Long–term neurological fate of Zika–exposed infants with ‘normal’ MRI remains uncertain.
During a recent trip Sarah B. Mulkey, MD, PhD, made to Colombia, where Children’s National Health System researchers are collaborating on a clinical study, she tested Zika–affected babies’ motor skills as they sat, stood, and lay facing upward and face down. The international study aims to answer one of the most vexing questions about Zika: If babies’ brains appear “normal” at birth, have they survived Zika exposure in the womb with few neurological repercussions?

According to the Centers for Disease Control and Prevention (CDC), one in 10 pregnancies across the United States with laboratory–confirmed Zika virus infection has resulted in birth defects in the fetus or infant. For the lion’s share of Zika–affected pregnancies, then, babies’ long–term prospects remain a mystery.

Dr. Mulkey, the lead author, presented the research group’s preliminary findings during the 2017 annual meeting of the Pediatric Academic Societies (PAS).

As one example, Dr. Mulkey’s research sought to evaluate the utility of using magnetic resonance imaging (MRI) to evaluate fetal brain abnormalities in 48 babies whose mothers had confirmed Zika infection during pregnancy. Forty–six of the women/infant pairs enrolled in the prospective study are Colombian, and two are Washington, D.C. women who were exposed during travel to a Zika hot zone.

The women were infected with Zika during all three trimesters and experienced symptoms at a mean gestational age of 8.4 weeks. The first fetal MRIs were performed as early as 18 weeks’ gestation. Depending upon the gestational age when they were enrolled in the study, the participants had at least one fetal MRI as well as serial ultrasounds. Thirty–six fetuses had a second fetal MRI at about 31.1 gestational weeks. An experienced pediatric neuroradiologist evaluated the images.

Among the 48 study participants, 45 had “normal” fetal MRIs. Three fetuses exposed to Zika in the first or second trimester had abnormal fetal MRI:

• One had heterotopia and an early, abnormal fold on the surface of the brain, indications that neurons did not migrate to their anticipated destination during fetal brain development. This pregnancy was terminated at 23.9 gestational weeks.
• One had parietal encephalocele. According to the CDC, this defect affects one in 12,200 births, or 340 babies, per year. It is not known if this rare finding is related to Zika infection.
• One had a thin corpus callosum, dysplastic brainstem, heterotopias, significant ventriculomegaly and generalized cerebral/cerebellar atrophy.

“Fetal brain MRI detected early structural brain changes in fetuses exposed to the Zika virus in the first and second trimester,” Dr. Mulkey says. “The vast majority of fetuses exposed to Zika in our study had normal fetal MRI, however. Our ongoing study, underwritten by the Thrasher Research Fund, will evaluate their long–term neurodevelopment.”