A small study on 11 intensive care COVID-19 patients suggests that the coronavirus may trigger an antibody reaction that attacks the brains of its victims.

A team of researchers examined the patients, who were experiencing unexplained neurologic symptoms, in two hospitals in Germany. The researchers wanted to find out if COVID-19 had a role in causing these symptoms which included delirium, epileptic seizures, and uncontrollable muscle contractions.

According to Newsweek Health, when the team examined the blood and cerebrospinal fluid of the patients, they didn’t find evidence of the coronavirus, but they did find autoantibodies in the fluid. An autoantibody is a type of protein that attacks an individual’s own proteins and could be triggered by a viral illness.

The researchers took the fluid and then placed it on slices of mouse brain tissue to see if the autoantibodies would attach to the tissue, and in most cases, it did. According to Newsweek Health, the study suggests that the neurological conditions suffered by COVID-19 patients may be triggered by the body’s own immune response to the virus.

Hospitals around the world have reported an array of neurological symptoms ranging from mild to severe, according to New Scientist. Experts say that the mounting evidence that the virus somehow attacks the brain as well as other organs, needs to be studied further in order for effective treatments to be developed.

“These findings in 11 patients with very different symptoms and signs need to be studied in large numbers,” Benedict D. Michael, from the University of Liverpool’s Institute of Infection and Global Health, who did not work on the study, told Newsweek.