A thoracic mechanism of mild traumatic brain injury due to blast pressure waves

Abstract

The mechanisms by which blast pressure waves cause mild-to-moderate traumatic brain injury (mTBI) are an open question. Possibilities include acceleration of the head, direct passage of the blast wave via the cranium, and propagation of the blast wave to the brain via a thoracic mechanism. The hypothesis that the blast pressure wave reaches the brain via a thoracic mechanism is considered in light of ballistic and blast pressure wave research. Ballistic pressure waves, caused by penetrating ballistic projectiles or ballistic impacts to body armor, can only reach the brain via an internal mechanism and have been shown to cause cerebral effects. Similar effects have been documented when a blast pressure wave has been applied to the whole body or focused on the thorax in animal models. While vagotomy reduces apnea and bradycardia due to ballistic or blast pressure waves, it does not eliminate neural damage in the brain, suggesting that the pressure wave directly affects the brain cells via a thoracic mechanism. An experiment is proposed which isolates the thoracic mechanism from cranial mechanisms of mTBI due to blast wave exposure. Results have implications for evaluating risk of mTBI due to blast exposure and for developing effective protection.

The big squeeze: scaling of constriction pressure in two of the world's largest snakes, Python reticulatus and P. molurus bivittatus

“…Interfering with the nervous system of prey hinders their defensive capabilities, further reducing the risk of injury to the snake. Neural tissue is sensitive to pressure and can deform, tear and cease function entirely (Toth et al, 1997;Courtney and Courtney, 2009). Shockwave and concussive-impact pressure effects on the brain cause neural damage and failure when in the range of 55-300 kPa during transient exposures (Courtney and Courtney, 2009).…”

“…Pressure is probably not a localized phenomenon that dissipates near impact sites, but can travel through tissues and structures from the site of impact (e.g. constriction coil) to the neural tissue, damaging it and perhaps immediately stopping function (Courtney and Courtney, 2009).…”

“…Pressure-wave impacts occur over milliseconds, whereas snakes constrict for orders of magnitude longer. Based on our current knowledge of how pressure affects tissues, it is likely that high constriction pressures are capable of interfering with, or completely disabling, both circulatory and neural function (Toth et al, 1997;Moon, 2000;Moon and Mehta, 2007;Courtney and Courtney, 2009;Boback et al, 2015). The world's largest snakes are capable of quickly incapacitating large and potentially dangerous prey by causing multiple kinds of injuries.…”

Blast-induced mild traumatic brain injury through ear canal: A finite element study

“…The mTBI is often sustained without any signs of external injury or any visible findings from magnetic resonance imaging, making it difficult to identify the exact cause and potential injury mechanisms. Several potential injury mechanisms are proposed, including direct transmission of pressure waves through the cranium, skull flexure, and propagation of pressure pulse through the thorax [3][4][5]. Recently, high incidence of ear injuries during blast events also led to a hypothesis that blast waves could surge into the brain through the ear canal or opening [6,7].…”

The dynamic response and shock-recovery of porcine skeletal muscle tissue

“…Where penetrating injury is observed, e.g. gunshot wounds to the abdomen, evidence suggests that remote injuries such as mild traumatic brain injury (mTBI) [1] may occur. Such evidence, when coupled with the limited understanding that exists regarding the influence of ballistic pressure waves on the cellular structures of bodily tissues, acts as primary motivation for this work.…”