Neuroimaging findings of Zika infected infants with microcephaly

In the United States, microcephaly occurs in 2 to 12 infants out of every 10,000. For a woman infected with the Zika virus, the risk soars to an estimated 1 in 100 births.⁽¹⁾ Radiologists and physicians from Brazil described the CT and MRI findings of 23 cases in an article published online in the British Medical Journal. The open access article includes images of microcephaletic brains resulting from presumed maternal Zika infection.

Maria de Fatima Vasco Aragao, MD, of the Centro Diagnostico Multimagem in Recife, and colleagues at the Federal University of Pernambuco and hospitals in Recife, reported their findings of 23 cases. The infants were born between July and December 2015 in the Brazilian state of Pernambuco to mothers who experienced Zika virus symptoms during their first (77%) and second (23%) trimesters of pregnancy.All infants underwent routine clinical evaluation as established by state and federal health departments which included neuroimaging. Seven of the infants underwent both CT and MRI scans, one infant underwent contrast-enhanced MRI only, and 15 noncontrast CT.

The authors reported severe cerebral damage on imaging in most of the infants. The features most commonly found were brain calcifications in the junction between cortical and subcortical white matter associated with malformations of cortical development, often with a simplified gyro pattern and predominance of pachygyria or polymicrogyria in the frontal lobes.

The CT images showed all 22 cerebral calcifications predominantly at the junction of the cortex and subcortical white matter. The calcifications were predominantly punctiform, but linear and coarse calcifications were also visible in some patients. Twenty-one infants had malformations of cortical development, 20 had a decreased brain volume, 19 had ventriculomegaly, and 11 had hypoplasia of the cerebellum or brainstem.

The sequences used for MRI imaging included T1- and T2-weighted imaging, susceptibility magnetic weighted imaging, or T2* gradient echo, and diffusion-weighted imaging. The authors considered T1-weighted images as the most useful sequence to assess normal brain maturation in infants up to six months of age.

The MRI images of all eight infants showed calcifications in the junction between cortical and subcortical white matter, malformations of cortical development occurring predominantly in the frontal lobes, and ventriculomegaly. Seven children each had enlarged cisterna magna and delayed myelination. The main cortical malformations were a simplified gyral pattern, pachygyria, and polymicrogyria, predominantly in the frontal lobes.

Malformations were symmetrical in 75% of the cases and present in the entire brain, except for the simplified gyro pattern seen in 6 cases. Hemimegaloencephaly and periventricular hetertorotopic grey matter were additional malformations seen.

The authors noted that by better visualizing the thin parenchyma, MRI enabled the two neuroradiologists to better localize the majority of the calcifications in the junction between cortical and subcortical white matter. This enabled the neuroradiologists to identify their true location on the CT images.

In an accompanying editorial, lead author Tiago Baptista, MD, a consultant neuroradiologist in the Department of Neuroradiology at Oxford University Hospitals NHS Foundation Trust in the United Kingdom, and co-authors recommended MRI as the neuroimaging modality of choice because it identified more abnormalities with greater clarity than CT, and did not expose such young pediatric patients to high doses of ionizing radiation. However, for 15 of the patients whose neuroimaging findings were reported in the article, MRI was not available.

These cases represent infants who were severely affected by presumed Zika related congenital infection. Because many of the findings reported are also seen in other types of congenital infections, radiologists need to be knowledgeable of the clinical history of the mother to learn if she may have contracted the Zika virus during pregnancy.

REFERENCES

1. Doshi P. Convicting Zika. BMJ 2016 353:i1847.
2. Aragao MFV, van der Linden V, Brainer-Lima AM, et al. Clinical features and neuroimaging (CT and MRI) findings in presumed Zika virus related congenital infection and microcephaly: retrospective case series study. BMJ 2016 353:i1901. Open access article.
3. Baptista T, Quaghebeur G, Alarcon A. Neuroimaging findings of babies with microcephaly and presumed congenital Zika virus infection. BMJ 2016 353:i2194.