Brain Injuries from Blast

Abstract

Traumatic brain injury (TBI) from blast produces a number of conundrums. This review focuses on five fundamental questions including: (1) What are the physical correlates for blast TBI in humans? (2) Why is there limited evidence of traditional pulmonary injury from blast in current military field epidemiology? (3) What are the primary blast brain injury mechanisms in humans? (4) If TBI can present with clinical symptoms similar to those of Post-Traumatic Stress Disorder (PTSD), how do we clinically differentiate blast TBI from PTSD and other psychiatric conditions? (5) How do we scale experimental animal models to human response? The preponderance of the evidence from a combination of clinical practice and experimental models suggests that blast TBI from direct blast exposure occurs on the modern battlefield. Progress has been made in establishing injury risk functions in terms of blast overpressure time histories, and there is strong experimental evidence in animal models that mild brain injuries occur at blast intensities that are similar to the pulmonary injury threshold. Enhanced thoracic protection from ballistic protective body armor likely plays a role in the occurrence of blast TBI by preventing lung injuries at blast intensities that could cause TBI. Principal areas of uncertainty include the need for a more comprehensive injury assessment for mild blast injuries in humans, an improved understanding of blast TBI pathophysiology of blast TBI in animal models and humans, the relationship between clinical manifestations of PTSD and mild TBI from blunt or blast trauma including possible synergistic effects, and scaling between animals models and human exposure to blasts in wartime and terrorist attacks. Experimental methodologies, including location of the animal model relative to the shock or blast source, should be carefully designed to provide a realistic blast experiment with conditions comparable to blasts on humans. If traditional blast scaling is appropriate between species, many reported rodent blast TBI experiments using air shock tubes have blast overpressure conditions that are similar to human long-duration nuclear blasts, not high explosive blasts.

Visual function, traumatic brain injury, and posttraumatic stress disorder

“…In our patient population, the oculomotor/BV deficits may point more to internal, organic damage as seen in TBI. If confirmed by future studies, oculomotor function measurements may prove helpful in establishing a history of TBI in some patients [33]. This is important because treatment methods vary between TBI, an organic injury, and PTSD, a psychiatric disorder [34].…”

Review: Managing posttraumatic stress disorder in combat veterans with comorbid traumatic brain injury

“…It is highly likely that cases of moderate to severe TBI resulted in medical treatment at a military facility, and the missed TBI cases are probably mTBI. Other potential contributors to possible underdiagnosis of mTBI include an incomplete appreciation of mTBI sequelae (including not fully considering TBI as a cause of psychiatric symptoms) and misperceptions of blast injury biomechanics, topics reviewed by the authors in 2012 that were addressed in a recent review article [56]. There are numerous complexities associated with both blast biomechanics and the challenges with accurately representing military or terrorist blast injury in the laboratory, and a full discussion of these topics is not within the scope of this article; interested readers may refer to our recent review cited previously [56].…”

“…Other potential contributors to possible underdiagnosis of mTBI include an incomplete appreciation of mTBI sequelae (including not fully considering TBI as a cause of psychiatric symptoms) and misperceptions of blast injury biomechanics, topics reviewed by the authors in 2012 that were addressed in a recent review article [56]. There are numerous complexities associated with both blast biomechanics and the challenges with accurately representing military or terrorist blast injury in the laboratory, and a full discussion of these topics is not within the scope of this article; interested readers may refer to our recent review cited previously [56]. The misperceptions of blast biomechanics are an important clinical factor in missed TBI diagnoses: blast injuries evaluated in a busy civilian trauma center resulted in a missed diagnosis rate of 36 percent of primary blast TBI cases [57].…”

“…TBI can present with a wide variety of neuropsychiatric signs and symptoms [13], and no single clinical picture or unifying pathophysiologic model exists for blunt, blast, and penetrating trauma [59]. It may be useful to inform the veteran that a clinically meaningful TBI can result from an injury that involved only an altered level of consciousness and did not include loss of consciousness.…”

Application of High-Intensity Focused Ultrasound to the Study of Mild Traumatic Brain Injury

“…Second, with the exception of peak pressure, the waveform is relatively impervious to modulation and dependent on tube dimensions and animal placement. Third, there are important considerations with respect to the scale difference between human exposures and animal models (Bass et al 2011). A free-field blast wave may operate at 30-cm wavelength and have significant variation within the human body, including within the head region.…”