Zika virus intrauterine infection causes fetal brain abnormality and microcephaly: tip of the iceberg?

An unexpected upsurge in diagnosis of fetal and pediatric microcephaly has been reported in the Brazilian press recently. Cases have been diagnosed in nine Brazilian states so far. By 28 November 2015, 646 cases had been reported in Pernambuco state alone. Although reports have circulated regarding the declaration of a state of national health emergency, there is no information on the imaging and clinical findings of affected cases. Authorities are considering different theories behind the ‘microcephaly outbreak’, including a possible association with the emergence of Zika virus disease within the region, the first case of which was detected in May 20151. Zika virus is a mosquito-borne disease closely related to yellow fever, dengue, West Nile and Japanese encephalitis viruses2. It was first identified in 1947 in the Zika Valley in Uganda and causes a mild disease with fever, erythema and arthralgia. Interestingly, vertical transmission to the fetus has not been reported previously, although two cases of perinatal transmission, occurring around the time of delivery and causing mild disease in the newborns, have been described3. We have examined recently two pregnant women from the state of Paraiba who were diagnosed with fetal microcephaly and were considered part of the ‘microcephaly cluster’ as both women suffered from symptoms related to Zika virus infection. Although both patients had negative blood results for Zika virus, amniocentesis and subsequent quantitative real-time polymerase chain reaction4, performed after ultrasound diagnosis of fetal microcephaly and analyzed at the Oswaldo Cruz Foundation, Rio de Janeiro, Brazil, was positive for Zika virus in both patients, most likely representing the first diagnoses of intrauterine transmission of the virus. The sequencing analysis identified in both cases a genotype of Asian origin. In Case 1, fetal ultrasound examination was performed at 30.1 weeks’ gestation. Head circumference (HC) was 246 mm (2.6 SD below expected value) and weight was estimated as 1179 g (21st percentile). Abdominal circumference (AC), femur length (FL) and transcranial Doppler were normal for gestational age as was the width of the lateral ventricles. Anomalies were limited to the brain and included brain atrophy with coarse calcifications involving the white matter of the frontal lobes, including the caudate, lentostriatal vessels and cerebellum. Corpus callosal and vermian dysgenesis and enlarged cisterna magna were observed (Figure 1). In Case 2, fetal ultrasound examination was performed at 29.2 weeks’ gestation. HC was 229 mm (3.1 SD below Figure 1 Case 1: (a) Transabdominal axial ultrasound image shows cerebral calcifications with failure of visualization of a normal vermis (large arrow). Calcifications are also present in the brain parenchyma (small arrow). (b) Transvaginal sagittal image shows dysgenesis of the corpus callosum (small arrow) and vermis (large arrow). (c) Coronal plane shows a wide interhemispheric fissure (large arrow) due to brain atrophy and bilateral parenchymatic coarse calcifications (small arrows). (d) Calcifications are visible in this more posterior coronal view and can be seen to involve the caudate (arrows).