Cerebrovascular reactivity alterations due to subconcussive repetitive head trauma in asymptomatic high school football players

Chronic neurological damage as a result of chronic repetitive head trauma is a major concern for football athletes today. Repetitive concussions have been linked to many neurological disorders. Recently, it has been reported that repetitive subconcussive events can contribute to long-term neurodegeneration. For these reasons, it is important to understand the effect repetitive subconcussive head trauma has on brain health in young athletes. Past research has demonstrated that cerebrovascular reactivity (CVR), an important mediator of cerebrovascular regulation, is impaired following mild traumatic brain injury (mTBI). This impairment increases susceptibility to secondary injury following mTBI. In this study, Breath-Hold (BH) task based functional Magnetic Resonance Imaging (fMRI) was used to track CVR changes in asymptomatic high school football athletes across three competition seasons. Athletes in the first competition season had higher exposure to head impacts than the athletes during the second and the third seasons. Baseline scans were acquired before the start of the season, and follow-up scans were obtained during and after the season to track the potential changes in CVR as a result of experienced trauma. Noncollision-sport athletes were scanned over two sessions as controls during the first and third competition season. CVR decreased significantly in football athletes during the first half of their season in the first completion season but not in any other competition seasons. Controls did not show any significant changes in CVR. The results suggest that athletes getting higher exposure to head impacts in short duration of time drives cerebrovascular changes that may place athletes at higher risk of getting injured. These results also indicate that the brain may not be able to adapt quickly to abrupt increases in contact activity (as associated with the beginning of practice and competition), transiently increasing risk for symptomatic injury