Zika virus

Brain damage in Zika babies may extend far beyond microcephaly, study suggests

PUBLISHED : Wednesday, 24 August, 2016, 10:14am
UPDATED : Wednesday, 24 August, 2016, 8:47pm

Much of the public alarm about Zika has focused on the dramatic, heart-breaking pictures of children with a condition known as microcephaly characterised by an abnormally small head.

But a paper published Tuesday from the epicentre of the epidemic in northeastern Brazil shows that the damage to a baby’s brain may be far more extensive and diverse than has been previously known.

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.

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In a series of 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 the how a child’s head circumference compares to 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 impacted.

“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 5th 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 to not only have small head sizes but skulls with a collapsed shape.

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It 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 build up] that then decompresses,” they wrote. They also noted that the babies sometimes have redundant or folded skin on their heads which may be “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 a condition known as ventriculomegaly. It’s characterised 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 a lot of different kind of infections, but what’s unusual in the babies with Zika is that it these regions are very dense and they are located near the gray matter-white matter juncture in the brain rather than on the outsides of the brain as is typically seen.

“We can only hypothesise 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.”