The role of brain tissue mechanical properties and cerebrospinal fluid flow in the biomechanics of the normal and hydrocephalic brain

Abstract

The intracranial system consists of three main basic components - the brain, the blood and the cerebrospinal fluid. The physiological processes of each of these individual components are complex and they are closely related to each other. Understanding them is important to explain the mechanisms behind neurostructural disorders such as hydrocephalus. This research project consists of three interrelated studies, which examine the mechanical properties of the brain at the macroscopic level, the mechanics of the brain during hydrocephalus and the study of fluid hydrodynamics in both the normal and hydrocephalic ventricles. The first of these characterizes the porous properties of the brain tissues. Results from this study show that the elastic modulus of the white matter is approximately 350Pa. The permeability of the tissue is similar to what has been previously reported in the literature and is of the order of 10-12m4/Ns. Information presented here is useful for the computational modeling of hydrocephalus using finite element analysis. The second study consists of a three dimensional finite element brain model. The mechanical properties of the brain found from the previous studies were used in the

construction of this model. Results from this study have implications for mechanics behind the neurological dysfunction as observed in the hydrocephalic patient. Stress fields in the tissues predicted by the model presented in this study closely match the distribution of histological damage, focused in the white matter. The last study models the cerebrospinal fluid hydrodynamics in both the normal and abnormal ventricular system. The models created in this study were used to understand the pressure in the ventricular compartments. In this study, the hydrodynamic changes that occur in the cerebral ventricular system due to restrictions of the fluid flow at different locations of the cerebral aqueduct were determined. Information presented in this study may be important in the design of more effective shunts. The pressure that is associated with the fluid flow in the ventricles is only of the order of a few Pascals. This suggests that large transmantle pressure gradient may not be present in hydrocephalus.