Assessing the impact of micro concussions is difficult. A new study tries a new approach.
There has been a significant drive, over recent years, to push the issue of concussion to the front of people's minds.
It's now common knowledge that someone who is concussed should not return to the field of play and should take care to rest.
The study that we are discussing today relates to a more common but much less understood phenomenon: subconcussive impacts, which are also known as micro concussions.
The study authors define micro concussions as "impacts to the skull, including those that do not produce acute concussion but nevertheless result in clinical signs and symptoms."
Across a college football season, a player might pick up well over 1,000 micro concussions. And, as research intensifies, scientists are growing increasingly concerned that they may have a significant cumulative effect.
To date, however, no concrete conclusions have been made about the specific brain regions that are affected by micro concussions. The authors of the new study sum up the confusion.
"Some studies find an effect on cognition, while others find no effect. The subconcussive effect of hits on balance," they write, "is also inconclusive with some reporting a positive effect and others reporting no effect."
Others have looked for changes in the anatomy of the brain, with some focusing on differences in white matter and others on gray matter.
The story here is similar. As the study authors explain, "Once again, however, these studies do not yield a clear consensus."
Reopening micro concussions
One researcher dedicated to getting to the bottom of this question is lead study author Nicholas Port, from Indiana University Bloomington.
He set out to explore whether or not there were measurable differences in brain activity between people who played contact sports and those involved in non-contact sports. His findings are now published in the journal NeuroImage: Clinical.
To begin, the researchers took brain scans of 21 football players and 19 cross-country runners using functional MRI technology. This type of imaging detects changes in blood flow related to activity in regions of the brain.
They chose football players due to their high risk of repeated blows to the head, and runners because they are at very low risk of head injuries. None of the footballers had sustained a concussion in the previous season.
The team also scanned the brains of 11 non-college-level athletes of a similar socioeconomic background to use as a control group.
In particular, Port and his colleagues were interested in the visual centers of the brain. He says, "We focused on these brain regions because physicians and trainers regularly encounter large deficits in players' ability to smoothly track a moving point with their eyes after suffering an acute concussion."
And, when the brain scans were analyzed, measurable differences were seen between the three groups. Those who played football showed much more activity in their visual regions than either the control group or the cross-country runners.
Although differences were seen, the next challenge is how to interpret the findings. Is the increase in visual activity among footballers due to a lifetime of minor head injuries, or because they play a visually demanding sport?
As Port explains, "Everyone from musicians to taxi drivers has differences in brain activity related to their specific skills."
At this stage, although the results are interesting, there is no way to tell why these differences were found. In the future, Port believes that the answer may come from wearable accelerometers.
Although this technology is already available, it is expensive and cumbersome. As the equipment improves, and players can play more naturally while wearing it, better data can be collected.
In this way, the number of blows to the head can be monitored in real-time and compared with cognitive deficits and changes in the brain at a later date.
Overall, though, the study only adds to the pile of inconclusive findings. Although differences were seen — footballers' visual centers were busier — accurate interpretation is impossible at this stage.