Non-Invasive Intracranial Pressure Monitoring

Abstract

(1) Background: Intracranial pressure (ICP) monitoring plays a key role in the treatment of patients in intensive care units, as well as during long-term surgeries and interventions. The gold standard is invasive measurement and monitoring via ventricular drainage or a parenchymal probe. In recent decades, numerous methods for non-invasive measurement have been evaluated but none have become established in routine clinical practice. The aim of this study was to reflect on the current state of research and shed light on relevant techniques for future clinical application. (2) Methods: We performed a PubMed search for "non-invasive AND ICP AND (measurement OR monitoring)" and identified 306 results. On the basis of these search results, we conducted an in-depth source analysis to identify additional methods. Studies were analyzed for design, patient type (e.g., infants, adults, and shunt patients), statistical evaluation (correlation, accuracy, and reliability), number of included measurements, and statistical assessment of accuracy and reliability. (3) Results: MRI-ICP and two-depth Doppler showed the most potential (and were the most complex methods). Tympanic membrane temperature, diffuse correlation spectroscopy, natural resonance frequency, and retinal vein approaches were also promising. (4) Conclusions: To date, no convincing evidence supports the use of a particular method for non-invasive intracranial pressure measurement. However, many new approaches are under development.

Keywords: intracranial hypertension; intracranial pressure; neurointensive care; non-invasive ICP measurement.

Figure 1

Invasive measurement methods. Possible localizations of pressure probes: (A) epidural; (B) subdural; (C) parenchymal; (D) intraventricular. Illustration created by J. Freimuth.

Figure 2

Pie chart of studies in PubMed. ONSD: optic nerve sheath diameter; TCD: transcranial Doppler; LP: lumbar puncture; EEG: electroencephalogram; CSF: cerebrospinal fluid; FVEP: flashed visual-evoked potentials; NIRS: near-infrared spectroscopy; CT: computed tomography; MRI: magnetic resonance imaging.

Figure 3

Concept of MR-ICP. Simultaneous (in and out) flow measurements of internal carotid (A) and vertebral (C) arteries, as well as venous flow in the jugular veins (B) and cerebrospinal fluids at the C2 level (D), enable the estimation of cerebral compliance, pressure gradients, and ICP. (Schematic overview made by S.J. Müller).

Figure 4

Ophthalmic methods. Left: schema of a coronary slice of the optic nerve 3 mm behind the globe (A); middle: illustration of intracranial (C) and extracranial (A) course of the optic nerve through the annulus of Zinn and the optic canal (B). Right: abstract illustration of ONSD and two-depth Doppler (G) measurements of intraorbital (E) and intracranial (F) ophthalmic artery branching from the internal carotid artery (D), following the descriptions of Raugaskaus with a pressure pad (H) on the eye. Illustrations were made by J. Freimuth.

Figure 5

Illustration of the inner and outer ear with the cochlear aqueduct (D) connecting the intracranial cerebrospinal fluid (E) and cochlea. (A) ear canal, (B) tympanic membrane, (C) auditory ossicles. Illustration made by J. Freimuth.