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 The current Zika outbreak was first detected last year in Brazil,
where the virus has been linked to more than 1,800 cases of
microcephaly, which can cause severe developmental problems.
Prior research has shown the Zika virus attacks neural progenitor
cells - a type of stem cell that develops into different types of
nerve or brain cells.
The latest research, published in the journal Radiology, draws from
imaging and autopsy findings linked with confirmed Zika infections
done on 17 infants and fetuses cared for at the Instituto de
Pesquisa, in Campina Grande in the state of Paraiba in northeastern
Brazil, where the infection has been especially severe.
The study also included reports on 28 fetuses or newborns with brain
anomalies whose mothers were suspected of having Zika during
pregnancy.
Nearly all babies in each group had ventriculomegaly, a condition in
which the ventricles, or fluid-filled spaces in the brain, are
enlarged.
While most of the fetuses had at least one exam showing abnormally
small head circumference, suggesting they had microcephaly, three of
the fetuses with ventriculomegaly had normal head circumference, but
severe ventriculomegaly.
Nearly all of the fetuses or babies in the confirmed Zika group and
nearly 80 percent of those in the presumed Zika group also had
abnormalities of the corpus callosum - a large bundle of nerves that
facilitates communication between the left and right hemispheres of
the brain.
In all but one of the cases studied, the researchers found instances
in which developing neurons did not travel to their proper
destination in the brain.
In many cases, the babies' skulls seemed to have collapsed on
themselves, with overlapping tissues and abnormal skin folds
suggestive of a brain that had stopped growing.
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"From an imaging standpoint, the abnormalities in the brain are very
severe when compared to other congenital infections,” said study
co-author Dr. Deborah Levine of Beth Israel Deaconess Medical Center
and a radiology professor at Harvard Medical School.
As with other reports, the paper suggests that Zika does the most
harm in the first trimester of pregnancy. The researchers plan to
keep following the cases to see what impact prenatal Zika infections
have on future brain development.
There is no vaccine or treatment for Zika, which is a close cousin
of dengue and chikungunya and causes mild fever, rash and red eyes.
An estimated 80 percent of people infected have no symptoms, making
it difficult for pregnant women to know whether they have been
infected.
Zika is carried by mosquitoes, which transmit the virus to humans. A
small number of cases of sexual transmission have been reported in
the United States and elsewhere.
(Reporting by Julie Steenhuysen; Editing by Dan Grebler)
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