Persistent Motor System Abnormalities in Formerly Concussed Athletes

De Beaumont L, Mongeon D, Tremblay S, Messier J, Prince F, Leclerc S, Lassonde M, Théoret H. Journal of Athletic Training. 2011:46(3):234-240

In the past, literature on concussions has focused on the acute phase; however, researchers have begun to examine the sequelae and long-term consequences of the injury.  Researchers have already reported that multiple concussions can result in lasting effects (e.g., earlier onset of Alzheimer’s, cognitive impairment, and depression) in some retired athletes (Guskiewicz et al., 2005; Guskiewicz et al., 2007).  This study also delves into the subject of a compromised motor system due to previous concussions.  A case-control study was performed in which 21 active football players who had suffered at least one prior concussion, nine months or longer before the testing, were assessed in addition to 15 control football players with no history of a concussion.  Injury information on the concussed group was taken either from their medical records (if their concussions occurred during their college career) or from self reporting (if their concussion occurred prior to them entering college).  Overall, the athletes had anywhere from one to five previous concussions that occurred in the last nine to 34 months.  The authors used a variety of methods to evaluate the motor system including postural control using a force plate.  Likewise, a rapid alternating movements (RAM) task (rotating 2 handheld spheres through pronation-supination) was performed to assess upper extremity motor performance and transcranial magnetic stimulation (TMS) evaluated changes in brain function (specifically the primary motor cortex).  This study found that football players with a history of concussions had compromised posture in the anteroposterior direction compared to the football players with no history of concussion but all RAM tasks were executed similarly by both groups.  Within the concussed group, TMS showed an increase in primary motor cortex inhibition compared to players with no history of concussions.  Furthermore, more primary motor cortex inhibition was found with each additional concussion a player experienced in the past.  This may suggest that more damage occurs to the motor system with each successive concussion an athlete experiences.

I found this study interesting because it further demonstrates the effect of concussion and how an athlete might be compromised long after suffering such an injury.  For sports medicine clinicians, this evidence further highlights the need for better concussion prevention and research evaluating ways to minimize the long-term consequences of concussions. To build on this study, I would be curious to see a similar study in which athletes are tested at several different intervals from the time of injury (i.e., days, months, or years after a concussion).  Perhaps these objective measures of changes in the motor system persist for years, or don’t manifest immediately after the injury occurs.  Either way, the author points out that assessing postural control with a force plate is not only a great tool when assessing a concussion, but a way to examine the long-term effects of such an injury. While these measurements are not clinically ready, we’ve seen previous SMR posts that suggest clinicians may in the next few years have the ability to test balance measures with cost-effective equipment (Clark RA, 2011).

Written by: Jacqueline Phillips