High-Resolution Ultrasound of Small Clinically Relevant Nerves Running Across the Posterior Triangle of the Neck.

: With the advent of high-frequency ultrasound (US) transducers, new perspectives have been opened in evaluating millimetric and submillimetric nerves that, despite their dimensions, can be considered relevant in clinical practice. In the posterior triangle of the neck, the suprascapular, long thoracic, phrenic, supraclavicular, great auricular, lesser occipital, and transverse cervical nerves are amenable to US examination and the object of special interest because they may be involved in many pathologic processes or have a value as targets of advanced therapeutic procedures. The correct identification of these nerves requires a deep knowledge of local neck anatomy and the use of a complex landmarks-based approach with US. This article describes the anatomy and US technique to examine small but clinically relevant nerves of the posterior triangle of the neck (excluding the brachial plexus), reviewing the main pathologic conditions in which they may be involved.