In yet more evidence raising concerns about the long-term neurological health of athletes in collision sports, an MRI brain study in Aussie rules football players has found that a history of sports-related concussion (HoC) has a measurable impact on white and grey matter.
The Melbourne study compared findings in 26 amateur football players with a history of concussion at least six months before the study, and 17 age-matched athletes from non-collision sports such as track and rowing and with no history of concussion.
The athletes were all male, with a median age of 24 years, and an average of 17 years playing sport.
Diffusion tensor MRI identified abnormalities in the white matter microarchitecture in players with a history of concussion.
These included reduced fractional anisotropy and increased radial diffusivity in the corpus collosum, superior longitudinal fasciculus, and corticospinal tract compared to the controls.
The study, published in Cerebral Cortex, also identified cortical thinning in the frontal, insula, and temporal regions of the right hemisphere and the frontal cortex and cingulate of the left hemisphere in players with a history of concussion.
“There were no differences between the groups on measures of subcortical brain structure volumes or the prevalence and severity of cavum septum pellucidum (CSP),” the study said.
The investigators said their findings of decreased diffusivity in major white matter tracts, and the locations of these abnormalities, were consistent with those previously described in other collision sports such as American football and ice-hockey.
“Despite different modes of injury across studies (e.g., sports, motor vehicle accidents, military injuries), these common abnormalities found in long-range white matter fibres suggest a point of vulnerability in the brain to mild TBI,” they said.
“It remains unclear whether it is the location of these structures (e.g., near the centre of mass) or physical properties (e.g., long axons) that make them so susceptible to the shear and strain forces induced in mTBI.”
“Considering the remote (>6 months) nature of past concussions in the current investigation, our evidence suggests that HoC is associated with either persistent or delayed microstructural abnormalities in white matter.”
They noted that the pathologies could be induced by biomechanical forces at the time of impact, and/or via secondary injury pathways such as oxidative stress and inflammation.
“Furthermore, we also found that serum levels of neurofilament light, a protein abundant in myelinated axons, continued to rise for at least 2 weeks after sports-related concussion (SRC).”
“These findings suggest that the immediate consequences of SRC can persist for at least several weeks and could potentially result in chronic changes.”
The investigators said their evidence of subtle cortical thinning also aligns with previous work in former collision sport athletes
They said further research was required including longitudinal studies to see if “…the observed abnormalities worse, recover or plateau with age”, as well as studies in female athletes.
“Notably, Australian football may provide the ideal sport for such studies given the similar full-contact rules in both men and women leagues,” they said.