The Complexities of Concussive Injury

Dr. Lowell Greib MSc ND CISSN

We, like many of you, are parents. The confusing world of technology and readily accessible information, seemingly makes it difficult for a parent to understand clearly what is happening to their child when concussive injury occurs. As clinically trained medical professionals, we, ourselves find the information that is being delivered confusing. We strongly feel that a vital aspect of concussion rehabilitation is effective knowledge distribution to all of those affected by concussive injury – including the athlete, parents, coaches, trainers and association administrators.  Clear, concise and consistent information about the evolving research in this form of brain injury allows for a course of treatment that best serves the athlete.  This series of articles that will follow will help bridge the knowledge gap and, ultimately, allow for more streamlined care.

A blow to the head can happen at any point in time and under varied circumstances.  One does not need to ‘get their bell rung’ in order to generate enough force to suffer concussive injury! It can result in a situation that seems benign and insignificant. Our beloved Canadian national sports (both lacrosse and hockey) have some of the highest concussion rates documented. Literature measures concussion rates based upon the number of ‘Athlete Exposures’ (AE).  Simply, this is a time frame, within the sport, when an injury can occur.  For instance, a hockey practice with 15 athletes is considered to have 15 AE.  One can easily see how a tournament can rapidly add up!  With a practice and 5 games for a team of 15 there would be 90 AE.  Incidence in youth hockey is estimated at 1.2/1000 AE.1 A factor to keep in mind is that this is the athletes ‘organized’ sport.  Don’t forget that recreational exposures and academic programming (gym and school teams)  that contribute to the the AE of  an athlete.

With advances in both biochemistry and physiology, researchers are gaining knowledge and insight into what is occurring in the brain when impact occurs.  It is now generally accepted that impact that causes common symptoms that an athlete experiences is a complex, multi-factorial process.

Our brain has a covering known as the ‘meninges’. This covering directly protects the vessels that supply the brain and contains cerebral spinal fluid (which also protects the brain). Without this covering (and of course our skulls) our brain cells and the important connections that allow those cells to transmit information to each other would be always exposed to injury.  None of us would survive very long if that were the case!  

On impact, there is thought to be a disruption to the meninges. This can not be seen on medical imaging such as MRI since it happens at a cellular level. This disruption leads to a complex cascade of events IN the brain that include2: 

  • Inflammatory responses
  • Damage to the axons (which are responsible to carrying impulses from nerve cell to nerve cell) 
  • Disruption of normal cellular metabolism
  • Disruption of the normal functioning at cell membranes
  • Disruption of mitochondria (the energy producing power house found in all of our cells)
  • Derangement of blood flow
  • Cellular damage (caused by oxidation of cell membranes, protein, DNA and RNA)

These changes all have the capacity to affect other systems in the body depending on how dominant each of the responses are in the brain and what part of the brain was affected by the trauma.  This only becomes more confounded when other metabolic and neuronal pathways are considered.  All in all, concussion is a VERY complex neurologic, immunologic and metabolic process.  Although it is not the responsibility of a parent to understand this complex system, it is that of a medical practitioners who assist with the care of an athlete.  Suffice to say, there are MANY processes occurring in the brain (and body) that lead to the symptoms that an athlete experiences.  The symptoms are a direct response to which of the body system is predominantly being affected. The system dictates which ‘trajectory’ of care needs to be followed.

1 Pfister, T et al.  British Journal of Sports Medicine. 2016;50(5):292–7.
2 Barrett, EC et al. Adv Nutr. 2014 May 14;5(3):268-277 

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