Electro-mechanical response of a 3D nerve bundle model to mechanical loads leading to axonal injury

TL;DR

This study develops a 3D electro-mechanical model of nerve bundles to understand cellular-level neural impairments caused by traumatic brain injuries, revealing how mechanical loads affect nerve signal transmission.

Contribution

It introduces a fully coupled 3D electro-mechanical model that simulates neural damage and electrophysiological impairments at the cellular level due to trauma.

Findings

Distribution of residual stresses affects nerve signal transmission

Mechanical loads induce strain and stress changes in nerve fibers

Trauma severity correlates with electrophysiological impairments

Abstract

Objective: Traumatic brain injuries and damage are major causes of death and disability. We propose a 3D fully coupled electro-mechanical model of a nerve bundle to investigate the electrophysiological impairments due to trauma at the cellular level. Methods: The coupling is based on a thermal analogy of the neural electrical activity by using the finite element software Abaqus CAE 6.13-3. The model includes a real-time coupling, modulated threshold for spiking activation and independent alteration of the electrical properties for each 3-layer fibre within a nerve bundle as a function of strain. Results: Results of the coupled electro-mechanical model are validated with previously published experimental results of damaged axons. Here, the cases of compression and tension are simulated to induce (mild, moderate and severe) damage at the nerve membrane of a nerve bundle, made of four fibres. Changes in strain, stress distribution, and neural activity are investigated for myelinated and unmyelinated nerve fibres, by considering the cases of an intact and of a traumatized nerve membrane. Conclusion: A fully coupled electro-mechanical modelling approach is established to provide insights into crucial aspects of neural activity at the cellular level due to traumatic brain injury. Significance: One of the key findings is the 3D distribution of residual stresses and strains at the membrane of each fibre due to mechanically induced electrophysiological impairments, and its impact on signal transmission.