Mean Consecutive Difference Research Articles

Concentric needle jitter analysis of the genioglossus muscle in patients with motor neuron disease

ABSTRACT Objectives 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. Methods 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. Results 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. Conclusion CNE jitter analysis of genioglossus muscle may provide an useful information that may be suggestive of a diagnosis of MND/ALS.

Utility of single fibre electromyography (SFEMG)and motor unit number estimation technique (MUNE) in the diagnosis and differentiation of polyneuropathies of different aetiology.

To determine whether single fibre electromyography and motor unit number index can distinguish between axonal and myelin lesions in polyneuropathies. This case-control study was conducted at the Department of Medical Physiology, School of Medicine, University of Duhok, Iraq, and the Neurophysiology Department, Hawler Teaching Hospital, Erbil, Iraq, from January 2021 to March 2022. Group A had patients diagnosed with polyneuropathy regardless of the aetiology, while group B had age-matched healthy controls. Both groups were subjected to single fibre electromyography and motor unit number index as well as conventional nerve conduction study and concentric needle electromyography. Data was analysed using SPSS 26. Of the 140 subjects, 60(43%) were patients in group A; 40(67%) males and 20(33%) females with mean age 55.3±7.2 years. There were 80(57%) controls in group B; 43(54%) females and 37(46%) males with mean age 53.81±7.15. Group A had significantly higher single fibre electromyography jitter, and mean consecutive difference (MCD) values than group B (p<0.05). Group A patients with axonal polyneuropathy had a higher mean jitter (MCD) value (36.476.7ms) than those with demyelinating polyneuropathy (23.262.31 ms) (P <0.05). Patients in group A had a motor unit number index value with a significantly lower mean value (p<0.05) when compared to the controls. Axonal polyneuropathy patients had a lower MUNIX value (99.612.8) than demyelinating polyneuropathy patients (149.845.7) (P< 0.05). Single fibre electromyography and motor unit number index could help differentiate between the pathophysiology of axonal and demyelinating polyneuropathy.

Muscle fiber conduction velocity in situ revisited: A new approach to an ancient technique.

The aim of this study was to measure the muscle fiber conduction velocity (MFCV) in situ in the tibialis anterior muscle in healthy subjects. A total of 36 subjects matched for age and sex were studied. The MFCV was measured with a concentric needle by intramuscular monopolar needle electrical activation at a distance of 50 mm. The mean consecutive difference (MCD) of <5 μs was obtained after a median of 62 muscle fiber action potentials (MFAPs), confirming a direct muscle fiber activation. The measuring latency was at the median point of ascending depolarizing line of the MFAP. The calculated MFCV from 784 MFAPs was 4.10 ± 0.66 m/s, 3.99 ± 0.57 for female subjects (95%, 2.85 to 5.13), and 4.20 ± 0.73 for male subjects (95%, 2.74 to 5.67). The MFCV was 5.22% faster in male subjects. The calculated fast-to-slow MFCV ratio (F/S ratio) was 1.47 for female subjects (95%, 1.27 to 2.54) and 1.67 for male subjects (95%, 1.31 to 3.74). Aging significantly increased the F/S ratio. As the MFCVs mainly depend on the muscle diameter, their assessment is a quick and helpful tool for estimating it. Its variability by the F/S ratio is also a powerful tool in the follow-up of some neuromuscular disorders.

P.108 Clinical and electrophysiological evaluation of fatigue in adult patients with spinal muscular atrophy (SMA)

Fatigue is common in SMA, and negatively interferes with quality of life of affected individuals, especially in repetitive daily activities. Despite that, few studies assessed potential electrophysiological correlates of fatigue in late-onset SMA. To assess fatigue severity and its correlation with neuromuscular jitter in a cohort of 25 adult patients with SMA. Fatigue was quantified with 2 scales: the modified fatigue impact scale (MFIS) and the fatigue severity scale (FSS). Simultaneously, concentric needle evaluation of the stimulated jitter in the frontalis muscle was performed. Jitter was expressed as the mean of mean consecutive differences (MCD) in at least 100 potentials. Three distinct MCDs were obtained in each evaluation. The motor function measure (MFM), expanded Hammersmith motor functional scale (HFMSE) and revised upper limb module (RULM) scales were used to assess motor function in each individual. There were 16 men and 9 women, with a mean age of 33.4 years. Mean MFM, HFMSE and RULM scores were 46.59, 21.08 and 22.82, respectively. Regarding fatigue, mean FSS and MFIS physical scores were 3.1 (max possible of 7) and 20 (max possible of 36). Considering an upper normal limit of 28 us, thirteen subjects had abnormal jitter results (mean=32.69us), whereas 12 had normal results (mean=17.97us). The proportion of patients with abnormal jitter was significantly higher among patients with more severe fatigue (FSS score>4) compared to those with less severe fatigue (FSS score<4) (p=0.04). Although preliminary, these results indicate that neuromuscular junction failure may play a role in SMA-related fatigue and jitter may be a neurophysiological marker to assess fatigue in this condition.

Electrophysiologic evaluation of myasthenia gravis and its mimics: real-world experience with single-fiber electromyography

ABSTRACT Objectives In centers which routinely perform single fiber electromyography (SFEMG) for suspected myasthenia gravis (MG), the additional benefit of other neurophysiologic investigations and the frequency of myasthenia mimics has not been ascertained. We aimed to illustrate the range of neurological and non-neurological myasthenia mimics referred for evaluation, and contrast features of their electrophysiologic evaluation with confirmed MG. Methods We reviewed all SFEMG studies performed at our center between 1 January 2018 and 31 December 2020. Patient demographics, clinical phenotype, antibody status and final diagnosis were recorded. Electrophysiologic findings were correlated with clinical features and sensitivity analyses performed. Results A total of 528 SFEMG studies were performed, of which 213 (41%) were abnormal. A diagnosis of MG was made in 101 individuals, including 46 with ocular MG and 35 with seronegative disease. Compared to myasthenia mimics with an abnormal SFEMG, individuals with MG had higher median jitter (mean consecutive difference 61 μs vs. 42 μs, p < 0.001) and a greater percentage of abnormal pairs (61% vs. 33%, p < 0.001) on SFEMG. Repetitive nerve stimulation was abnormal in 27.1% of people with MG and was associated with a generalized clinical phenotype (OR 4.17; 95% CI 1.67–10.48). Thirteen (2%) individuals with MG had normal SFEMG, of whom 10 were in clinical remission. Functional neurological disorders, cranial nerve palsies, primary ocular disease and myopathy were frequent myasthenia mimics. Conclusion SFEMG can be abnormal in a number of myasthenia mimics, and routine nerve conduction studies and electromyography should always be undertaken. In centers where SFEMG is performed routinely for the investigation of suspected MG, extensive proximal repetitive nerve stimulation can be foregone without substantially affecting diagnostic evaluation. Normal SFEMG in those with confirmed myasthenia gravis may help indicate clinical remission.

Concentric needle jitter: Reference values in stimulated Tibialis Anterior muscle.

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.

Impaired neuromuscular transmission in facial muscles of amyotrophic lateral sclerosis: A single‐fiber electromyography study

AbstractBackgroundDecremental responses in repetitive nerve stimulation studies have been reported in the limb muscles of patients with amyotrophic lateral sclerosis (ALS).AimTo reveal the function of neuromuscular junction (NMJ) in the frontalis muscle, which is less affected in ALS.MethodsWe performed axonal‐stimulated single‐fiber EMG studies in the frontalis muscles in 27 patients with ALS, 32 with myasthenia gravis (MG), and 12 healthy controls were performed.ResultsThe mean value of mean consecutive difference (MCD) in ALS was greater than controls (P &lt; .05), but smaller than MG (P &lt; .01) [ALS; 26.5, MG;47.7, control;16.4 (µs)]. The percentage of endplates with increased jitter (MCD &gt;51μs) in ALS was also greater than controls (P &lt; .001) but smaller than MG (P &lt; .001) [ALS; 7.7, MG; 29.4, control; 0.8 (%)]. In ALS, the mean MCD was negatively correlated with the bulbar subset of ALS functional rating scale revised (ALSFRS‐R) (r = −0.67, P &lt; .01). No axonal blocking was observed in all cohorts. In the facial muscles that are relatively preserved in ALS, jitter in single‐fiber EMG was significantly increased, possibly caused by dysfunction of the presynaptic NMJ and motor nerve terminals.ConclusionsAssessment of neuromuscular transmission could provide a new insight into the pathophysiology of motor nerve terminal dysfunction in ALS.

Physical and Mental Fatigue in Subjects Recovered from COVID-19 Infection: A Case-Control Study.

PurposeMuch effort has been directed toward studying COVID-19 symptoms; however, the post–COVID-19 phase remains mysterious. The aim of this work was to conduct a clinical and neurophysiological evaluation of physical and mental fatigue in COVID-19 long-haulers and to study whether markers of COVID-19 severity are able to predict the likelihood of developing postinfectious fatigue syndrome (PIFS) in such patients.Patients and MethodsThis case–control study was conducted on 46 COVID-19 long-haulers who met the criteria for PIFS and 46 recovered COVID-19 subjects without any residuals. Clinical assessment of fatigue was done using a fatigue questionnaire. Repetitive nerve stimulation and single-fiber electromyography were done after excluding neuropathy and myopathy.ResultsThe median value for physical fatigue was 4 (IQR 2–7), while that for mental fatigue was 2 (IQR 0–3). Each day’s increase in the period of COVID-19 illness increased the odds of PIFS in COVID-19 long-haulers 1.104-fold, and each unit increase in ferritin increased the odds of PIFS 1.006-fold. A significant decrement in at least one muscle was observed in 50% of patients. Patients with PIFS had significantly higher mean consecutive difference (MCD) in the extensor digitorum communis than the control group. There were statistically significant positive correlations between MCD values and physical, mental, and total fatigue scores.ConclusionHigher ferritin levels and prolonged COVID-19 infection were independent predictors of PIFS in COVID-19 long-haulers. There was electrophysiological evidence of abnormalities in the peripheral portion of the motor unit in COVID-19 long-haulers with PIFS.

Dispersion of mean consecutive differences in single-fiber electromyography increases diagnostic sensitivity for myasthenia gravis.

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, 26.3μs; 13.5μs [median]; P< .0001), MCD SD (MG: control,12.8μs; 5.1μs [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 7.2μs, 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.

Experimental sleep restriction increases latency jitter in pain elicited cortical responses

ObjectivePrevious studies have shown increased pain scores to painful stimulation after experimental sleep restriction, but reduced or unchanged magnitude of the event related potentials (ERPs) when averaged in the time-domain. However, some studies found increased response magnitude when averaging in the time-frequency domain. The aim of this study was to determine whether ERP-latency jitter may contribute to this discrepancy. MethodsNinety painful electrical stimuli were given to 21 volunteers after two nights of 50% sleep restriction and after two nights of habitual sleep. ERPs were analyzed in the time-domain (N2-and P2-peaks) and time-frequency domain (power spectral density). We quantified latency jitter by the mean consecutive difference (MCD) between single-trial peak latencies and by phase locking value (PLV) across trials. ResultsP2-MCD increased from 20.4 ± 2.1 ms after habitual sleep to 24.3 ± 2.2 ms after sleep restriction (19%, p = 0.038) and PLV decreased from 0.582 ± 0.015 after habitual sleep to 0.536 ± 0.015 after sleep restriction (7.9%, p = 0.009). We found no difference for N2-MCD. ConclusionsOur results indicate that partial sleep restriction increase latency jitter in cortical responses to experimental pain. SignificanceLatency jitter may contribute to the discrepancies between ERP-responses in the time-frequency domain and time-domain. Latency jitter should be considered when ERPs are analyzed.

Reference jitter values for the sternocleidomastoid muscle with concentric needle electrodes.

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.

Jitter patterns in conventional concentric needle electromyography recordings of regenerating motor units.

The time interval between two potential components of the same motor unit potential (MUP) is measured for jitter analysis. Enhanced jitter is generally thought to result from impaired neuromuscular transmission as occurs in myasthenia gravis or during reinnervation. Within a database of conventional video-electromyography (EMG) recordings 4 MUP with peculiar jitter patterns were identified. In 1 spontaneously discharging MUP, massive and chaotic jitter was seen with a mean consecutive difference (MCD) of 9.3 ms. In 2 spontaneously discharging MUP a certain potential subgroup jittered relative to the other part(s) of the MUP (MCD 2.0 and 3.3 ms). A jittering satellite was detected in a fourth voluntarily recruited MUP (MCD 0.6 ms). These different jitter patterns recorded with conventional EMG technique may mainly result from dysmyelination. A new look at the contribution of dysmyelination to abnormal jitter is also warranted in single fiber EMG recordings.

Reference Jitter Values for Concentric Needle Electrode of Orbicularis Oculi and Frontalis Muscles Using Voluntary Activation Method in Sudanese Population

Single fibre electromyography is the most sensitive neurophysiological test for the diagnosis of neuromuscular junction disorders, particularly myasthenia gravis. The study aimed at establishing concentric needle (CN) normal jitter values for voluntarily activated orbicularis-oculi (V-OOc) & Frontalis (V-FRO) muscles in Sudanese population. 57 healthy volunteers (20 males & 37 females) were included in the study (mean Age 43.6 ± 14.2 years, range 18–70 years). V-OOc and V-FRO were tested in the same individual using CN. Jitter values were expressed as the mean consecutive difference (MCD) of 30 potential pairs in microseconds. The mean jitter, mean individual fibre pairs jitter & mean outliers jitter values with (upper 95% Confidence Limit-CL) for [OOc] were [26.9 ± 3.3 (31.97), 26.1 ± 8.9 (41.8) & 38.5 ± 5.7 (49.0) µs] & for [FRO] were [27.1 ± 3.0 (31.32), 26.4 ± 9.4 (42.9) & 39.9 ± 5 (49.2) µs] respectively. The suggested practical upper limits for mean jitter & for outliers were (32, 49 µs) for OOc & (31, 49 µs) for FRO. Our CN-jitter values were within the range of the few published studies. The study was unique in that it established and compared between CN reference jitter values of two voluntarily activated facial muscles (V-OOc & V-FRO) in the same individual in large number of healthy subjects.

Average proportional consecutive interval difference accurately differentiates spontaneous activity from motor unit potentials.

An objective method is required to detect spontaneous activity (SA) for prevalence studies in needle electromyography (EMG). Because of frequent similarities in the morphology of SA and motor unit potentials (MUP), identification of SA depends on assessment of firing regularity, which has not yet been quantitated through a modern interface. Prospective recordings obtained from patients referred for electrodiagnostic evaluation were analyzed by using decomposition-based quantitative EMG (DQEMG) customized to calculate descriptive statistics. Forty-four MUP recordings (39 participants) and 80 SA recordings (62 participants) were analyzed. One hundred one of 124 recordings successfully interfaced with DQEMG. The remaining recordings were analyzed in Audacity. Average proportional consecutive interval differences differentiated SA from MUPs with 97.5% sensitivity (confidence interval [CI] 91.3%-99.7%) and 100.0% specificity (CI 92%-100%). There was substantial overlap, however, for SD and mean consecutive differences. Average proportional consecutive interval difference accurately differentiates SA from MUPs and may be useful in future prevalence studies of SA.

P48-F Exercise provokation of stimulated SFEMG, an attempt to increase the diagnostic yield in myathenya gravis

Single-fiber EMG provides the most useful test in diagnosis of myasthenia gravis suspected patients. Stimulated SFEMG is a useful, easier technique as compared to volitional SFEMG,as it needs lesser cooperation of the patient, in an attempt to increase its diagnostic yield, it is done after exercise, detection of the post exercise exhaustion in the form of increased jitter and neuromuscular blocking. Objective: To estimate jitter values in myasthenia gravis patients pre and post exercise and to detect if any prolongation of the jitter or blocking occur. Methods Twenty confirmed myasthenia gravis patients, being 12 females,8 males (aged 28.34 ± 10.1 years-old). All diagnosed by VSFEMG to be myasthenia gravis, SSFEMG was carried for the EDC muscle pre and post exercise, the parameters for evaluation were Jitter,expressed as the mean consecutive difference (MCD) and presence of blocking. Results The sensitivity of SSFEMG increased from 60% (12 patients) pre exercise to 80% (18 patients) post exercise in the form of prolonged jitter, however 10 patients developed blocking after exercise, while only 5 patients showed blocking pre exercise. Conclusion Exercise provocation for Stimulated SFEMG increased the diagnostic yield in myasthenia gravis diagnosis.

P89-F Neurophysiological findings in 11 cases of dropped head syndrome

Background Dropped head syndrome (DHS) is a rare disorder characterized by weakness of the cervical paraspinal muscles with inability to extend the neck. It can be a part of several generalized neuromuscular processes or secondary to local conditions. Also, a restricted myopathy, “isolated neck extensor myopathy” (INEM), has been described. Material and methods 11 cases of DHS were referred to our Neurophysiology department in the period 2015–2018 for evaluation, with suspected neuromuscular etiology. ENG/EMG, repetitive nerve stimulation, sfEMG or all of them were performed according to the clinical suspicion and findings. Results In 4 patients, neurophysiological studies were compatible with neuromuscular junction disorder (one of them with overlapping myopathic features): findings showed clearly positive repetitive nerve stimulation in facial and spinal nerves. sfEMG mean consecutive difference (MCD) was above 80 μs, with some blocking, in these cases. In 6 patients, EMG proved myopathic changes: mild spontaneous activity in all of them (positive waves, mainly), and short, small motor unit action potentials in 5. Of particular interest, in the myopathic group, sfEMG showed increased jitter in few pairs of fiber, but normal mean jitter and without blocking. In 2 cases, the evaluation could not be concluded. The final diagnosis in 4 cases was myasthenia gravis, and myopathy in 7 (inflammatory myopathy or isolated neck extensor myopathy). All patients improved with specific treatment. Conclusions In our series, miastenia gravis and myopathy (INEM or inflammatory) were the main etiologies. Neurophysiological studies revealed distinctive features in both groups, with high diagnostic yield.

Motor unit recruitment in myopathy: The myopathic EMG reconsidered

Motor unit recruitment is abnormal in myopathies. We have addressed this subject by recording motor unit potentials (MUPs) using a standard concentric needle electrode in tibialis anterior muscles of clinically normal strength in a group of patients with myopathy (15 with myositis and 4 with facioscapulohumeral muscular dystrophy Type 1). In each recording site, a minimal voluntary contraction was sought in order to activate only 2 MUPs. At least 5 pairs of MUPs were recorded in each muscle. We analysed the recruitment rate of the first activated MUP and the mean consecutive difference (MCD) of firing frequency between the individual MUPs of each recruited pair. Results were compared with 30 healthy control subjects. In myopathy the first recorded MUs fired at similar rates to controls (8.2 vs 8.0 Hz, respectively), but the MCD of the firing rate difference between the first two recruited MUPs was less than in controls (median difference 1.78 Hz vs median difference 2.47 Hz, p = 0.02). This change suggests increased lower motor neuron excitability as a functional adaptation, since muscle strength was normal in the studied muscles. These findings are consistent with spinal cord adaptation to the functional changes associated with myopathic muscle disease, although a primary muscle fibre feedback sensing mechanism could also be involved.

T77. Reference values for jitter recordings with concentric needle electrodes on stimulated frontalis

Single fiber electromyography (SFEMG) serves as the most sensitive technique to assess neuromuscular transmission (NMT). In recent years, disposable concentric needle electrodes (CNE) become an alternative to single fiber electrodes for recordings because of concerns about the risk of transmitting infections. Reference values for this new method should be established first before its clinical use in differential diagnosis of neuromuscular junction disorders. We recruited 73 patients, 32 males and 41 females (18–83 years, mean age 52.2 ± 14.0 years), with eyelid, ocular, or weakness symptoms other than myasthenia gravis (MG). None of them had neuromuscular junction diseases, facial nerve palsy or myopathies. The facial nerve was stimulated at the temporal branch with surface electrodes. CNE recorded 20 apparent single fiber action potentials (ASFAPs) from the frontalis for each subjects. Jitter was measured with amplitude level trigger method and expressed as the mean consecutive difference (MCD). The mean MCD were 17.68 ± 3.30 μs for subjects and 17.66 ± 7.81 μs for individual potentials. For ensuring higher specificity, we set the mean values plus 3 SD as the upper normal limits, and figured out the corresponding cut-offs of 28 μs for mean jitter values and 42 μs for jitter values of individual potentials. Our data derived from disease control subjects are similar to those of previous studies by other authors on healthy controls. It is a helpful supplement to the reference value pool of CNE-SFEMG of the frontalis. Introducing patients with confusing diseases into the reference population will increase the ability of this technique to differentiate MG from non-NMT disorders.

Role of concentric needle Single Fiber Electromyography in detection of subclinical motor involvement in carpal tunnel syndrome

BackgroundConventional motor nerve conduction studies are usually normal in early and mild carpal tunnel syndrome (CTS). Single-fiber electromyography (SFEMG) measures the mean consecutive difference (MCD) as an expression of the variability in impulse transmission over the motor endplates and along the nerve fibers distally to the last branching point and along the muscle fibers.Application of concentric needle SFEMG in a group of CTS patients who showed pure sensory abnormalities in nerve conduction studies to examine for subclinical motor involvement.MethodsThirty CTS patients having only sensory involvement proved clinically and by conventional electrophysiological studies were included in addition to 30 control subjects. Concentric needle SFEMG was performed to the abductor pollicis brevis (APB), abductor digiti minimi (ADM), and extensor digitorum communis (EDC) muscles.ResultsThere was a statistically significant difference in the MCD between the patient and control groups in the APB only (p = 0.038).ConclusionsThe results suggest the presence of a subclinical motor median neuropathy at the wrist in patients with early and mild carpal tunnel syndrome and highlight the validity of the concentric needle SFEMG in early neuropathies.Trial registrationPACTR201802002971380 registered 12 February 2018, retrospectively registered.

Differentiating motor phenomena in tilt-induced syncope and convulsive seizures.

We assessed motor phenomena in syncope and convulsive seizures to aid differential diagnosis and understand the pathophysiologic correlates. We studied video-EEG recordings of tilt-induced syncope and convulsive seizures in participants aged 15 years and older. Syncope was defined as (1) loss of consciousness (video-assessed), (2) circulatory changes (accelerating blood pressure decrease with or without bradycardia/asystole), and (3) EEG changes ("slow" or "slow-flat-slow"). We assessed myoclonic jerks and tonic postures of the arms and noted time of occurrence, laterality, synchrony, and rhythmicity (mean consecutive differences of interclonic intervals). Video-EEG records of 65 syncope cases and 50 convulsive seizures were included. In syncope, postures occurred in 42 cases (65%) and jerks in 33 (51%). Fewer jerks occurred in syncope (median 2, range 1-19) compared to convulsive seizures (median 48, range 20-191; p < 0.001). Jerks were more rhythmic in seizures compared to syncope (p < 0.001). Atonia was seen in all syncope cases, while this was not observed in any seizure. Jerks predominantly occurred during the slow and postures during the flat EEG phase. Jerks and tonic postures were common in syncope, but semiology differed from convulsive seizures. The lack of overlap in the number of jerks suggests that less than 10 indicates syncope and more than 20 a convulsive seizure: the "10/20 rule." Loss of tone strongly favors syncope. The EEG correlates imply that jerks in syncope are likely of cortical origin, whereas tonic postures may result from brainstem disinhibition.