Optimal reference electrode placement for accessory and axillary nerve conduction studies

Area of Science:

• Neuroscience
• Clinical Electrophysiology
• Neuromuscular Diagnostics

Background:

• Nerve conduction studies (NCSs) are vital for diagnosing peripheral nerve disorders.
• Accurate electrophysiological measurements depend on optimal electrode placement.
• Proximal motor NCSs, particularly for accessory and axillary nerves, require careful technique.

Purpose of the Study:

• To evaluate alternative reference electrode (E2) locations for proximal motor nerve conduction studies.
• To determine the impact of different E2 sites on the accuracy and reliability of accessory and axillary NCS.
• To identify optimal reference electrode placements for improved compound muscle action potential (CMAP) assessment.

Main Methods:

• Multi-channel recordings were performed using various belly:E2 montages for accessory and axillary nerve conduction studies.
• Recordings were made from trapezius or deltoid muscles, referred to different sites and then to a remote electrode.
• Statistical comparison, including grouped statistics and correlation analysis, was used to analyze response variability and distortion.

Main Results:

• Accessory NCSs showed comparable responses across different belly:E2 montages.
• Axillary NCSs exhibited greater variability with certain reference electrode placements.
• Low amplitude contamination and signal distortion were observed with specific E2 sites, while the sternal reference demonstrated favorable characteristics.

Conclusions:

• Reference electrode (E2) site selection significantly influences the measured compound muscle action potential (CMAP) in NCSs.
• A sternal reference electrode is recommended for accessory and axillary NCSs due to its favorable characteristics.
• Ipsilateral acromion or deltoid insertion sites may yield less representative CMAP values, potentially impacting diagnostic accuracy.