One season of football causes changes to brain

Study of high-schoolers finds alterations though no one suffered a concussion

Without sustaining a single concussion, members of a high school football team showed worrisome brain changes after a single season of play, a new study has shown.

A detailed effort to capture the on-field experiences of 24 high school football players in North Carolina showed that, at the end of a single season, teammates whose heads sustained the most frequent contact with other moving bodies had the most pronounced changes in several measures of brain health.

The new research findings, recently presented at a meeting of the Radiological Society of North America, are a key first step in discovering how the developing brain responds to the repeated blows that come with youth football. Researchers underscored that they don’t yet know whether the young brains they studied might recover completely in the offseason, or whether normal development will be impeded by the impacts.

Only long-term research on a larger number of players will tell, said the study’s authors, who come from the University of Texas Southwestern Medical Center.

Those studies are already underway. Across the country, neuroscientists and sports injury experts have combined their efforts to conduct brain-imaging research on participants in youth contact sports. In the course of the high school football season just completed, the resulting consortium conducted studies that will supplement the University of Texas Southwestern Medical Center findings.

“It’s important to understand the potential changes occurring in the brain related to youth contact sports,” said Elizabeth Moody Davenport, a postdoctoral researcher who led the latest study.

“We know that some professional football players suffer from a serious condition called chronic traumatic encephalopathy, or CTE,” said Davenport. “We are attempting to find out when and how that process starts, so that we can keep sports a healthy activity for millions of children and adolescents.”

The researchers focused on 24 members of a high school football team. Researchers wired each player’s helmet with six accelerometers. During practices as well as during games, the sensors gathered detailed data on the location and strength of impact, and the direction of any blows to a player’s head.

Called the Head Impact Telemetry System, or HITS, this suite of sensors allowed researchers to record how many and what types of blows to the head a given player endured over the course of a season, as well as how forceful the blows were. Data from the helmets were then uploaded to a computer for analysis.

The study’s 24 subjects were 17 years old on average. None had ever had a diagnosed concussion, and no concussions were seen in the course of the team’s season.

When they have detailed before-andafter brain imaging studies, researchers can use the HITS results to infer links between certain kinds of brain impacts and observed brain changes.

Before the season began, and again after it ended, the North Carolina players underwent brain-imaging scans that measured the density of key brain structures and analyzed certain patterns of electrical activity generated by their working brain cells.

Using two kinds of specialized MRI scans, scientists sought to measure the integrity of the brain’s “white matter” — the bundles of insulated wiring that carry electrical signals both among cells and between groups of cells on either side of the brain’s two hemispheres. Earlier research has suggested that blows to the head that cause the brain to move side to side in its casing — such as the blows sustained by boxers — can twist and shear these bundles of connective tissue and disrupt their ability to conduct electrical signals efficiently.

One type of scan, a magnetoencephalography, or MEG, scan, recorded and analyzed the magnetic fields produced by brain waves. Among the many patterns they might listen for, researchers were attuned to delta waves, a form of slow-wave activity described by Davenport as “a type of distress signal” emitted by an injured brain.

The scans showed that the condition of the brain’s white matter was most affected in players whose helmets had recorded the most linear acceleration — the kind of direct frontal hit a receiver might get when returning a kick, or that a lineman might sustain repeatedly when lunging forward on every play.

Changes on the MEG scan were most often seen in players whose helmets showed they had sustained the most rotational impact. In rotational impact, the brain twists within the skull, usually in response to a sideways impact.

Boxers, who can receive frequent punches to the side of the head, often show the effects of rotational impacts. In football, the brain of a quarterback or ball carrier who is tackled laterally will likely withstand strong rotational forces.

Davenport said such results “demonstrate that you need both” brain imaging that measures changes in the brain’s structure and imaging that detects changes in its workings. Different kinds of brain changes are linked to “very different” kinds of impacts, she noted. And as researchers begin to recognize whether long-term behavioral effects — say, depression, memory loss or movement disturbances — come with certain brain changes, they can begin to protect players accordingly.

Given the North Carolina team’s concussion-free season, it is important to have both types of brain imaging to discern what effects repeated subconcussive blows to the head might have, Davenport and her colleagues said.