A Finite Element Model of Cerebral Vascular Injury for Predicting Microbleeds Location

Finite Element (FE) models of brain mechanics have improved our understanding of the brain response to rapid mechanical loads that produce traumatic brain injuries. However, these models have rarely incorporated vasculature, which limits their ability to predict the response of vessels to head impacts. To address this shortcoming, here we used high-resolution MRI scans to map the venous system anatomy at a submillimetre resolution. We then used this map to develop an FE model of veins and incorporated it in an anatomically detailed FE model of the brain. The model prediction of brain displacement at different locations was compared to controlled experiments on post-mortem human subject heads, yielding over 3,100 displacement curve comparisons, which showed fair to excellent correlation between them. We then used the model to predict the distribution of axial strains and strain rates in the veins of a rugby player who had small blood deposits in his white matter, known as microbleeds, after sustaining a head collision. We hypothesised that the distribution of axial strain and strain rate in veins can predict the pattern of microbleeds. We reconstructed the head collision using video footage and multi-body dynamics modelling and used the predicted head accelerations to load the FE model of vascular injury. The model predicted large axial strains in veins where microbleeds were detected. A region of interest analysis using white matter tracts showed that the tract group with microbleeds had 95th percentile peak axial strain and strain rate of 0.197 and 64.9 s(-1) respectively, which were significantly larger than those of the group of tracts without microbleeds (0.163 and 57.0 s(-1)). This study does not derive a threshold for the onset of microbleeds as it investigated a single case, but it provides evidence for a link between strain and strain rate applied to veins during head impacts and structural damage and allows for future work to generate threshold values. Moreover, our results suggest that the FE model has the potential to be used to predict intracranial vascular injuries after TBI, providing a more objective tool for TBI assessment and improving protection against it.

Automated summary

Finite Element (FE) models have been used to study the brain response to mechanical loads. However, these models often lack the incorporation of vasculature, limiting their predictive ability for vascular response to head impacts. In this study, a high-resolution MRI scan was used to map the venous system and develop an FE model that includes veins. The model was compared to experimental data and showed good correlation. It was also used to predict the distribution of strain and strain rate in the veins of a rugby player with microbleeds. The study provides evidence for a link between vein strain and microbleeds, and suggests the potential of FE models in predicting intracranial vascular injuries after traumatic brain injury (TBI).