New research suggests another serious neurological condition can be added to the list of those connected to Zika virus infection. According to a small study, the mosquito-borne illness could cause an autoimmune condition known as acute disseminated encephalomyelitis (ADEM), which shares some traits with multiple sclerosis. The researchers will present their findings this week at the American Academy of Neurology’s 68th Annual Meeting in Vancouver, British Columbia.
The small study involved six patients admitted to the emergency room and neurology outpatient department at Hospital da Restauração in Pernambuco, Brazil. Each had fever and rash, symptoms common in people stricken by the Zika virus and other mosquito-borne illnesses. Some patients in the study also developed severe itching, muscle and joint pain and red eyes, which are also symptoms of a Zika infection. All six patients tested positive for the Zika virus. The doctors ruled out other mosquito-borne viruses, including dengue and chikungunya.
The patients began to experience neurological symptoms, such as numbness and weakness in the extremities and headaches, either right away or within 15 days after presenting with signs of an acute Zika infection. Physicians diagnosed two of the patients with ADEM, which occurs when a person’s immune system launches an attack on the myelin sheaths that surround the nerve fibers of the brain and spinal cord. This leads to severe inflammation, similar to MS. However, MS is a relapsing-remitting illness, while ADEM flares typically occur just once and a person should have a full recover within a few months. Brain scans of patients diagnosed with ADEM detected lesions in the brain’s white matter, which indicate damage to myelin.
Four of the six patients in the study were diagnosed with Guillain-Barré syndrome (GBS), another autoimmune disease that targets the peripheral nerves. Existing research and case studies suggest the Zika virus is linked to GBS. There is also a strong body of research suggesting the virus can also cause microcephaly, a condition in which a baby has an abnormally small skull and incomplete brain development. More than 4,000 infants in Brazil have been born with the condition since the outbreak began about a year ago.
In follow-ups with all six patients involved in this study, nearly all continued to experience some problems related with the central nervous system. Five had loss of motor function, one reported vision problems and one experienced difficulty with memory and cognitive function.
Dr. Maria Lucia Brito Ferreira of Restoration Hospital in Recife, Brazil, and lead researcher of the study, says much more work is needed to understand how—and why—the Zika virus has a strong association with autoimmune conditions of the central nervous system.
“This doesn’t mean that all people infected with Zika will experience these brain problems,” she said in a statement. “Of those who have nervous system problems, most do not have brain symptoms,” said Ferreira. “However, our study may shed light on possible lingering effects the virus may be associated with in the brain.”