Jitter Values on Voluntary Active Periocular Muscles of Healthy Subjects with Conventional (37 mm) Concentric Needle Electrode

The aim of this study was to re-evaluate jitter values of healthy subjects in whom pairs of single-fiber-like potentials were recorded from voluntary activated periocular muscles using a disposable 37-mm concentric needle electrode (CNE) with 2-kHz low-cut filtering. We reviewed the recordings of 129 subjects (85 women; 44 men; mean age, 43.8±15.3 years). The m. frontalis group included 116 subjects, and the m. orbicularis oculi group included 18 subjects. Jitter values were expressed as the mean consecutive difference (MCD) of 20 different pairs. The mean MCD (n=2680) was 22.5±9.7 μs (range, 5-121 μs), and the upper 95% confidence limit (CL) was 39 μs. The mean of 134 MCD values for each subject was 22.5±3.7 μs (range, 15-33 μs), and the upper 95% CL was 30 μs. The outer limit of the 18th highest MCD values out of 20 recordings for each subject was 31.3±6.5 μs (range, 18-53 μs), with an upper 95% CL of 43.3 μs. Using a conventional 37-mm CNE with 2-kHz low-cut filtering may be a cost effective alternative to a single-fiber electrode in periocular muscles if strict criteria are used for acceptable signals. Jitter values of >44 μs that were calculated from single-fiber-like action potential pairs should alert the physician regarding the possibility of neuromuscular junction disorders and constitute an indication for a further diagnostic investigation.