The mean jitter values were analyzed as the calculation of the mean MCD of at least 20 consecutive discharges (9).
In this study, we established reference values for jitter in voluntary activated periocular muscles with a disposable 37-mm CNE, which is the most conventional and most common used in routine electrodiagnosis.
A few laboratories have reported reference values for jitter using a 25-mm CNE and a monopolar needle electrode in different muscles (1,2,3,4,11,14,15,16,17,18).
In practice, we prefer to use the smallest CNE (25 mm) with filter settings of 1 or 2 kHz for neuromuscular jitter analysis.
The retrospective design and obtaining the normative data from the subjects who had been referred to exclude ocular myasthenia are the main limitations of this study Nevertheless, jitter values higher than 44 [micro]s calculated from the single-fiber-like action potential pairs, which were recorded by using a 37-mm CNE with 2-kHz high-pass filtering, should alert the physician to the possibility of neuromuscular junction disorder and constitute an indication for a further diagnostic investigation.
Effect of triggering potential on calculations of jitter in single-fiber EMG.
When studied with CN electrodes, the CN-jitter was recorded as the jitter data listed in the SFEMG program, and the spike number was recorded as the FD listed in the SFEMG program, although the anatomical substrates of the CN-jitter and spike number are different from those of the SFN-jitter and SFN-FD.
In this study, we found that both CN and SFN electrodes showed significantly increased jitter in ALS patients compared with healthy controls.
each spike represents one muscle fiber), which allows for the measurement of FD and jitter between two different muscle fibers.
Our data showed that the mean jitter and spike number recorded with CN electrodes in ALS patients were significantly higher than those in healthy controls.
CN electrodes may be an alternative to SFNs in ALS studies to quantitatively evaluate the changes in jitter and spike number.