Do blast induced skull flexures result in axonal deformation?

Area of Science:

• Biomechanics
• Neuroscience
• Computational Modeling

Background:

• Blast-induced traumatic brain injury (TBI) is a significant concern.
• Understanding the mechanisms of axonal injury from blast waves is crucial for developing protective measures.

Purpose of the Study:

• To investigate axonal deformation caused by blast-induced skull flexures using subject-specific finite element models.
• To quantify axonal strain rates under various blast loading conditions and cerebrospinal fluid (CSF) properties.

Main Methods:

• Developed and verified subject-specific finite element models of the human head, incorporating axonal tractography via the embedded finite element method.
• Simulated blast loading scenarios with varying overpressures and directions, focusing on the initial shock (< 5 milliseconds).
• Conducted 138 simulations, including 128 for loading scenarios and 10 for CSF material model variations, totaling 10,702 simulation core hours.

Main Results:

• Identified extreme axonal strain rates ranging from 150 to 378 s-1 resulting from blast-induced skull flexures.
• Demonstrated that skull flexural displacement is a primary driver of high strain rates in axonal fiber tracts.
• Documented strains and strain rates across all simulated fiber tracts and loading conditions.

Conclusions:

• Blast-induced skull flexures generate high strain rates that could cause rate-dependent micro-structural axonal damage.
• The findings provide critical data for understanding TBI mechanisms and informing the design of protective equipment.
• Computational modeling offers a powerful tool for investigating the complex biomechanics of blast-induced head injuries.