ICP monitoring is usually used on patients who have decreased score on the Glasgow Coma Scale, indicating poor neurologic function.
This relationship is dictated by the Monro-Kellie doctrine, which states that as the brain swells, intracranial pressure (ICP) rises and cerebral perfusion decreases.
This is dangerous as it can result in the compression of important areas like the brainstem that regulate breathing leading to significant neurological impairment or death.
Benefits of an EVD include its ability to not only measure changes in pressure but also drain CSF as needed, thus making it both diagnostic and therapeutic.
[citation needed] There are three types of intraparenchymal pressure monitors (IPM), also called bolts: fiber optic, strain gauge, and pneumatic sensors.
Strain gauge monitors use a diaphragm that is bent by surrounding pressure, which is then converted into electrical signals used to calculate changes in ICP.
[4] IPMs are as equally accurate as EVDs, but cannot be recalibrated after placement, which is a major clinical limitation of this method of intracranial pressure monitoring.
[2] There are many noninvasive methods for intracranial pressure monitoring such as transcranial doppler (TCD), and optic nerve sheath diameter (ONSD).