Brain scans may help identify athletes who suffer from brain damage after mild concussions, a small study of current and former professional football players suggests.

Researchers examined results from what's known as positron emission tomography (PET) scans for four current and 10 former National Football League (NFL) players who had at least one previous concussion as well as for 16 similar men who weren't athletes and had no history of concussions.

They measured levels of a substance called translocator protein 18KDa (TSPO), which are thought to rise when the brain responds to traumatic injuries.

Compared with men who weren't in the NFL, the football players had higher levels of TSPO and greater changes in the brain's white matter, the study found.

"The study showed that there is a measurable degree of this biomarker of brain injury and repair even in young NFL players, suggesting that the insult to their brains could have occurred long before they were scanned for the study - perhaps dating to collegiate or pre-collegiate play," said senior study author Dr. Martin Pomper, a researcher at Johns Hopkins Medical School in Baltimore.

"That could be a cautionary note for young athletes participating in contact sports," Pomper added by email.

While more research is needed to confirm the results from this small study, one day it may be possible to use PET to look for TSPO and determine which athletes might be at risk for neurological or psychiatric problems after a head trauma, Pomper said.

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One of the most vexing issues with treating concussions in athletes is that the full extent of brain injuries can be difficult to assess while players are still alive. In particular, a condition tied to sports concussions known as chronic traumatic encephalopathy (CTE) can only be diagnosed during an autopsy.

For the current study, researchers focused on resident immune cells of the central nervous system called microglia that are thought to play a role in the brain's response to injury and other neurodegenerative processes.

Scientists think it's possible prolonged microglial activation can happen after single or and repeated traumatic brain injuries. When this happens, normally low levels of TSPO in brain tissue may rise.

The NFL players, who reported an average of seven years since their last concussion, showed higher TSPO in 8 of 12 regions of the brain examined in the study, researchers report in JAMA Neurology.

Beyond its small size, other limitations of the study include a lack of data to explain exactly when TSPO levels rose relative to the timing of brain injuries, the authors note.

Even so, the results point to a potential way to better pinpoint the extent of brain damage in living athletes, as well as the possibility of one day of developing experimental treatments to target inflammation in the brain as tool for minimizing the health impact of concussions, Jonathan Godbout of Ohio State Wexner Medical Center in Columbus writes in an accompanying editorial.

"These findings are not limited to NFL players," Godbout said by email. "Prolonged brain inflammation (chronic microglia activation) is likely a key component to myriad neurological diseases and perhaps even normal brain aging."

"Like anything, if you can identify the source of the problem prior to the development of neurological complications then you can intervene," Godbout added. "How to intervene in humans and target this inflammatory cell population is the tough question, but it is an active area of study."