2025 Workshop Handout Bundle-W45AS Advanced US of the Lower Limb Nerves

W45AS Advanced US of the Lower Limb Nerves - Shook

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This document presents an advanced overview of the use of high-resolution ultrasound (US) in the evaluation and management of lower limb peripheral nerve disorders, emphasizing its role alongside traditional diagnostic modalities like nerve conduction studies (NCS) and electromyography (EMG).<br /><br />Ultrasound offers excellent resolution and dynamic imaging capabilities that make it ideal for assessing peripheral nerves along their course. However, limitations include difficulty imaging through bone or deep nerves, operator dependence, and the need for significant training. Physicians with neuromuscular and electrodiagnostic experience are well-positioned to develop competency in neuromuscular US.<br /><br />Ultrasound complements electrodiagnostic testing by identifying surgically amenable nerve pathology, variant anatomy, and trauma-related discontinuities earlier than EMG can. It has been shown to have higher sensitivity than MRI for detecting peripheral nerve pathology and better identification of multifocal lesions, often making it the initial imaging choice.<br /><br />Normal nerve anatomy on ultrasound shows a “honeycomb” pattern in cross-section and a “tram track” in the long-axis, with adjacent structures (e.g., blood vessels, tendons) distinguishable by characteristics such as compressibility and anisotropy.<br /><br />In pathology, ultrasound can detect focal nerve swelling (e.g., entrapment, tumors), loss of fascicular architecture, or adjacent masses affecting nerve continuity. For common conditions:<br /><br />- Carpal Tunnel Syndrome (CTS): Increased median nerve cross-sectional area at the pisiform reliably diagnoses CTS; US also identifies structural causes like aberrant muscles or persistent median artery which affect surgical planning.<br /><br />- Ulnar Neuropathy: US localizes ulnar nerve entrapment at the elbow when electrodiagnostic tests are equivocal, identifies anatomical variants, adjacent pathology (ganglia, accessory muscles), and assists prognosis and surgical management.<br /><br />- Peroneal Mononeuropathy: US detects increased cross-sectional area at the fibular head, localizing lesions missed by NCS, especially in axon loss conditions. It also identifies intraneural ganglion cysts, which can be surgically removed with good outcomes.<br /><br />US effectively visualizes peripheral nerve sheath tumors—distinguishing neurofibromas, schwannomas, and malignant tumors based on characteristic appearances—and guides biopsy/surgical planning.<br /><br />In nerve trauma, US enables early detection of nerve transection and neuromas, guiding timely surgical intervention. It remains valuable in post-surgical follow-up to identify complications such as graft discontinuity or scar tissue encasement.<br /><br />Overall, ultrasound significantly enhances the diagnostic accuracy, localization, and management of peripheral nerve disorders when integrated with clinical and electrodiagnostic evaluations, ultimately improving patient outcomes.

Keywords

high-resolution ultrasound

peripheral nerve disorders

lower limb neuropathy

nerve conduction studies

ncs

electromyography

EMG

carpal tunnel syndrome

CTS

ulnar neuropathy

peroneal mononeuropathy

nerve sheath tumors

nerve trauma imaging