Identification of the Cerebrospinal Fluid System Dynamics

[Team Members] - [Overview] - [Control Challenges] - [Pulsatile Dynamics and MRI] - [Student Projects] - [Recent Publications]

A multidisciplinary project at Umeå University aimed at developing state-of-the-art control and estimation techniques for studying the human cerebrospinal fluid (CSF) system, with application to the clinical diagnosis of hydrocephalus.

Team Members

The following people are currently working on the CSF system identification project:
  • UmU = Umeå University, NTNO = Norwegian University of Science and Technology, UIC = University of Illinois, Chicago.
  • This work forms part of a large project, lead by Jan Malm, studying the causes, diagnosis, and treatment of hydrocephalus.

    Overview of the Cerebrospinal Fluid System and Hydrocephalus

    The cerebrospinal fluid provides physical support for the brain, and is believed to absorb and carry away toxic metabolic byproducts. It is generated and introduced to the brain cavity at an approximately constant rate, and it leaves the brain cavity by being reabsorbed into the bloodstream in the dural sinuses.

    cerebrospinal fluid diagram

    Circulation of the cerebrospinal fluid (light blue)

    An obstruction to the normal flow can lead to a condition known as hydrocephalus, the symptoms of which can include gait imbalance, urinary dysfunction, and dementia. It is well established that these symptoms can be reduced or eliminated by implanting a shunt, a small valve with an attached drainage tube, into the patient’s skull, thereby altering the system and increasing the CSF flow.

    Neurologists and neurosurgeons use a number of different diagnostic tests to decide whether or not the patient is likely to benefit from a shunt surgery. One important procedure is to estimate the outflow resistance of the CSF system using an infusion test. Artificial CSF is injected with a particular flow-rate pattern into the CSF system at the base of the spinal column - at the lumbar region - and the resulting CSF pressure variations are recorded. From this data, and a mathematical model of the fluid dynamics, an estimate of the outflow resistance can be obtained. Higher than average resistance values are believed to be an indicator of hydrocephalus.

    Such tests are currently performed regularly at Umeå University Hospital, and many other hospitals around the world. However, all current procedures involve recording a lengthy data sets, and performing an off-line analysis of the data. Minimizing time of infusion tests is important for both patient comfort and efficient use of hospital resources, so a key aim of this project is provide real-time estimates to the clinical staff, so that the procedure can be stopped when a good estimate has been achieved.

    Control and Estimation Challenges for Infusion Tests

    The CSF system is an infinite-dimensional distributed parameter system, however it has been shown experimentally to be well approximated by a finite-dimensional lumped-parameter model, introduced by Anthony Marmarou, in which the intracranial pressure and other variables are assumed to be spatially invariant. The model takes the form of a first-order nonlinear differential equation.

    Some remarks:

    Pulsatile Dynamics - Magnetic Resonance Imaging

    The beating of the heart and the resulting arterial and venous flows produce periodic pressure variations and flows between the various chambers of the CSF system. This is another level of dynamics, occuring on a much faster time-scale than the creation-absorption process.

    There is much current research activity in studying the pulsatile dynamics by way of magnetic resonance imaging (MRI). In particular, the technique of phase-contrast MRI, which allows one to capture detailed images of flow velocities at approximately 30 frames per second.

    There are two primary aims of this research:

    One promising class of mathematical models for studying the pulsatile CSF dynamics with MRI is muti-input multi-output systems, possibly nonlinear, consisting of pressures, flows, and compliances between the major compartments of the CSF system, and the venous and arterial blood flows driving the oscillations. Analysing the system-theoretic properties (observability, identifiability, experiment design, disturbance propagation, etc, etc) of such models is a very new area of research.

    Projects for Bachelor and Masters Students

    There is a lot of work to be done in this field, and there is ample opportunity to create exciting projects for students.

    For projects focusing on control and estimation aspects, please contact Ian or Anton. For projects focusing on biomedical engineering, please contact Anders. Suitable backgrounds of study would be engineering, mathematics, physics, or related fields.

    Selected recent publications

    Journal:

    K. S. Andersson, I. R. Manchester, N. Andersson, A. S. Shiriaev, J. Malm, A. Eklund,
    Assessment of Cerebrospinal Fluid Outflow Conductance Using an Adaptive Observer - Experimental and Clinical Evaluation,
    to appear in Physiological Measurement.

    I. R. Manchester, K. S. Andersson, A. Eklund, A. S. Shiriaev, N. Andersson,
    A Nonlinear Observer for On-line Estimation of the Cerebrospinal Fluid Outflow Resistance,
    to appear in Automatica.

    A. Eklund, P. Smielewski, I. Chambers, N. Alperin, J. Malm, M. Czosnyka, A. Marmarou,
    Assessment of cerebrospinal fluid outflow resistance (Review Article)
    Medical and Biological Engineering and Computing, 45:719-735, 2007.

    J. Malm, A. Eklund
    Idiopathic normal pressure hydrocephalus.
    Practical Neurology, 6:14–27, 2006.

    N. Andersson, J. Malm, T. Backlund, A. Eklund
    Assessment of cerebrospinal fluid outflow conductance using constant-pressure infusion-a method with real time estimation of reliability.
    Physiological Measurement 26:1137–48, 2005.

    Conference:

    I. R. Manchester, K. S. Andersson, A. Eklund, A. S. Shiriaev,
    Experimental Testing of a Method for On-Line Identification of the Cerebrospinal Fluid System,
    Proceedings of the 29th International Conference of the IEEE Engineering in Medicine and Biology Society, Lyon, France, August 2007.

    I. R. Manchester, K. S. Andersson, A. Eklund, A. S. Shiriaev,
    Identifiability of the Parameters of a Nonlinear Model of the Cerebrospinal Fluid System,
    Proceedings of the 7th IFAC Symposium on Nonlinear Control Systems, Pretoria, South Africa, August, 2007.

    I. R. Manchester, K. S. Andersson, A. Eklund, A. S. Shiriaev,
    Towards the Simultaneous On-line Estimation of the Compliance and Outflow Resistance of the Cerebrospinal Fluid System,
    Proceedings of the 2007 European Control Conference, Kos, Greece, July 2007.

    A. Shiriaev, N. Andersson, P.X. Miranda La Hera, M. Lilliehook, A. Eklund, 
    Nonlinear Observer Design for an On-line Estimation of the Cerebrospinal Fluid Outflow Resistance
    Proceedings of the 44th IEEE Conference on Decision and Control, 2005 and 2005 European Control Conference. CDC-ECC '05.


    Last updated 15th of August, 2007.