Brain mechanics in hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is a growing neurological disorder in older adults, recognised radiologically by enlargement of the ventricles. It has remained unknown whether that enlargement produces mechanical loading large enough to drive the brain’s morphological changes and tissue damage, or whether it is only a marker of something else.

We developed an anatomically detailed biomechanical model of the ageing human brain and applied ventricular enlargement to it using a three-dimensional displacement field derived from MRI of iNPH patients and age-matched controls.

The model reproduces the radiological markers used to diagnose iNPH, including Evans index, callosal angle, and high-convexity sulcal narrowing. It predicts large mechanical strains in periventricular white matter, particularly within the corona radiata, corpus callosum and anterior thalamic radiations, tracts consistently implicated in iNPH imaging abnormalities. This is evidence that ventricular enlargement induces the mechanical strain contributing to iNPH brain abnormalities, and that the strain may be reversible following shunting surgery.