Article: Functional brain effects of acute concussion in Australian rules football players
Journal of Concussion, vol. 3, First Published July 8, 2019.
DOI: 10.1177/2059700219861200
https://journals.sagepub.com/doi/full/10.1177/2059700219861200
Authors:
Graeme D Jackson1, 2, 3, 4*, Michael Makdissi1, 5*, Mangor Pedersen1*, Donna M Parker1, Evan K
Curwood1, Shawna Farquharson1, Alan Connelly1, 2, David F Abbott1, 2, 4, Paul McCrory1, 2
Affiliations:
1The Florey Institute of Neuroscience and Mental Health, Melbourne, VIC, Australia
2Florey Department of Neuroscience and Mental Health, The University of Melbourne,
Melbourne, VIC, Australia
3Department of Neurology, Austin Health, Melbourne, VIC, Australia
4Department of Medicine, The University of Melbourne, VIC, Australia
5Olympic Park Sports Medicine Centre, Melbourne, VIC, Australia
*The first three authors are joint first authors.
Funders:
This study was supported in part by the National Health and Medical Research Council
(NHMRC) of Australia, grant number #1127007, #1060312 (GJ Practitioner Fellowship) and
#1026383 (PM Practitioner Fellowship). DA and SF are supported by fellowship funding from
NIF. Funding for the MRI scans was provided by the AFL.
Aim:
The symptoms of acute Sports-Related Concussion (SRC) such as headaches, confusion and
issues with balance are thought to be driven by altered brain function instead of physical brain
injury or pathology.
Current research suggests that there are spots within three key brain networks that change after
mild brain trauma like a concussion. These include:
• The cognitive control network used for high-level thinking like decision making and
attention (right frontal cortex, right intraparietal lobe)
• The salience network used for changing between tasks (right anterior insula, anterior
cingulate)
• The brain’s core default mode network used when a person is not fixated on the outside
world, like daydreaming (precuneus / posterior cingulate cortex, superior parietal lobules
and ventromedial prefrontal cortex)
The aim of this study is to discover the links between SRC and connectivity changes within these
brain networks using fMRI.
Terminology:
Sports-Related Concussion: A type of mild traumatic brain injury that results from a force
applied to the brain that usually brings about neurological changes
Functional Magnetic Resonance Imaging (fMRI): Imaging technique that looks at changes in
blood flow and oxygen levels to measure brain activity
Functional Connectivity: Statistical relationship between the brain activity signals in time as
measured using techniques such as fMRI
Method:
MRI scans were performed on a group of AFL players who had experienced an acute SRC
within one month of the study. The initial diagnosis was made by team doctors. 20 participants
met a range of clinical symptoms and inclusion criteria such as witnessed impact and cognitive
impairment, which were further reviewed before the scans took place. Each participant who had
experienced a concussion was age-matched by a non-concussed control.
Imaging was obtained using a 3 T Siemens Skyra MRI System. This included a fMRI sequence
(taken at rest) and T1 weighted image of the brain.
The data was statistically compared to help understand functional connectivity between
concussed and non-concussed groups.
Results:
The concussed players showed a significant decrease in functional local connectivity compared
to controls. This was noted in brain regions that included the right dorsolateral pre-frontal
cortex, right inferior parietal lobe and right anterior insula. The structures of the brain were also
assessed with imaging and no deformities were found in either group.
Conclusion:
In concussed players, functional connectivity was decreased in areas of the brain that match with
the cognitive control and salience network. No changes were detected in the core default
network.
Relevance:
There is currently a gap of knowledge in the underlying biological mechanisms that drive
symptoms seen in SRC. Standard imaging shows that brain structures are not usually disturbed
after acute SRC. What appears true is that rather functional network changes are responsible for
SRC symptoms as shown with fMRI technology and statistical analyses. These findings could
help with better understanding how SRC affects AFL players. Additionally, it could provide
more signs for diagnosis based on current knowledge of the different roles of areas in the brain.
HRA Comment:
Animal models are often used to investigate traumatic brain injuries, like concussion. However,
research suggests that SRC symptoms in humans (e.g. headache) reflect functional connectivity
changes in certain spots of the brain rather than structural brain deformities. This makes
simulating SRC difficult but also unnecessary in non-human models. Furthermore, the distinct
differences between the brains of humans and other animals make humans the most ideal
subject to study SRC symptoms.
