There are different methods to measure the pressure inside the skull, and the more invasive surgeries are commonly-used modalities. Invasive techniques consist of inserting an intraventricular catheter into a burr hole in the skull. This connects to an external pressure transducer, which measures the waveform of the cerebrospinal fluids (CSF). The catheter can also be used to provide medication through and to drain CSF fluids.
Invasive methods pose various risks — particularly the risk of infection, hemorrhaging, misplacement or malposition of instruments, and obstructions. Other invasive procedures consist of lumbar puncturing for means of measuring, epidural and subdural procedures, and intraparenchymal monitors.
The number of complications related to invasive ICP monitoring has led to a greater need for non-invasive techniques, and more research is being done on this. Along with the increase in traumatic brain injuries, which is a global health risk issue, non-invasive techniques will be able to minimize complications making it more efficient to use for more cases.
Non-Invasive ICP Monitoring Techniques
According to research reviews, ICP monitoring techniques can fall into multiple categories, each with many different associated methods.
Below are some common techniques, namely the Transcranial Doppler, Optic Nerve Sheath Diameter (ONSD), Tympanic Membrane Displacement, and other imaging-based techniques.
Transcranial Doppler (TCD) uses ultrasound to measure blood flow and cerebrovascular hemodynamics in the brain’s basal arteries. This method is convenient as a non-invasive ICP monitoring system because it can be done quickly to detect any vascular changes.
Optic Nerve Sheath Diameter (ONSD)
Intracranial pressure can be detected whenever there is an increase in the optic nerve sheath diameter. This is measured by ocular sonography, which involves placing a linear ultrasound probe on the closed upper eyelid where it will be perpendicular to the optic nerve.
This method is efficient and can be done quickly. It can also be used for screening purposes when other methods can’t be used, since it can detect the changes in intracranial pressures.
Tympanic Membrane Displacement
Tympanic Membrane Displacement is an audiologic method, measuring sound stimulation in the TMD. The contraction of the stapedius muscle, which is located in the middle ear, causes the stimulation.
Although this is a valid non-invasive technique to use, especially once a baseline ICP has been indicated, it requires various criteria to be met to do the test — namely, normal middle ear pressure, a functioning stapedial reflex, and a patent cochlear aqueduct.
Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) can also be used to detect any changes that occur in the body from ICP. Various studies have shown that MRIs and CTs can detect normal to elevated levels in ICP, however as a stand-alone method to monitor ICP, these methods are not efficient or reliable enough to indicate the necessary diagnostics for ICP.
A Pursuit for Something Better
The continually increasing search for non-invasive methods to measure ICP will inevitably increase demands in the industry from different health professionals and organizations, increasing the load on manufacturers.
Current reports indicate that there will be a 5.9% CAGR over the next five years in the worldwide market for ICP monitoring devices, and price predictions will reach 600 million USD in 2024 compared to 450 million USD in 2019.
Top manufacturers worth noting in the ICP market include:
- Johnson and Johnson
- Integra LifeSciences
- Sophysa Ltd
- HeadSense Medical
From analyzing the growth of ICP monitoring, it is evident that health organizations and professionals are moving toward more affordable and efficient methods to measure ICP. Although no technique is yet to be as effective as the invasive methods, which are expensive and restrictive in terms of accessibility, various techniques are plausible, especially in developing countries where access to surgery is not always possible.
The market for non-invasive ICP monitoring is definitely on the uprise, with numerous studies being done to prove its efficacy not only in ICU but eventually for “bedside” use.