Non-Invasive ICP Monitoring Methods: What Hospitals Should Know

Why look for non-invasive intracranial pressure monitoring?

Invasive monitoring needs a neurosurgeon, an OR or a sterile bedside procedure, and consumables. It carries risks of haemorrhage and infection and is not available in every hospital or for every patient, for example when coagulation is abnormal. A reliable non-invasive approach could help triage patients, support transfer decisions and flag who needs an invasive monitor.

At present, non-invasive methods are best regarded as supportive. For the clinical context see our comparison of invasive versus non-invasive ICP monitoring.

Equally important is who interprets the result and under which protocol: a finding of raised ICP should be confirmed by a clinician rather than accepted from an automatic output alone.

Main non-invasive ICP measurement methods

Several techniques are used or studied. Optic nerve sheath diameter (ONSD) with ultrasound relies on the fact that the sheath around the optic nerve distends when pressure rises. Transcranial Doppler measures flow velocity and the pulsatility index in cerebral arteries. Pupillometry tracks pupillary reflexes, tympanic membrane displacement looks at middle-ear changes, and near-infrared or CT/MRI-based signs offer additional information.

None of them gives a continuous, calibrated pressure in mmHg in the way an EVD or a parenchymal probe does. Most produce an estimate or a probability of raised ICP and depend on operator skill and patient factors.

For a hospital, the practical choice depends on what the unit can support. Transcranial Doppler needs a trained operator and a suitable ultrasound system, optic nerve sheath scanning needs a standardised technique, and pupillometers add a dedicated device and consumables.

• Ultrasound of optic nerve sheath diameter
• Transcranial Doppler and pulsatility index
• Automated pupillometry
• Tympanic membrane displacement
• Imaging signs on CT or MRI as supportive indicators

Optic nerve sheath ultrasound and Nisonic FAST-ICP

Nisonic AS of Trondheim, Norway, develops FAST-ICP, software that analyses transorbital ultrasound images. It measures the static and dynamic properties of the optic nerve sheath, namely the diameter (ONSD) and a Deformability Index (DI), guides probe positioning in real time and estimates image-derived biomarkers of raised ICP. According to the manufacturer, an examination typically takes less than a minute and needs no equipment calibration. See FAST-ICP.

The Nisonic P-100 is an ultrasound trolley with a touch screen, an AI computer and a probe tailored for optic nerve sheath scanning, CE marked in May 2021. The manufacturer states that FAST-ICP is currently labelled for research use only and is used in investigator-initiated studies. It should therefore be viewed as a research tool and not as a substitute for invasive monitoring.

Guidelines, consensus and how to judge a device

Neurocritical care societies and expert groups have discussed the role of non-invasive ICP assessment, and consensus statements and guideline positions evolve. Read the current versions rather than relying on a vendor's summary, and note that they typically describe non-invasive methods as adjuncts with a defined place in the pathway.

When assessing a non-invasive ICP monitoring device, ask for the intended use statement, the regulatory status, validated populations, sensitivity and specificity against a reference method, training requirements and the data privacy approach for image analysis. For a wider list of questions see ICP monitoring devices overview.

Supply of non-invasive ICP systems in the UAE

Because the research-use status affects how a device can be procured and used, confirm the local requirements with the relevant UAE authority and your ethics committee before purchase.

Beckfinity supplies the Nisonic P-100 in the UAE. To discuss a research project or request more information, contact our specialists.