REELBRAIN

The tolerance limits of the human head to impacts have been mainly studied in the field of automotive industry, in connection with road safety. Nonetheless, head impacts are also frequent and need to be further studied in the field of defense. In particular, the effects of head exposure to low-level blasts or LLB have been recently of interest in a huge number of clinical and preclinical studies. This “craze” is linked to awareness that soldiers and law enforcement members are frequently, if not daily, exposed to these types of blasts. The latter, in the context of their professional activities, are required to use different types of firearms or explosives, as it is the case for breachers, snipers or mortar men. Although the underlying mechanisms have not been elucidated yet and without any real epidemiological study in support, it seems that chronic, repetitive, exposure to LLB can significantly alter the central nervous system. If the hypothesis according to which repeated exposure to LLB is associated with brain injuries and chronic neurological deficits is verified (or true), it will therefore become necessary to define new safety rules / good practices and potentially develop new protections for individuals using detonation devices generating LLB. This is what the research project presented here is aiming for. We propose to fill the gap in knowledge regarding the occurrence of brain injury following repeated exposure to blast threats and identify underlying mechanisms. This will be done through experiments on an instrumented headform, on the one hand, and on an animal model of “breachers” that can recapitulate neurologic symptoms that may arise from repeated use of LLB-generating weapons, on the other hand. The results obtained will then be used as boundary conditions for a new finite element model (FEM) developed within the framework of this project. This FEM will include, in an original way, the development and implementation of a new constitutive law of brain matter including the anisotropic architecture of this tissue (axonal fibers). In addition, it will take into account the mechanical-biological aspects of previous traumatic events in the mechanical model, in order to propose, for the first time ever, brain tolerance limits to repeated head impacts.