Intracranial Pressure Assessments - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 374

Chapter 27
Intracranial Pressure Assessments
Carla S. Jung and Andreas W. Unterberg
Abstract
Different methods have been used to assess intracranial pressure (ICP). ICP is affected and often increased
in the course of subarachnoid hemorrhage (SAH). An increase in ICP may impede cerebral blood fl ow and
induce ischemia. This chapter describes techniques of assessing intracranial pressure in animal models after
SAH. The fi rst part of the chapter explains how intracranial pressure can be measured and the second
describes how cerebrospinal fl uid (CSF) can be reached and drained to study the CSF and to infl uence ICP
after SAH. Each technique offers advantages and disadvantages and selection of one over the other depends
upon the operator's choice and availability of instruments.
Key words: Intracranial pressure, Rat, Subarachnoid hemorrhage, Intraparenchymal, Ventricular,
Cisterna magna cannulation
1. Introduction
The basic principles of intracranial pressure are summarized in the
Kellie-Monro doctrine: The brain is encased by the nonexpand-
able skull. As the cranium and its constituents (blood, CSF, and
brain tissue) create a state of volume equilibrium, any increase in
volume of one of the constituents has to be compensated by a
decrease in volume of another to keep stable ICP ( 1-3 ). A nonlin-
ear pressure volume curve, which can be divided into three parts,
describes the relationship between ICP and intracranial volume
( 4, 5 ). (Details concerning clinical relevance as well as interpretation
of intracranial pressure waveforms and ICP derived indexes can be
found in the reviews of Steiner & Andrews and Czosnyka &
Pickard) ( 4, 6 ). Increased intracranial pressure can occur at any
time after subarachnoid hemorrhage (SAH) and can be caused by
different factors: brain edema, intracerebral or intraventricular
hematoma, re-bleeding, and hydrocephalus ( 7, 8 ).