2026 Workshop Handout Bundle-W58G - Basic US of Upper Limb Nerves - Median and Ulnar

W58G - Basic US of Upper Limb Nerves - Median and Ulnar - Shanina

Pdf Summary

High-resolution ultrasound is a rapid, relatively inexpensive method for assessing peripheral nerves and can complement electrodiagnostic testing by showing nerve structure, surrounding anatomy, and dynamic movement. It may be used when MRI is unsuitable and has reported greater sensitivity than MRI for peripheral nerve disorders. Its main limitation is dependence on operator skill.<br /><br />For superficial upper-limb nerves, use a high-frequency linear transducer, typically 6–18 MHz. Optimize image brightness, focus, depth, and frequency for the structure being examined. Begin by locating the nerve in transverse (short-axis) view using anatomical landmarks, then follow it along its course while keeping it centered. Apply minimal probe pressure, as compression can distort nerves and vessels. Examine suspicious areas in longitudinal (long-axis) view and use Doppler when needed to identify blood flow.<br /><br />Normal nerves show a “honeycomb” pattern in short axis: hypoechoic fascicles surrounded by brighter connective tissue. Cross-sectional area (CSA), traced along the inner hyperechoic border, is generally more reliable than diameter. Changes in size, shape, or echogenicity may indicate pathology. Compared with tendons, nerves have less angle-dependent echogenicity and a fascicular rather than fibrillar appearance. Dynamic scanning assesses nerve movement; the ulnar nerve normally remains in the groove behind the medial epicondyle during elbow flexion.<br /><br />Focal entrapment commonly causes nerve enlargement and reduced echogenicity. At the wrist, a median nerve CSA of 10 mm² or greater supports carpal tunnel syndrome; a wrist-to-forearm CSA ratio of 1.4 or greater can improve detection. At the elbow, ulnar nerve enlargement behind the medial epicondyle, often with CSA of 10 mm² or greater, suggests cubital tunnel neuropathy. Ultrasound can also identify ulnar nerve dislocation and other structural causes. Generalized hereditary neuropathies tend to produce diffuse nerve enlargement, while immune-mediated neuropathies more often show patchy enlargement.<br /><br />Overall, ultrasound provides useful anatomical and functional information alongside electrophysiology and can help localize and characterize nerve disorders.

Keywords

high-resolution ultrasound

peripheral nerves

electrodiagnostic testing

nerve structure

high-frequency linear transducer

cross-sectional area

carpal tunnel syndrome

CTS

cubital tunnel neuropathy

nerve entrapment

dynamic scanning