Patient-informed biomechanical modelling reveals mechanical mechanism of brain damage in idiopathic normal pressure hydrocephalus

Abstract

Idiopathic normal pressure hydrocephalus (iNPH) is a globally growing neurological disorder in older adults, radiologically characterised by enlargement of ventricles. However, it remains unknown whether ventricular enlargement can produce biomechanical loading large enough to drive brain morphological changes and tissue damage. Here, we develop an anatomically detailed biomechanical model of ageing human brain and apply ventricular enlargement using a three-dimensional displacement field derived from MRI of iNPH patients and age-matched controls. The model accurately reproduces radiological markers of iNPH, including Evans index, callosal angle and high-convexity sulcal narrowing. It further predicts large mechanical strains in periventricular white matter, particularly within the corpus callosum and anterior thalamic radiations, tracts consistently implicated in iNPH imaging abnormalities. These findings provide strong evidence that ventricular enlargement induces mechanical strain that contributes to iNPH brain abnormalities, which can potentially be reversed by reducing strain following shunting surgery. The biomechanical brain model forms the foundation of a predictive digital platform and future "digital twin" technology to support diagnosis, patient stratification and treatment planning in iNPH. Key PointsO_LIWe develop an anatomically detailed biomechanical model of the brain, incorporating sulci, septum pellucidum and all four ventricles. C_LIO_LIA novel data-driven loading approach is introduced which uses 3D displacement fields from finite element-based registration of healthy and iNPH patient MRI, replacing the arbitrary pressure gradients of previous models. C_LIO_LIThe model predictions closely match established radiological markers measured in iNPH patients, including Evans index, callosal angle and high-convexity sulcal narrowing. C_LIO_LIVentricular enlargement generates large mechanical strains concentrated in periventricular white matter, providing a biomechanical explanation for the structural abnormalities observed in iNPH. C_LI