Infants exposed to Zika virus (ZIKV) commonly had neuroimaging abnormalities on computed tomography (CT) and/or magnetic resonance imaging (MRI) scans, according to data published in JAMA Network Open.
The neuroimaging results and clinical outcomes of 110 infants exposed to ZIKV from a maternity ward of a children’s hospital in Rio De Janeiro, Brazil, were retrospectively reviewed following the 2015 to 2016 epidemic. Imaging results were reviewed for structural abnormalities and other forms of brain injury.
The mean gestational age of the infants was 38.4 weeks; 65% had abnormal neuroimaging results and 96% were classified as having severe ZIKV infection at birth. Structural abnormalities including brain calcifications, especially at the cortico-subcortical white matter junction; cortex malformations; ventriculomegaly; and reduced brain volumes were the most common, followed by brainstem hypoplasia, cerebellar hypoplasia, and corpus callosum abnormalities. Infants without clinical findings classic to ZIKV infection had a higher frequency of abnormal imaging than infants with these specific findings. Findings in these cases included fetal brain disruption sequence (100% vs 35%), microcephaly (100% vs 30%), congenital contractures (100% vs 58%), ophthalmologic abnormalities (95% vs 44%), hearing abnormalities (100% vs 58%), and neurologic symptoms (94% vs 10%).
Of the infants exposed to ZIKV but had a normal neurologic examination at birth, 10% later had abnormal imaging findings. Notable imaging findings included periventricular microhemorrhages and Dandy-Walker malformations. Further, results showed that neuroimaging abnormalities differed by trimester during which infants were infected with ZIKV. Abnormalities on neuroimaging were more commonly seen in infants who were exposed to the virus during the first trimester, compared with the second and third trimester (63%, 13%, and 1%, respectively). Researchers highlighted that brainstem or cerebellar hypoplasia or cortex malformations (63%–67%) were more common when ZIKV exposure occurred in the first trimester, compared with second and third (11%–15% and 0%–2%, respectively).
Investigators reported several study limitations. The population of infants exposed to ZIKV was heavily weighted toward severely affected infants, which may present biases and reduce the generalizability of the results, particularly in less severely affected infants. Also, most infants could not receive both CT and MRI despite the fact that each method is better suited to detect distinct abnormalities. Serial imaging to detect changes over time was also not available in the study and investigators were unable to assess whether infants had resolving calcifications. Finally, the frequency data from the study may not reflect incidence data because the cohort was entirely composed of children followed at a referral center for ZIKV who had undergone CT or MRI neuroimaging.
The study found that neuroimaging abnormalities in this group were common and they occurred primarily in severely affected infants, especially when infection occurred in the first trimester. According to investigators, “neuroimaging of antenatally ZIKV-exposed infants is an important component in a comprehensive evaluation that may help identify and determine the extent of CNS involvement associated with in utero ZIKV infection.”
Pool KL, Adachi K, Karnezis S, et al. Association between neonatal neuroimaging and clinical Outcomes in Zika-exposed infants from Rio de Janeiro, Brazil. JAMA Netw Open. 2019;2:e198124.