Mehmet Baris Baslo

Prediction of externally applied forces to human hands using frequency content of surface EMG signals

In this work, a new signal processing method was proposed in order to predict externally applied forces to human hands by deriving a relationship between the surface electromyographic (SEMG) signals and experimentally known forces. This relationship was investigated by analyzing the spectral features of the SEMG signals. SEMG signals were recorded from three subjects during isometric contraction and from another three subjects during anisometric contraction. In order to determine force-SEMG signal relationship, higher order frequency moments (HOFMs) of the signals were calculated and used as characterizing features of SEMG signals. Subsequently, artificial neural networks (ANN) with backpropagation algorithm were trained by using the HOFMs. Root mean square difference (RMSD) between the actual and predicted forces was calculated to evaluate force prediction performance of the ANN. In addition to RMSD, cross-correlation coefficients between actual and predicted force time histories were also calculated for anisometric experiment results. The RMSD values ranged from 0.34 and 0.02 in the isometric contraction experiments. In the anisometric contraction tests, RMSD results were between 0.23 and 0.09 and cross-correlation coefficients ranged from 0.91 to 0.98. In order to compare the performance of the HOFMs with a widely used EMG signal processing technique, root-mean-squared (RMS) values of the EMG signals were also calculated and used to train the ANN as another characterizing feature of the signal. Predicted forces using HOFMs technique were in general closer to the actual forces than those of obtained by using RMS values. The results indicated that the proposed signal processing method showed an encouraging performance for predicting the forces applied to the human hands, and the spectral features of the EMG signal might be used as input parameter for the myoelectric controlled prostheses.

Jitter analysis with concentric needle electrode in the masseter muscle for the diagnosis of generalised myasthenia gravis

OBJECTIVES The purpose of our study was to show neuromuscular transmission abnormality in the masseter muscle of generalised myasthenia gravis (MG) patients and to compare motor end-plate failure of the masseter with the extensor digitorum communis (EDC) and periocular muscles. METHODS Motor end-plate function was evaluated during voluntary contraction of the masseter muscle of 20 generalised MG patients aged between 16 and 63 years, as well as 20 age-matched healthy volunteers. The mean jitter value was calculated for each group and compared. The upper limit of normal jitter was also calculated and the number of jitters exceeding this cut-off value was counted for each group for comparison. In MG patients, jitter analysis was also performed in periocular and EDC muscles along with the masseter and the number of single fibre-like potentials with abnormal jitter was counted for each muscle. All tests were performed during the same session with a concentric needle electrode (CNE). RESULTS For the masseter muscle, the mean jitter of all potential pairs was significantly higher in the patient group (24.7 ± 9.6 μs in healthy volunteers, 71.9 ± 41 μs in patients). The calculated mean jitter for the 18th highest value in healthy volunteers was 33.8 ± 5.9 μs (upper 95% confidence limit was 45.6 μs). The number of abnormal jitters (≥ 46 μs) was significantly higher in the patient group (276 out of 402 jitters) compared to healthy volunteers (10 out of 400 jitters). In the patient group, the number of single fibre-like potentials with abnormal jitter was found to be similar for the masseter, periocular and EDC muscles. CONCLUSION The masseter muscle has diagnostic importance in generalised MG. The ratio of high jitters to all of the calculated jitters in a particular muscle was similar for masseter, periocular and EDC muscles. SIGNIFICANCE Jitter analysis of the masseter muscle during voluntary contraction is easy to perform and it was found as informative as other muscles in patients with generalised MG.

Possible reflex pathway between medial meniscus and semimembranosus muscle: an experimental study in rabbits

Meniscus is a well innervated tissue with four types of receptors. These receptors are mainly concentrated at the anterior and posterior horns. Although they are intended to be a part in reflex arc, this function has not been thoroughly evaluated. We hypothesized that electrical stimulation of the normal meniscus would elicit electromyographic activity of the hamstring muscle via the reflex arc. Five adult domestic male rabbits were used in this study. Under general anesthesia, knee arthrotomy and thigh dissection were done to expose medial meniscus and semimembranosus muscle. Menisci were stimulated by Teflon-coated bipolar needle electrodes. Needles were placed in the posterior horn of the medial menisci. Two Teflon-coated monopolar needle electrodes were placed in semimembranosus muscle. A four-channel electromyograph was used for recording. Two different potentials were recorded from the target muscle. The first response had a very short distal latency and its amplitude was changing in accordance with the strength of the stimulus, suggesting that this response was being elicited by direct muscle stimulation. The second delayed response with less amplitude also appeared in some traces. The latency and the amplitude of this second response were fairly stable stating that this delayed response was being generated by a reflex pathway and seen in all subjects.

Repetitive nerve stimulation and jitter measurement with disposable concentric needle electrode in newly diagnosed myasthenia gravis patients

INTRODUCTION The aim of this study was to define the diagnostic accuracy of concentric needle (CN)-jitter in newly diagnosed myasthenia gravis (MG) patients and to compare CN-jitter with repetitive nerve stimulation. METHODS In 30 MG patients, repetitive nerve stimulation in 4 muscles (orbicularis oculi, nasalis, trapezius and abductor digiti minimi) and CN-jitter of extensor digitorum (ED) and frontalis muscles were evaluated. RESULTS Twenty-eight of 30 patients (93%) had high jitter in at least one muscle. Repetitive nerve stimulation was abnormal in 23 of the patients (77%). Eighty-six percent of the patients in whom repetitive nerve stimulation test was negative could be diagnosed with CN-jitter. The most frequent muscle showing abnormal decrement was orbicularis oculi. The results of CN-jitter were similar between patients with different serological groups. Of 13 patients with generalized weakness, all had high jitter in both muscles studied whereas of 17 patients only with ocular weakness, 15 had high jitter in at least one muscle studied. CONCLUSION Abnormal RNS was present in 77% of newly diagnosed MG patients, being less than CN-jitter (93%) but more than antibody positivity (73.3%).

Electrophysiological study of patients with spinocerebellar and Friedreich's ataxia

Presented in: This study was presented in the Turkish Annual Congress of Neurology, Antalya, Turkey (19 November, 2012). Abstract Objective: Spinocerebellar (SCA) and Friedreich’s ataxia (FRDA) patients were selected in order to undergo standardized protocol for the evaluation of bioelectrical activity of their nerves and muscles. We aimed to gather information on the severity and distribution of their peripheral nerve involvement.

S101. A novel automatized F-wave MUNE method: A preliminary analysis

Introduction The aim of this study was to test a novel automatized F-wave MUNE method by comparing its results with those elicited with the manual method performed in patients with amyotrophic lateral sclerosis (ALS) and healthy controls. Methods Ninety F-waves elicited with supramaximal stimuli were recorded from thenar and hypothenar muscles in 10 ALS patients and 4 healthy controls. For manual analysis, F-waves with the same amplitude, latency and shape were selected visually by the same examiner. For automatized analysis, similar signals were grouped according to latencies of negative and positive peaks and peak-to-peak amplitudes in MATLAB by using the original software developed for this study. The mean amplitudes of F-waves repeating more than once were defined as sMUPs and MUNE value for each case was calculated by dividing the CMAP amplitude by mean sMUP amplitude. Results Data of two healthy controls and 1 ALS patient were excluded from the analysis since no repeater F-waves were detected by one of the methods. sMUP and F-wave MUNE values calculated by both methods were found to be highly correlated (Spearman’s rho, p μ V and 406.55  μ V, respectively in thenar muscles and 412.53  μ V and 332.77  μ V in hypothenar muscles). Similar F-wave MUNE values were also calculated by using both methods (26.00 and 28.58, respectively in thenar muscles and 36.04 and 30.18 in hypothenar muscles). Conclusion Our automatized F-wave MUNE method seems to be promising in reflecting motor unit numbers in the hand muscles in patients with ALS and healthy controls.

T40. Comparison of MScanFit MUNE and other parameters derived from the CMAPScan in ALS patients

Introduction The aim of this study was to analyse MScanFit MUNE, D50 and step% values elicited from the CMAP scan curves of thenar and hypothenar muscles in patients with amyotrophic lateral sclerosis (ALS) and healthy controls. Methods Thirty-four ALS patients (31 definite, 1 probable and 2 possible, according to Awaji criteria) and 24 healthy controls were included. CMAP scan curves were recorded from both thenar and hypothenar muscles by applying 500 stimuli. Step% and D50 values were calculated semi-automatically and MScanFit MUNE was calculated by using the freeware version of Qtrac software. Results Mean MScanFit MUNE and D50 values were lower and step% values were higher significantly in patients (48.8, 25.0, 32.5 in thenar muscles and 66.5, 28.9, 17.0 in hypothenar muscles, respectively) as compared to healthy controls (112.5, 45.6, 4.0 in thenar muscles and 124.5, 46.6, 1.1 in hypothenar muscles; p p Conclusion Step% and MScanFit MUNE are parameters correlated with each other and they are sensitive tools in revealing the severities and the courses of the electrophysiological abnormalities in ALS.

F52. Repeater F-waves: Electrophysiologic manifestations of upper or lower motor neuron involvement?

Introduction The aim of this study is to compare repeater F-wave parameters with CMAP amplitudes recorded from the hand muscles (as indicators of the amount of lower motor neuron [LMN] loss) and with the triple stimulation technique (TST) ratios in the same muscles (as indicators of upper motor neuron [UMN] involvement) in 19 patients with amyotrophic lateral sclerosis (ALS). Methods Ninety F-waves were recorded from thenar and hypothenar muscles by supramaximal stimuli applied to the relevant nerves at the wrist level. Repeater F-waves (F rep ) were visually defined as those presented with the same amplitude, latency and shapes. Repeater neuron (RN) index, F rep index, persistances of F-waves, F/M amplitude ratio and the neurophysiologic index (NI) were calculated. By depending our laboratory normals, TST ratio values lower than 82% and 86% were accepted as abnormal showing UMN involvement in thenar and hypothenar muscles respectively. Results TST ratios were abnormal in 13 thenar and 11 hypothenar muscles. None of the F rep parameters showed any significant relationship with the abnormal TST ratios, except the lower F rep index in thenar muscles, in patients with UMN involvement according to low TST ratios. However, there was a strong negative correlation with the CMAP amplitudes and F rep index and RN index values in hypothenar muscle (Spearman’s rho, p Conclusion These findings imply that repeater F waves might be a manifestation of LMN loss more than being a result of UMN involvement.

T78. CMAP scan and scanning EMG in the same muscle: Two cases with post-polio muscular atrophy

Introduction Post-polio muscular atrophy (PPMA) is characterized by new onset or increased weakness in patients with prior poliomyelitis after a stable period of time. Loss of highly reinnervated motor units during ageing has been accused for the development of this syndrome which is also known as “unstable-polio”. These patients have less number of motor units that can be estimated by conventional electrophysiological methods. By showing the large steps, CMAP scan provides information about the amount of collateral reinnervation in the construction of total muscle response (CMAP). As well as the number of motor units, their territory is also an object of curiosity. It is possible to record bioelectrical activity of motor unit lengthwise by scanning EMG and depict the temporal and spatial features of motor unit action potential (MUAP). This presentation aims to combine the findings in CMAP scan with scanning EMG and draw attention to reinnervation status of 2 PPMA patients whose tibialis anterior (TA) muscles were affected in different degrees. Methods Two patients aged 39and 41 years were included. Patient 1 had PPMA for 8 years and his TA muscle strength was 3-/5, whereas Patient 2 showed PPMA findings for 1 year and his TA strength was 4/5. CMAP scan of TA muscle on recently affected side was performed with a commercially available software. In scanning EMG, MU territories were scanned with a concentric needle electrode (CNE) which is attached to a stepper motor. Another CNE is used for sweep triggering with the rate of selected motor units’ firing frequency. Acquired signals were processed by the dedicated software designed by the authors. Results CMAP scan of Patient 1 revealed a 1.65 mV CMAP constituting of 4 very large steps and Patient 2 revealed a 5.5 mV CMAP containing a few smaller steps. In scanning EMG, both patients’ motor units showed increased voltage in different parts corresponding to dense areas arisen from collateral reinnervation. Interestingly, the patient with more pronounced weakness for a longer period revealed both huge steps in his CMAP scan and also showed electrically silent areas in his scanned motor units. On the other hand, the patient with stronger TA muscle did not show very large steps or silent areas in his CMAP scan and MU scan, respectively. Conclusion Loss of dense motor units leads to PPMA. However, in PPMA patients with severe weakness which is depicted by less number of motor units and presence of huge steps in CMAP scan, loss of fractions in motor unit territory might be a principal contributing factor which can only be demonstrated by scanning EMG.

S68 SFAP to MUAP: Temporal and spatial characteristics of MU

Introduction Motor unit action potential (MUAP) represents the summated activity of single fiber action potentials (SFAP) coming from individual muscle fibers those reside in the pick-up territory of recording needle. Calculated features of MUAP give reliable information concerning the architecture of motor unit under investigation but they also depend on the recording site and technique. Methods In this presentation, features of SFAP will be discussed first as a measure of individual muscle fiber conductivity. Then, how MUAP features are changed by moving the needle near to tendon is questioned. Measuring the bioelectrical activity of motor unit across its territory by scanning EMG will be revisited. Results SFAP represents the moving quadrupole in near field recordings. The faster the quardupole moves, the quicker the phases of SFAP change and lead to shorter “spike duration” in turn. The distribution of “spike duration” shows less central tendency in myopathic muscle, which can be related to increased variability among the muscle fibers. Furthermore, moving the recording site near to tendon exaggerates this conduction difference and leads to more spiky and temporally dispersed MUAP, a finding that is especially detected in simulation studies. Scanning the electrical activity of motor unit from side to side informs the examiner about the motor unit structure. New algorithms and methods were developed for extracting features from scanning EMG signals. Conclusion The recorded activity of motor unit during voluntary drive changes by the placement of needle electrode. As it changes, it teaches us a lot!