Objective

To study longitudinal recovery trajectories of white-matter after sports-related concussion (SRC), we performed diffusion tensor imaging (DTI) on collegiate athletes who sustained SRC. 

Methods

Collegiate athletes (n=219, 82 concussed athletes, 68 contact-sport controls, and 69 non-contact-sport controls) were included from the Concussion Assessment, Research and Education (CARE) Consortium.  The participants completed clinical assessments and DTI at four time points: 24-48-hours post-injury, asymptomatic state, seven days following return-to-play, and six-months post-injury.  Tract-based spatial statistics were used to investigate group differences in DTI metrics and identify white-matter areas with persistent abnormalities.  Generalized linear mixed models were used to study longitudinal changes and associations between outcome measures and DTI metrics.  Cox proportional hazards model was used to study effects of white-matter abnormalities on recovery time. 

Results

In the white matter of concussed athletes, DTI-derived mean diffusivity was significantly higher than the controls at 24-48 hours post-injury and beyond the point when the concussed athletes became asymptomatic.  While the extent of affected white matter decreased over time, part of the corpus callosum had persistent group-differences across all the time points.  Furthermore, greater elevation of mean diffusivity at acute concussion was associated with worse clinical outcome measures (i.e., Brief-Symptom-Inventory scores and symptom-severity scores) and prolonged recovery time.  No significant differences in DTI metrics were observed between the contact-sport and non-contact-sport controls. 

Conclusions

Changes in white matter were evident after SRC at six-months post-injury, but were not observed in contact-sport exposure.  Further, the persistent white-matter abnormalities were associated with clinical outcomes and delayed recovery time.