Influence of the Lateral Ventricles and Irregular Skull Base on Brain Kinematics due to Sagittal Plane Head Rotation

Abstract

Two-dimensional physical models of the human head were used to investigate how the lateral ventricles and irregular skull base influence kinematics in the medial brain during sagittal angular head dynamics. Silicone gel simulated the brain and was separatedfrom the surrounding skull vessel by paraffin that provided a slip interface between the gel and vessel. A humanlike skull base model (HSB) included a surrogate skull base mimicking the irregular geometry of the human. An HSBV model added an elliptical inclusion filled with liquid paraffin simulating the lateral ventricles to the HSB model. A simplified skull base model (SSBV) included ventricle substitute but approximated the anterior and middle cranial fossae by a flat and slightly angled surface. The models were exposed to 7600 rad/s2 peak angular acceleration with 6 ms pulse duration and 5 deg forced rotation. After 90 deg free rotation, the models were decelerated during 30 ms. Rigid body displacement, shear strain and principal strains were determined from high-speed video recorded trajectories of grid markers in the surrogate brains. Peak values of inferior brain surface displacement and strains were up to 10.9X (times) and 3.3X higher in SSBV than in HSBV. Peak strain was up to 2.7X higher in HSB than in HSBV. The results indicate that the irregular skull base protects nerves and vessels passing through the cranial floor by reducing brain displacement and that the intraventricular cerebrospinal fluid relieves strain in regions inferior and superior to the ventricles. The ventricles and irregular skull base are necessary in modeling head impact and understanding brain injury mechanisms.

Using a gel/plastic surrogate to study the biomechanical response of the head under air shock loading: a combined experimental and numerical investigation

“…Mechanical properties of the silicone gel brain simulant are similar to those of brain tissues reported for car crash environment (Brands et al 1999;Ivarsson et al 2002;Parnaik et al 2004;Zhang et al 2007;Margulies et al 2003) and intense ballistic/blast loading environment (Zhu et al 2009). The shape of the surrogate was meant to mimic an animal head, and its dimensions are ideally characterized by its length (l = 90.0 mm), major diameter (d = 66.7 mm), and thickness (h = 3.0 mm), as shown in Fig.…”

“…This surrogate consists of a commercially available external polyethylene shell filled with a silicone gel brain simulant, Sylgard 527 A&B (Dow Corning, Midland, MI, USA), with the two agents A and B mixed at a ratio of 1 to 1 in volume, is a scientifically accepted brain surrogate (Brands et al 1999;Ivarsson et al 2002;Parnaik et al 2004;Zhang et al 2007). Mechanical properties of the silicone gel brain simulant are similar to those of brain tissues reported for car crash environment (Brands et al 1999;Ivarsson et al 2002;Parnaik et al 2004;Zhang et al 2007;Margulies et al 2003) and intense ballistic/blast loading environment (Zhu et al 2009).…”

The Mechanics of Traumatic Brain Injury: A Review of What We Know and What We Need to Know for Reducing Its Societal Burden

“…Subsequent studies using similar technologies highlighted how high stresses can also appear at the craniocervical junction [98]. Direct visualization of grid patterns or embedded markers within a transparent silicone gel also provided direct evidence for the unique patterns of deformations that occur with accelerations imposed in different directions and the influence that different skull/gel boundary conditions and ventricular structures have on intracranial strains, showing that the ventricles can redistribute and, in some regions, reduce the strains appearing within the brain after impact [99][100][101][102]. In some instances, these models have been used to assess the effectiveness of different animal models to recreate the deformation patterns that appear during impact and have led to a redesign of animal models to produce deformation patterns that more closely resemble the strains within the hemispheres during injury [103][104][105].…”

Finite-element models of the human head and their applications in forensic practice

“…Correlation of pressures with temporary cavity in the time domain may also assist in characterising projectile dynamics. The research performed by Zhang et al, using a brain stimulant (Dow Corning Sylgard 527 A&B, Midland, MI, USA), a silicone dielectric gel, used as brain surrogate in blunt impact studies, the mechanical properties of which are similar to brain tissues, also demonstrating rate-sensitive properties, was designed to quantify temporary cavity dynamics with high-speed digital video images and dynamic pressure changes at various locations and correlate gel disruption with pressure change due to projectile penetration in geometrically appropriate models [40][41][42][43]. Experimental data were used to develop a validated FEM to further investigate penetrating traumatic brain injury biomechanics.…”