Commentary: are postconcussive symptoms and exercise testing appropriate tools to identify autonomic impairment after mild traumatic brain injury?

Abstract

Objective: After mild traumatic brain injury (mTBI), autonomic nervous system dysfunction is thought to contribute to exercise intolerance and self-reported postconcussive symptoms (e.g. dizziness, lightheadedness, brain fog) but little has been done to establish this relationship in the literature.

Methods: Through recent literature review, it appears that few studies have assessed both autonomic function and exercise intolerance, and for those that have utilized varying methodologies making comparison across studies difficult. Some emerging research has identified potential impairment within the sympathetic nervous system after mTBI but no relationship between exercise tolerance testing and postconcussive symptoms has been established.

Conclusion: For neuropsychologists, a physiologic understanding of the scope of autonomic dysfunction and appropriate assessment is vitally important, as autonomic nervous system impairment has the potential to impact sleep and mood, and subsequently cognitive function and mental health. When working in collaboration with other disciplines, referrals to exercise intolerance testing and laboratory based autonomic assessments may occur. However, given the lack of an established evidence, the use of exercise intolerance and/or related symptoms to clinically insinuate dysfunction of the autonomic nervous system function is likely premature, and a more thorough assessment of autonomic function via established batteries is more appropriate.

Keywords: Autonomic nervous system; baroreflex function; cardiovascular control; concussion; mild traumatic brain injury.