Blast overpressure induces shear-related injuries in the brain of rats exposed to a mild traumatic brain injury

Miguel A Gama Sosa,Frank J Yuk,Nathan P Dorr,Mikulas Chavko,Michael C Shaughness,Eric Maudlin-Jeronimo,Gregory A Elder,Paul E Pricop,Aaron A Hall,Patrick R Hof,Dara L Dickstein,Richard M Mccarron,William G M Janssen,Stephen T Ahlers,Alejandro J Paulino,Rita De Gasperi

doi:10.1186/2051-5960-1-51

Abstract

BackgroundBlast-related traumatic brain injury (TBI) has been a significant cause of injury in the military operations of Iraq and Afghanistan, affecting as many as 10-20% of returning veterans. However, how blast waves affect the brain is poorly understood. To understand their effects, we analyzed the brains of rats exposed to single or multiple (three) 74.5 kPa blast exposures, conditions that mimic a mild TBI.ResultsRats were sacrificed 24 hours or between 4 and 10 months after exposure. Intraventricular hemorrhages were commonly observed after 24 hrs. A screen for neuropathology did not reveal any generalized histopathology. However, focal lesions resembling rips or tears in the tissue were found in many brains. These lesions disrupted cortical organization resulting in some cases in unusual tissue realignments. The lesions frequently appeared to follow the lines of penetrating cortical vessels and microhemorrhages were found within some but not most acute lesions.ConclusionsThese lesions likely represent a type of shear injury that is unique to blast trauma. The observation that lesions often appeared to follow penetrating cortical vessels suggests a vascular mechanism of injury and that blood vessels may represent the fault lines along which the most damaging effect of the blast pressure is transmitted.

Highlights

Blast-related traumatic brain injury (TBI) has been a significant cause of injury in the military operations of Iraq and Afghanistan, affecting as many as 10-20% of returning veterans
Multiple blast exposures have been common in the conflicts in Iraq and Afghanistan and Hoge et al [2] found that more than 50% of soldiers returning from Iraq who reported no injuries still reported at least two episodes in which an improvised explosive devices (IED) exploded near the soldier
Behavioral alterations associated with blast-related focal lesions We have previously shown that rats exposed to 3 × 74.5 kPa blast exposures exhibit a variety of post-traumatic stress disorder-related traits [8]

Summary

Introduction

Blast-related traumatic brain injury (TBI) has been a significant cause of injury in the military operations of Iraq and Afghanistan, affecting as many as 10-20% of returning veterans. How blast waves affect the brain is poorly understood. To understand their effects, we analyzed the brains of rats exposed to single or multiple (three) 74.5 kPa blast exposures, conditions that mimic a mild TBI. Due to the prominent use of improvised explosive devices (IED) in Iraq and Afghanistan, a characteristic feature of TBI in these conflicts has been its association with blast exposure [2]. Direct tissue damage, bleeding, and diffuse axonal injury (DAI) are the best known pathophysiological mechanisms associated with the type of non-blast TBI most commonly encountered during blunt impact injuries in civilian life [4,5]. The degree to which the primary blast wave injures the brain remains controversial [3,4]

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Conclusion