UNASSIGNED: Difficulty relaxing the genioglossus muscle makes the evaluation of spontaneous activity problematic in patients with motor neuron disease (MND). We performed jitter analysis using conventional disposable concentric needle electrodes (CNEs) of the voluntarily activated genioglossus muscle in patients with and without MND to detect the denervation-reinnervation process.
UNASSIGNED: CNE jitter analysis was performed at the genioglossus muscle in 21 MND(+) patients and 22 MND(-) subjects. The jitter analysis was considered abnormal if the jitter values exceeded these limits for the mean consecutive difference (MCD) or the individual MCD in more than 10% of readings.
UNASSIGNED: Seventeen MND(+) patients (81%) had at least three abnormal individual jitter values whereas denervation findings were obtained in eleven of them during the needle electromyographic examination at genioglossus muscle. None of the MND(-) subjects showed CNE jitter abnormality.
UNASSIGNED: CNE jitter analysis of genioglossus muscle may provide an useful information that may be suggestive of a diagnosis of MND/ALS.

UNASSIGNED: The aim of this study is to demonstrate the conduction disturbance at the neuromuscular junction in a cranial muscle by measuring jitter with a concentric needle (CN) electrode in the diagnosis of Amyotrophic Lateral Sclerosis (ALS) and to investigate the utility of evaluating the peak number as an ongoing reinnervation marker.
UNASSIGNED: Twelve patients diagnosed with ALS were included in this study. Single fiber electromyography (SFEMG) was performed using a CN electrode during the voluntary contraction of the right extensor digitorum communis (EDC) and left frontalis muscles.
UNASSIGNED: In SFEMG from the right EDC muscle, the mean jitter value was high in all of them. The average jitter calculated in EDC muscles was 57.76±24.17 μs. The mean jitter value in the frontal muscles was 28.91±10.21 μs. In all patients, the number of CN electrode peaks was more than 4 in the EDC muscle and above 4 in 91.67% of the frontal muscle.
UNASSIGNED: Detection of high jitter in SFEMG examination indicates that the examined muscle undergoes a denervation-reinnervation process in the case of increased peak number values. When such a determination is made in the extremity muscles, it becomes important for the diagnosis of ALS.

In an active motor unit (MU), the time intervals between the firings of its muscle fibers vary across successive MU activations. This variability is called jitter and is increased in pathological processes that affect the neuromuscular junctions or terminal axonal segments of MUs. Traditionally, jitter has been measured using single fiber electrodes (SFEs) and a difficult and subjective manual technique. SFEs are expensive and reused, implying a potential risk of patient infection; so, they are being gradually substituted by safer, disposable, concentric needle electrodes (CNEs). As CNEs are larger, voltage contributions from individual fibers of a MU are more difficult to detect, making jitter measurement more difficult. This paper presents an automatic method to estimate jitter from trains of motor unit potentials (MUPs), for both SFE and CNE records. For a MUP train, segments of MUPs generated by single muscle fibers (SF MUP segments) are found and jitter is measured between pairs of these segments. Segments whose estimated jitter values are not reliable, according to several SF MUP segment characteristics, are excluded. The method has been tested in several simulation studies that use mathematical models of muscle fiber potentials. The results are very satisfactory in terms of jitter estimation error (less than 10% in most of the cases studied) and mean number of valid jitter estimates obtained per simulated train (greater than 1.0 in many of the cases and less than 0.5 only in the most complicated). A preliminary study with real signals was also performed, using 19 MUP trains from 3 neuropathic patients. Jitter measurements obtained by the automatic method were compared with those extracted from a commercial system (Keypoint) and the edition and supervision of an expert electromyographer. From these measurements 63% were taken from equivalent interval pair sites within the time span of the MUP trains and, as such, were considered as compatible measurements. Differences in jitter of these compatible measurements were very low (mean value of 1.3 μs, mean of absolute differences of 2.97 μs, 25% and 75% percentile intervals of -0.85 and 3.82 μs, respectively). Although new tests with larger number of real recordings are still required, the method seems promising for clinical practice.

Calculating the reference values for jitter parameters utilizing a disposable concentric needle have been already done for the most often tested muscles. Jitter, expressed as the mean consecutive difference (MCD), was measured in the Tibialis Anterior (TA), not routinely tested muscle. Jitter measurement was taken using the intramuscular microaxonal stimulation technique in 32 healthy subjects. The mean MCD and the mean MCD of the 27th value from the 32 subjects had a normal distribution and were 19.79 ± 2.72 μs and 26.88 ± 3.56 μs, respectively. The suggested limit for the mean MCD is ≥ 26 μs and for the individual values is > 34 μs.

OBJECTIVE: The aim of this simulation study was to evaluate the resulting value of jitter measured from a simulated examination recording and to analyze its dependence on both the number of SFPs contributing either to the triggering peak or the non-triggered peak, and time shifting (delays of triggering at the end-plate) of individual SFPs in these paired potentials.
METHODS: We simulated potentials recorded using a concentric needle electrode with two well separated peaks, and performed a simulated examination (consisting of 50 trains of 100 discharges) with an assumed number of fibers forming peaks. For each train, fiber diameters were chosen at random within the allowed ranges. For each discharge the delay of triggering for each fiber at the end-plate was selected at random from an assumed range. The mean jitter values were calculated, together with the median and 95% quantile.
RESULTS: The results suggest that jitter is related to the mean of the individual SFP shifts.
CONCLUSIONS: These findings extend the understanding of reduced jitter measurements using a concentric needle electrode. If more than one fiber forms the peak, then jitter decreases due to averaging of individual time shifts of potentials constituting the peak, rather than due to detection of the SFP with the earliest peak.

Objective: Obstructive sleep apnea (OSA) is a sleep disorder accompanied by intermittent hypoxia. Neuromuscular transmission (NT) is known to be disturbed under chronic hypoxia. In this descriptive study, it has been aimed to test NT under intermittent hypoxia in OSA. Methods: Thirty-nine newly diagnosed OSA patients without any comorbidities or conditions that alter NT were included in the study. Jitter analysis was performed using a concentric needle electrode. Results: The mean jitter value of 39 OSA patients was 25.9 ± 3.7 μs. When compared to the mean reference jitter values, patients in the present study had significantly higher jitter (p < 0.001). Seven (17.9%) patients met the electrophysiological criteria for NT failure. Conclusion: The authors propose that intermittent hypoxia can be the trigger for NT failure in OSA. The interaction between increased oxidative stress and disturbed mitochondrial functions may also contribute.

In this study we aimed to investigate the dispersion of mean consecutive difference (MCD) of concentric needle jitter studies of patients with myasthenia gravis (MG) and its effect on diagnostic sensitivity for MG.
One hundred fifty-three patients, including 76 patients with MG and 77 controls with possible MG who later received another diagnosis, underwent stimulated concentric needle jitter studies of the frontalis muscle. MCD mean, standard deviation (SD), and coefficient of variation (CV) were calculated. Diagnostic sensitivity and specificity were determined using receiver operating characteristic (ROC) analyses.
MG patients showed a significantly greater MCD mean (MG: control, 26.3 μs; 13.5 μs [median]; P < .0001), MCD SD (MG: control, 12.8 μs; 5.1 μs [median]; P < .0001), and MCD CV (MG: control, 46.1; 37.5 [median]; P < .001) than those without MG. An ROC curve of SD showed a large area under the curve (0.88), and a cut-off value of 7.2 μs, which was calculated by maximum Youden index, exhibited high diagnostic sensitivity (86%) for MG. Combined MCD mean, outliers, and SD criteria showed higher sensitivity (88%) than conventional criteria alone (82%), at the expense of lower specificity. Five MG patients with normal MCD mean and abnormal MCD SD had only ocular symptoms.
The dispersion of MCD as measured by MCD SD greater than 7.2 μs is significantly increased in patients with MG and may be a useful measure of abnormal jitter in the diagnosis of MG, especially for identifying patients with mild disease.

Objectives: To estimate the jitter parameters (single-fiber electromyography) in myasthenia gravis patients mostly by electrical activation in Frontalis, Orbicularis Oculi, and Extensor Digitorum muscles using a concentric needle electrode. Methods: Between 2009 and 2019, a total of 97 myasthenia gravis patients, 52 male, and mean age 54 years were included. Results: Any abnormal jitter parameter in individual muscles was 90.5% (Frontalis), 88.5% (Orbicularis Oculi), and 86.6% (Extensor Digitorum). Any jitter parameter combining Orbicularis Oculi and Frontalis muscle was abnormal in 100% for the ocular, and in 92.9% for the generalized myasthenia gravis. The most abnormal muscle was Orbicularis Oculi for the generalized, and Frontalis for the ocular myasthenia gravis. The decrement was abnormal in 78.4%, 85.9% for the generalized, and 25% for the ocular myasthenia gravis. The mean jitter ranged from 14.2 to 86 μs (mean 33.3 μs) for the ocular myasthenia gravis and from 14.4 to 220.4 μs (mean 66.3 μs) for the generalized myasthenia gravis. The antibody titers tested positive in 86.6%, 91.8% for the generalized, and 50% for the ocular myasthenia gravis. Thymectomy was done in 48.5%, thymoma was found in 19.6%, and myasthenic crisis occurred by 21.6%. Conclusion: The jitter parameters achieved a 100% abnormality in ocular myasthenia gravis if both the Orbicularis Oculi and Frontalis muscles were tested. There was a high jitter abnormality in generalized myasthenia gravis cases with one muscle tested, with about a 2% increase in sensitivity when a second is added. Concentric needle electrode jitter had high sensitivity similar to the single fiber electrode (93.8%), followed by antibody titers (86.6%), and abnormal decrement (78.4%).

This study was designed to analyze the sensitivity, specificity, and accuracy of jitter parameters combined with repetitive nerve stimulation (RNS) in congenital myasthenic syndrome (CMS), chronic progressive external ophthalmoplegia (CPEO), and congenital myopathies (CM). Jitter was obtained with a concentric needle electrode during voluntary activation of the Orbicularis Oculi muscle in CMS (n = 21), CPEO (n = 20), and CM (n = 18) patients and in controls (n = 14). RNS (3 Hz) was performed in six different muscles for all patients (Abductor Digiti Minimi, Tibialis Anterior, upper Trapezius, Deltoideus, Orbicularis Oculi, and Nasalis). RNS was abnormal in 90.5% of CMS patients and in only one CM patient. Jitter was abnormal in 95.2% of CMS, 20% of CPEO, and 11.1% of CM patients. No patient with CPEO or CM presented a mean jitter higher than 53.6 µs or more than 30% abnormal individual jitter (> 45 µs). No patient with CPEO or CM and mild abnormal jitter values presented an abnormal decrement. Jitter and RNS assessment are valuable tools for diagnosing neuromuscular transmission abnormalities in CMS patients. A mean jitter value above 53.6 µs or the presence of more than 30% abnormal individual jitter (> 45 µs) strongly suggests CMS compared with CPEO and CM.

The aim of this study was to establish reference jitter values for the voluntary activated sternocleidomastoid (SCM) muscle using a concentric needle electrode (CNE).
The study included 39 healthy participants (20 female and 19 male) aged 18-77 y. Jitter was expressed as the mean consecutive difference (MCD) of 80-100 consecutive discharges. Filters were set at 1 and 10 kHz. The mean MCDs for all participants were pooled, and the mean value +2.5 SD was accepted as the upper limit for the mean MCD. The upper limit for individual MCD was calculated using +2.5 SD of the upper 10th percentile MCD for individual participants.
Mean age of the participants was 45 ± 14.5 y. Mean MCD was 16.20 ± 2.23 μs (range: 12-21 μs), and the upper limit of normal for mean MCD was 21.8 μs. The mean value for 823 individual jitters was 23.3 ± 4.61 μs (range: 6.6-36.9 μs), and the upper limit of normal for each individual jitter was 34.6 μs.
The present findings indicate that upper normal limit for mean MCD is 22 μs and for individual data it is 35 μs.