Measuring elevated intracranial pressure through noninvasive methods: a review of the literature

Elevated intracranial pressure (ICP) is an important cause of secondary brain injury, and a measurement of ICP is often of crucial value in neurosurgical and neurological patients. The gold standard for ICP monitoring is through an intraventricular catheter, but this invasive technique is associated with certain risks. Intraparenchymal ICP monitoring methods are considered to be a safer alternative but can, in certain conditions, be imprecise due to zero drift and still require an invasive procedure. An accurate noninvasive method to measure elevated ICP would therefore be desirable. This article is a review of the current literature on noninvasive methods for measuring and evaluating elevated ICP. The main focus is on studies that compare noninvasively measured ICP with invasively measured ICP. The aim is to provide an overview of the current state of the most common noninvasive techniques available. Several methods for noninvasive measuring of elevated ICP have been proposed: radiologic methods including computed tomography and magnetic resonance imaging, transcranial Doppler, electroencephalography power spectrum analysis, and the audiological and ophthalmological techniques. The noninvasive methods have many advantages, but remain less accurate compared with the invasive techniques. None of the noninvasive techniques available today are suitable for continuous monitoring, and they cannot be used as a substitute for invasive monitoring. They can, however, provide a reliable measurement of the ICP and be useful as screening methods in select patients, especially when invasive monitoring is contraindicated or unavailable.