While there have been sporadic case studies about fetal abnormalities beyond microcephaly, this is the first to provide a comprehensive breakdown of the type of defects that radiologists are seeing in the womb and after babies are born.
In striking images in the journal Radiology, researchers detail a half-dozen brain defects that they found in nearly all the babies in their study. This is significant because, technically speaking, microcephaly is a superficial diagnosis that is based on how a child’s head circumference compares with others. Some children with the condition go on to develop normally or have only minimal delays. This study confirms fears that the babies with Zika may be more severely affected.
“What this tells you is that Zika is a devastating infection. There is evidence the brain just didn’t form normally,” Deborah Levine, a professor of radiology at Harvard Medical School and a study co-author, said in an interview.
The research involved 45 children, including one set of twins, who were referred to the Instituto de Pesquisa in Campina Grande in the state of Paraiba from June 2015 to May 2016. Most of them had a head circumference below the fifth percentile and were confirmed or presumed to have been infected with Zika while in utero. Researchers used magnetic resonance or other imaging technology to track their development over time.
In total, researchers documented eight main types of brain abnormalities and presented a theory for the unusual appearance of the heads of Zika babies, many of whom have not only small head sizes but also skulls with a collapsed shape.
These effects may be “due to a combination of the small brain as it develops and a result of what, at some point, was likely a larger head size [as a result of fluid buildup] that then decompresses,” they wrote. They also noted that the babies sometimes have redundant or folded skin on their heads, “likely due to the head and skin continuing to grow, while the size of the brain regresses."
One of the most common abnormalities, which showed up in 43 of the babies, is ventriculomegaly. This condition is characterized by the fluid-filled structures in the brain being too large. In some cases it can be left untreated. But in others, surgery or other intervention is necessary to try to prevent serious, long-term neurological damage.
Forty-three babies also had intracranial calcifications (deposits of calcium in the tissue), which can impair brain function. This is common in many different types of infections, but what’s unusual in the babies with Zika is that these regions are very dense, and they are located near the gray matter-white matter juncture in the brain rather than on the outside of the brain, as is typically seen.
“We can only hypothesize why,” Levine said. “Maybe it has to do with the way the virus is attacking the neurons as they migrate.”
Thirty-eight of the children had abnormalities of the corpus callosum, the tract of nerve fibers that joins the two hemispheres of the brain.
Levine said this and some of the other findings aren't necessarily “catastrophic” in themselves, but the combination may be.
“The likelihood the babies in our series are going to have normal development because of so many abnormalities — the prognosis is not good,” Levine said. “There are not enough functional areas there.”
The researchers have posted a large number of images and several videos as references to aid other radiologists in diagnosis or monitoring the progress of their patients.
U.S. health officials are monitoring at least 400 pregnant women with Zika and have estimated that some of these children could require care estimated to cost more than $10 million during their life. If the virus continues to spread in the country, it could create the first large outbreak of serious birth defects since rubella hit in 1954, killing 21,000 and leaving 20,000 others with issues ranging from deafness and heart damage to microcephaly.
This post has been updated.