With
a clear link to microcephaly established, international health care
agencies now recommend serial ultrasounds for women with positive Zika
testing.
World Health Organization
Centers for Disease Control and Prevention (CDC)
Pan American Health Organization (PAHO)
European Centre for Disease Prevention and Control (ECDC)
Public Health England
Detailed
imaging guidelines are available from the International Society of
Ultrasound in Obstetrics and Gynecology and highlight a balance of
measurements, specific intracranial findings, detection of other
abnormalities and local resources including the availability of
ultrasound imaging. Amniocentesis for Zika viral detection is considered
with extrapolation from other viral teratogens such as cytomegalovirus
infections.
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Ultrasound
changes, often in the CNS, can appear later in pregnancy after initial
early images without concern. Ultrasound remains the modality for
imaging surveillance. For some affected fetuses, head circumference is
maintained, but CNS damage is evident supporting the need for detailed
intracranial evaluations in addition measurements. A new study from
Brazil utilizing ultrasound and subsequent CT/MRI offers further
delineation of the pattern of CNS changes including enlarged ventricles,
abnormalities of the corpus callosum, brainstem abnormalities and
calcification in the transition zone between the white and gray matter.
The latter appears to be unique to Zika.
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As
with all aspects of Zika infection, from absolute risk, confounders of
risk, testing methods to treatment, the discrete imaging patterns are
emerging as the pandemic evolves. First trimester exposure is likely to
result in the greatest risk; although potential damage especially to the
CNS can occur following exposure at all trimesters. Hydrops, genital
hypoplasia, multiple pteygium, placental signs of inflammation
(thickening, calcifications) and growth restriction have all been noted.
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Long-term
studies will be essential to evaluate the outcomes of exposed infants.
For all infants with Zika exposure, it is critical to gain knowledge
about this emerging infectious teratogen. International efforts is
needed and we encourage you to participate.
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