LONDON – Brazilian scientists studying possible links between birth defects and the mosquito-borne Zika virus have found that babies born with microcephaly have severe brain damage with a range of abnormalities.
In a study published in the British Medical Journal (BMJ), the researchers said their findings could not prove Zika causes microcephaly, but did confirm a link and pointed to potentially severe consequences for babies of mothers who become infected with the virus while pregnant.
Microcephaly is a rare birth defect where a child is born with an abnormally small head. Since 2015, Brazil has reported thousands of suspected cases of the condition and linked them to a large and spreading outbreak of Zika virus infection.
The World Health Organization (WHO) declared in February that the Zika outbreak and its links to microcephaly constitute an international public health emergency.
Last month, WHO said there was now strong scientific consensus that the Zika virus can cause microcephaly. The WHO has also said Zika can cause Guillain-Barre syndrome, a rare neurological disorder that can result in paralysis.
For the research reported in the BMJ, a team of doctors from Recife, a city at the center of the Zika outbreak, and led by Professor Maria de Fatima Vasco Aragao, analyzed the types of abnormalities and lesions in brain scans of the first cases of microcephaly associated with the Zika virus in Brazil.
The study involved 23 babies diagnosed with a congenital infection associated with the Zika virus. Of these, 15 had a computed tomography (CT) scan, seven had both CT and magnetic resonance imaging (MRI) scans, and one had only a MRI scan.
The scans showed the majority of babies had brain damage that was "extremely severe", the researchers said, "indicating a poor prognosis for neurological function".
All babies who had a CT scan showed signs of brain calcification, a condition in which calcium builds up in the brain. The researchers said the hypothesis is that the Zika virus destroys brain cells, and forms lesions similar to "scars" on which calcium is deposited.
Other findings included malformations of cortical development, decreased brain volume, and ventriculomegaly - a condition where the brain cavities are abnormally enlarged.
The team also found underdevelopment of the cerebellum, which plays an important role in motor control, and the brainstem which connects the cerebrum with the spinal cord and communicates messages from the brain to the rest of the body.
The babies studied were all born in the Brazilian state of Pernambuco between July and December 2015.