Researchers evaluated brain scans of fetuses and infants with suspected Zika infection and found that in addition to microcephaly there were severe abnormalities in 94 percent of infants. The researchers studied 17 babies and fetuses with confirmed Zika diagnosis and 28 with suspected Zika infection.
Viral infection of a pregnant woman has been linked to increased risk of microcephaly in the fetus, but researchers are still learning how the virus affects brain development.
Dr. Dorothy Bulas, the section head of ultrasound and fetal imaging in the Division of Diagnostic Imaging and Radiology at Children’s National Health System in Washington, D.C., said the Zika infection has a "unique" effect on developing fetuses compared to other infections.
"This is a very unique virus that seems to attack the fetus directly," she said. "We haven’t really seen [brain abnormalities] as severe in other infections.”
Researchers reported finding serious abnormalities of the corpus callosum, the thick bundle of nerves that connects the two halves of the brain. Abnormalities there can cause severe neurological problems. They also noted that the majority of babies had calcium deposits throughout the brain that tended to occur in the spot where the gray matter on the outer portion of the brain meets the white matter within the inner portion of the brain. A small portion of the babies also had abnormalities of the eyes.
They also saw ventriculomegaly -- enlargement of the fluid spaces in the brain -- in over 94 percent of babies.
In some of these children, the oversize ventricles made up for the missing brain tissue, so their head size was not abnormally small. This could be a worrying sign since it means that even fetuses who appear "normal" on fetal ultrasound could be suffering from birth defects related to Zika exposure.
Bulas pointed out that the paper and the detailed fetal MRI scans published will help radiologists evaluating pregnant women who have had Zika infection to determine if fetuses are showing effects of Zika infection.
"The power of fetal MRI is that it allows us to examine the details of the brain," she said. "I think fetal MRI has been underutilized, and I think in a scenario like this it can be very helpful for confirming an injured brain."
The new paper was published as Florida doctors confirmed today they are studying an infant who has signs of past Zika infection but not microcephaly. Doctors from the University of Miami Miller School of Medicine said an infant girl they are treating did not have microcephaly but had calcium deposits in her brain and pigment changes in her retina.
"It just tells us that there was a bacteria or a virus in the brain and that virus has left us with some calcifications," Dr. Audina Berrocal of the Bascom Palmer Eye Institute at the University of Miami told ABC News affiliate WPLG-TV. "Babies with early intervention and the right support, sometimes they compensate for those changes that we find early."