Transorbital Sonography for Early Prognostication of Hypoxic‐Ischemic Encephalopathy After Cardiac Arrest

Abstract

Early and reliable prognostication of outcomes in patients with HIE can be simplified by ONSD values gathered with the use of TOS. Main advantages compared to other established markers are prognostication within the first 24 hours and independence from therapy with hypothermia. A higher level of accuracy can be reached by combining computed tomography (gray-to-white matter ratio values) and ONSD values.

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

“…This is the first metanalysis of normal OND and ONSD assessed by TOS, reporting a mean OND of 3.08 mm (95% CI, 2.9‐3.25) and a mean ONSD value was 4.78 mm (95% CI, 4.63‐4.94) across all eligible studies. In the recent years, TOS became increasingly established as a fast, noninvasive, and easy repeatable technique in several neurological diseases, particularly with alteration of intracranial pressure . With regard to the technical implementation of the analyzed studies, a consistent acquisition of the measured values 3 mm behind the optic disc was found.…”

“…The interrater reliability has been shown to be very high in several studies, so that for trained examiners no relevant variability effect on the measured values should occur. In over two thirds of the evaluated studies, authors used the mean value from three subsequent measurements to reduce further the effect of intrarater variability.…”

“…The main areas of application are diseases with increased intracranial pressure such as idiopathic intracranial hypertension, intracranial hemorrhage, and neuro‐traumatological diseases . In this context, TOS provides a helpful diagnostic tool for early prognostication of hypoxic‐ischemic encephalopathy after cardiac arrest . Orbital sonography can also be a helpful method for the diagnosis and follow‐up of optic neuritis .…”

“…3,4 In this context, TOS provides a helpful diagnostic tool for early prognostication of hypoxic-ischemic encephalopathy after cardiac arrest. 5 Orbital sonography can also be a helpful method for the diagnosis and follow-up of optic neuritis. 6 Recently, it was shown that even optic nerve atrophy can be detected reliably by means of TOS in patients with chronic demyelinating diseases of the central nerve system, as TOS findings correlated significantly to findings of optic coherence tomography.…”

“…With regard to ONSD measurement, in the vast majority of published studies, ONSD is defined as the distance between the external borders of the hyperechogenic area surrounding the optic nerve, which represents the subarachnoidal space including the arachnoid mater. 1,5,7 In some studies, however, the ONSD includes also the outer hypoechogenic rim, which represents the dura mater, resulting to a large heterogeneity of reported reference values. 8 Several studies have further investigated the relationship between age, gender, and body-mass-index (BMI) and ONSD, but with inconsistent results.…”