The Effects of Subconcussive Head Trauma in Athletics

Open Access
Author:
Johnson, Brian
Graduate Program:
Kinesiology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
February 15, 2013
Committee Members:
  • Semyon Slobounov, Dissertation Advisor
  • Karl Maxim Newell, Committee Member
  • Wayne Joseph Sebastianelli, Committee Member
  • Thomas Neuberger, Committee Member
Keywords:
  • concussion
  • subconcussive
  • neuroimaging
Abstract:
There is a growing concern in clinical practice regarding the immediate and long-lasting effects of multiple and frequent subconcussive blows in athletes participating in full contact sports. The effects of repetitive subconcussive head trauma, occurring in full contact sports, on brain structural, functional and metabolic integrity has not been sufficiently investigated. It is yet to be determined whether these multiple subconcussive blows induce transient alterations in the brain or long-term deficits. Our central hypothesis is that previous concussive episodes lead to chronic cognitive and functional deficits in the brain. Additionally, a history of prior concussion may increase an athletes' vulnerability to repetitive subconcussive blows leading to a compromise in metabolic, structural, and/or functional brain integrity. Thus, specific alteration of brain functional/structural integrity in the acute phase of injury may identify athletes at high risk for recurrent concussion. In order to assess the effect of subconcussive blows advanced neuroimaging techniques (functional magnetic resonance imaging, magnetic resonance spectroscopy, and neuropsychological testing) was completed during two (pregame and postgame) identical testing sessions that occurred within 24 hrs prior to a scheduled full contact game and within 24 hrs of the end of that game. All subjects under study displayed no signs or symptoms of a concussion at either testing session and were also observed during and after the game by a medical professional. Virtual reality assessment of balance, reaction time, and working spatial memory revealed poorer performance in the group with a history of previous concussion compared to those with no prior concussion. Furthermore, there were significant reductions in neurometbolite ratios in the group with a history of concussion as assessed by magnetic resonance spectroscopy. Resting-state functional magnetic resonance imaging revealed reduced connectivity in the group with previous concussion, yet no changes in functional connectivity pre-game to post-game. However, the group with no history of concussion showed a iv significant decrease in connectivity in the right lateral parietal and medial pre-frontal cortex following a full contact game. Pre-game to post-game changes did not reveal any significant changes in metabolite ratios or performance on virtual reality modules, although an interesting trend was observed. Consistent across all modalities the group with a previous concussion tended to improve in their post-game evaluations compared to their pre-game assessment. Conversely the group without a history of prior concussion exhibited the opposite trend and consistently performed worse in the post-game evaluation. This unexpected trend brings up the question of whether or not a prior concussion may elicit a neuroprotective effect on the brain when repetitive subconcussive head trauma.