Description of an Alternative Method for the Electrodiagnostic Evaluation of the Sensory Radial Nerve

Objectives: The aim of this study was to describe an alternative method for the electrodiagnostic (EDX) evaluation of the sensory radial nerve (SRN).

Methods: In this retrospective study, all patients from a French EDX center (November 2022-April 2023) for whom SNAP amplitudes of the same SRN were obtained through both a conventional and an alternative method were included. In the conventional method, the active recording electrode was placed at the base of the snuff box, whereas in the alternative method, it was placed 3-4 cm proximally on the lateral border of the radial bone. The SNAP amplitudes of both methods were compared and the ratio of alternative to conventional amplitude was determined within the same patient. A secondary objective was to compare SNAP amplitudes and ratios between patients with peripheral neuropathy and those without (control group).

Results: Among the 117 patients included, the mean ± SD SNAP amplitude was 50.0±28.9 µV in the alternative method compared to 31.0±17.9 µV in the conventional method. The ratio of alternative to conventional amplitudes was 1.64±0.4 in all patients. No significant difference in amplitude ratios was found between the peripheral neuropathy group (1.63 ± 0.4) and the control group (1.65 ± 0.3; p =0.75).

Discussion: The alternative method, based on a more proximal placement of the recording electrodes, consistently provided larger SNAP amplitudes than the conventional method. This method could be useful in particular clinical settings but could prove more challenging in obese or muscular patients.