Optic Nerve Ultrasound Predicts Elevated Intracranial Pressure
In a small meta-analysis, ultrasound measurement of optic nerve sheath diameter had a sensitivity of 90% for predicting elevated ICP.
Bedside emergency department ocular ultrasound is increasingly used to detect retinal detachment, but does it also have other uses? Researchers performed a meta-analysis of six prospective studies (231 patients) in which researchers compared intracranial pressure (ICP) monitoring and ultrasound measurement of optic nerve sheath diameter (ONSD) in consecutive adult patients with suspected elevated ICP. ONSD was measured 3 mm behind the globe; ICP and ONSD measurements were performed within 1 hour of each other.
The pooled sensitivity for ONSD detection of elevated ICP was 90% and the pooled specificity was 85%. The pooled diagnostic odds ratio was 51, meaning that patients with elevated ICP were 51 times more likely to have a positive ONSD test than those without elevated ICP.
Comment: With a 90% sensitivity for ruling out elevated intracranial pressure, bedside ultrasound measurement of optic nerve sheath diameter shows promise as a new tool to guide decision making, including prioritizing patients for diagnostic studies and determining whether computed tomography is needed before an unstable polytrauma patient is taken to the operating room.
Kristi L. Koenig, MD, FACEP
Published in Journal Watch Emergency Medicine May 20, 2011
Citation(s): Dubourg J et al. Ultrasonography of optic nerve sheath diameter for detection of raised intracranial pressure: A systematic review and meta-analysis. Intensive Care Med 2011 Apr 20; [e-pub ahead of print]. (http://dx.doi.org/10.1007/s00134-011-2224-2)