The best way to determine ICP is through continuous monitoring. The neurological examination may not reliably correlate with ICP elevations, especially in patients in coma. Most of the data available regarding selection of patients for ICP monitoring come from TBI patients and most practitioners have extrapolated such criteria for patients with various intracranial abnormalities. Current recommendations indicate that ICP monitoring is appropriate in patients with severe TBI (Glasgow Coma Scale [GCS] of 3 to 8 after cardiopulmonary resuscitation) with an abnormal admission head computed tomography (CT) scan. An abnormal head CT scan is defined as one that demonstrates hematomas, contusions, edema, or compressed basal cisterns. ICP monitoring is also appropriate in patients with severe TBI with a normal head CT scan but who present with two or more of the following: age >40 years, unilateral or bilateral motor posturing, and systolic blood pressure <90 mm Hg. Essentially, any patient with GCS ≤8 should be considered for ICP monitoring regardless of the underlying intracranial or systemic condition.

Several types of ICP-monitoring devices are commercially available today. These include intraventricular catheters (IVCs),
parenchymal catheters, subarachnoid bolts, epidural catheters, and lumbar drains (to measure the cerebrospinal fluid [CSF] pressure in the lumbar spinal space). When IVCs are inserted, a pressure transducer can be connected to measure the fluid pressure of the CSF that drains. IVCs are considered the gold standard of direct ICP monitoring, because fluid conveys a pressure wave reliably. They also have the added benefit of treating ICP elevations by draining CSF. IVCs are associated with infections that may range from 5% to 20% and are more common after day five of insertion. Accordingly, some practitioners have recommended replacing catheters that are more than 5 days old. Other clinicians believe changing the catheter should be done only if there is evidence of an infection that has not been localized to a source other than the central nervous system (CNS). Other devices include parenchymal catheters, such as the Camino and Codman MicroSensor catheters, which are inserted through a burr hole in the skull with the catheters being inserted through the dura into brain parenchyma (or the ventricles, if so desired). Hemorrhagic and infectious complications appear to be about the same as with an IVC. Subarachnoid bolts and epidural catheters are less commonly used.