Repetitive Impact and Understanding Concussions

Are mild, run-of-the-mill impacts of the head and neck as much to blame for concussions as big hits and impacts? Do they cause similar damage to brain blood vessels?

If scientists at Trinity College Dublin are correct in their findings, the answer is yes. In a study whose results were published in the Journal of Neurotrauma, the Concussion Research Interest Group (CRIG) announced their findings that repetitive impacts, not single events, cause the most critical damage to blood vessels in the brain. They also shared how this finding may affect management and treatment of concussive brain injury going forward.


One major challenge to doctors in diagnosing and treating concussive brain injury is often the lack of strong biomarkers or clear and objective imaging approaches in managing the injuries.

Recent studies have revealed much about concussions and mild head trauma in recent years. I’ve written and podcasted about this very subject previously. These injuries are usually thought of as connected to contact and combat sports like football, rugby, MMA, boxing, lacrosse and hockey. However, concussions have been on the rise in sports like soccer and even among children and young adults in the “non-athlete” population.

“This was a hypothesis-driven project whereby we challenged the hypothesis that repetitive head trauma would induce damage to small blood vessels in the brain that we would then be able to image with a novel form of MRI-based brain scans,” said Dr Matthew Campbell, Assistant Professor at Trinity.

Collision sports athletes in sports like rugby and combat athletes in MMA took part in the four-year-long clinical study. CRIG utilized a combination of dynamic contrast-enhanced MRI and sensor-enabled mouthguard technology developed at Stanford University by Professor David Camarillo and his working group. The MRI procedure was designed to confirm how many head impacts it would take for “leaky” blood vessels to appear in the brain and how severe those impacts would have to be.

As part of a broader longitudinal study, the work is ongoing.

We know that concussive brain injuries are typically marked by clinical symptoms like nausea, dizziness and confusion. What doesn’t always accompany those symptoms is clear-cut physical evidence. It’s not uncommon for CT or MRI scans to be free of positive signs of injury or for the blood to be free of obvious biomarkers. As a result, new technologies must be developed to meet the challenge and help doctors in the diagnosis, management and rehabilitation of concussive brain injuries.

Dr Colin Doherty, Consultant Neurologist at St James’s Hospital and clinical lead on the study, added: “Our findings, for the first time, suggest that repetitive head trauma can lead to an MRI signal that we can definitively link to the number and severity of impacts to the head. It appears that the repetitive nature of these impacts as opposed to single events are causing damage to the capillaries of the brain.”

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According to the study, changes can be caused in the micro-vessels of the brain by repetitive impacts to the head that do not result in concussions. Using a novel form of MRI-based imaging can make these changes readily visible.

The researchers believe their findings may lead to more robust and objective return-to-play guidelines and improvements in player safety long-term and in a variety of sports.

“This study has highlighted the critical importance of continued efforts to study the underlying effects of concussive brain injuries in all sports. It is imperative that the governing bodies take note of these findings and work together to protect athletes now and in the future,” added co-author Professor Mick Molloy, former Chief Medical Officer of World Rugby.

Concussive brain injuries are traumatic for the injured and often tricky for doctors and those involved in the rehabilitation. The more research that’s done and the more we learn, the nearer we get to understanding these injuries, and the more athletes and people who get to avoid long-term damage from them.

Keep the faith and keep after it!

Journal Reference – Eoin O’Keeffe, Eoin Kelly, Yuzhe Liu, Chiara Giordano, Eugene Wallace, Mark Hynes, Stephen Tiernan, Aidan Meagher, Chris Greene, Stephanie Hughes, Tom Burke, John Kealy, Niamh Doyle, Alison Hay, Michael Farrell, Gerald Grant, Alon Friedman, Ronel Veksler, Michael Molloy, James Meaney, Niall Pender, David Benjamin Camarillo, Colin Doherty, Matthew Campbell. Dynamic blood brain barrier regulation in mild head trauma. Journal of Neurotrauma, 2019

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