The intracranial pressure (ICP) represents the pressure exerted by the essentially incompressible components (brain tissue and interstitial fluids, blood and CSF) contained within the rigid confines of the skull 1-3.
ICP has a normal pulsatile variation derived from the transient changes in blood volume associated with the cardiac and respiratory circles 2.
Under a dynamic equilibrium, the normal range of CSF pressure is between 5 and 15 mmHg (7.5-20 cm H2O) 2-4. In children, however, there are different upper tolerated limits, defined for age groups - in general the normal interval is considered to be 3 to 7 mmHg for young children and 1.5 to 6 mmHg for term infants 4.
The Monro-Kellie hypothesis explains the pressure-volume relationship that aims to keep this dynamic equilibrium among the essentially non-compressible components inside the skull 1.
Changes in ICP have been shown to depend on four variables:
- CSF production rate
- intracranial compliance
- outflow resistance
- intradural sinus pressure
Physiological elevations of intracranial pressure can occur briefly (e.g. due to coughing, head-down tilt, and neck vein compression). As they are equally distributed throughout the spinal axis and last for a short period of time, they do not cause neurological damage 2.
See also
- elevated intracranial pressure: neurosurgical emergency
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