Comparison of Proximal and Distal Techniques for the Medial Antebrachial Cutaneous Sensory Nerve Conduction Study

Purpose: The medial antebrachial cutaneous (MAC) sensory nerve conduction study (NCS) is a technique performed to evaluate for medial cord/lower trunk plexopathies. Low-amplitude responses and muscle artifact pose technical challenges for MAC NCS. To compare the recorded sensory NCS responses using a proximal MAC (pMAC) NCS technique with a distal (dMAC) technique.To compare the recorded sensory NCS responses using a proximal MAC (pMAC) NCS technique with a distal (dMAC) technique.

Methods: Adults referred to our neurophysiology laboratory for whom MAC NCS were clinically indicated were included. Medial antebrachial cutaneous NCS were performed using dMAC (stimulating at the elbow) and pMAC (stimulating in upper arm) techniques. Amplitudes and peak latencies were compared.

Results: Forty-eight patients (82 arms: 39 right and 43 left) were studied. The mean amplitude difference (95% confidence interval) in right pMAC over right dMAC was 4.4 μV (range, 2.78-6.09 μV; P < 0.0001) and that of left pMAC over left dMAC was 5.23 μV (range, 3.35-7.12 μV; P < 0.0001).

Conclusions: The pMAC technique recorded larger mean amplitudes than the dMAC technique, which may improve the technical reliability and diagnostic accuracy when identifying plexopathies.