2025 Workshop Handout Bundle-W58B Basic US upper

W58B Basic US upper - Shanina

Pdf Summary

This lecture by Dr. Elena Shanina reviews the use of high-resolution ultrasound (US) for imaging the median and ulnar nerves in the upper limb from elbow to wrist, highlighting its principles, techniques, and clinical applications.<br /><br />Ultrasound has gained popularity for peripheral nerve evaluation due to superior sensitivity (93% vs 67%) compared to MRI, and advantages including lower cost, speed, dynamic real-time imaging, safety for patients contraindicated for MRI, and the ability to scan the entire nerve and compare contralateral sides easily. However, ultrasound is operator-dependent and requires specific training.<br /><br />Key equipment involves high-frequency linear array transducers (6-18 MHz) suitable for superficial nerves. Image optimization relies on adjusting settings such as gain, focus, depth, and frequency to achieve clear visualization. Terminology includes anechoic (fluid, black), hyperechoic (bright), and hypoechoic (gray) structures, with standard views being short axis (transverse) and long axis (longitudinal).<br /><br />The normal peripheral nerve on ultrasound displays a “honeycomb appearance” due to hypoechoic fascicles surrounded by hyperechoic perineurium. Cross-sectional area (CSA) measurement is the primary metric, providing reliable data over diameter due to irregular nerve shapes. CSA norms differ by nerve site and patient demographics but commonly range for median nerve around 5.6-8.4 mm² and ulnar nerve 2.9-5.6 mm².<br /><br />Dynamic scanning involves following the nerve course, using anatomical landmarks like arteries and bones, and assessing nerve movement with joint motion to detect entrapment or dislocation.<br /><br />Pathological findings include focal hypoechoic enlargement proximal to compression sites. For median neuropathy at the wrist (carpal tunnel syndrome, CTS), CSA >10 mm² and wrist-forearm CSA ratio >1.4 are diagnostic with ~78% sensitivity and 87% specificity; ultrasound is recommended as a first-line diagnostic tool. Ulnar neuropathy at the cubital tunnel appears as focal enlargement (>10 mm²) and hypoechogenicity near the medial epicondyle, with dynamic assessment useful for detecting dislocations or snapping triceps.<br /><br />Ultrasound also aids in diagnosing generalized neuropathies, showing diffuse nerve enlargement in hereditary demyelinating neuropathies and patchy irregularities in inflammatory neuropathies such as CIDP.<br /><br />In summary, ultrasound is an effective, noninvasive adjunct to electrodiagnostic studies, improving anatomical assessment and diagnosis of peripheral nerve disorders, and is increasingly established as a diagnostic subspecialty in neurology and rehabilitation medicine.

Keywords

high-resolution ultrasound

median nerve imaging

ulnar nerve imaging

peripheral nerve evaluation

carpal tunnel syndrome diagnosis

cross-sectional area measurement

dynamic nerve scanning

ultrasound sensitivity vs MRI

nerve entrapment detection

neuropathy ultrasound features