Abstract:
Post-Concussion syndrome (PCS) is a set of symptoms which persist after suffering a mild traumatic brain injury (MTBI). Uncertainty exists around how the condition develops and persists. Some research suggests psychological variables are involved while Leddy et al. (2007) suggests that autonomic dysregulation occurring after suffering an MTBI fails to recover, leading to PCS. Cardiovascular autonomic dysregulation may be a result of impairments in central autonomic network (CAN) function. Autonomic regulation is achieved through bidirectional communication between the brain and heart via top down and bottom up processing within the CAN. In order to evaluate this, heart rate (HR) and heart rate variability (HRV) were assessed in PCS sufferers (n=11; 3-12 months post-injury) and non-head injured controls (n=11) during a Stroop task, which challenges higher order cortical structures involved in top down processing; and an orthostatic stressor, which challenges lower order cortical structures coordinating bottom up processing. No group differences of HR and HRV were found at baseline. Evidence of autonomic dysregulation was found during the stressor tasks. While the control participants HR increased during the Stroop task the PCS group’s did not suggesting a failure to demonstrate flexibility in autonomic regulation in response to task demands. The PCS group also had a sharp increase in parasympathetic activity (increased HRV) upon returning to a sitting position following standing during the orthostatic challenge which may signify overcompensation due to disturbances in lower order cortical areas such as the brainstem. However, this effect was only demonstrated during one phase of the orthostatic challenge and could therefore indicate disturbances in baroreceptor sensitivity. Compared to the non-head injured group, the PCS group suffered a higher frequency of PCS symptoms, reported more psychological distress and had a significantly lower perceived health related quality of life while correlational analysis between time since injury and the subjective measures found a relationship only with the physical role subscale of the SF-36 survey.
