Abnormal Jitter Research Articles

Diagnostic accuracy of voluntary and stimulated neuromuscular jitter studies in ocular myasthenia gravis.

There is a lack of studies comparing the accuracy of neuromuscular jitter analysis during voluntary activation (v-jitter study) versus axonal stimulation (s-jitter study). The study aimed to compare these two techniques in the same population of patients with suspected ocular myasthenia gravis (OMG). Fourteen control subjects (mean age: 55.5 ± 15.2 years) and 34 patients with suspected OMG (mean age: 59 ± 13.9 years) were prospectively evaluated. Twenty spike pairs and 30 individual spikes were analyzed during v-jitter and s-jitter study, respectively. Two different criteria for abnormal individual jitter values were evaluated: ≥ or > than 10% values exceeding the upper normal limit. OMG was diagnosed in 19 patients based on clinical and laboratory findings, without considering jitter measurements. In most patients, v-jitter and s-jitter analyses provided comparable results. The maximum sensitivity (89%) was achieved with s-jitter study using the ≥10% criterion, while the maximum specificity (93%) was found with v-jitter study using the >10% criterion. Both v-jitter and s-jitter studies showed good to very good accuracy for the diagnosis of OMG, in the absence of any statistically significant difference. Therefore, the patient's cooperation level and examiner's experience should guide the choice of performing v-jitter or s-jitter analysis in patients with suspected OMG.

Research on Solving the Structural Instability of Composite Propellants by Using Non-Ablative Cladding Layers

In a high-temperature test of the gas generator with a free-loading composite propellant, an abnormal jitter appeared in the latter part of the internal ballistic curve, whereas no such abnormality was observed in the low-temperature and normal-temperature tests. To investigate the cause, quasi-steady-state simulations of the internal flow field, as well as strength and buckling simulations of the grain, were conducted. The strength simulation revealed that the maximum stress experienced by the composite propellant during operation at 323 K is 0.7 MPa, which is lower than the ultimate stress of the grain (1.01 MPa), indicating no stress failure. The buckling simulation demonstrated that the instability arises from an imbalance of pressure on the inner and outer surfaces of the grain. In the original structure, the ventilation effect on each surface of the grain varied with the regression of the burning surface, leading to a pressure imbalance on the inner and outer surfaces of the composite propellant. Consequently, a non-ablative cladding layer was applied to ensure that the ventilation effect of each channel remains constant. The simulation demonstrated that the pressure on the surfaces of the composite propellant gradually balanced with the operation of the gas generator. Upon retesting at high temperatures, no abnormal jitter was observed in the internal ballistic curve. This indicates that maintaining a constant ventilation area for the combustion chamber and preventing changes in the ventilation effect can ensure the structural integrity of the composite propellant during operation. The working state of the composite propellant with this non-ablative cladding layer is not affected by variations in the design of the solid rocket motor. This approach enhances the adaptability and reliability of the free-loading composite propellant under different motor structures.

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.

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.

State of charge estimation of lithium-ion battery based on improved forgetting factor recursive least squares-extended Kalman filter joint algorithm

In order to solve the problem that forgetting factor recursive least squares (FFRLS) is prone to abnormal jitter and even divergence under complex working conditions, improved forgetting factor recursive least squares based on dynamic constraint and parameter backtracking is proposed. A joint algorithm of improved forgetting factor recursive least squares and extended Kalman filter (EKF) is used to estimate the state of charge (SOC) of lithium-ion battery. Firstly, parameters of Thevenin equivalent circuit model are identified on-line by the improved FFRLS considering dynamic constraint and parameter backtracking, and then the SOC of lithium-ion battery is estimated by extended Kalman filter. The results show that the improved forgetting factor recursive least squares has high accuracy of battery model parameters identification and the joint algorithm also has high accuracy and robustness of SOC estimation under dynamic stress test (DST) condition, the maximum absolute SOC estimation error is 2.49 % and the average absolute SOC estimation error is 1.39 %.

Tightly-Coupled Fusion of VINS and Motion Constraint for Autonomous Vehicle

In this paper, we develop a novel visual-inertial navigation system with motion constraint (VINS-Motion), which extends the visual-inertial navigation system (VINS) to incorporate vehicle motion information for improving the autonomous vehicles localization accuracy. We introduce the vehicle stop detection module in the pre-processing measurement procedure. During the back-end processing, if the vehicle is detected to be in a stopping state, we perform optimization based on the stop constraint to help eliminate the abnormal jitter of the estimated pose, thus ensuring the reasonability of the trajectory. Otherwise, besides the prior information, IMU measurement residual, and visual measurement residual utilized in VINS, vehicle orientation/velocity constraint built by Ackerman steering model is first exploited to constitute residuals. We minimize the sum of priors and Mahalanobis norms of three kinds of residuals to obtain a maximum posterior estimation, thus increasing system consistency and accuracy. The proposed approach is validated on public datasets and compared with state-of-the-art algorithms, which demonstrates that the motion constraint proposed in this paper improves the standard VINS performance and achieves significantly higher positioning accuracy.

Prevention and Detection Research of Intelligent Sports Rehabilitation under the Background of Artificial Intelligence.

Artificial intelligence can bring convenience to human life. In the field of sports rehabilitation, the application of artificial intelligence is becoming more and more in-depth. This paper is aimed at studying the prevention and detection of sports rehabilitation in the context of artificial intelligence and proposing a compliance control method for lower limb rehabilitation robots based on artificial neural networks. In this paper, a double closed-loop control system is designed: the outer loop is an adaptive impedance control model based on sEMG feedback, and the purpose is to adjust the predicted desired joint trajectories. In the inner loop, a sliding mode iterative learning controller is designed to suppress periodic disturbance and abnormal jitter and achieve stable tracking of the target trajectory. Finally, the control method is simulated and verified by matlab/simulink, and a statistical experiment is done on the patient's recovery. The experimental results show that the use of artificial intelligence technology can effectively increase the sensitivity of the control system and improve the recovery rate of patients. Compared with the traditional sports rehabilitation control system, the sensitivity is increased by 22.7%, and the patient recovery rate is increased by 10.4%, which is of great significance in the field of sports rehabilitation.

Acoustic voice and spectrographic measures in children with the phonological process of devoicing

IntroductionChildren with speech sound disorders (SSDs) who present the devoicing of plosive and/or fricative sounds may have difficulties with glottal respiratory control. ObjectiveTo analyze acoustic vocal measures, spectrographic aspects and the risk of dysphonia among children with devoicing SDDs and compare the results with those of other groups of children. MethodsTwenty-five boys aged between six and 12 years participated. They were divided into four groups: the SSD-devoicing (PPDG), dysphonia (DG), SSDs other than devoicing (PPOG) and control groups (CG). The vocal tasks were recorded, and perceptual-auditory and acoustic voice analyses were performed. The children's parents answered questions about voice-related aspects (to determine a dysphonia risk score). All data were compared among the groups. ResultsDue to the sample size, an effect size analysis was considered, and the results showed possible differences between the PPDG and the other groups in measures of fundamental frequency (F0), jitter, shimmer, harmonic-to-noise ratio, maximum frequency of harmonic definition and dysphonia risk score. ConclusionsThe PPDG showed a high F0 and abnormal jitter and shimmer values. Although the voices of the children in this group had more harmonics than noise, the maximum frequency for defining the harmonics was very restricted. The PPDG had the lowest dysphonia risk score among all of the groups. Variations in F0, jitter and shimmer may indicate difficulties with controlling vocal adjustments, which appear to be hyperfunctional and not to impact vocal projection or voicing.

Vehicle abnormal jitter detection based on multi-task convolutional neural network

In order to overcome the problems of poor convergence, long detection time and high misjudgement rate existing in traditional methods, this paper proposes a vehicle abnormal jitter detection method based on multi-task convolutional neural network. The causes of abnormal vehicle jitter were analysed, and the equivalent taper of vehicles under different mileage was calculated to obtain the abnormal vehicle jitter frequency, and the time-frequency characteristics of vehicle vibration were obtained. The multi-task convolutional neural network is used to establish the calculation model of wheel matching geometric relationship under the condition of dithering, and the dithering degree of the vehicle body at different moments is obtained by sections, so as to realise the detection of abnormal vehicle dithering. The convergence coefficient of the method in this paper is higher than 0.9, the detection time of abnormal jitter is always below 1.2s, and the lowest misjudgement rate is only 0.6%.

Vehicle abnormal jitter detection based on multi-task convolutional neural network

Vehicle abnormal jitter detection based on multi-task convolutional neural network

The prognostic value of diagnostic tools in patients with seropositive myasthenia gravis: a retrospective study of 31 cases

To confirm the diagnosis of myasthenia gravis (MG), in addition to clinical observation of the muscle weakness dynamics, pharmacological and functional tests, Computed tomography/Magnetic resonance imaging (CT/MRI) of the mediastinum, detection of antibodies to acetylcholine receptors (AChR) and to muscle specific tyrosine kinase (MuSK)/; electrophysiological tests are used: rhythmic nerve stimulation (RNS)/decrement test and electro­myography of a single muscle fiber (single-fiber EMG (SF-EMG)/jitter). The aim of our study is to determine the possible relationship between the level of antibodies to AChR and the decrement test value, to verify a correlation between SF-EMG and the severity of MG seropositive to AChR. To evaluate the effectiveness of pathogenetic treatment and prediction of the duration of remission according to the results of the study. A total of 31 patients with myasthenia gravis seropositive to AChR were examined, among whom there were 19 (61.3%) women aged 19 to 74 years. The pattern of muscle weakness was evaluated by a score of the International Clinical Classification of Severity of Myasthenia gravis scale (MGFA). The presence of respiratory failure and its degree was assessed by spirography. The number of antibodies to AChR was determined using enzyme-linked immunosorbent assay (ELISA). The criteria for inclusion in the study were the confirmed diagnosis of seropositive myasthenia gravis with an AChR antibody level of more than 0.5 nmol/L. All patients underwent electrophysiological studies. Patients were examined three times: 1) at the time of visiting the doctor (in the hospital or on an outpatient basis); 2) in 16 and 3) in 24 weeks from the start of the study. Depending on the clinical condition of the patients the following treatment was prescribed: pyridostigmine, methylprednisolone, azathioprine. Statistical analyses were performed using the statistical computing environment R (R Core Team). In the dynamics of observation, a decrease in the level of antibodies to AChR and an improvement in the condition of patients according to the MGFA classification were generally observed but no correlation was found between the severity of MG and the level of antibodies to AChR during the first visit (Kruskal-Wallis test: H (4, N=31)=2.23 p=0.69); during the second visit (Kruskal-Wallis test: H (5, N=31)=9.44 p=0.09), as well as during the third visit (Kruskal-Wallis test: H (2, N=30)=2.74 p=0.25). A correlation was found between the concentration of antibodies to AChR and a thymectomy in the clinical history (Kruskal-Wallistest: H (1, N=7)=3.153752 p=0.07): over time, the level of antibodies decreased. Decrement test deviations were detected in 23 (74.2%) of the 31 patients, SF-EMG – in 20 (95%) of 21 patients. Abnormal jitter was recorded in 100% of cases with a generalized form of myasthenia gravis. During all three visits, a correlation was determined between the highest decrement test of symptomatic muscle and MG severity according to MGFA (r=0.39; p=0.042), (r=0.35; p=0.048), (r=0.41; p=0.039); and also between the jitter value and MG severity (r=0.54; p=0.032) (r=0.35; p=0.048), (r=0.61; p=0.034 respectively). Analysis of the contingency tables using the exact Fisher test provided information on the best method of treating patients. We consider that the most effective prognostic test that may affect the choice of further treatment is SF-EMG. However, due to the difficulties of using this method in routine practice, rhythmic nerve stimulation (RNS) test in clinically weak muscles should be recommended. It is not recommended to monitor antibodies to AChR in order to predict the course of the disease, it is better to use this test only for the diagnosis of seropositive myasthenia gravis.

P-PN007. A case presenting with clinical and laboratory characteristics of fisher syndrome and lambert-eaten myasthenic syndrome (LEMS)

Introduction . Although Fisher syndrome and LEMS are classified into autoimmune neuromuscular diseases, we cannot find the coincidence of them in a single patient in the previous literature. Results . A 70-year-old female was admitted to our hospital because of bilateral hand numbness, double vision and unsteadiness which had developed 2 weeks. She had no history of preceding infection and/or related illness. On admission, her condition was characterized by mydriasis, extraocular muscle weakness, mild proximal muscle weakness and truncal ataxia. In addition, the tendon reflexes were absent at rest, and improved with brief exercise. Motor nerve conduction studies showed significantly low compound muscle action potentials (CMAPs) and increments of more than 200% after brief exercise (post-exercise facilitation) in several nerves. Sensory nerve conduction studies showed significantly low sensory nerve action potential (SNAPs) of median and ulnar nerves, and normal SNAPs of sural nerves. We also demonstrated the impairment of neuromuscular transmission in several muscles based on abnormal decrements in the repetitive nerve stimulation (RNS) test and abnormal jitter in the single-fiber electromyography (SFEMG). Both anti-GQ1b and GT1a ganglioside antibodies and P/Q-type voltage-gated calcium channel (VGCC) antibodies were positive in her sera. Her conditions improved spontaneously. She accomplished walking alone in six weeks, and paralysis of the eye muscles recovered in five months. Median and ulnar SNAPs returned to normal in accordance with recovery of clinical findings. On the other hand, low CMAPs with post-exercise facilitation remained after complete recovery. Positron emission tomography and gastrointestinal endoscopy did not show any malignancy. Conclusion . Some electrophysiological studies revealed the impairment of neuromuscular transmission using RNS and/or SFEMG in patients with Fisher syndrome. Also, it has been known that autoimmune neurological phenotypes are diverse among patients with P/Q-type VGCC antibodies. This may be the first case who showed clinical and laboratory characteristics of Fisher syndrome and LEMS simultaneously.

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.

Concentric Needle Jitter in 97 Myasthenia Gravis Patients.

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%).

Electrophysiological study of neuromuscular junction in congenital myasthenic syndromes, congenital myopathies, and chronic progressive external ophthalmoplegia

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.

Jitter Evaluation in Distant and Adjacent Muscles after Botulinum Neurotoxin Type A Injection in 78 Cases.

To study the jitter parameters in the distant (DM) and the adjacent muscle (AM) after botulinum neurotoxin type A (BoNT/A) injection in 78 patients, jitter was measured by voluntary activation in DM (n = 43), and in AM (n = 35). Patients were receiving BoNT/A injections as a treatment for movement disorders. Mean age 65.1 years (DM) and 61.9 years (AM). The mean jitter was abnormal in 13.9% (maximum 41.4 µs) of DM, and 40% (maximum 43.7 µs) of AM. Impulse blocking was sparse. We found no correlation of the mean jitter to age, BoNT/A most recent injection (days/units), number of muscles injected, total BoNT/A units summated, number of total BoNT/A sessions, beta-blockers/calcium channel blockers use, and cases with local spread symptoms such as eyelid drop/difficulty swallowing. Maximum mean jitter (41.4/43.7 µs) for DM/AM occurred 61 and 131 days since the most recent BoNT/A, respectively. The far abnormal mean jitter (32.6/36.9 µs) occurred 229 and 313 days since the most recent BoNT/A. We suggested that jitter measurement can be done after BoNT/A in a given muscle other than the injected one, after 8 (DM) and 11 (AM) months, with reference >33 µs and >37 µs, respectively.

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.

Sub-clinical neuromuscular dysfunction after envenoming by Merrem’s hump-nosed pit viper (Hypnale hypnale)

Envenoming by hump-nosed pit vipers (genus Hypnale) causes local effects, mild coagulopathy, and rarely, acute kidney injury. Neuromuscular dysfunction has not been clinically reported but, in vitro studies show a weak, reversible, neurotoxic effect on the neuromuscular junction. We investigated the neuromuscular dysfunction in H. hypnale envenoming. Eighteen patients with authenticated H. hypnale envenoming were included. All 18 had serial clinical and neurological examinations. We evaluated neuromuscular dysfunction using stimulated concentric needle single-fibre electromyography (sfEMG) of orbicularis oculi in the patients within two days of the bite and compared to 29 normal subjects. Patients with abnormal jitter were reviewed six weeks later. All 18 patients had local effects and one-third had non-specific systemic symptoms. No patient had clinical features of neuromuscular paralysis. Median jitter values of patients were statistically significantly higher than normal subjects (19.6 ± 13.0 µs compared with 15.6 ± 7.4 µs.). None of the patients or normal subjects had neuromuscular blocks. Three patients had median jitter values higher than the maximum in normal subjects, which returned to normal by six weeks. H. hypnale envenoming leads to sub-clinical neuromuscular dysfunction, despite patients not showing any clinically detectable neurotoxicity.

Electrophysiological Findings of Subclinical Lower Motor Neuron Involvement in Degenerative Upper Motor Neuron Diseases

The present study is an examination of possible subclinical involvement of lower motor neuron (LMN) in patients with primary lateral sclerosis (PLS) and hereditary spastic paraparesis (HSP) electrophysiologically. Nine PLS patients and 5 HSP patients were prospectively analyzed. Jitter measurement with concentric needle electrode (25 mm, 30 G) (CN-jitter) recorded from right extensor digitorum muscle during voluntary contraction with 1 kHz high-pass frequency filter set. European Myelopathy Score (EMS) was used to evaluate disability. The relationship between disability score and jitter values was investigated. HSP patients had suffered from the disease for longer period of time (p<0.001). Mean jitter values of patients with PLS and HSP were 26.5±12.1 µs and 30.8±34.8 µs, and the number of individual high jitters (>43 microseconds) observed in the PLS and HSP groups was 16/180 and 9/100, respectively without a significant intergroup difference. The ratio of patients with an abnormal jitter study were higher in HSP group (60%) compared to PLS (22%) (p<0.05). Potential pairs with blocking were present in HSP group (7 of 100 potential pairs) but not seen in PLS patients. EMS values were significantly lower in patients having potential pairs with high jitter and blocking compared to those without high jitter and blocking. The present study has demonstrated that early signs of LMN dysfunction can be detected electrophysiologically by CN-jitter in patients with UMN involvement. These electrophysiological findings in these patients with longer disease duration and lower clinical scores may be explained by spreading of the disease to LMNs or transsynaptic degeneration and its contribution in disease progression.

Problems in Comparing Jitter Values Obtained with Voluntary Activation and Electrical Stimulation.

Comparing results from jitter studies performed with voluntary and electrical activation is difficult to perform quantitatively, particularly in complex signals as seen in reinnervation. High jitter values in individual spikes in these multispike signals can be missed with both activation methods, which introduces a bias towards more normal values.With voluntary activation, triggering on a spike from an abnormal end-plate in multispike potentials will overestimate individual jitter values and the number of abnormal jitter values.With electrical stimulation, artefactually-increased jitter may be caused by subliminal stimulation, which causes uncertainty at the stimulation point. Electrical stimulation also may activate many axons, causing signal summation, with erroneous or impossible jitter estimation.Awareness of such pitfalls can improve the correct performance and interpretation of jitter recordings. Quantitative comparisons of results can be made between studies in reinnervated muscle performed with the same activation method, but not between results obtained with different activation methods.