2024 Workshop Handout Bundle-24W58B Basic US of Upper Limb Nerves Median and Ulnar from Elbow to Wrist Shanina

24W58B Basic US of Upper Limb Nerves Median and Ulnar from Elbow to Wrist Shanina

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This document is a detailed guide prepared by Dr. Elena Shanina for the 2024 AANEM Annual Meeting on the use of high-resolution ultrasound (US) for assessing peripheral nerve disorders in the upper limb, specifically the median and ulnar nerves from the elbow to the wrist. The major objectives are explaining the principles of ultrasound imaging, demonstrating scanning techniques and dynamic testing, and discussing sonographic findings of common entrapment neuropathies.<br /><br />Ultrasound has grown in popularity due to its high sensitivity (93%, compared to MRI's 67%) for detecting peripheral nerve disorders. It offers advantages such as lower cost, quicker procedures, and suitability for patients with MRI contraindications. Despite its operator dependency, proper training can mitigate this limitation.<br /><br /><strong>Equipment Needed:</strong><br />- A linear array high-frequency transducer (6-18 MHz).<br />- Basic systems and single transducers are relatively affordable, whereas comprehensive systems are more costly.<br /><br /><strong>Image Optimization Controls:</strong><br />- <em>Gain</em>: Adjusts the overall brightness.<br />- <em>Focus</em>: Enhances resolution at specific depths.<br />- <em>Depth and Frequency</em>: Modify for best visualization.<br /><br /><strong>Terminology and Techniques:</strong><br />- <em>Anechoic</em>, <em>hyperechoic</em>, and <em>hypoechoic</em> define different echoic structures.<br />- <em>Short axis</em> (transverse view) and <em>long axis</em> (longitudinal view) relate to probe orientation.<br />- <em>Dynamic assessments</em> involve observing nerve movement relative to adjacent tissues, useful for identifying neuropathies such as carpal tunnel syndrome (CTS) and ulnar neuropathy.<br /><br /><strong>Sonographic Appearance:</strong><br />- Normal nerves exhibit a "honeycomb" appearance in the short axis.<br />- Focal neuropathies show nerve enlargement proximal to the injury or compression.<br />- For CTS, a cross-sectional area (CSA) cut-off value of 10 mm² at the wrist is an indicator of pathology.<br /><br /><strong>Abnormal Findings:</strong><br />- Diagnostic ultrasound complements electrodiagnostic studies and identifies abnormal fascicular patterns in both focal and generalized neuropathies, such as CIDP.<br /><br />This method is integral to neurology and physical medicine, providing crucial anatomical insights that improve diagnostic accuracy alongside traditional electrophysiological practices.

Keywords

high-resolution ultrasound

peripheral nerve disorders

median nerve

ulnar nerve

entrapment neuropathies

carpal tunnel syndrome

CTS

ultrasound imaging

sonographic findings

dynamic testing

AANEM Annual Meeting

CTS

carpal tunnel syndrome