Simulations of recently observed shear shock wave physics amplify local brain accelerations by a factor of 40 in head drop experiments – future implications for concussion

    loading  Checking for direct PDF access through Ovid

Abstract

Objective

Shear waves that travel in the brain are highly nonlinear and can develop into shock waves. This newly observed phenomenon could have implications for concussion. Our objective was to determine the effect of the brain’s nonlinear shear wave propagation behaviour on laboratory acquired head impact kinematics through numerical simulations.

Design

Head impact kinematics, obtained from controlled laboratory drops to cadaveric human heads, provided inputs to a one dimensional simulation of a cubically nonlinear shear wave equation solved with a piecewise parabolic method. Of the 292 drops, 125 caused significant motion about one axis. We assumed this would provide optimal conditions to create shears waves. The nonlinear and attenuation properties for the simulation were experimentally measured in fresh porcine brains with high frame-rate ultrasound.

Setting

Labratory.

Subjects

None.

Intervention

Independent variable – Nonlinear and attenuating properties of the brain.

Outcome measures

Peak Linear Tangential Acceleration (PLTA) measured at the skull was compared to the max PLTA acquired from the simulation for each of the 125 trials.

Results

There were 17 cases where nonlinearity overcame attenuation and resulted in the PLTA amplifying as high as 40 times the initial PLTA at the skull.

Conclusions

Our models of previously unobserved shear shock wave physics strongly suggest that nonlinearity is a first order parameter in brain kinematics and may have a fundamental influence on brain injury. Expanding these nonlinear simulations to three dimensions could better link head impact kinematics collected in the field with concussion risk and other head injuries.

Competing interests

Head drop data were obtained in collaboration with Drs. Cameron “Dale” Bass and Jason F. Luck (Duke University, USA) and Dr. David B. Camarillo (Stanford University, USA)

Competing interests

None.

Related Topics

    loading  Loading Related Articles