2022 Workshop Handout Bundle-Basic US of the Upper Limb Nerves- Median and Ulnar from elbow to wrist

Basic US of the Upper Limb Nerves- Median and Ulnar from elbow to wrist

Pdf Summary

Peripheral nerve evaluation using ultrasonography (US) has become a valuable tool in recent years. US offers several advantages over magnetic resonance imaging (MRI) for peripheral nerve assessments, including lower cost, faster results, real-time imaging, and dynamic testing. Ultrasonography is especially useful in emergency settings and can be used to confirm electrodiagnostic findings and provide additional information about nerve anatomy and surrounding tissues. However, US is operator-dependent and requires proper training for optimal imaging and interpretation of results.<br /><br />Equipment requirements for neuromuscular US range from basic systems costing around $25,000 to more comprehensive radiology systems costing over $300,000. The transducer is the most important part of the device, and a linear array high-frequency transducer is recommended for peripheral nerve US, with a frequency of 6-18 MHz for superficial nerves of the upper extremity.<br /><br />Basic image optimization techniques include adjusting gain for overall brightness, focus for improved resolution, depth to show the desired structure, and frequency to modify resolution and penetration. It is important to distinguish nerves from tendons, and anisotropy can help differentiate between the two. Color Doppler imaging can be used to identify vessels associated with nerves.<br /><br />When performing the scan, the transducer should be held firmly with minimal pressure on the tissues to avoid altering nerve configuration or compressing surrounding veins. Scanning technique involves identifying the nerve and then sliding the transducer along its course, looking for focal changes in size, shape, and echogenicity. Anatomic landmarks such as arteries and bones can be used to locate the nerve.<br /><br />The sonographic appearance of a normal peripheral nerve includes individual fascicules surrounded by a hyperechoic perineurium, giving a honeycomb appearance. Cross-sectional area (CSA) is commonly measured and has established normative values for different nerves. Changes in echogenicity or size along the course of the nerve can indicate pathology.<br /><br />Abnormal nerves may present with focal enlargement proximal to the site of injury or compression. For example, in carpal tunnel syndrome, a CSA cut-off value of >10 mm2 is considered indicative of pathology. Ultrasound has also been shown to be useful in evaluating hereditary and inflammatory neuropathies.<br /><br />In summary, ultrasonography is an effective method for evaluating peripheral nerves and provides additional anatomical information compared to electrodiagnostic testing alone. It is a valuable diagnostic tool for neurologists and physical medicine and rehabilitation physicians.

Keywords

ultrasonography

nerve assessments

real-time imaging

dynamic testing

equipment requirements

cross-sectional area

pathology

focal enlargement

carpal tunnel syndrome

diagnostic tool

CTS