About 160,000 Canadians sustain brain injuries each year, and this number is rising. Today, over one million individuals live with the consequences of such injuries, which can include memory loss, confusion, problems with balance and a flurry of other debilitating symptoms. While it is increasingly clear that concussions are a significant public health issue, the mechanisms by which concussions affect the brain are still shrouded in mystery. We spoke to Professor François Tremblay, a researcher at the Bruyère Research Institute and the University of Ottawa’s Brain and Mind Research Institute, whose recent article in Clinical Neurophysiology sheds light on some formerly unknown effects of concussions on the brain.
Q: As a neuroscience researcher, what led you to study the impact of concussions?
A: This study was conducted in the context of a PhD thesis by my graduate student at the time, Travis W Davidson. Travis was involved in contact sports, and witnessed first-hand the impact of concussions in sports. He was the one who suggested that we explore the possible impacts of concussions. As a clinical neuroscientist, I was well aware of all the issues of concussions in sports and their impact of the brain. Concussions are a hot topic in neuroscience, with growing evidence linking concussive injuries to alterations in the brains of professional players, as was highlighted in a 2006 paper by Dr. Bennet Omalu, which inspired the movie Concussion, with Will Smith.
Q: How do you measure the effects of concussions on patients’ brains?
A: We use a technique called transcranial magnetic stimulation, by which we induce a small current in the brain to excite nerve cells. This allows us to stimulate the motor area of the brain involved in planning and executing movements, and record the responses in limb muscles. This technique not only allows us to measure changes in excitability within one hemisphere of the brain, but also allows us to examine interactions between the two hemispheres. In our study on concussions, we explored changes within each hemisphere and within the corpus callosum, which connects the two sides of the brain, and found that participants with a history of concussions presented significant alterations in communication between the two hemispheres.
Q: Your recent research pointed to long-term changes in the way the brain transmits information. What exactly did you find?
A: We knew that concussions alter the white matter, which represents 50% of the brain’s mass and enables efficient communication within each hemisphere and between hemispheres. What we didn’t know is how that affects patients in the long run. For the first time, we have found that concussions affect the transmission of information between the hemispheres of the brain many years after the injury.
Q: How could those changes to the white matter affect patients with brain injuries?
A: Since communication within and between hemispheres is critical for the full repertoire of human behaviour, any disruptions in the transmission of information could have major consequences on brain functions, including cognitive, perceptual and motor abilities. We also know that lesions or dysfunctions in the brain’s white matter are involved in the development of dementia, including Alzheimer’s disease, as well as chronic traumatic encephalopathy (CTE), a degenerative disease commonly detected in athletes and caused by repeated or violent blows to the head.
Q: How can your research results be used in the medical field?
A: Our study confirms the vulnerability of white matter to concussive injury and provides a potential neurological marker to monitor the long-term impacts of concussions on the brain’s functions. Detecting alterations involving white matter and the corpus callosum in particular could lead to early detection of the potential long-term consequences of concussions - and earlier treatment. It will also enable us to follow the evolution of brain injury patients and measure how their cognitive, motor and perceptual abilities change with time.
Q: Do you intend to push your concussion research further, and what are you hoping to find?
A: The logical next step would be to monitor changes in the brain, ideally before and after a concussive injury, to follow the evolution of the condition at different time points. This requires a very close collaboration between different stakeholders, including athletes, their parents, coaches and managers. Despite all the media attention, concussions remain a very “sensitive” topic. It’s very hard for a young hockey player or footballer who is fully committed to their sport to foresee consequences that may affect their health years down the road. For now, our next step will be to investigate whether the changes in communication between brain hemispheres that we measured have any impact on the study participants’ ability to perform specific tasks, such as tying their shoes, which requires coordination and the action of both hands.
Media Relations Officer
 Brain Injury Canada, http://braininjurycanada.ca/acquired-brain-injury/