Axillary motor nerve conduction study: description of technique and provision of normative data

Publication date: Available online 10 February 2018
Source:Journal of Electromyography and Kinesiology
Author(s): Panagiotis Zis, Marios Hadjivassiliou, Dasappaiah Ganesh Rao
BackgroundAxillary nerve lesions can commonly occur secondary to trauma or brachial plexopathy. Our aim was to describe our technique of axillary nerve motor conduction studies and provide the respective normal values.MethodsActive electrode was positioned over the most prominent portion of the middle deltoid, approximately 5-7cm distal to the acromion. Reference electrode was positioned over the acromion. Ground electrode was placed between the active and the reference electrodes. Supramaximal stimulation was at the Erb's point.ResultsA total of 154 participants (61% male, age range 18-84) were included. There was a significant positive correlation between the subjects' age and the onset latency Spearman's rho 0.312, p<0.001) and a significant negative correlation between the participants' age and the CMAP (Spearman's rho -0.481, p<0.001).For the total male population the lower normal value for the CMAP was 7.6mV and the higher normal value for the onset latency was 5.0msec. For the total female population the respective normal values were 6.5mV and 3.5msec.In order to detect an axillary nerve lesion, asymmetry of >40% in the CMAPS between the symptomatic and the asymptomatic side show a sensitivity of 95.2% and a specificity of 96.6%.ConclusionWe described our technique of axillary nerve motor conduction studies and provided the respective normal values stratified for age and gender. When suspecting an axillary nerve lesion it is always worth performing axillary motor NCS bilaterally and compare the CMAPs.



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