Penetrating brain injury in military conflict: does it merit more research?

One of the primary goals of the military scientist addressing the prevention of trauma, is to develop new concepts for attenuating energy transfer to the body from either penetrating, non-penetrating or blast impacts. Personal armours have deficiencies, both in the body coverage achievable without degrading military performance, and in the inherent ability of the materials to attenuate high energy impacts, particularly from high energy bullets and anti-personnel fragments. Protection of the head from these types of projectiles is a difficult task – personal armour materials are available to stop very high energy projectiles (even up to 12.7 mm bullets), but the weight of these technologies precludes them from use on helmets. It is inevitable, therefore, that practical military helmets cannot stop high energy penetrating projectile impacts; they are remarkably effective however, against the principal threat in war – low energy antipersonnel fragments. The development of practical helmets capable of stopping high energy bullets is constrained by the limitations of currently available materials. Penetrating wounds to the brain continue to be a feature of military conflict. There are two types of traumatic brain injury (TBI), blunt and penetrating. The mechanisms are very different. Blunt injury involves the coupling of linear and rotational acceleration and deceleration forces into the brain tissue. The resultant impacts of brain tissue within the skull, and the tortional forces in particular, lead to primary brain injury, complicated by secondary damage as a result of subsequent pathological processes. Penetrating brain injury (PBI) involves local forces and stress waves that radiate out from the injury track, especially in the case of high available energy bullet and fragment injury. What is the status of research into the medical management of brain trauma – penetrating and non-penetrating, civil and military? Experimental research to enhance management (and indeed protection) requires models – tools to develop principles.There are several different models of TBI, both penetrating and blunt; using techniques such as fluid percussion, cortical contusion, single artery occlusion, forebrain ischaemia and stab wounds, but few address the issues relevant to PBI in the military environment. The established experimental models of TBI understandably focus on severe blunt head injury; this is much more frequent than PBI in a civilian setting. Furthermore, PBI in a civilian environment is different both in the characteristics of injury and outcome to that seen on the battlefield when helmets are frequently worn. Militarily relevant PBI is an underinvestigated field and receives little attention in research laboratories. Indeed, previous models of PBI involving the use of projectiles fired into the brain have succumbed to political pressure following animal rights activism (1). The aims of this article are to: • examine the nature and extent of the problem of PBI in the military environment; • identify the key clinical issues wherein the military scientist may profitably focus research to result in more effective treatment of the brain-injured casualty, particularly in the early stages of the injury; • provide a clinical basis for new approaches to the protection of the head from high energy penetrating projectiles; specifically, recognising the current inability to stop high energy projectiles and the merit in transforming a high energy transfer penetrating wound to the brain into a low energy transfer wound using lightweight materials.