Ultrasonographic Assessment of Optic Nerve Sheath Diameter as a Screening Tool for Intracranial Hypertension in Traumatic Brain Injury.

Abstract

Severe traumatic brain injury (TBI) is a condition burdened by high morbidity and mortality. Prevention of secondary insults is 1 of the main goals of management and intracranial pressure (ICP) monitoring is a cornerstone in management of TBI. The relationship between ICP and optic nerve sheath is known from the literature. Optic nerve sheath ultrasonography could represent a method added to our armamentarium for monitoring ICP. We investigated how ultrasound-measured optic nerve sheath diameter (ONSD) varies as a function of ICP in a cohort of patients with severe blunt head injury in whom an intraparenchymal sensor was placed. We evaluated the accuracy of ONSD in distinguishing dichotomized ICP cut-offs and analyzed the learning curve and its potential as screening tool to select TBI patients most in need of invasive ICP monitoring in a setting with constraints on resources. ONSD and ICP have a linear relationship. Nevertheless, there are limits of evaluating the one-to-one correspondence between those 2 variables. We selected a cut-off of sonographic ONSD above which there is a concernable elevation of ICP (ICP >15 mmHg) worthy of invasive second-line monitoring. Thus, it is possible to use ONSD as a first-line noninvasive tool to intercept patients at risk of developing frank intracranial hypertension. We propose the use of ONSD ultrasound as a screening investigation for post-traumatic intracranial hypertension in the context of an emergency department, especially in contexts where there is limited availability of ICP monitors.