The effects of Zika virus on fetuses can be better analyzed using MRI over ultrasound as the imaging modality. According to ongoing research by the Children’s National Health System in Washington, D.C., MRI provides more detailed images that reveal more extensive areas of damage to the developing fetal brain.
“The objective of our study is to compare fetal MRI with fetal ultrasound imaging, which is the standard right now, to detect any abnormalities in the brains of these fetuses at an earlier point than has been able to be found with ultrasound,” said Roberta DeBiasi, MD, division chief of infectious disease and the senior author of the study. “And likewise, we seek to determine how we can use MRI and ultrasound together to get the best picture of potential injury to the fetus and get that information as quickly as possible during the pregnancy.”
The study, thus far, has enrolled 48 pregnant women exposed to Zika virus in the first or second trimester of their pregnancy whose infection is confirmed by reverse transcription polymerase chain reaction. Forty-six of the women live in Barranquilla, Colombia, where Zika infections are endemic. Two live in Washington but were exposed to Zika while traveling elsewhere.
All women underwent at least one diagnostic imaging session (MRI or ultrasound) while pregnant at 25 weeks, and 36 underwent a second set of MRI/US imaging at 31 weeks.
Three of the 48 pregnancies (6 percent) were marked by abnormal fetal MRI.
- The first fetus on MRI showed heterotopias and abnormal cortical indent. The ultrasound for this fetus showed normal brain development.
- The second fetus on MRI showed parietal encephalocele and Chiari malformation Type II. The ultrasound for this fetus also detected the same abnormalities.
- The third fetus on MRI showed a thin corpus callosum, an abnormally developed brain stem, temporal cysts, subependymal heterotopias and general cerebral/cerebellar atrophy. The ultrasound for this fetus showed significant ventriculomegaly, a hallmark of microcephaly.
After they were born, infants underwent a follow-up MRI and ultrasound. For nine infants, these ultrasounds revealed cysts in the choroid plexus or germinal matrix. And one infant's ultrasound after birth showed lenticulostriate vasculopathy, or brain lesions.
“MRI lets us see more subtle changes and at least in one of the cases, allowed us to find significant findings that were not seen at all on ultrasound,” DeBiasi added. “The fact that we can do this imaging early in the pregnancy means that we can provide this information to women earlier in their pregnancy and we can prepare to take care of these babies.”
Though MRI provides more detail and clearer representation of damage to the brain, DeBiasi wrote MRI used in conjunction with ultrasound can detect some smaller changes that are still of unclear significance, but are not shown well on MRI.
DeBiasi stated this study opens up an opportunity to use MRI in a nearly unlimited number of applications in fetal imaging and medicine. But for now, the team is focused on the present study. They are still awaiting the birth of 25 more babies to complete the imaging and evaluation for analysis. DeBiasi said there will be continued follow up with the infants in the years to come.
“We are also performing developmental follow up of these babies,” DeBiasi said. “Even though the infants appeared normal because of MRI, no one knows if they will continue to develop normally over the next four to five years. The follow up of those babies of a period of years is really important and we have been astounded by the motivation of the families that have been involved in the study because they really do want information to give the best life to their kids.”