No neurochemical evidence of brain injury after blast overpressure by repeated explosions or firing heavy weapons

Background - Psychiatric and neurological symptoms are common among soldiers exposed to blast without suffering a direct head injury. It is not known whether such symptoms are direct consequences of blast overpressure. Objective - To examine if repeated detonating explosions or firing if of heavy weapons is associated with neurochemical evidence of brain damage. Materials and methods - Three controlled experimental studies. In the first, army officers were exposed to repeated firing of a FH77B howitzer or a bazooka. Cerebrospinal fluid (CSF) was taken post-exposure to measure biomarkers for brain damage. In the second, officers were exposed for up to 150 blasts by firing a bazooka, and in the third to 100 charges of detonating explosives of 180 dB. Serial serum samples were taken after exposure. Results were compared with a control group consisting of 19 unexposed age-matched healthy volunteers. Results - The CSF biomarkers for neuronal/axonal damage (tau and neurofilament protein), glial cell injury (GFAP and S-100b), blood-brain barrier damage (CSF/serum albumin ratio) and hemorrhages (hemoglobin and bilirubin) and the serum GFAP and S-100b showed normal and stable levels in all exposed officers. Discussion - Repeated exposure to high-impact blast does not result in any neurochemical evidence of brain damage. These findings are of importance for soldiers regularly exposed to high-impact blast when firing artillery shells or other types of heavy weapons.