Pathophysiology of Increased ICP

The intracranial space is bounded by thick bone that is essentially non-distensible, and it is filled to capacity with essentially non-compressible contents. These can be divided into three fluid compartments, brain tissue water, intravascular blood, and CSF. The intracranial space is vented from the supratentorial compartment to the posterior fossa through the tentorial incisura and through the foramen magnum to the spinal canal. In addition, intravascular blood and CSF can be expressed into the extracranial vascular system. Thus, the intracranial space contains displaceable fluid in the form of CSF and blood. CSF volume is approximately 10% of the intracranial volume; values for intracranial blood volume have varied from 2–11%.