Investigation of role of falx and tentorium on brain simulant strain under impact loading.

Mild Traumatic brain injury (mTBI) is a major health concern. The role of the falx and tentorium (i.e., membranes) in exacerbating mTBI has been conjectured due to the involvement of clinically confirmed midbrain regions. Recent brain biomechanics investigations, mainly using computational head models, also support such a hypothesis. However, data in this regard is limited. Towards this end, using a surrogate head model, we investigate the role of membranes on brain biomechanics. Two different materials-thermoplastic polyurethane with various elastic moduli values (20, 150, 205 MPa) and polylactic acid (elastic modulus 1500 MPa) were used to examine the effect of membrane stiffness on brain simulant strain. The head surrogate was mounted on the Hybrid-III neck and subjected to coronal and sagittal plane rotations using a linear impactor system. Corresponding 6-DOF head kinematics and 2D brain simulant strains in midcoronal and midsagittal planes were measured. Our results elucidate the paradigm of strain evolution in the brain simulant in the presence of membranes. The cortical strains are decreased, whereas strains in the subcortical regions are either equivalent or increased in the presence of membranes. The elastic modulus of the membranes governs the amount of strain reduction or increase. We found that the falx displacement and constraints on stress wave propagation are dominant mechanisms dictating the mechanics of the interaction of membranes with the brain simulant. Overall, these results provide novel experimental insights into the role of membranes on brain deformations, which will motivate futuristic investigations in numerous subdomains of brain injury biomechanics.