Hydrodynamics of the Human Brain

We are currently actively participating in an interdisciplinary research effort to investigate the hydrodynamics in the human brain. The research is conducted in close collaboration with Richard Penn, M.D., a leading neuro-surgeon from the University of Chicago. We use clinical data and medical analyses to develop a dynamic model for the pulsating flow of the cerebrospinal fluid. A better understanding of the dynamics of the fluid flow is expected to improve treatment of hydrocephalus.

Cerebrospinal fluid (CSF) is a colorless fluid with the appearance of water. It is formed mostly in the choroid plexus and flows from there into the ventricular spaces, further to the subarachnoid spaces and is eventually absorbed back into the bloodstream through the arachnoidal villi. Hydrocephalus is a pathological condition of enlarged ventricular spaces. Since the scull limits the available volume for the brain, ventricular expansion necessarily compresses sensitive brain tissue leading to severe functional damage or, if persistent, even to death of the patient.

Beyond the current theory explaining hydrocephalus as steady-state process of CSF malabsorption in the arachnoid villi, our group is working on a dynamic one-dimensional flow model of CSF pulsations, not bulk flow of CSF. In our emerging view, increased impedance to the pulsating CSF flow may cause higher amplitudes in flow variations in the ventricular spaces. In effect, stress beyond the elastic limits of the tissues lining the walls of the ventricular spaces may cause plastic deformation and eventually permanent damage observed as hydrocephalus. If experiments on live animals (e.g. dogs, rats) validate our hypothesis, the dynamic model could serve as starting point for improving the diagnosis of hydrocephalus and offer insights towards better surgical procedures and therapeutic options.

A two-dimensional model of the CSF flow started to develop using both finite elements and finite volumes methods to discretize the continuity and Navier-Stokes equations for an incompressible fluid. Some initial results are in agreement with those published for the aqueduct of Silvius (between third and fourth ventricle) [1] and the one-dimensional model is in agreement with the two-dimensional. Also the validation of our numerical results completes a very competent commercial code (FLUENT).

A particularly promising avenue lies in designing and testing a wireless feedback control micro-system for a hydrocephalus shunt valve to limit the damaging high amplitude pulsations in the CSF flow.