From Monro and Kellie to Mountains and Concussion; the Science of Slosh

From Monro and Kellie to mountains and concussion; the science of slosh

Damian M. Bailey

Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales, Glamorgan, UK and Faculty of Medicine, University of British Columbia-Okanagan, Kelowna, British Columbia, Canada

Protecting the brain from inside-out rather than outside-inadds a creative twist in the elusive tale of concussion prevention researchpopularizing altitude exposure (2)and jugular occlusion (3)as alternative interventions with the potential to promote a “tighter fit”brain and reduceslosh-induced injury.This is an adaptation of an original hypothesis developed by Ross (4)who applied the Monro-Kellie doctrine to explain the random nature of acute mountain sickness (AMS). While I agree with Smoliga and Zavorsky(5), it is important to acknowledge that the original findings are at the very least hypothesis generating and we cannot be overly dismissive of the underlying physiological rationale. I too consider it unreasonable to attributethe lower incidence of concussions reported at suchminorelevations to this mechanism given that the hypoxic stimulus is hardly sufficient to altercraniospinalhemodynamics. Indeed, we originally questionedthis mechanismeven in response to far more severe hypoxia (~4,600 m)albeit within the context of AMS, though both entities share the common feature of vasogenic brain swelling. However, retrospective analysis reveals that compared to healthy controls, those prone to AMSalready exhibited elevatedbrain to intracranial volume ratiosin normoxia, a baseline difference that was almost triplethe increase observed during hypoxia(1). Thus, I would encourage future investigators to simplyaddressif the “tighter fit” athlete presents with fewerpost-concussivesequelae at sea-levelin the absence of any additional, unnecessary confounds,to add some scientific flesh to the hypothetical bones and resolve the current controversy.

References

1.Kallenberg K, Bailey DM, Christ S, Mohr A, Roukens R, Menold E, Steiner T, Bartsch P, and Knauth M. Magnetic resonance imaging evidence of cytotoxic cerebral edema in acute mountain sickness. Journal of Cerebral Blood Flow and Metabolism 27: 1064-1071, 2007.

2.Myer GD, Smith D, Barber Foss KD, Dicesare CA, Kiefer AW, Kushner AM, Thomas SM, Sucharew H, and Khoury JC. Rates of concussion are lower in National Football League games played at higher altitudes. The Journal of Orthopaedic and Sports Physical Therapy 44: 164-172, 2014.

3.Myer GD, Yuan W, Barber Foss KD, Thomas S, Smith D, Leach J, Kiefer AW, Dicesare C, Adams J, Gubanich PJ, Kitchen K, Schneider DK, Braswell D, Krueger D, and Altaye M. Analysis of head impact exposure and brain microstructure response in a season-long application of a jugular vein compression collar: a prospective, neuroimaging investigation in American football. British Journal of Sports Medicine 50: 1276-1285, 2016.

4.Ross R. The random nature of cerebral mountain sickness. Lancet 1: 990-991, 1985.

5.Smoliga JM, and Zavorsky GS. "Tighter fit" theory - physiologists explain why "higher altitude" and jugular occlusion are unlikely to reduce risks for sports concussion and brain injuries. Journal of Applied Physiology jap 00661 02016, 2016.