About this Research Topic
Repeated exposures to blast loadings are experienced by service members (SMs) during training and combat. In this Research Topic, we focus our attention on the effects of primary blasts (shock loading) with blast overpressures (BOP) ranging up to 25 psi, exclusively in the mild blast Traumatic Brain Injury (TBI) range. The bulk of these injurious events fall into two exposure types, each with distinct loading conditions. One such exposure type occurs as SMs undergo heavy weapons and explosive training programs periodically throughout their military career. These training involve BOPs in the range of range of 2 to 15 psi in quick succession, and are termed as repeated occupational low-level blasts (LLB). Additionally, in combat settings, SMs are exposed to a single blast or multiple blasts from improvised explosive devices (IEDs) with varying inter-blast time intervals.
Repeated head impacts resulting in mild TBI, with or without concussion, have clearly demonstrated long-term neurological consequences, e.g. Chronic Traumatic Encephalopathy, and increased vulnerability to many neurological disorders, e.g. Alzheimer’s disease. Though no definitive link has yet been shown between repeated (low and medium level) blast TBI and long-term health effects, we cannot rule out that connection. At the molecular, cellular and tissue levels external mechanical forces (impact, inertia, or pressure wave) impart localized energy quickly disturbing the normal homeostasis of the neurovascular unit triggering secondary cascades. Though the sources of biomechanical forces are different in repetitive head impacts and repetitive blast exposures, the neural consequences are likely to be similar.
Ongoing research on repeated blast exposures has focused on self-reported post-concussive syndromes in LLBs as the medical end points. However, returning SMs from combat report a multitude of long-term neurological and psychological symptoms including migraines, sleeplessness and anxiety, five to ten years past their separation from the services. Many pre-clinical small and large animal models have been developed to simulate field loadings and to study the effect of exposures on neuro-biochemical, cognitive, motor and behavioral consequences with limited success. The articles in Research Topic will provide a comprehensive update on the patho-physiological, neuro-biochemical and mechanistic basis for the observed effects following repeated mild blast loadings, with the aim of facilitating the translation of experimental findings into clinical benefit.
Keywords: Low-level blast, High-level blasts, Military training, Law enforcement, Civilian exposures, Clinical data, Small animals, Large animals, Computational model Neuropathology, Neuroimaging, Electrophysiology, BBB disruption, Reactive Oxygen Species, Field measurements, Axonopathy
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