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Scans show severe brain damage in Zika-affected babies

Extremely severe brain abnormalities indicate poor neurological prognosis, say doctors

Louise Prime

Thursday, 14 April 2016

Scans have shown a range of serious brain abnormalities in babies born with microcephaly associated with Zika virus infection, according to a report* by doctors in Brazil. Their study, published in today’s BMJ, found that most affected babies had such severe brain damage that they were likely to have a very poor prognosis for neurological function.

Thousands of babies have been born with microcephaly – a usually rare birth defect – in Brazil since October 2015, associated with an increasing number of Zika virus infections in the country since March 2015. A team of doctors from the city of Recife, at the centre of the Zika crisis, aimed to be the first to distinguish the abnormalities in babies with microcephaly associated with Zika virus infection, from the patterns seen in babies with other congenital infections.

They investigated 23 babies born with microcephaly between July and December 2015, and who had been diagnosed with a congenital infection associated with the Zika virus (based on their mothers’ report of a rash during pregnancy). Of these babies, six tested positive for antibodies related to the Zika virus and the other 17 met the protocol criteria for microcephaly. The investigators ruled out other infectious causes of microcephaly including toxoplasmosis, cytomegalovirus, rubella, syphilis, and human immunodeficiency virus (HIV).

The doctors gave 15 of the babies a computed tomography (CT) scan, one baby a magnetic resonance imaging (MRI) scan, and seven babies both CT and MRI scans. They reported that in all the babies who had a CT scan, they saw signs of brain calcification – which is hypothesised to result from scarring when the Zika virus destroys brain cells. They also commonly found malformations of cortical development, decreased brain volume, and ventriculomegaly, and observed underdevelopment of the cerebellum and the brainstem. Most babies who had MRI scans had an enlarged cistern magna, which the researchers said was probably because of reduced brain volume, and there was also delayed myelination and abnormalities of the corpus callosum.

The study authors pointed out: “Several features found in children with presumed Zika virus related infection are similar to those encountered in congenital infections of the central nervous system due to other agents such as Toxoplasma gondii, cytomegalovirus, rubella, and herpes simplex virus (TORCH), including decreased brain volume, ventriculomegaly, malformations of cortical development, and simplified gyral pattern, delayed myelination, and cerebellar hypoplasia.”

The researchers said they had produced the “largest and most detailed case series of neuroimaging findings in children with microcephaly and presumed Zika virus related infection to date”. However, they acknowledged that one limitation of their observational study was the reliance on mothers’ recall of rash during pregnancy, as there were no routinely available tests for definitive confirmation of Zika virus infection.

They concluded that most of the babies in their study suffered brain damage that was “extremely severe, indicating a poor prognosis for neurological function”.

* de Fatima Vasco Aragao M, van der Linden V, Mertens Brainer-Lima A 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. DOI: 10.1136/bmj.i1901

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