Zika Brain Damage May Occur Without Microcephaly

Zika Brain Damage May Occur Without Microcephaly

Study suggests microcephaly birth defect isn't always present; cases may be underreported

WebMD News from HealthDay

By Dennis Thompson

HealthDay Reporter

WEDNESDAY, June 29, 2016 (HealthDay News) -- In the ongoing crisis around Zika-linked birth defects, attention has been largely focused on infants born with too-small heads, or microcephaly.

However, a new report suggests that newborns with normal-sized heads may also sometimes be affected by the mosquito-borne virus, including brain damage.

Of the more than 600 cases of "definite or probable" Zika virus infection in Brazilian infants involved in the new study, more than 100 had head circumferences within the normal range, researchers reported June 29 in The Lancet.

"Therefore, the current focus on microcephaly screening alone is too narrow," study lead author Cesar Victora, of the Federal University of Pelotas, in Brazil, said in a journal news release.

"Although we believe that the underreporting of microcephaly cases is rare during the epidemic, newborns infected with the virus late in pregnancy may go unreported due to their head size being within normal range," Victora said.

He also noted that another sign of maternal Zika infection -- a rash in late pregnancy -- was also absent in one-third of the cases.

In some cases, women experienced the Zika-linked rash in late pregnancy and delivered babies with brain damage -- even though their babies were born with normal-sized heads.

Victora's team noted that a baby's skull typically finishes its development by week 30 of gestation, suggesting that Zika infection in newborns might be causing brain damage without the telltale sign of microcephaly.

"Our findings suggest that among pregnancies affected by Zika virus, some fetuses will have brain abnormalities and microcephaly, others will have abnormalities with normal head sizes, and others will not be affected," Victora said.

Brazilian experts Dr. Jorg Heukelbach of the University of Ceara, and Dr. Guilherme Loureiro Werneck of the University of Rio de Janeiro, wrote a journal commentary on the new findings. They explained that what's sorely needed is a definitive test for Zika infection.

"The development of an accurate [blood] test that could be incorporated into routine prenatal care will be essential, and its validation a research priority," the two experts wrote.

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