Pulsatile Cerebrospinal Fluid Dynamics in the Human Brain

Abstract

Disturbances of the cerebrospinal fluid (CSF) flow in the brain can lead to hydrocephalus, a condition affecting thousands of people annually in the US. Considerable controversy exists about fluid and pressure dynamics, and about how the brain responds to changes in flow patterns and compression in hydrocephalus. This paper presents a new model based on the first principles of fluid mechanics. This model of fluid-structure interactions predicts flows and pressures throughout the brain's ventricular pathways consistent with both animal intracranial pressure (ICP) measurements and human CINE phase-contrast magnetic resonance imaging data. The computations provide approximations of the tissue deformations of the brain parenchyma. The model also quantifies the pulsatile CSF motion including flow reversal in the aqueduct as well as the changes in ICPs due to brain tissue compression. It does not require the existence of large transmural pressure differences as the force for ventricular expansion. Finally, the new model gives an explanation of communicating hydrocephalus and the phenomenon of asymmetric hydrocephalus.

Dynamics of lateral ventricle and cerebrospinal fluid in normal and hydrocephalic brains

“…We have used MRI techniques to measure the lateral ventricle (LV) size change and its temporal relationship with intracranial blood flow and CSF movement along the CSF pathways. The ventricular size changes and CSF flow patterns that we have found are consistent with the dynamics of intracranial phenomena predicted by a first-principles model introduced by Linninger et al (6). This model, in turn, can be used to predict intracranial pressure (ICP) dynamics in normal and hydrocephalic brains.…”

“…The accuracy of this model was validated by its relatively close match with the MRI flow rate measurement at the region between the AS and V4 (Fig. 7), given that our simulations were performed with a standard sinusoidal function (6). The mean pulsatile flow estimated from the model for this region was 2.84 mL/minute.…”

“…A first-principles model for pulsatile CSF flow, whose mathematical formulation has been presented by Linninger et al (6), relates three dynamically interacting systems: the cerebral vascular system, the CSF-filled ventricular and subarachnoid spaces (SASs), and the brain parenchyma. With the inputs from MR measurements, the CSF pressure and velocity fields throughout the brain can be derived, as well as the dynamics of parenchyma stresses, strains, and displacements using the laws of elastodynamics.…”

“…The mathematic equations and assumptions applied to build a CSF hydrodynamic model have been fully discussed by Linninger et al (6). Building a subject-specific model requires a set of fixed variables and a set of input boundary conditions that are assumed to be the same across subjects, as well as a set of subject-specific brain variables.…”

“…In this hydrocephalic case study, the following subject-specific variables have been used in building the model: volume of LV ϭ 250.2 mL, volume of V3 ϭ 11.3 mL, volume of V4 ϭ 4.57 mL, and volume of SAS ϭ 105.0 mL; the dimensions of the foramina were the same as in the normal subject case study except that a radius of 2 mm instead of 1 mm was estimated for the AS. A condition of CSF malabsorption at the arachnoid granulations was applied in the model, based on clinical evidence (6). The accuracy of this model is validated by comparing the predicted CSF volumetric flow cardiac time course with MRI measurement at the region between the AS and V4 (Fig.…”