout the first trimester has shown a decreased risk of neural defects in almost 50% of the pregnancies.
Images: MD Jose Roberto Festugatto.