HRV Biofeedback and postconcussion syndrome

Concussion and head injuries in sport are now recognised as important incidents that should not be dismissed as minor - it can be argued convincingly that there is no such thing as a mild traumatic brain injury.

Whilst a majority of people with sport-related concussion recover within 7 to 10 days and non-althletes within 3 months, there are many tht continue to experience symptoms beyond this time. This we are labelling as Post Concusion Syndrome (PCS)

According to the World Health Organisation (WHO) this can involve at least three or more of persistent symptoms such as headache, dizziness, fatigue, irritability, sleeplessness and cognition difficulties  (difficulties with memory or attention and concentration).  Beyond these sysmptoms concussion affects the heart and the autonomic nervous system (ANS)  (Leddy et al 2007).  Concussed athletes can have exaggerated Sympathetic Nervous System (SNS) activation and increased heart rates when compared with controls.  Cerebral autoregulation, which is the ability of the brain to maintain constant perfusion pressure and cerebral blood plow are disturbed after concussion.

In response to a concussion injury, the cardiac sympathetic nerves are activated.  In some situations the autonomic nervous system imbalance is temporary. Chronic activation of the SNS leads to a sustained imbalance which has widespread consequences throughout the central and peripheral nervous system.

The primary forms of treatment of PCS have typically involved rest, education, cognitive rehabilitation and antidepressants without particular evidence of success. Prolonged rest with athletes leads to deconditioning and may cause secondary issues of anxiety and depression. The insistence on rest has been challenged by some studies showing that some exercise increases parasympathetic activity, reduces sympathetic activity and improves cerebral blood flow.

Lagos et al (2016) suggest that Heart Rate Variability (HRV) biofeedback is an approach that has the potential to reduce activation of the SNS and increase control of the parasympathetic nervous system. Bringing the ANS into balance may limit or reduce at least the secondary effects of PCS such as depression. Whether the effects of HRV biofeedback extend to the primary set of symptoms is the focus of reseach.

References
Lagos, L et al (2016)
Heart rate variability biofeedback for postconcussion syndrome: Foundations
in "Foundations of Heart Rate Variability Biofeedback: A book of readings"
A publication of the AAPB, ISBN 978-0-9842979-5-5
p82

Leffy JJ et al (2010)
"A preliminary study of subsystem threshold exercise training for refractory post-concusion syndrome"
Clinical Journal of Sports Medicine, 20, p 21-27