The current range of clinical applications for cerebrospinal fluid (CSF) dynamics testing includes hydrocephalus, idiopathic intracranial hypertension, craniosynostosis, and traumatic brain injury. CSF dynamics depends on interaction between four components: CSF production, flow, absorption, and pulsations. The mathematical model of CSF pressure-volume compensation provides a theoretical basis for the differential diagnosis in hydrocephalus. Components of this model are identified in many clinical scenarios and are in use in clinical diagnostic procedures. In all pressure-volume testing techniques, parameters of model are estimated using various algorithms and various volume-adding techniques. Pulse amplitude of intracranial pressure (ICP) is synchronized with pulse amplitude of arterial pressure and the pulse amplitude of blood flow velocity in the middle cerebral artery. Pulse amplitude increases proportionally to mean CSF pressure during the infusion study. The resistance to CSF outflow demonstrates significant associations with cerebrovascular reactivity: patients with lower Rout tend to have more frequently disturbed cerebrovascular reactivity.

This chapter describes the cerebrospinal fluid (CSF) dynamics and how fluid inside the central nervous system (CNS) is generated, stored, and absorbed within the context of a mathematical model developed by A. Marmarou. It explains the main Lumbar infusion techniques in theory and their practical applications by various clinics. Clinical prognostic applications of infusion methods can be classified into two groups: transient and steady-state. External lumbar drainage (ELD) is a prognostic tool for which the accuracy of prediction rate can be more than 90%. The test is based on the idea of simulating the shunt operation in real life by withdrawing CSF for relatively long time durations at drainage rates roughly comparable to regular shunt drainage. ELD yields the most accurate prognostic indications since it simulates the shunt for an extended time duration, which also helps to exclude some placebo effects.