Prenatal Ultrasound Detects Most Zika Brain Abnormalities

While prenatal ultrasound imaging detected fetal abnormalities among most infants with intrauterine exposure to Zika virus, a few had abnormalities that were only seen during postnatal imaging, researchers found.

In a cohort of 82 pregnant women, where the large majority of fetuses had normal prenatal imaging results, three cases of fetal abnormalities were detected with MRI scans, of which two were seen in prenatal ultrasound scans, reported Sarah B. Mulkey, MD, PhD, of Children's National Health System in Washington, D.C., and colleagues.

Postnatal ultrasound detected mild brain abnormalities in seven of 57 examined infants with normal prenatal imaging, the authors wrote in JAMA Pediatrics.

An accompanying editorial by Margaret A. Honein, PhD, of the CDC, and Denise J. Jamieson, MD, of Emory University, both in Atlanta, provided some context, stating that early in the 2016 Zika outbreak, "investigators expressed optimism about the potential benefits of fetal brain MRI, remarking that 'the superior soft-tissue resolution of fetal brain MRI might be more sensitive to developmental and encephaloclastic changes, thereby expediting the detection of evolving brain anomalies.'"

The editorialists cited current CDC guidelines, which recommend that pregnant women with potential Zika virus infection should consider serial ultrasounds every 3 to 4 weeks of pregnancy. They added that given that prenatal ultrasound identified most brain abnormalities, "the additional cost, stress, time, and discomfort for the patient, as well as limited accessibility of MRI for patients who are pregnant, should be considered in making individualized decisions about how to monitor fetal growth and neuroanatomy during pregnancy."

Mulkey and colleagues examined 80 from Colombia and two from the U.S. who at least met clinical criteria for probable Zika infection. They received one or more MRI and ultrasound examinations during the second and/or third trimester, and infants had a brain MRI and cranial ultrasound postnatally.

Overall, women's mean age was 24; 81 of 82 women had clinical evidence of Zika virus infection during pregnancy, and the first 52 cases tested positive for Zika infection. There were 80 live-born infants, including 75 born at term.

Of 82 fetuses examined, three had MRI abnormalities consistent with congenital Zika infection, one of whom had normal fetal ultrasound, the authors said. Two of the cases showed heterotopias and malformations in cortical development, and one showed parietal encephalocele, Chiari II malformation, and microcephaly.

In 79 fetuses, brain biometry and sulcal maturation were normal per fetal ultrasound and MRI. The authors noted that the three cases of severe fetal MRI abnormalities had no postnatal MRI or ultrasound, meaning "all infants with postnatal imaging had normal results of fetal studies."

Of these 79 cases, 53 underwent postnatal brain MRI, and "mild abnormalities" were detected in seven of these cases.

There were 57 infants who underwent postnatal cranial ultrasound, which "detected changes in 37% of the infants, which were not well recognized on postnatal MRI," they said. These changes included lenticulostriate vasculopathy, choroid plexus cysts, germinolytic/subependymal cysts, and/or calcification.

"In our study, we detected mild brain abnormalities on postnatal neuroimaging for babies whose imaging was normal during pregnancy. Therefore, it is important for clinicians to continue to monitor brain development for Zika-exposed infants after birth," Mulkey said in a statement.

The authors' initial hypothesis was that fetal MRI would detect Zika-induced brain abnormalities earlier than ultrasound. They found that "overall, MRI and [ultrasound] were complementary and in combination provided a more complete evaluation of the fetal and neonatal brain" after Zika exposure in utero.

"Fetal MRI study findings were either strikingly abnormal or did not show the spectrum of anomalies we had anticipated," they wrote. But the authors concluded that postnatal imaging "can detect changes not seen on fetal imaging," which supports the CDC's recommendation for a postnatal cranial ultrasound in these infants.

Limitations to the data included variation in timing of maternal infection and symptoms, testing for Zika, MRI and ultrasound timing, fetal MRI technique, and incomplete postnatal imaging.