Abstract
Quantifying injury tolerance for concussion is complicated by variability in the type, severity, and time course of post-injury physiological and behavioral changes. The current study outlined acute and chronic changes in behavioral metrics following rotational acceleration-induced concussion in rats. The Medical College of Wisconsin (MCW) rotational injury model independently controlled magnitude and duration of the rotational acceleration pulse. Increasing rotational acceleration magnitude produced longer recovery times, which were used in this study and our prior work as an assessment of acute injury severity. However, longer duration rotational accelerations produced changes in emotionality as measured using the elevated plus maze. Cognitive deficits were for the most part not apparent in the Morris water maze assessment, possibly due to the lower severity of rotational acceleration pulses incorporated in this study. Changes in emotionality evolved between acute and chronic assessments, in some cases increasing in severity and in others reversing polarity. These findings highlight the complexity of quantifying injury tolerance for concussion and demonstrate a need to incorporate rotational acceleration magnitude and duration in proposed injury tolerance metrics. Rotational velocity on its own was not a strong predictor of the magnitude or type of acute behavioral changes following concussion, although its combination with rotational acceleration magnitude using multivariate analysis was the strongest predictor for acute recovery time and some chronic emotional-type behavioral changes.
Highlights
It is becoming clear that rates of diagnosed concussion in contact sports are increasing
Prior to the injury procedure, rats were exposed to anesthesia for 479 ± 82 s consisting of 5 min in the induction box and nose cone anesthesia for the remaining time until just prior to head rotational acceleration
Linear regression analysis revealed that magnitude of rotational acceleration and rotational velocity were significant predictors for acute recovery time (p < 0.001) (Fig. 3)
Summary
It is becoming clear that rates of diagnosed concussion in contact sports are increasing. Other studies have highlighted the significant increase in concussion rate in high school sports over a 6-year period, indicating that five of nine investigated sports had statistically significant increases.[32] While explanations for these increases may include increased awareness about concussions by coaches, medical professionals, and athletes, increased legislation, and better reporting of concussions at the high school level, the possibility of increasing concussion incidence should not be ignored. This comes at a time of increased awareness of the chronic effects of concussions. The work of Guskiewicz, McCrea and colleagues has outlined significantly increased rates of chronic cognitive difficulties and emotional disturbances, including depression, for retired professional football players that had sustained
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