Close-proximity concentric and modified single fiber electromyographic recordings using revised techniques with a paired wire electrode.

Using a combined concentric (CN) and modified single fiber (MSF) electromyographic needle electrode with both recording surfaces at the tip approximately 25 microns apart, 24 motor unit potentials (MUPs) were recorded from one extensor digitorum communis muscle, triggering from either the CN or MSF channel in equal numbers and averaging both CN and MSF recordings. Filter settings were 20-10,000 Hz. Correlations of MUP amplitude, phases, turns, negative turns (NTs), and main spike duration, but not rise time or duration, between the CN and MSF recordings were statistically significant (P < 0.05). Mean +/- SD numbers of estimated single fiber potentials (ESFPs) and NTs for the MSF recordings were 1.17 +/- 0.38 and 1.54 +/- 0.72. Correlations between numbers of ESFPs and turns, NTs and phases, NTs and turns, and NT and main spike duration for the MSF and CN MUP recordings, respectively, were statistically significant (P < 0.05). The study findings using these techniques continue to support evidence that one or a few muscle fibers contribute to the main spike component of the MUP.