Ultrasound evaluation of anencephaly in antenatal scan

Clinical History

A 28-year-old female patient with 8 months of pregnancy came for regular antenatal check-up for the first time with no systemic complains. She had 2 children, all delivered full term normally with no anomaly.

Imaging Findings

Antenatal ultrasound shows evidence of prominent orbits (Fig. 1a-b) with non-visualisation of cranial vault along with polyhydraminos with AFI of 20. Besides, no other associated cardiac, respiratory, gut or genitourinary system anomalies were noted. Clinical image of the same baby after delivery at 8 months by caesarean section shows complete absence of cranial vault with presence of variable cortical tissue (Fig. 2). Due to the high mortality rate of this condition the baby died 1 day after delivery.

Discussion

A. Anencephaly is the most common anomaly affecting the central nervous system and results from failure of closure of the rostral portion of the neural tube between 23rd and 26th day after conception and is characterised by the absence of cortical tissues and cranial vault, however, a variable amount of tissues can be present. [1]
B. Anencephaly can be detected as early as at 11 weeks, most effectively and easily with ultrasound. Usually when in-utero, patients may not have any symptoms, but the condition can be detected during routine imaging. It can be associated with other spinal or systemic anomalies; hence the patient should be routinely scanned at regular intervals as some of the anomalies may present later, and imaging can help the clinician to plan a proper medical or surgical treatment, considering the fetal as well as maternal mortality rate.
C. Ultrasound shows absent calvarium with no tissues above the orbits, which will be prominent showing a "frogs eye view" appearance (Fig. 1a) in coronal section along with polyhydramnios. It has to be distinguished from amniotic band syndrome, where an echogenic amniotic band passing through the head causes amputation defects[2], which is absent in this case. Another differentiation should be made from severe microcephaly, where the cranial vault will be present.
D. Anencephaly, being one of the most lethal anomaly, has a very poor prognosis even if the child is born alive. However, folic acid supplementation 0.4 mg are effective in reducing the risks of neural tube defect in future pregnancies. Once diagnosed in ultrasound, regular follow-up with proper consultations regarding termination of pregnancy should be done.
E. Regular ultrasound antenatal imaging with proper antenatal medications and counselling of the parents should be done along with appropriate laboratory test, especially maternal serum alpha protein.

Differential Diagnosis List

Final Diagnosis

Anencephaly

URL:	https://www.eurorad.org/case/12643
DOI:	10.1594/EURORAD/CASE.12643
ISSN:	1563-4086