Prenatal diagnosis of fetal microhydranencephaly: a case report and literature review

The prenatal diagnosis of microhydranencephaly is important and needs to be distinguished from anencephaly, because unlike anencephaly, fetuses with microhydranencephaly can survive after birth. Herein, we report a case of microhydranencephaly that was diagnosed and distinguished from anencephaly prenatally.

The patient was an 18-year-old woman, 2 gravida nullipara, who presented at 15 weeks of gestation. Ultrasonography showed a normal biparietal diameter (BPD) and no major anomalies. At 23 weeks of gestation, an ultrasound examination revealed a BPD of 40 mm (-5.3 standard deviation, SD). At 29 weeks, anencephaly was suspected despite difficulty in visually examining the fetal head above the orbit. At 34 weeks, insertion of a metreurynter made it possible to observe the skull. Three-dimensional computed tomography (CT) and magnetic resonance imaging (MRI) confirmed the presence of the fetal skull, a prominent occipital bone, sloping forehead, marked microcephaly, cerebral loss, and excess cerebrospinal fluid. This allowed differentiation between microhydranencephaly and anencephaly. She delivered vaginally at 37 weeks, and the child had a birth weight of 2342 g and a head circumference of 24 cm (-5.4 SD). The baby's head was flat above the forehead, with a suspected partial head defect. The baby received desmopressin acetate due to central diabetes insipidus 6 months after birth.

The use of multiple imaging modalities and physical manipulation of the fetal head are required to accurately differentiate between microhydranencephaly and anencephaly.