Biomarkers Predict Problems Associated With Traumatic Brain Injury

Kimbra Kenney, MD

New study findings from a team at the American Academy of Neurology give insight into how a blood test can help investigators understand which people can take years to recover from a concussion.

Kimbra Kenney, MD, and colleagues found those with a history of >3 concussions were more likely to have high levels of a biomarker called neurofilament light chain—a nerve protein that can be detected in blood when nerve cells are injured or die—than people who did not have a concussion. Increased levels of neurofilament light chain were also linked to more severe symptoms like post-traumatic stress disorder and depression years after the concussion happened.

Many with mild concussions completely recover, but some never get their lives back fully, Kenney, a Fellow of the American Academy of Neurology, said.

“These people may benefit greatly from a test that could predict those disabilities years ahead of time,” she said in a statement. “Our study found there’s great potential for this protein to predict the problems people with concussions may experience years after their injuries.”

Participants were enrolled in the Chronic Effects of Neurotrauma Consortium Multicenter Observational Study, which was designed to understand the mild traumatic brain injury late effects for post-9/11 era veterans and service members. A total of 195 military veterans with an average age of 38 years old participated. A majority (85%) were male.

Kenney and the team divided participants into 3 groups: 45 people with no history of concussions, 94 people with 1 or 2 concussions, and 56 people with >3 concussions. For patients who had a concussion, it had taken place at least 7 years before the study. The participants were all tested to confirm if they had symptoms of post-traumatic stress disorder, depressive, or post-concussive syndrome.

Each participant had blood samples taken so the investigators could better understand their protein levels. The investigators also measured protein levels in the blood overall and exosomes found in the blood.

Overall, there were significant group differences for exosomal (P=.0226) and plasma neurofilament light (P=.003). There was a marginally significant difference between control and repetitive minor traumatic brain injury groups for plasma neurofilament light (P=.0623).

Increased exosomal and plasma levels of neurofilament light were linked with repetitive minor traumatic brain injuries, along with chronic post-concussive syndrome, post-traumatic stress disorder, and depression symptoms. Plasma tumor necrosis factor levels were associated with post-concussive and post-traumatic stress disorder symptoms. The number of brain injuries a participant had correlated with exosomal and plasma neurofilament light levels and plasma IL-6.

“The main finding in the study is that people with multiple concussions have more of these proteins in their blood, even years after the last injury,” Kenney said.

Such proteins could also predict who might experience more severe symptoms like post-traumatic stress disorder and depression.

“That’s exciting because we may be able to intervene earlier to help lessen the overall effects of concussions over time,” she concluded.

The study, “A prognostic biomarker for remote symptoms after mild traumatic brain injury?” was published in Neurology, the medical journal of the American Academy of Neurology.