Intracranial pressure: a review of clinical problems, measurement techniques and monitoring methods.

Intracranial hypertension is a dangerous condition and is common in patients suffering from a severe head injury or from a variety of pathological problems. Measurement of intracranial pressure (ICP) is considered by many to be a valuable aid in the management of such patients. Despite the invasive nature of the more widely-used measurement techniques, and hence their associated risks, results from many centres have convincingly shown that ICP measurement enables management of intracranial hypertension to be rationally approached, and a direct measure of the progress and outcome of treatment to be obtained. This paper begins with a description of normal cerebrospinal fluid (c.s.f.) pressure. This is followed by an account of the pressure-volume relationship of the intracranial system, and the control mechanisms that regulate the ICP during limited increases in mass volume within the cranium. The consequences of these for patient management are discussed. Reasons why ICP is monitored, and the benefits arising, are described. The paper then concentrates upon the methods of measuring ICP and discusses their relative merits and limitations. A selection of typical pressure sensors is described. Finally, methods that have been devised to monitor ICP and to anticipate intracranial hypertension are reviewed, and the direction of work in this area is assessed.