Microstructural damage progression in the pia-arachnoid complex.

Area of Science:

• Biomechanics
• Neurotrauma
• Tissue Engineering

Background:

• Traumatic brain injury (TBI) is a significant cause of death and disability globally.
• The pia-arachnoid complex (PAC) at the brain-skull interface is crucial for brain mechanics during head impacts but is understudied.
• Understanding PAC response to mechanical loading is vital for repetitive TBI research.

Purpose of the Study:

• To investigate microstructural damage progression in the PAC under sub-failure cyclic mechanical loading.
• To quantify changes in PAC stiffness and identify factors influencing its mechanical response.

Main Methods:

• A novel inflation technique was used to measure arachnoid membrane displacement in piglets, pigs, and sheep.
• Optical coherence tomography imaging and direct pressure measurements quantified stiffness changes.
• Cyclic low-pressure and high-pressure inflation cycles were applied to simulate mechanical loading.

Main Results:

• Tensile loading caused significant PAC softening, with damage severity correlating to deformation.
• Damage progressed with subsequent loading cycles, showing an exponential decrease with strain severity.
• Mechanical changes were largely permanent and age-dependent, with piglets exhibiting higher stiffness than adult pigs.

Conclusions:

• Sub-failure cyclic loading induces progressive, largely irreversible softening and microstructural damage in the PAC.
• PAC mechanics are significantly influenced by age, with younger specimens being stiffer.
• These findings provide insights into damage accumulation mechanisms in repetitive TBI at the brain-skull interface.