2025 Workshop Handout Bundle-W88C EDX US upper limb nerve Litchy Boon

W88C EDX US upper limb nerve Litchy Boon
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This document by Drs. William J. Litchy and Andrea Boon from Mayo Clinic provides a detailed guide on performing electrodiagnostic (EDX) and ultrasound studies for proximal upper and lower limb mononeuropathies. It focuses on nerve conduction study (NCS) techniques that are relevant, reliable, reproducible, and reasonably comfortable for both patient and examiner. The paper covers preparation, equipment, electrode placement, stimulation procedures, measurements, troubleshooting tips, and ultrasound guidance for various nerves prone to mononeuropathies. 

General preparation emphasizes skin cleaning, temperature control (limb temperature at 31°C), proper electrode placement, and equipment calibration to ensure accurate and reproducible results. Both motor and sensory nerve conduction studies involve incremental nerve stimulation to obtain maximal muscle (CMAP) or sensory (SNAP) responses, with averaging to improve signal quality.

Key nerves discussed include:

- <strong>Proximal Upper Limb Nerves:</strong>  
  - <em>Spinal Accessory nerve</em>: Tested for shoulder dysfunction; electrode placement from C7 to acromion; ultrasound locates nerve in lateral neck.  
  - <em>Axillary nerve</em>: Evaluated post shoulder trauma; stimulator placed in supraclavicular space; ultrasound identifies C5 root and trunk.  
  - <em>Musculocutaneous nerve</em>: Affects biceps brachii; stimulation high in axilla or supraclavicular; ultrasound tracks nerve near coracobrachialis.  
  - <em>Suprascapular nerve</em>: Injuries often from sports or compression; recording over infraspinatus, stimulation in supraclavicular fossa; ultrasound visualizes from C5 root.  
  - <em>Lateral and Medial Antebrachial Cutaneous nerves</em>: Sensory nerves tested at elbow region, useful in brachial plexopathy evaluation.  

- <strong>Proximal Lower Limb Nerves:</strong>  
  - <em>Phrenic nerve</em>: Evaluated via diaphragm recordings for respiratory integrity; dual electrode montages used; stimulation at lateral neck; ultrasound locates nerve superficial to anterior scalene.  
  - <em>Femoral nerve</em>: Injury common in surgeries/trauma; stimulated in femoral triangle; recording over rectus femoris; needle stimulation may be needed.  
  - <em>Lateral Femoral Cutaneous nerve</em>: Compression neuropathy near ASIS; sensory responses recorded in proximal thigh; ultrasound helps locate nerve.  

Each nerve study includes detailed electrode placement diagrams, stimulation procedures, measurement techniques (latency, amplitude, duration), and troubleshooting strategies addressing artifacts, electrode placement, and measurement errors. Reference values from established clinical neurophysiology sources are provided to allow side-to-side comparisons critical for diagnosing mononeuropathies.

Ultrasound guidance is advocated to improve nerve localization, especially in anatomically challenging regions, enhancing study accuracy. Safety considerations note no known adverse effects from phrenic nerve stimulation and minimal risk even with implanted cardiac devices, with precautions advised.

This practical guide serves as an educational resource for clinicians learning to perform EDX and ultrasound evaluations for proximal limb mononeuropathies, emphasizing technical precision, patient comfort, and diagnostic reliability. Additional clinical context and pathophysiology are beyond the scope but referenced in bibliographic sources for further study.
Keywords
Electrodiagnostic studies
Ultrasound guidance
Proximal upper limb mononeuropathies
Proximal lower limb mononeuropathies
Nerve conduction study techniques
Spinal Accessory nerve
Axillary nerve
Phrenic nerve evaluation
Electrode placement
Nerve localization