Optic Nerve Sheath Ultrasound

The use of point-of-care ultrasound (POCUS) has expanded considerably over the past two decades allowing for enhanced and swift evaluations, rapid triage, improved diagnostic capabilities in austere situations, and real-time assessment of focused clinical questions in critically ill patients in the intensive care unit (ICU). Emergency medicine physicians have led the way in establishing and educating bedside use of ultrasound. In 2001, the American College of Emergency Physicians (ACEP) published the first Emergency Ultrasound Guidelines to clarify the primary indications, the scope of practice, training, and continuing education regarding the use of emergency ultrasound. These guidelines have continued to expand alongside the ever-growing use of ultrasound. They have been adopted by several other specialties, especially in applying “procedural ultrasound” to assist in real-time guidance of vascular access, peripheral nerve blockade, and pre-surgical evaluations. The main difference between POCUS and dedicated ultrasound exams is the ability to rapidly answer a focused clinical question, facilitate serial examinations in clinical deterioration, or guide a bedside procedure rather than provide a detailed report with the grading of pathology. With small, portable ultrasound models becoming available, advanced diagnostics are becoming more accessible in remote environments and on the battlefield. Physicians and advanced paramedical providers in these settings are becoming trained to perform extended focused assessment with sonography in trauma (eFAST), optic nerve sheath ultrasound (ONSUS) for the evaluation of intracranial hypertension, inferior vena cava collapsibility assessments for the evaluation of volume status, and countless other examples of image-guided procedures. This article will focus on optic nerve sheath ultrasound for the diagnosis, monitoring, and management of elevated intracranial pressure (ICP).