Prenatal Diagnosis of Anencephaly: A Case Report and Review of Literature

Anencephaly is an inborn deformity of the central nervous system that results to the failure of closure of the cranial end of the embryologic neural tube, typically happens between the 23rd to 26th days after conception. It represents 40% of neural tube deformities, which is the second foremost cause of nervous system abnormalities after spina bifida. The occurrence rate is 1/1,000. Diagnosis is made by the 1st trimester ultrasound between the 11th and 14th week. Etiologies are multifactorial (toxic, metabolic, nutritional, iatrogenic and exceptionally chromosomal). The importance of this case report is to highlight the role of imaging in the making prenatal diagnosis and thereby reiterating the usefulness of anomaly scan in pregnant women in our clime. Ultrasound is a non-ionizing imaging modality which is highly operator dependent and is repeatable. Our case study is a 36-years-old woman Gravida 3 Para 1+2 (None Alive) at 24weeks 1day Gestation age (GA) who presented to the Radiology department for routine obstetric scan for the first time in index pregnancy. The obstetric ultrasound shows absence of the cranium in an active fetus with good cardiac activity (fetal heart rate =158bpm) with increase amniotic fluid in transverse lie. Frog eye sign was also appreciated. The placenta is sited anteriorly and not low lying. Femoral length (FL) measures 4.31cm with a GA of 24 weeks 1 day.