Ultrasonographic Optic Nerve Sheath Diameter Technical Pitfalls and Imaging Artifacts.

Ultrasonographic optic nerve sheath diameter (ONSD) is a non-invasive intracranial pressure (ICP) surrogate. This article discusses the effect of ultrasound settings and imaging artifacts on ONSD assessment. Ultrasound settings that may affect ONSD assessment include gain, dynamic range, frequency, harmonic imaging, and focal zones. Artifacts can be related to imaged structures (acoustic shadowing, enhancement, comet tail, and speckle artifacts) or to beam properties (partial volume and refraction artifacts). In addition, optic nerve sheath (ONS) properties such as echogenicity changes based on ICP or ONS kinking are discussed.