STEP 2: Concussion Live Course - October 21-22, 2025, in Salt Lake City, UT-Autonomic Dysfunction after Mild Traumatic Brain Injury

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This document by Dr. Kathleen R. Bell explores the complex interaction between the autonomic nervous system (ANS) and traumatic brain injury (TBI), particularly concussions. The ANS regulates cardiovascular and other bodily functions through interconnected brainstem, hypothalamic, limbic, and cortical circuits. It balances sympathetic (stress) and parasympathetic (rest) influences to maintain flexibility and adaptability, reflected in heart rate variability (HRV). <br /><br />Following concussion or mild TBI, dysregulation or "uncoupling" of the ANS and cardiovascular control often occurs, evidenced by altered HRV, increased sympathetic activity, elevated heart rates, and impaired emotional and cognitive functions. Changes in cerebral blood flow, especially in areas like the insular cortex integral to cardiovascular-ANS integration, may persist up to a month post-injury. Youth and female sex show differences in HRV profiles, affecting recovery patterns and symptom presentation. <br /><br />Moderate to severe TBI can provoke exaggerated sympathetic nervous activity called "sympathetic storming," while military populations with concussions face chronic ANS activation and higher risk of persistent symptoms. Post-traumatic symptoms linked to ANS dysfunction include headaches, sleep disturbances, emotional disorders, and orthostatic intolerance such as Postural Orthostatic Tachycardia Syndrome (POTS), especially in young females.<br /><br />Diagnosis and management remain challenging due to symptom overlap and lack of reliable biomarkers. Therapeutic approaches focus on addressing co-morbidities, cautious use of medications especially those affecting autonomic balance, cardiovascular symptom management (e.g., beta blockers, midodrine), and graded exercise protocols. HRV measurement offers promise for monitoring ANS function during recovery and potentially guiding return-to-activity decisions.<br /><br />Overall, the ANS plays a crucial role in the pathophysiology and symptomatology following concussion and TBI. Understanding and targeting ANS dysfunction may improve long-term outcomes and reduce cardiovascular risks associated with brain injury.

Asset Subtitle

Kathleen R. Bell, MD

Keywords

autonomic nervous system

traumatic brain injury

concussion

heart rate variability

sympathetic nervous activity

parasympathetic nervous activity

cerebral blood flow

Postural Orthostatic Tachycardia Syndrome

sympathetic storming

graded exercise protocols