Acrania–exencephaly–anencephaly (AEAS) – A case study

A 28-year-old woman, G2P1L1, with a BMI of 32 and a homemaker, presented with no significant surgical history or history of teratogenic drug intake. She had a family history of diabetes. Her glycosylated hemoglobin level was 9.2%, and her fasting and postprandial blood glucose levels were 122 mg/dL and 167 mg/dL, respectively. She was initiated on human mixtard insulin and medical nutritional therapy. She was counseled about the risk of congenital malformations and the importance of maintaining adequate glycemic control. 

Married for five years, she previously had a vacuum-assisted delivery four years ago, and gave birth to a healthy child.

During regular follow-up––after a dating scan that correlated with gestational age––an NT scan revealed the absence of the fetal cranial vault (bony calvarial ossification). The brain parenchyma was seen protruding freely into the amniotic fluid, and facial views showed a frog-like appearance with prominent bulging eyeballs, consistent with a diagnosis of acrania-exencephaly sequence. The femur length and abdominal circumference were normal, and the chest, outflow tracts, and diaphragm were intact.

After discussions with the radiology, blood bank, and maternofetal units, and with maternal consent, termination of the pregnancy was advised due to its incompatibility with life. The patient was given 200 mg of oral mifepristone, followed 48 hours later by 800 mcg of intravaginal misoprostol for cervical ripening. Eight hours later, a fetus with acrania-exencephaly without other major malformations was expelled. The fetal autopsy showed a male fetus around 12 weeks gestation, weighing 110 grams and measuring 14.3 cm in crown-to-heel length. The placenta was morphologically normal. She was discharged after adequate counseling within 48 hours.

On examination, the fetal cranium was absent, but the facial features were normal. The cranial defect measured 2.1 × 1.9 cm. The cervical, thoracic, and lumbar spine appeared normal, as did the inter and intra-orbital distance, nasal bone, lips, intra-abdominal organs, and extremities. The final impression was acrania-exencephaly.

Prognostication cannot be done with genetic testing alone; therefore, prenatal sampling with chromosomal microarray analysis (CMA) should be offered when exencephaly-anencephaly sequence (AEAS) is suspected. This provides information on the risk of recurrence and prenatal diagnosis, essential for pre-conceptional counseling. Additionally, 4 mg of folate should be recommended pre-pregnancy to reduce the recurrence risk of neural tube defects (NTD). 

For couples unwilling to undergo prenatal testing, postnatal testing and pregnancy termination are more beneficial than cell-free DNA screening. It is also crucial to conduct programs that train neurosonographers in the detection and diagnosis of NTDs according to the Carnegie Classification to improve understanding and application in clinical practice.

Source: Shenoy HT, Kunju NI, Khan NA, et al. Indian Journal of Obstetrics and Gynecology Research. 2024;11(2):304–307