A Model of Low-Level Primary Blast Brain Trauma Results in Cytoskeletal Proteolysis and Chronic Functional Impairment in the Absence of Lung Barotrauma

Shock-wave exposure from improvised explosive devices (IEDs) has been implicated as a possible contributing factor to neurological impairment reported in combat veterans. However, evidence-based substantiation of this implication, particularly for low-level exposure in the absence of external signs of trauma, remain elusive. Accordingly, we constructed an open-ended shock tube producing a short-duration, low-amplitude shockwave. Low-level (11.5 kPa static overpressure) complex shock-wave exposure in rats resulted in no histological evidence of lung injury. By contrast, delayed cytoskeletal proteolysis of alpha II-spectrin was detected in the cortex and hippocampus by 12 h post-injury. Cell death was minimal and localized predominantly in the corpus callosum and periventricular regions. These regions, with presumably different density interfaces, exhibit biological responses to shockwaves consistent with interface turbulence described by Richtmyer-Meshkov instability. Evoked compound action potential (CAP) recordings from the corpus callosum showed a significant increase in the duration of CAP responses at 14 and 30 days post-injury, and a gradual depression in the unmyelinated fiber amplitude. Shielding the head attenuated alpha II-spectrin cytoskeletal breakdown, thus directly implicating low-level shock-wave exposure as a cause of brain injury in the rat. Despite anatomical and scaling differences in rats compared to humans, the results suggest the potential for undiagnosed traumatic brain pathologies occurring in combat veterans following shock-wave exposure.