Measuring tape is a critical tool for following Zika virus-exposed children

Invited commentary by Children’s National prenatal-neonatal neurologist emphasizes importance of studying this population long term

A simple measuring tape could be the key to identifying which children could develop
neurological and developmental abnormalities from Zika virus exposure during gestation.
This is according to an invited commentary published July 7 in JAMA Network Open and
written by Sarah Mulkey, M.D., Ph.D., prenatal-neonatal neurologist in the Division of
Prenatal Pediatrics at Children’s National Hospital.

Zika virus (ZIKV), first isolated in 1947 in the Ziika Forest in Uganda, made headlines in
2015-2016 for causing a widespread epidemic that spread through parts of North and
South America, several islands in the Pacific and parts of Southeast Asia. Although
previously linked with no or mild symptoms, researchers discovered during this epidemic
that Zika can cross from a pregnant woman to her gestating fetus, leading to a syndrome
marked by microcephaly (decreased brain growth), abnormal neurologic tone, vision and
hearing abnormalities, and joint contractures.

“For the 90% to 95% of ZIKV-exposed infants who fortunately were not born with severe
abnormalities at birth and were normocephalic, our hope was that these children would
have normal neurodevelopmental outcomes,” Dr. Mulkey writes in the commentary.
“Unfortunately, this has not been the case.”

Her commentary expands on a study in the same issue entitled “Association between
exposure to antenatal Zika virus and anatomic and neurodevelopmental abnormalities in
children” by Cranston et al. In this study, the researchers find that head circumference —
a simple measure taken regularly at postnatal appointments in the U.S. — can provide
insight into which children were most likely to develop neurologic abnormalities. Their
findings show that 68% of those whose head circumference was in the “normal” range at
birth developed neurologic problems. Those whose head circumference was at the
upper end of this range were significantly less likely to have abnormalities than those at
the lower end.

Just this single measurement offers considerable insight into the risk of developing
neurologic problems after Zika exposure. However, notes Dr. Mulkey, head
circumference growth trajectory is also key. Of the 162 infants whose heads were initially
in the normocephalic range at birth, about 10.5% went on to develop microcephaly in the
months after birth.

“Because early head growth trajectory is associated with cognitive outcomes in early
childhood,” Dr. Mulkey writes, “following the head circumference percentile over time can
enable recognition of a child with increased risk for poor outcome who could benefit from
early intervention therapies.”

This simple assessment could be significantly augmented with neuroimaging, she adds.
The study by Cranston et al., as well as others in the field, have shown that brain
imaging often reveals problems in ZIKV-exposed children, such as calcifications and
cerebral atrophy, even in those with normal head circumferences. This imaging doesn’t
necessarily need to take place at birth, Dr. Mulkey says. Postnatal development of
microcephaly, failure to thrive or developmental delay can all be triggers for imaging later
on.

Together, Dr. Mulkey says, the study by Cranston et al. and others that focus on ZIKVexposed children support the need for following these patients long term. Children
exposed to ZIKV in the epidemic nearly five years ago are now approaching school age,
a time fraught with more complicated cognitive and social demands. Through her own
research at Children’s National’s Congenital Zika Virus Program and collaboration with
colleagues in Colombia, Dr. Mulkey is following multiple cohorts of ZIKV exposed
children as they grow. She recently published a study on neurological abnormalities in
one of these cohorts in JAMA Pediatrics in January 2020.

“It’s really important to follow these children as long as possible so we’ll really know the
outcomes of this virus,” Dr. Mulkey says.

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Media contact: Beth Riggs | [email protected] | 301-233-4038

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