On the characterization of the heterogeneous mechanical response of human brain tissue

The mechanical characterization of brain tissue is a complex task that scientists have tried to accomplish for over 50 years. The results in the literature often differ by orders of magnitude because of the lack of a standard testing protocol. Different testing conditions (including humidity, temperature, strain rate), the methodology adopted, and the variety of the species analysed are all potential sources of discrepancies in the measurements. In this work, we present a rigorous experimental investigation on the mechanical properties of human brain, covering both grey and white matter. The influence of testing conditions is also shown and thoroughly discussed. The material characterization performed is finally adopted to provide inputs to a mathematical formulation suitable for numerical simulations of brain deformation during surgical procedures.</p

Infant brain subjected to oscillatory loading: material differentiation, properties, and interface conditions

Past research into brain injury biomechanics has focussed on short duration impulsive events as opposed to the oscillatory loadings associated with Shaken Baby Syndrome (SBS). A series of 2D finite element models of an axial slice of the infant head were created to provide qualitative information on the behaviour of the brain during shaking. The test series explored variations in subarachnoid cerebrospinal fluid (CSF) representation, brain matter stiffness, dissipation, and nonlinearity, and differentiation of brain matter type. A new method of CSF modelling based on Reynolds lubrication theory was included to provide a more realistic brain–CSF interaction. The results indicate that solid CSF representation for this load regime misrepresents the phase lag of displacement, and that the volume of subarachnoid CSF, and inclusion of thickness variations due to gyri, are important to the resultant behavior. Stress concentrations in the deep brain are reduced by fluid redistribution and gyral contact, while inclusion of the pia mater significantly reduces cortex contact strains. These results provide direction for future modelling of SBS