Are Athletes Really Ready? Brain Changes After Concussion Persist Beyond Medical Clearance

Credit: Adobe Stock/rocketclips

A study that followed concussed athletes over time using brain scans to see whether changes in brain function and structure persisted beyond medical clearance revealed that even after they returned to play, brain blood flow and white matter integrity were still altered, with some effects lasting up to a year. This suggests that medical clearance may not mean full brain recovery, and further research is needed to ensure safe return to play decisions.

Current recovery protocol is based on a combination of symptom assessments and tests of visual function, balance and cognition. However, research suggests that the physiologic brain recovery may continue after the clinical symptoms have disappeared. In fact, some studies show disturbances in the brain months to years after clinical resolution.

“This raises concerns about possible long-term effects of concussion on neural physiology, the consequences of which may be exacerbated by repetitive injury,” wrote a team of investigators led by Nathan W. Churchill, Ph.D., associated with the Brain Health and Wellness Research Program, St. Michael’s Hospital, University of Toronto.

The prospective observational study, published in Neurology, recruited healthy athletes with no history of psychiatric diseases, neurologic disorders or sensory-motor conditions from the University of Toronto sport medicine clinic. Clinical information and MRI data were collected at baseline. Athletes who experienced a concussion were reassessed at one to seven days after the injury, when they returned to play, one to three months after that, and one year after. A group of athletes who were uninjured were also reassessed to identify any differences between the two cohorts.

The study focused on changes in MRI measures of cerebral blood flow (CBF), fractional anisotropy (FA) and white matter mean diffusivity (MD). Other end points included differences in MRI change scores and correlations with change scores with days to return to play.

A total of 187 athletes were included in the study, of which 25 had concussions with follow-up imaging. The mean age of students was 20.3 years, 56% were male and 44% were female. These athletes were compared with 27 controls with a mean age of 19.7 years, 56% female and 44% male.

The average time to full clinical recovery was three weeks, although significant variability was observed. Between the groups, there were no significant differences in demographics or in concussion characteristics in the history of concussion subgroups.

Those who experienced a concussion had significant changes from baseline when compared with controls. These included decreased frontoinsular CBF, increased MD and reduced FA in the corona radiata and internal capsule. Observed changes continued even after they returned to play.

For athletes who took longer to recover from a concussion, significantly greater changes in medial temporal CBF were noted.

Investigators said the findings allow for unprecedented insights into recovery. However, they noted a loss of some longitudinal and clinical data as a limitation. Future research should focus on recruiting a more directly comparable group of athletes in the control cohort and results should be confirmed through further research.

“Findings in the absence of persistent clinical issues suggest that changes represent a functional ‘new normal’; it is not clear at present whether renormalization of brain physiology occurs on sufficiently long time lines, making this an important area of further research,” investigators concluded. “Nevertheless, the presence of significant, long-lasting brain changes after injury reinforces concerns about the consequences of repeated concussions and to what extent these effects accumulate over time.”