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L. Geregele et al.
or distribution of stress-strain in the brain tissue in deformation modelling. In
clinical practice, dynamics of the pressure may be easily monitored (although
invasively, with directly placed pressure transducers), and dynamics of CSF flow
and CBF can be imaged with phase-contrast MRI (PC-MRI, noninvasively). These
two methods have an established clinical application in diagnosis and management
of diseases associated with CSF circulatory dysfunctions, like hydrocephalus of
various types, idiopathic intracranial hypertension, syringomyelia, etc.
This chapter describes the methodology of modelling of CSF dynamics and
attempts to illustrate some most common clinical applications to give a reader a taste
of links between physics and a practice of clinical neurosciences. Before embarking
on the particulars, it is worth considering the question: why quantitatively assess
CSF dynamics? Quantitative assessment in general provides robust evidence to support clinical intuition as well as imparting a measure of the degree of dysfunction,
particularly useful where clinical parameters are subtle and ambiguous [1]. For
normal pressure hydrocephalus (NPH), where this is particularly true, theoretical
consensus regarding the use of physiological parameters in conjunction with clinical
information and imaging has been reached. It has been published in the latest
guidelines for the management of NPH [2].
More specifically, the ability to obtain variables that describe CSF dynamics
allows us to more categorically address some key questions in the clinical decisionmaking process: (1) Scope for improvement with CSF shunting: shunts work by
providing an alternative (normal resistance) pathway for CSF outflow. If resistance
to CSF outflow (R CSF ) is in the normal range, a shunt will theoretically not
be of benefit [3]. (2) To determine which is the best shunt system to use. (3)
In suspected shunt failure, providing a baseline for postshunt comparison. Shunt
failure occurs at a rate of approximately 20–30% in the first year and 3–5%
per annum subsequently [4]. Deterioration is often gradual and subtle rather than
sudden and dramatic, and in such cases, it can be difficult to justify revision
without quantitative evidence and comparative analysis [5–7]. Similarly, in patients
presenting with persistent symptoms postshunting, CSF dynamics assessment is
a useful means of excluding revision, if relative normalisation of CSF dynamics
has been demonstrated [8]. The current range of clinical application for CSF
dynamics testing includes hydrocephalus, idiopathic intracranial hypertension [9],
craniosynostosis, and traumatic brain injury (TBI) – the latter useful in differentiating posttraumatic hydrocephalus from atrophy [10] and assessing CSF pathways
following decompressive craniectomy [11].
8.2 Physiology and Pathophysiology
CSF dynamics comprises the interaction between five components: CSF production,
flow, absorption, pulsations, and dynamics of CBF. CSF production occurs by active
secretion at a relatively constant rate, but is dependent upon brain metabolic rate and
reducing with age [12]. The role of free, unobstructed flow of CSF is threefold: (1)
L. Geregele et al.
or distribution of stress-strain in the brain tissue in deformation modelling. In
clinical practice, dynamics of the pressure may be easily monitored (although
invasively, with directly placed pressure transducers), and dynamics of CSF flow
and CBF can be imaged with phase-contrast MRI (PC-MRI, noninvasively). These
two methods have an established clinical application in diagnosis and management
of diseases associated with CSF circulatory dysfunctions, like hydrocephalus of
various types, idiopathic intracranial hypertension, syringomyelia, etc.
This chapter describes the methodology of modelling of CSF dynamics and
attempts to illustrate some most common clinical applications to give a reader a taste
of links between physics and a practice of clinical neurosciences. Before embarking
on the particulars, it is worth considering the question: why quantitatively assess
CSF dynamics? Quantitative assessment in general provides robust evidence to support clinical intuition as well as imparting a measure of the degree of dysfunction,
particularly useful where clinical parameters are subtle and ambiguous [1]. For
normal pressure hydrocephalus (NPH), where this is particularly true, theoretical
consensus regarding the use of physiological parameters in conjunction with clinical
information and imaging has been reached. It has been published in the latest
guidelines for the management of NPH [2].
More specifically, the ability to obtain variables that describe CSF dynamics
allows us to more categorically address some key questions in the clinical decisionmaking process: (1) Scope for improvement with CSF shunting: shunts work by
providing an alternative (normal resistance) pathway for CSF outflow. If resistance
to CSF outflow (R CSF ) is in the normal range, a shunt will theoretically not
be of benefit [3]. (2) To determine which is the best shunt system to use. (3)
In suspected shunt failure, providing a baseline for postshunt comparison. Shunt
failure occurs at a rate of approximately 20–30% in the first year and 3–5%
per annum subsequently [4]. Deterioration is often gradual and subtle rather than
sudden and dramatic, and in such cases, it can be difficult to justify revision
without quantitative evidence and comparative analysis [5–7]. Similarly, in patients
presenting with persistent symptoms postshunting, CSF dynamics assessment is
a useful means of excluding revision, if relative normalisation of CSF dynamics
has been demonstrated [8]. The current range of clinical application for CSF
dynamics testing includes hydrocephalus, idiopathic intracranial hypertension [9],
craniosynostosis, and traumatic brain injury (TBI) – the latter useful in differentiating posttraumatic hydrocephalus from atrophy [10] and assessing CSF pathways
following decompressive craniectomy [11].
8.2 Physiology and Pathophysiology
CSF dynamics comprises the interaction between five components: CSF production,
flow, absorption, pulsations, and dynamics of CBF. CSF production occurs by active
secretion at a relatively constant rate, but is dependent upon brain metabolic rate and
reducing with age [12]. The role of free, unobstructed flow of CSF is threefold: (1)