The role and diagnostic significance of cellular barriers after concussive head trauma

The onset of concussive head trauma often triggers an intricate sequence of physical consequences and pathophysiological responses. These sequelae can be acute (i.e., hematoma) or chronic (i.e., autoimmune response, neurodegeneration, etc.), and may follow traumas of any severity. A critical factor for prognostication of postconcussion outcome is the pathophysiological response of cellular barriers, which can be measured by several biomarkers of the acute and chronic postinjury phases. We present herein a review on the postconcussion mechanisms of the blood–brain barrier, as well as the diagnostic/prognostic approaches that utilize differential biomarker expression across this boundary. We discuss the role of the blood–saliva cellular barrier as a regulatory filter for brain-derived biomarkers in blood, and its implications for saliva-based diagnostic assays.