Modeling of CSF Dynamics: Legacy of Professor Anthony Marmarou

Abstract

The mathematical model of cerebrospinal fluid (CSF) pressure volume compensation, introduced by Anthony Marmarou in 1973 and modified in later studies, provides a theoretical basis for differential diagnosis in hydrocephalus. The Servo-Controlled Constant Pressure Test (Umea, Sweden) and Computerised Infusion Test (Cambridge, UK) are based on this model and are designed to compensate for inadequate accuracy of estimation of both the resistance to CSF outflow and elasticity of CSF pressure volume compensation.Dr. Marmarou's further works introduced the pressure volume index (PVI), a parameter used to describe CSF compensation in hydrocephalic children and adults. A similar technique has been also utilized in traumatic brain injury (TBI).The presence of a vascular component of intracranial pressure (ICP) was a concept proposed in the 1980s. Marmarou demonstrated that only around 30% of cases of elevated ICP in patients with TBI could be explained by changes in CSF circulation. The remaining 70% of cases should be attributable to vascular components, which have been proposed as equivalent to raised brain venous pressure.Professor Marmarou's work has had a direct impact in the field of contemporary clinical neurosciences, and many of his ideas are still being investigated actively today.

Patient Specific Hardware-in-the-Loop Testing of Cerebrospinal Fluid Shunt Systems

“…Thus, lumped parameter models are best suited. In 1973, Marmarou [27] published a lumped parameter model of the CSF dynamics whose parameters are even used to characterize hydrocephalus [28]. Today, there are a number of ICP models that build upon the exponential function of this model that describes the pressure dependence of the compliance and extend it to capture also other characteristics of the CSF system [29].…”

Shunt infusion studies: impact on patient outcome, including health economics

“…Objective testing of implanted shunts through infusion studies is a well-refined method based on both in vitro and in vivo knowledge of all marketed shunts' hydrodynamics, primarily the shunt critical pressure and its resistance [6,10,13]. Validation of the methodology in relationship to clinical and intraoperative findings of shunt revision has recently been performed in a large paediatric population from two European centres [17].…”

“…Provision of a separate subcutaneous CSF reservoir is of proven benefit in allowing access to the cerebral ventricles to measure ICP and allow removal of CSF in an emergency [30]. CSF infusion tests are an elaboration of the tap-test that were introduced into clinical practice over 45 years ago and have been reported to be a minimally invasive, low risk and potentially useful diagnostic tool for testing shunt function in vivo [10,13,20,21,31]. However, they still lack widespread endorsement.…”

Non-canonical, potassium-driven cerebrospinal fluid clearance

“…5D, E). The C i and R CSF are estimated from the ICP vs. time curve using Marmarou's model of CSF dynamics (Czosnyka et al, 2012) (Supplementary Fig. 9A).…”

“…The procedure was terminal. Parameters of the Marmarou model of CSF dynamics for constant rate infusions were estimated by a non-linear least squares fit of the model to the ICP data (Czosnyka et al, 2012)…”