Effects of nerve bundle geometry on neurotrauma evaluation

Ilaria Cinelli, Michel Destrade, Peter McHugh, Maeve Duffy

We confirm that alteration of a neuron structure can induce abnormalities in signal propagation for nervous systems, as observed in brain damage. Here, we investigate the effects of geometrical changes and damage of a neuron structure in two scaled nerve bundle models, made of myelinated nerve fibres or unmyelinated nerve fibres. We propose a 3D finite element model of nerve bundles, combining a real-time full electro-mechanical coupling, a modulated threshold for spiking activation and independent alteration of the electrical properties for each fibre. We then simulate mechanical compression and tension to induce damage at the membrane of a nerve bundle made of four fibres. We examine the resulting changes in strain and neural activity by considering in turn the cases of intact and traumatized nerve membranes. Our results show lower strain and lower electrophysiological impairments in unmyelinated fibres than in myelinated fibres, higher deformation levels in larger bundles, and higher electrophysiological impairments in smaller bundles. We conclude that the insulation sheath of myelin constricts the membrane deformation and scatters plastic strains within the bundle; that larger bundles deform more than small bundles; and that small fibres tolerate a higher level of elongation before mechanical failure.