Intracranial pressure, harmful when increased.

Intracranial pressure monitoring is done using a device placed inside the head which senses the pressure inside the brain cavity and sends data to a recording device. There are three procedures to monitor intracranial pressure:
1) A intraventricular catheter threaded into one of the two cavities of the brain, called lateral ventricles
2) A subarachnoid screw or bolt placed just through the skull in the space between the arachnoid membrane and cerebral cortex
3) A epidural sensor placed into the epidural space beneath the skull.