Biomechanical modelling of normal pressure hydrocephalus

Area of Science:

• Biomedical Engineering
• Computational Mechanics
• Neuroscience

Background:

• Normal pressure hydrocephalus (NPH) is a condition characterized by enlarged ventricles.
• The mechanical basis of NPH growth is not fully understood.
• Previous models have not fully captured the complex mechanics of NPH.

Purpose of the Study:

• To investigate the mechanics of normal pressure hydrocephalus (NPH) growth using a 3-D computational model.
• To determine the critical transmantle pressure difference required to induce NPH.
• To compare the efficacy of single-phase versus biphasic models for brain parenchyma in NPH simulations.

Main Methods:

• Developed a generic 3-D brain mesh and modeled brain parenchyma as single-phase and biphasic continua.
• Employed hyperelastic constitutive law and finite deformation theory to describe brain parenchyma deformations.
• Utilized transmantle pressure difference to load the model and applied nonlinear, implicit finite element procedures.

Main Results:

• A transmantle pressure difference of 1 mm Hg (133.416 Pa) did not produce NPH in either model.
• A minimum transmantle pressure difference of 1.764 mm Hg (235.44 Pa) was required to simulate NPH.
• No significant differences in ventricular volumes were observed between biphasic and single-phase models.

Conclusions:

• The hypothesis of a purely mechanical basis for NPH growth may require revision.
• A nearly incompressible single-phase model of the brain parenchyma is adequate for NPH modeling.
• Simplifying the model to a single-phase treatment significantly reduces computational time and complexity.