Biomechanics of Acute Subdural Hematoma in the Elderly: A Fluid-Structure Interaction Study.

Acute subdural hematoma (ASDH) caused by bridging vein (BV) rupture is a frequent and lethal brain injury, especially in the elderly. Brain atrophy has been hypothesized to be a primary pathogenesis associated with the increased risk of ASDH in the elderly. Although decades of biomechanical endeavors have been made to elucidate the potential mechanisms, a thorough explanation for this hypothesis appears lacking. Therefore, a recently improved finite element head model, in which the brain-skull interface was modeled using a fluid-structure interaction (FSI) approach with special treatment of the cerebrospinal fluid as arbitrary Lagrangian-Eulerian fluid formulation, is used to partially address this understanding gap. Models with various degrees of atrophied brains and thereby different subarachnoid thicknesses are generated and subsequently exposed to experimentally determined loadings known to cause ASDH or not. The results show significant increases in the cortical relative motion and BV strain in the atrophied brain, which consequently exacerbates the ASDH risk in the elderly. Results of this study are suggested to be considered when developing age-adapted protecting strategies for the elderly in the future.