Researchers found that two patients with Zika also developed ADEM, with scans showing signs of damage to white matter in their brains.
The findings are due to be presented at the American Academy of Neurology's (AAN) 68th Annual Meeting later this week in Vancouver, Canada.
Zika virus has previously been linked to fetal brain abnormalities, microcephaly and Guillain-Barré syndrome - an autoimmune disorder that attacks the nervous system, leading to long-term weakness and paralysis.
The new study, conducted by Dr. Maria Lucia Brito Ferreira and colleagues at Restoration Hospital in Recife, Brazil, suggests that another condition called acute disseminated encephalomyelitis (ADEM) could be added to this list.
"Though our study is small, it may provide evidence that in this case the virus has different effects on the brain than those identified in current studies," says Dr. Ferreira.
"Much more research will need to be done to explore whether there is a causal link between Zika and these brain problems."
ADEM typically occurs after an infection, with 50-75% of cases developing after a viral or bacterial infection, according to the Cleveland Clinic. In what could be an immune reaction to the infection, swelling occurs in the brain and spinal cord that damages the myelin, the protective coating that surrounds nerve fibers.
The damage to the myelin leads to symptoms that are very similar to those caused by multiple sclerosis (MS), including fatigue, weakness to the point of paralysis and signs of white matter tissue damage in the brain.
For their study, Dr. Ferriera and colleagues followed every patient that visited the hospital presenting symptoms associated with the family of viruses that includes Zika virus, along with dengue and chikungunya. The period of observation ran from December 2014-June 2015.
Each patient that was followed during the study came to the hospital with a fever that was followed by the development of a rash. Other symptoms shown by these patients included itching, red eyes and joint or muscle pain. All patients were found to have Zika virus.
Findings suggest clinicians 'should be vigilant' for ADEM in cases of Zika
Of these patients, a total of six went on to develop neurological symptoms that were indicative of an autoimmune disorder. For some, these symptoms developed instantly, while for others, the symptoms manifested up to 15 days later. These patients underwent additional examination and blood testing.
The researchers found that two of these six patients had developed ADEM. Scans of their brains showed signs that their white matter had been damaged. The other four patients had developed Guillain-Barré syndrome.
After they had been discharged from the hospital, five of the patients still showed problems with the working of their muscles. One patient had problems with their memory and thinking skills, while another had problems with their vision.
Dr. Ferreira suggests that caution should be taken when interpreting the findings of the study, stating that they do not mean that all people infected with Zika will experience these brain problems.
"Of those who have nervous system problems, most do not have brain symptoms," she explains. "However, our study may shed light on possible lingering effects the virus may be associated with in the brain."
Dr. James Sejvar, a member of the AAN, states that the findings suggest clinicians "should be vigilant for the possible occurrence of ADEM and other immune-mediated illnesses of the central nervous system."
The most pressing question for Dr. Sejvar, however, is why the Zika virus has been strongly associated with diseases such as ADEM and Guillain-Barré syndrome.
"Hopefully, ongoing investigations of Zika virus and immune-mediated neurologic disease will shed additional light on this important question," he concludes.
Recently, the US Food and Drug Administration (FDA) gave the go-ahead for an investigational test to be used to screen blood donations for Zika.