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CHICAGO – Magnetoencephalography revealed different patterns of activity at rest among teens with a long-term history of concussion versus their peers who had never sustained a brain injury, researchers reported here.

High school football players, ages 16-18, with a history of concussion had significantly lower default mode network correlations from pre‐season to postseason, according to Elizabeth Davenport, PhD, of the University of Texas Southwestern Medical School O'Donnell Brain Institute in Dallas, and colleagues.

Study participants with previous concussions had a negative change in correlation whereas those without a history of concussion had, on average, a positive change, they reported at Radiological Society of North America annual meeting.

The results demonstrate that concussions from previous years can influence the changes occurring in the brain during the current season, suggesting that there are longitudinal effects of concussion that affect brain function, the authors noted.

"How the default network is operating at rest is a good measure of brain health. We have to look into this more because something is going on in the brains of these adolescents," Davenport told 麻豆传媒.

But Davenport said the findings should be looked at with some caution because, of the 20 players tested, only five had a history of concussion, and not necessarily a sports-related one. "The only recommendation that we could make based on the information we have now to parents is just to observe the child. You know your kid; watch him to see if his behavior changes," she said. "Our information is pointing to the idea that if a person has any concussion during one's lifetime, their brain may not fully recover -- although we don't know that at this time."

Her group analyzed the default mode network, which is active during wakeful rest. Changes in the network are observed in patients with mental disorders. Decreased connectivity within the network is also associated with traumatic brain injury.

"The default mode network exists in the deep gray matter areas of the brain," Davenport explained "It includes structures that activate when we are awake and engage in introspection or processing emotions, which are activities that are important for brain health."

The 20 players had a mean age of 16.9 and were all right handed. Eight minutes of eyes‐open, resting‐state MEG data were acquired for each participant using a 275 channel CTF whole‐head system, pre‐ and post‐season. Structural anatomic MRI was acquired for co-registration with MEG. There were no significant differences in age, BMI, or head impact exposure between the two groups.

They analyzed the Magnetoencephalography power associated with the eight brain regions (left and right) of the default mode network:

• Inferior parietal
• Medial orbitofrontal
• Posterior cingulate
• Superior frontal

Max Wintermark, MD, of Stanford University in Stanford, California, told 麻豆传媒 that was study was interesting, "because the diagnosis of concussion is very elusive. When you do a regular CT scan in a patient with a concussion, you don't see anything; when you do a regular MRI in a patient with a concussion you don't see anything either. It is something that is hard to diagnose, and it is even harder to characterize."

Davenport's group offers a potentially new way to diagnose concussion and gain a better understand of the mechanisms of concussion, added Wintermark, who was not involved in the study.

"That is the promise of this study -- that we may have found a good tool that can help us diagnose concussion," he stated.

However, he echoed Davenport's warning that the study population was small. "You have to take everything with a grain of salt. It will be interesting to see how this difference in resting state patterns evolve over time and if it makes a clinical difference. The question remains whether these changes are permanent or can they be reversed," he said.