With a primary insult to the brain, as in traumatic brain injury, there is irreparable brain damage from the direct disruption of the brain parenchyma. Subsequently, potentially reversible secondary injury can occur as a result of altered cerebral hemodynamics, metabolic and cellular derangement. The avoidance of systemic hypotension and hypoxemia is important in minimizing the secondary damage that may result in ischemia or cellular edema.

In monitoring a child with raised intracranial pressure (ICP), a stable hemodynamics is essential in minimizing the secondary damage. CT scan will be able to indicate the severity of the brain damage but is unable to allow continuous assessment of the progression.

The gold standard of ICP monitoring would be an intraventricular drain with an external transducer. This will allow drainage of CSF if necessary. The external gauge allows for re-zeroing. Intra-parenchymal monitoring with a fiber optic catheter has a potential for measurement drift as the zeroing is only done once just before insertion. Subdural, subarachnoid and epidural catheters are less accurate.

There is about 5% risk of infection with these invasive monitors especially after 5 days of insertion. But these monitors would only be accurate if CSF circulates freely, hence pressure is equilibrated uniformly. But in severe cerebral edema, there is little CSF flow, hence the measurement of the catheter may not be accurate as it may be reflecting the pressure of the brain tissue just around the catheter. Non-invasive measurements of ICP includes transcranial Doppler which relies on blood flow through cerebral vessels like the Circle of Willis.

Measuring ICP will enable the clinician to institute therapy like volume reduction, hyperventilation, hyperosmolar state, hypothermia and barbiturate coma to reduce the raised ICP but although it is almost a routine that ICP monitoring is done in severe head injury with a low GCS score, yet there have been no randomized controlled trials to confirm its use.

NCPCC 2005 - Conference Abstracts.Pediatric Oncall [serial online] 2006 [cited 15 May 2006(Supplement 5)];3. Available from:
http://www.pediatriconcall.com/fordoctor/Conference_abstracts/
Monitoring_intracranial_pressure.asp