A blood test may help predict recovery from traumatic brain injury

Elevated blood levels of a specific protein may help scientists predict who has a better chance of bouncing back from a traumatic brain injury.

The protein, called neurofilament light or NfL for short, lends structural support to axons, the tendrils that send messages between brain cells. Levels of NfL peak on average at 10 times the typical level 20 days after injury and stay above normal a year later, researchers report September 29 in Science Translational Medicine. The higher the peak NfL blood concentrations after injury, the tougher the recovery for people with TBI six and 12 months later, shows the study of 197 people treated at eight trauma centers across Europe for moderate to severe TBI.

Brain scans of 146 participants revealed that their peak NfL concentrations predicted the extent of brain shrinkage after six months, and axon damage at six and 12 months after injury, neurologist Neil Graham of Imperial College London and his colleagues found.

These researchers also had a unique opportunity to check that the blood biomarker, which gives indirect clues about the brain injury, actually measured what was happening in the brain. In 18 of the participants that needed brain surgery, researchers sampled the fluid surrounding injured neurons. NfL concentrations there correlated with NfL concentrations in the blood.

“The work shows that a new ultrasensitive blood test can be used to accurately diagnose traumatic brain injury,” says Graham. “This blood test can predict quite precisely who’s going to make a good recovery and who’s going to have more difficulties.”

Study participants were adults and mostly male, so more work needs to be done to determine if these findings apply to women, children and people with mild TBI.

Finding a reliable biomarker for the severity and outlook of TBI, a head injury that disrupts brain function, could improve millions of lives. Studies of U.S. football players have brought attention to the injury (SN: 12/13/17), but it’s a far more widespread problem. Around 55 million people globally were living with a TBI in 2016, and there’s no one-size-fits-all treatment.

“No two traumatic brain injuries are alike,” says David Okonkwo, director of the Neurotrauma Clinical Trials Center at the University of Pittsburgh. Scientists have been looking for biomarkers of TBI injury such as NfL to develop injury-specific interventions, and Okonkwo says these new findings are promising for patients whose injury has damaged their axons.

“We have not had the tools to measure a specific injury type of an individual patient,” Okonkwo says. While this test probably is still a few years from use in U.S. clinics, other large research groups are looking for ways to use NfL and other blood-based biomarkers for diagnosing TBI and creating opportunities for intervention.