Quantification of Optic Nerve and Sheath Diameter by Transorbital Sonography: A Systematic Review and Metanalysis

Abstract

BACKGROUND AND PURPOSE To date, normal values for optic nerve diameter (OND) and optic nerve sheath diameter (ONSD) for transorbital sonography (TOS) have only been reported by individual small‐scale studies, exposing a great variability in the measurement of the OND and ONSD. METHODS We performed a systematic review and metanalysis of available to date studies on TOS evaluation of adults without elevated intracranial pressure to provide an overview of the published literature, measuring methods and further specify normal values for OND and ONSD. RESULTS In total, we included 39 studies with 2,927 healthy volunteers (mean age 36.1 years, 44.4% female), so that a total of 5,854 eyes were examined. All pooled analyses were based on random effect models. Mean values for OND were provided in 13 studies. Calculated mean pooled OND value was 3.08 mm (95% confidence interval [CI], 2.9‐3.25), with low heterogeneity across studies (I2 = 12.7%). Thirty‐four studies provided mean values for ONSD measurement. The pool of mean ONSD measurements was 4.78 mm (95% CI, 4.63‐4.94), with evidence of substantial heterogeneity between estimates ONSD (I2 = 50.6%). There were no significant differences (P = .139) in the subsequent subgroup analysis for the different geographic continents. Also, no significant differences could be recorded for the effect of age (P = .824) or gender (P = .093). CONCLUSIONS TOS is a frequently described and widely used method. We provide reference values of OND and ONSD that are based on metanalytical analysis. Different measuring methods of ONSD result in higher heterogeneity. Subgroup analysis revealed no significant correlation between ONSD and age, gender, or geographic origin.

Neuromonitoring Using Neurosonography and Pupillometry in A Weaning and Early Neurorehabilitation Unit

“…ONSD measurement is becoming increasingly popular as a noninvasive method of ICP evaluation in a variety of neurological diseases 12,17,23‐28 . The reliability of sonographic ONSD measurements has been consistently rated according to published data in healthy individuals, and although there was no blinded review in our study, the supervising experienced neurologists (FS and DB) assured high quality 29‐31 .…”

Optic Nerve Sheath Diameter Measured by Point‐of‐Care Ultrasound and MRI

“…ONSD and OND have often been investigated in healthy individuals using methods such as US, computed tomography (CT), and magnetic resonance imaging (MRI). 7,8,12,13,14 MRI measurements of the ONSD and OND have been shown to correlate well with increased ICP and exhibit less variation when compared to the sonography literature. [4][5][6]8,9,[12][13][14][15][16] However, MRI examinations may not be readily available in Emergency Department (ED) or may be deemed undesirable due to the significant amount of time required to obtain imaging and for the official interpretation of the images.…”

“…[1][2][3][4] Multiple studies have demonstrated a direct correlation between an enlarged ONSD and elevated ICP in patients with severe head injury, intracranial bleeding, and hemorrhagic stroke or idiopathic intracranial hypertension (IIH), and as a prognostic measure in hypoxic-ischemic encephalopathy after cardiac arrest. [3][4][5][6][7] The correlation of high ICP with an enlarged ONSD can be explained by the continuity of the subarachnoid space into the orbit, surrounding the optic nerve. 8,9 This communication renders the ONS susceptible to ICP changes.…”

“…10,11 Some studies have demonstrated high intra-and interobserver reliability of ONSD using US. 7,12,13 However, in our practice, measurement of ONSD and OND is subject to a substantial variability related to the technique, the depth of measurement, anatomical variations, and the presence of artifacts. To correctly interpret ONSD and OND measurements, precise and reliable methods of measurement are necessary.…”

“…Point‐of‐care ultrasound (US) assessment of the optic nerve sheath diameter (ONSD) and optic nerve diameter (OND) has been widely used to screen for an increased intracranial pressure (ICP) 1‐4 . Multiple studies have demonstrated a direct correlation between an enlarged ONSD and elevated ICP in patients with severe head injury, intracranial bleeding, and hemorrhagic stroke or idiopathic intracranial hypertension (IIH), and as a prognostic measure in hypoxic‐ischemic encephalopathy after cardiac arrest 3‐7 …”