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Objective: To evaluate the value of single-fibre electromyography (SFEMG) with monopolar electrode (MNPE) in revealing neuromuscular transmission dysfunction., Material and Methods: We examined the extensor digitorum communis muscle by using single-fibre electrode (SFE) and MNPE sequentially, in randomly assigned 20 healthy volunteers and in 17 patients with known myasthenia gravis (MG). The high-pass filter setting was 3 kHz for MNPE. Ten individual jitter values were calculated for each electrode in every muscle. Repetitive nerve stimulation (RNS) test on trapezius muscle was performed on 15 patients., Results: In controls, the mean jitter values were 27 +/- 9 (10-59) micro s with SFE, and 21 +/- 7.2 (9-56) micro s with MNPE (P = 0.001). In the MG group, the mean jitter values were 52.4 +/- 38 (12-221) micro s with SFE, and 51.8 +/- 34.7 (12-179) micro s with MNPE. Both electrodes identified junction dysfunction in 14 patients. RNS revealed decrement in four patients but 11., Conclusion: SFEMG with SFE is still the gold standard; however, SFEMG with MNPE is superior to RNS like SFEMG with SFE.

Objective: To clarify the optimum trace count for jitter calculation., Materials and Methods: Single-fiber electromyography was performed during voluntary contraction (VC-SFEMG) of extensor digitorum muscle in six healthy and five myasthenic subjects. Twenty single-fiber action potential (SFAP) pairs were recorded from each subject. For each pair, 100 consecutive traces were recorded and stored for off-line analysis. Ten different jitters were calculated in 10 consecutive steps for each SFAP pair by increasing the number of traces included to analysis (from 10 to 100). The jitter calculated in each step was compared with that calculated from 100 traces., Results: Sixty was the optimum number of trace count for both myasthenics and normal controls. Using less than 60 traces for jitter calculation revealed lower values., Conclusion: Jitter calculation should be performed from at least 60 traces in VC-SFEMG. Less numbers yield lower jitter and may cause diagnostic error.