Cerebrovascular Regulation is Impaired Immediately Post Concussion and Associated with Increased Estimated ICP

Abstract

Concussions have recently been recognized as a possibly significant cause of long term cognitive and health problems among athletes. Despite increasing evidence that concussions may not be benign, there is a lack of data on the physiological effects of a concussion on cerebral blood flow regulation. The goal of this work was to determine if concussion cause impairment of cerebral blood flow regulation in the first few hours after injury. 54 subjects (25 with concussions) were recruited during recreational rugby tournaments and tested on the field to assess cerebral blood flow using Doppler, beat-by-beat blood pressure, and end-tidal CO2. Subjects performed three sit to stand. All data was collected ~2 hours following the head trauma. We found that concussed players showed increased mean arterial pressure (Concussed: 95±1; Controls: 89±1 mmHg, P=0.005) and increased cerebrovascular resistance (Concussed: 0.95±0.01; Controls: 0.88±0.01 mmHg/%, P=0.001). However cerebral blood flow changes from sitting to standing were unaffected. Similarly cerebral autoregulation measures were also not different. Using a non-invasive estimate of intracranial pressure (ICP), we found that concussed players had significantly greater ICP (Concussed: 14±3; Controls: 7±1 mmHg, P=0.032). These data suggest that players with concussions demonstrated increased ICP that is associated with increased cerebrovascular resistance and results in reduced cerebral perfusion pressure. Thus, to maintain cerebral perfusion concussed players increase mean arterial pressure. Further work is needed to determine if players with impaired cerebrovascular responses have long term problems.