"Facial" and standard concentric needle electrodes are not interchangeable.

Motor unit action potentials (MUAPs) were recorded using a standard concentric needle (SCN), a "facial" concentric needle (FCN) and a monopolar needle (MN) in the biceps brachii and first dorsal interosseous manus muscles of 7 normal subjects. For each muscle, the MUAP durations were similar for all electrodes. However, the FCN electrode more frequently registered high-amplitude MUAPs compared to the SCN electrode. Hence, the FCN and SCN needles should not be considered interchangeable in assessment of EMG signal amplitude. Although, the pattern of changes in amplitude and duration on FCN and MN recordings is similar, the electrodes have different uptake areas.