Given that at least 75% of traumatic brain injuries in the U.S. are mild, concussions are a serious public health concern that cause significant neurological damage and negatively impact individuals’ quality of life. Due to the rotational forces that occur during a concussion, immediate damage to the corpus callosum is common, resulting in neurological and behavioral deficits. However, the longitudinal damage to the integrity of the corpus callosum is unclear and may differ across sections of the corpus callosum. Our primary aim was to compare the white matter integrity across eight corpus callosum tracts in concussed individuals to healthy controls 3-4 weeks after injury and at a 10-month follow-up.

Seventeen concussed participants completed a diffusion tensor imaging (DTI) scan 3-4 weeks after receiving a concussion and again 10 months after injury. Nineteen control participants completed a single DTI scan. DTI data were analyzed using the automated fiber quantification (AFQ) pipeline, which extracts fractional anisotropy (FA) values from 100 nodes in eight tracts of the corpus callosum (listed anterior to posterior): orbital frontal, anterior frontal, superior frontal, motor, superior parietal, posterior parietal, occipital, and temporal. Given the non-linearity, high multicollinearity, and large number of data points, a cubic smoothing spline was used to fit a penalized regression to the FA values in each tract, allowing us to compare the FA values of each node in each tract between groups and across time. To assess acute damage, a spline model for the concussed participants at 3-4 weeks was compared to a spline model for the control participants in each tract. To assess longitudinal damage, a spline model of the FA difference value (10-month minus acute visit) in concussed participants was compared to a spline model of the FA difference value for controls (zero, representative of a theoretical no change in FA values). Significant nodes were defined as p-values less than 0.006 (alpha of .05/8, given 8 tracts).

Acutely following injury, concussed participants showed lower FA values than controls in the anterior frontal, posterior parietal, occipital, and temporal tracts. In the orbital frontal tract, concussed participants had higher FA values on the left, but decreased FA values compared to controls in the middle. Longitudinally, concussed participants showed continued decreased white matter integrity in the orbital frontal, superior parietal, and occipital tracts, but improved white matter integrity in the anterior frontal and superior frontal tracts. The motor, posterior parietal, and temporal tracts showed mixed longitudinal results of decreased or improved white matter integrity within each tract.

Concussed individuals show decreased white matter integrity across the corpus callosum acutely after injury. Longitudinally, the most anterior and posterior portions of the corpus callosum (i.e., genu and splenium) show continued damaged while the more medial sections of the corpus callosum may show some recovery. Results suggest the corpus callosum displays differential patterns of damage acutely and longitudinally following concussion, with some tracts improving while others continue to deteriorate.