Congenital Zika virus infection: a neuropathological review

Background A relationship between Zika virus (ZikV) infection in pregnancy and the occurrence of microcephaly was established during the Zika outbreak in Brazil (2015-2016). Neuropathological findings in congenital Zika syndrome helped to understand its pathogenetic mechanisms. Results The most relevant postmortem findings in the central nervous system (CNS) of fetuses and neonates infected with ZikV early in gestation are microcephaly with ex-vacuo ventriculomegaly and large head circumference associated with obstructive hydrocephalus due to severe midbrain and aqueduct distortion. Babies with severe brain lesions are born with arthrogryposis. Histologically, there is extensive destruction of the hemispheric parenchyma, calcifications, various disturbances of neuronal migration, reactive gliosis, microglial hyperplasia and occasional perivascular cuffs of lymphocytes, also in the meninges. Hypoplastic lesions secondary to the lack of descending nerve fibers include small basis pontis, pyramids and spinal corticospinal tracts. Cerebellar hypoplasia is also common. Severe nerve motor nerve cell loss is observed in the anterior horn of the spinal cord. Conclusion A spectrum of neuropathological changes, from severe microcephaly to obstructive hydrocephalus was observed. The severity of the lesions is directly related to the gestational age, the most severe occurring when the mother is infected in the first trimester. Infection of progenitor cells at the germinal matrix was demonstrated. The lack of spinal motor neurons is responsible for fetal acynesia and consequent arthrogryposis.