After a season of college football, portions of players’ brains can show worrying signs of damage, even if they did not experience a concussion, according to a timely new study of contact sports and brain health. The study, which concentrated on changes to white matter in players’ brains, amplifies growing concerns about the effects of repeated, subconcussive hits to the head and whether we are doing enough to protect athletes from knocks that once might have seemed minor.

Few athletes, parents, coaches, fans or researchers involved with football — and other contact sports, including soccer, lacrosse and hockey — are unaware of the evidence linking sports-related concussions and later cognitive problems, including, at the extreme, chronic traumatic encephalopathy, a form of degenerative dementia.

But many sports-related hits to the head do not cause concussions, a condition that, by definition, is a cluster of symptoms. Someone with a concussion might lose consciousness, have a headache, feel dizzy or disoriented, be unable to follow a moving finger with his or her eyes, and hear ringing in the ears after a resounding hit to the head.

Someone else might absorb a similar hit, however, without displaying those symptoms and would not, then, be said to have suffered a concussion.

Most past research about head trauma during sports has focused on formal concussions. Whether subconcussive hits, which can range in intensity from small dings to hard slams, similarly affect and possibly harm the brain has remained unclear.

For a new study, which was published this month in Science Advances, Bradford Mahon, an associate professor at Carnegie Mellon University and the scientific director of the Program for Translational Brain Mapping at the University of Rochester, decided to document what happens inside the skulls of football players whose heads repeatedly collide with the ground and each other but who have not had concussions.

To start, he and one of his students, Adnan Hirad, who is completing an M.D./Ph.D., and other collaborators, gained permission to scan the brains of the players on the University of Rochester’s football team, a Division III program. They scheduled the scans for the week before the start of the preseason and focused in particular on each player’s midbrain.

The midbrain, which is part of the brainstem, is positionally vulnerable to pummeling blows to the head. Because it controls motor functions of the eyes and ears, those blows tend to cause ringing ears and problems focusing.

It also can be a “canary in the coal mine” for brain injury, Dr. Mahon says. If the midbrain shows tissue damage, it is likely that other portions of the brain also are being rattled and possibly harmed by impacts, he says.

After the scans were complete, the players began playing. During all subsequent practices and games, they wore helmets containing specialized accelerometers that tracked the number and intensity of every head impact and how the athletes’ heads moved when they were hit.

At the end of the season, the researchers gathered the helmet data and re-scanned players’ midbrains. Two of the athletes had sustained concussions; their information was removed. The other 38 players had not been concussed but had whacked their heads with regularity, their helmets recording a total of 19,128 impacts, some slight and others packing a wallop.

When the researchers next compared the scans and the helmet data, they saw a disconcerting pattern. Most of the players’ midbrains were subtly different. The area’s white matter, which is the tissue that connects neurons, was slightly less healthy now, the scans showed.

“There was a kind of fraying” of the tissue, Dr. Hirad says.

The players whose heads had absorbed the most hits, especially if those hits involved slightly off-center impacts and head rotations, showed the greatest disruption inside their midbrain’s white matter.

For all of them, Dr. Mahon says, these brain injuries “were clinically silent,” causing no symptoms.

The researchers next scanned the brains of 28 athletes who had been diagnosed with a recent concussion, to check whether the subconcussive brain changes mimicked those seen in these players and found the same pattern of slight disintegration in their midbrains’ white matter.

Taken together, the scans and helmet data suggest that head impacts from sports can injure brain tissue, whether they result in a concussion or not, Dr. Hirad says.

The researchers did not test players’ thinking or motor skills, though, so they do not know if the midbrain changes affected the young men’s bodies and minds. None of them seemed to be experiencing unusual academic difficulties, Dr. Hirad says.

The researchers also did not re-scan the men’s brains, to see if their white matter later returned to normal. Presumably there would be some healing, Dr. Mahon says, since collegiate athletes have completed many football seasons, and the scans did not show ragged midbrains before the season, only afterward.

The scientists plan to study those issues in coming experiments. They also are soliciting crowdsourced data from any sports teams that use accelerometer-equipped helmets, Dr. Mahon says. The data can be uploaded to his lab’s new Open Brain Project and will be used to help scientists begin to better understand just what happens when athletes’ heads are shaken during play.

Source: The New York Times