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Background: Little is known about how different outlier estimation methods affect cutoff limits for outliers in single fiber electromyography., Methods: We compared in a prospective fashion the established 18th jitter value (18thjv) method to three, whole-distribution based, outlier detection methods: the interquartile range (IQR), the log-normal, and the Z-score method. The reference limits were probed in a normal cohort and in myasthenia gravis (MG) patients., Results: Differences in outlier cutoff values between the different methods were in the range of 2 μs. The number of abnormal muscles according to the computed criteria was similar for all four methods in the control group. Classification metrics (sensitivity, specificity, Youden's statistic, and predictive values) were also similar among the different methods. In the MG group, however, the Z-score method failed to identify the abnormal jitter values. Accordingly, Kappa agreement was substantial to perfect (0.658 to 1) between the three methods (18thjv, IQR, and log-normal), but was equivalent to chance between the three methods and the Z-score in the MG group., Conclusions: The established 18thjv method proved largely robust when compared to whole-distribution based methods, and its use in clinical practice is justified. Simple estimation of outlier limits by adding two SDs to the mean of the data, leads to unacceptable deviations from the true cutoff values. Moreover, in a clinical scenario in which the final electrodiagnosis depends only on the number of outliers, it is meaningful to accept a tolerance zone of about 2 μs, which is the approximate variation range among the different methods., (© 2020 Wiley Periodicals LLC.)

Fatigability is the hallmark of myasthenia gravis (MG). It is not clear, however, whether there is an analogous increase in jitter during the course of a single fiber electromyography (SFEMG) session. The individual jitter values of all potentials of 76 normal and 44 myasthenic orbicularis oculi muscles were assigned a rank number according to their temporal order in which they were collected and linear regression was performed to determine if the slope of the regression line was significantly different from zero. Control and MG subjects displayed rather flat linear regression lines with non-significant positive or negative slopes. Accordingly, ROC analysis yielded areas under the curve near 0.5. We conclude that there is no systematic jitter increase during the collection of 20 potential pairs in a typical SFEMG session.

The aim of this study was to record all patients referred to a private outpatient clinic for electrodiagnostic consultation during one calendar year. The demographic data of the patients, the specialty of the referring physicians, the referral diagnosis, the electromyographic (EMG) diagnosis and the concordance of referral and EMG diagnosis among all the referring physician's specialties were recorded. There were one thousand patients (385 men and 615 women). 65.7% of the patients were referred from orthopedists and 22.4% from neurologists. EMG was normal in 498 patients (49.8%). Abnormal in 47.3% of the patients referred by orthopedists and 58.9% of those referred by neurologists. Carpal tunnel syndrome (CTS) was the most frequent electrophysiological diagnosis (26.8%), followed by polyneuropathy (8.9%), radiculopathy (7.1%) and mononeuropathy (4.6%). In this study electrodiagnostic consultation was abnormal in only half of the referred patients. The high proportion of normal EDX tests in this study denotes the need for more accurate clinical diagnosis in order to reduce the time spent and resources. The orthopedist is the initial physician to whom patients with neuromuscular symptoms are seen in the majority of cases. Neurologists seem to be more familiar with neuromuscular symptoms and diseases., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Purpose: The aim of our study was the comparison of active denervation (fibrillation and/or positive sharp wave potentials) in thoracic paraspinal muscles with rectus abdominis in patients with definite amyotrophic lateral sclerosis., Methods: Ninety-five consecutive patients with clinically definite amyotrophic lateral sclerosis according to the revised El Escorial criteria were studied prospectively over a 5-year period. Concentric needle electromyogram was performed in thoracic paraspinal muscles, in the rectus abdominis at the T9 level, and in limb muscles., Results: Active denervation was present in thoracic paraspinal muscles in 75 patients (79%) and in rectus abdominis in 62 patients (65.3%) (P = 0.02). No significant difference was found between the two muscles regarding the type of onset (bulbar, upper, and lower limbs), amyotrophic lateral sclerosis functional rating scale values, and creatine phosphokinase levels., Conclusions: Thoracic paraspinal muscles are the first to be tested in patients with amyotrophic lateral sclerosis. Absence of active denervation in T-PSM is rarely associated with active denervation in rectus abdominis.

To assess the rate of fibrillation and/or positive sharp waves (FPSW) in the paraspinal muscles (PM) of patients with chronic lumbosacral radiculopathy, PM and leg muscles of 179 patients, 111 men and 68 women, aged 24-68 years (mean 49.0 +/- 9.3), were tested. Illness duration ranged from 8 months to 40 years (9.4 +/- 7.5 years). FPSW were detected in 38 patients (21.2%). In 28 of them (15.6%), FPSW were present in the limb muscles only, in eight (4.5%) in both PM and limb muscles, and in two (1.1%) solely in the PM. FPSW were accompanied in all the above patients by chronic neurogenic changes of motor unit potentials. Logistic regression analysis did not show any significant difference between: (i) the patients with and without fibrillations in leg and/or PM muscles, and (ii) between those with FPSW in both the PM and leg muscles and those with FPSW in the leg muscles only, when the effect of age and duration of illness were considered. These suggest that the paucity of FPSW in the PM is rather genuine and does not depend on the timing of the examination. In consequence, PM electromyography seems to be not as valuable in chronic radiculopathy as it is in the acute stage.

Twenty-six patients with unequivocal, clinically and radiologically confirmed cervical myelopathy were investigated electrophysiogically using needle electromyography (EMG), motor and sensory conduction velocity, F-wave latency and the electromyographic recording of the tendon reflexes (TR) of the biceps brachii, brachioradialis and triceps brachii muscles. Normal latency and amplitude values of the reflex evoked compound muscle potentials (T-wave) were calculated from 74 healthy volunteers. Pathological TR were found in 73.1% of the patients, while EMG--which was the next more effective method--was positive in 38.5% of the cases. Eight pathologically delayed T-waves were recorded from muscles with clinically normal or even exaggerated reflexes. TR recording appears to be a useful method in the assessment of segmental functional disturbance in cervical myelopathy.

Abstract: Objective: To explore the presence and grade of denervation in three mimic muscles in facial nerve palsy. Methods: The frontalis, orbicularis oculi (OO), and mentalis muscles were explored in 54 patients with Bell''s palsy, after 30 days from the beginning of symptoms. Concentric needle electromyography, including fibrillation detection, was performed in the three muscles on the affected side. Compound muscle action potentials (CMAP) were recorded on both sides and a CMAP ratio was calculated from each muscle. The House–Brackman scale was used to assess the initial clinical evaluation and the follow-up until recovery. Results: Fibrillation was recorded in 32 patients on the 30th day after the onset and was present in 100% of mentalis and in 90% of frontalis, but in only 34% of OO, a statistically significant difference. The grade of fibrillation in OO was also statistically lower from those in the other two muscles. The 32 patients were grouped according to the presence (A) or not (B) of fibrillation in OO. In group A, CMAP ratios (affected/normal side) did not differ significantly among the three muscles. However, in group B they were significantly greater in OO and frontalis than in mentalis. In between-group comparison, group B muscles had significantly higher CMAP ratios, lower degree of fibrillation, and better functional recovery. Conclusion: In facial palsy, the presence and grade of fibrillation in OO are lower than in frontalis and mentalis muscles and prognosis is more favorable for the non-fibrillating OO group of patients. [Copyright &y& Elsevier]

Abstract: Objectives: Mirror movements (MMs) are unintended and unnecessary movements accompanying voluntary activity in homologous muscles on the opposite side of the body, particularly in distal arm muscles. Congenital MMs may be sporadic or familial. Several mechanisms have been proposed to explain persistent congenital MMs. Hypothesis 1 assumes the existence of an ipsilateral corticospinal pathway, and Hypothesis 2 the activation of both motor cortices. We report a new case of congenital mirror movements in a healthy woman. Methods: Electromyographic recordings and focal transcranial magnetic stimulation (TMS) were used for neurophysiological evaluation. Results: Voluntary contraction of either abductor pollicis brevis (APB) elicited mirror activation of the other APB. Focal TMS of either M1 elicited motor evoked potential (MEP) of normal latency and amplitude in both resting APB. TMS of the left cortex upon maximal contraction of the right APB and mirror contraction of the left APB produced interhemispheric inhibition (IHI) in the former and silent period (SP) in the later. Conclusions: The electrophysiological evaluation using transcranial magnetic stimulation provides evidence of the concurrent action of both mechanisms in this patient. Significance: The combination of more than one hypothesis could be more appropriate for understanding the underlying mechanism in some MM cases. [ABSTRACT FROM AUTHOR]