Assessment of Cerebral Blood Flow Changes Following Concussion in Collegiate and High School Athletes

Current recommendations for diagnosis and management of sport related concussion include patient-reported symptom inventories, computerized neurocognitive testing, and assessment of balance. There is a dire need for tools that are easily accessible and able to objectively measure physiological, not just functional, changes associated with concussion. The Brain Acoustic Monitor may offer a solution through examination of alterations in arterial functioning post-concussion. In this study, our purpose was to evaluate the potential usefulness of the Brain Acoustic Monitor in detecting changes in cerebral blood flow via measures of arterial stiffness in concussed individuals. In manuscript one, we sought to describe the test-retest reliability of Brain Acoustic Monitor measures and our results indicated moderate reliability over a 24 to 48 hour time period. Very low reliability was seen, however, in one of the eight measures, left systolic interval, suggesting potential sensor malfunction or inconsistency in processing methods. In manuscript two, we sought to describe post-concussion changes in arterial stiffness at 24 to 48 hours post-injury, resolution of symptoms, and return-to-activity. No significant differences in these three time points were found within our concussed sample; however, the concussed group displayed significantly higher right systolic interval at initial assessment and resolution of symptoms compared to a group of healthy age, gender, and sport-matched controls. These findings suggest the need for baseline measurements in future studies as well as a re-examination of processing procedures as there was large variability in some measures. In the third manuscript, we sought to determine how measures of arterial stiffness relate to current standards of concussion assessment, particularly computerized neurocognitive test performance. The results of this study suggested that improvement in arterial stiffness, shown by an increase in left peak interval, resulted in a worsening, or increase, in processing speed performance on the Concussion Resolution Index neurocognitive test battery. While this relationship was not expected, it was observed that the arterial stiffness waveforms of many of the concussed sample displayed an anomalous second reflection. This additional reflection could, in theory, be due to poor or lack of standardized placement of sensors or the result of a wave reflection from secondary sites within the arterial tree. Based on these findings, it seems that the Brain Acoustic Monitor is not a conclusively strong addition to current concussion assessment practices and management of concussion should remain reliant upon a multifactorial approach including symptom inventory, balance assessment, and neurocognitive test performance.