Optic Nerve Sheath Ultrasound

The use of point-of-care ultrasound (POCUS) has expanded considerably over the past 2 decades, enabling rapid evaluations, expedited triage, improved diagnostic capabilities in austere settings, and real-time assessment of focused clinical questions in patients with critical illness in the intensive care unit. Emergency medicine clinicians have led efforts to establish and educate clinicians on the use of bedside ultrasound. In 2001, the American College of Emergency Physicians published the first Emergency Ultrasound Guidelines to clarify primary indications, scope of practice, training requirements, and continuing education for emergency ultrasound. Checklists, grading criteria, and formal educational recommendations have been published to optimize appropriate use and training in POCUS modalities. These guidelines have continued to expand alongside increasing use of ultrasound. Adoption has extended to multiple other specialties, particularly for procedural ultrasound applications, including real-time guidance for vascular access, peripheral nerve blockade, and presurgical evaluation. The main distinction between POCUS and dedicated ultrasound examinations lies in the ability to rapidly answer a focused clinical question, facilitate serial assessments during clinical deterioration, or guide a bedside procedure, rather than generate a detailed report with graded pathology. The availability of small, portable ultrasound devices has increased access to advanced diagnostics in remote environments and battlefield settings. Physicians and advanced paramedical practitioners in these environments receive training in extended focused assessment with sonography in trauma, optic nerve sheath ultrasound (ONSUS) for evaluation of intracranial hypertension, inferior vena cava collapsibility assessments for volume status, and multiple other image-guided procedures. This article focuses on ONSUS for the diagnosis, monitoring, and management of elevated intracranial pressure (ICP).