Blast Traumatic Brain Injury

Understanding and treating blast traumatic brain injury in the combat theater

Authors: Wang EW, Huang JH.

OBJECTIVES: Blast injury is a frequent cause of traumatic brain injury (TBI) in the modern combat theater. We sought to explain the research and treatment associated with this injury.
METHODS: We reviewed literature on the prevalence of blast TBI (bTBI), blast injury mechanisms, research, and perspectives on the neurosurgical experience treating bTBI.
RESULTS: A majority of combat-related casualties in recent wars are due to blast. A majority of survivors of blast injuries are diagnosed with TBI. Blast injury may induce changes in the brain not seen with non-blastrelated mechanisms. However, long-term symptoms are not significantly different from non-blast mechanisms. Aggressive decompressive craniectomies are commonly performed in the combat theater.
DISCUSSION: Due to the prevalence and debilitating nature of bTBI, understanding injury mechanisms is crucial in treating the injury before symptoms become permanent. Treatment is currently limited to decompressive craniectomies, which are the most effective treatment for a relatively young and fit military population.

Head orientation affects the intracranial pressure response resulting from shock wave loading in the rat

Authors: Dal Cengio Leonardi A, Keane NJ, Bir CA, Ryan AG, Xu L, Vandevord PJ.

Since an increasing number of returning military personnel are presenting with neurological manifestations of traumatic brain injury (TBI), there has been a great focus on the effects resulting from blast exposure. It is paramount to resolve the physical mechanism by which the critical stress is being inflicted on brain tissue from blast wave encounters with the head. This study quantitatively measured the effect of head orientation on intracranial pressure (ICP) of rats exposed to a shock wave. Furthermore, the study examined how skull maturity affects ICP response of animals exposed to shock waves at various orientations. Results showed a significant increase in ICP values in larger rats at any orientation. Furthermore, when side-ICP values were compared to the other orientations, the peak pressures were significantly lower suggesting a relation between ICP and orientation of the head due to geometry of the skull and location of sutures. This finding accentuates the importance of skull dynamics in explaining possible injury mechanisms during blast. Also, the rate of pressure change was measured and indicated that the rate was significantly higher when the top of the head was facing the shock front. The results confirm that the biomechanical response of the superior rat skull is distinctive compared to other areas of the skull, suggesting a skull flexure mechanism. These results not only present insights into the mechanism of brain injury, but also provide information which can be used for designing more effective protective head gear.

Neuropathology of Explosive Blast Traumatic Brain Injury

Authors: Magnuson J, Leonessa F, Ling GS.

During the conflicts of the Global War on Terror, which are Operation Enduring Freedom (OEF) in Afghanistan and Operation Iraqi Freedom (OIF), there have been over a quarter of a million diagnosed cases of traumatic brain injury (TBI). The vast majority are due to explosive blast. Although explosive blast TBI (bTBI) shares many clinical features with closed head TBI (cTBI) and penetrating TBI (pTBI), it has unique features, such as early cerebral edema and prolonged cerebral vasospasm. Evolving work suggests that diffuse axonal injury (DAI) seen following explosive blast exposure is different than DAI from focal impact injury. These unique features support the notion that bTBI is a separate and distinct form of TBI. This review summarizes the current state of knowledge pertaining to bTBI. Areas of discussion are: the physics of explosive blast generation, blast wave interaction with the bony calvarium and brain tissue, gross tissue pathophysiology, regional brain injury, and cellular and molecular mechanisms of explosive blast neurotrauma.

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