Diffuse axonal injury (DAI) is described as widely scattered abnormalities in the axonal morphology of the white matter in the cerebral hemispheres. In experiments which subjected primates to nonimpact acceleration of the head, DAI was present when a lesion of the corpus callosum or superior cerebellar peduncle was seen macroscopically. These experiments also showed that the direction of head motion is important to the severity of the injury.
It is belieyed that such inertial loads induce tensile and shear strains resulting in brain injury. As a first step towards quantifying these strains, simplified experimental models approximating both sagittal and coronal cross-sections were constructed (1-2) wherein a surrogate brain material was subjected to various inertial loadings and boundary conditions between the skull and surrogate brain material to assess these effects, as well as directional loading effects on induced strains.
To supplement the above laboratory studies, finite element modeling (FEM) of selected physical model (PM) tests has been initiated. This paper discusses preliminary results of FEM activities aimed at simulating selected PM tests. Specifically, engineering estimates of the PM gel material properties are established and initial grid deformation comparisons are made for a simple half-cylinder no-slip PM configuration. To supplement earlier studies which investigated the effect of boundary layer friction on strains induced in a half-cylinder representation of the brain, these material properties were then used to simulate strains induced in a mid-coronal cross-section incorporating an anatomic partition to simulate the falx, along with effects of various boundary conditions. Results indicted significantly higher strains were experienced at the tip of the anatomic partition.