Routine EMG Research Articles

248 Tremor frequency can be measured using smartphone video

Textbook descriptions of tremulous disorders typically mention the tremor frequencies characteristic of particular conditions, and determination of frequency can aid diagnosis. However, current clinical practice does not involve routine accelerometry or EMG for most tremulous patients, or use of smartphone accel- erometer, and the human eye cannot accurately measure tremor frequency.37 hand videos were recorded with smartphone camera from 5 essential tremor participants, 10 Parkin- son’s participants and 1 functional tremor participant, either showing a hand resting or held in posture. Tremor was simiultaneously measured using a commercially available accelerometer for clinical use (‘Natus Neurology’). The computing technique of ‘optical flow’ was applied to the smartphone video to measure pixel movement over time in two directions perpendicular to the long axis of the hand. Dominant frequencies were extracted from smartphone video optical flow and from clinic accelerometer data using fast Fourier transform.Bland-Altman analysis showed a mean of the difference in measurements between smartphone video (pixel optical flow) and accelerometer of 0.05 Hz (SD 0.16 Hz) with 95% confidence intervals for this mean difference of -0.26 Hz to +0.36 Hz.We demonstrate excellent agreement between our computing method for smartphone video tremor measurement and the gold standard of accelerometry. Our computing technique suggests that neu- rologists already have ‘point and press’ contactless equipment in their pocket that has the potential to augment routine clinical assessment by measuring tremor frequency.stefanwilliams@doctors.org.uk

WS4.2. My Approach to Quantitative EMG (with Demonstration)

The routine needle EMG examination is usually performed by observing the waveforms on the display screen and listening to their sound. It is subjective. Quantitative analysis (QA) is considered time consuming and not used. In this workshop, I will describe the “objective and interactive” approach. It adds elements of QA to record and measure EMG signals. It does not add time for analysis, and provides quantitative data to document abnormalities. The techniques of recording and measurements will be demonstrated. This includes use of dual time base, amplitude trigger, cascaded traces, etc. The “quality” control of the recording will be emphasized. The various signal displays help better assessment of amplitude, duration, phases, turns, stability, and firing rate of motor unit potentials (MUPs). It is also useful to assess the fullness of the interference pattern and its amplitude. The additional information captured by this approach will improve the quality of the needle EMG examination. Finally, I will demonstrate the fully automated methods for MUP analysis (Multi-motor unit analysis) and IP (Turns & amplitude). This requires just a few minutes per muscles. Using modern algorithms, QA is not time consuming. It should be included in the laboratory routine.

S67 Special phenomena in the motor unit during voluntary and electrical activation

Different information is obtained about the motor unit (MU) from various EMG methods. Single Fiber EMG (SFEMG) explores individual muscle fibers and endplates, conventional EMG a larger part of the MU and Macro EMG represents the entire MU. The presentation will first discuss consequences for routine EMG of the temporal and spatial variation in the activation of MUs that may lead to misinterpretation of some EMG features. It will also highlight some physiological parameters of conduction along a muscle fiber based on SFEMG. The muscle fiber velocity shows a short-term facilitation by previous activity, which gives rise to variation in arrival time to the recording electrode, seen both at voluntary and electrical stimulation. During long term activity on the other hand, the velocity decreases, seen and heard as change in frequency spectrum of the EMG signals. A special phenomenon is the decrease in action potential amplitude in some myotonic disorders. A surface recorded amplitude drop at repetitive stimulation seen in these cases not sign of neuromuscular junction disturbance, but reflects amplitude changes of individual fiber action potentials. Amplitude of single fiber action potentials also varies in relationship to just previous activity, with lower amplitude for short intervals, also seen in conventional EMG. Different types of reflexes involving just one or a few neurons can be studied with SFEMG. Different single cell phenomena can be studied in situ in man, and many of these details can be seen in routine EMG, once we are aware of them.

47. Quantitative EMG (qEMG)

Routine EMG studies are based on subjective, ordinal data representing the motor unit action potential (MUAP) electrical activity expressed in qualitative terms that do not have always physiologic bases and it’s very dependent on the examiner experience. Quantitative Electromyography (qEMG) on the other hand evaluates cardinal data and allows to make numerical and statistical comparisons in terms of physical units and it’s more objective. qEMG can detect earlier changes in the morphology of the motor units and help better to understand the natures pathologic changes occurring in neuromuscular disorders. Using a trigger and delay line 20 MUAPS can be obtained and analyzed either manually or automatically. The MUAP direct parameters like amplitude, duration, and number of phases are measured in order to distinguish normal from abnormal, and between neuropathic and myopathic disorders. Evaluating the presence of outliers MUAPs improves the sensitivity. Duration is the parameter that better represents the number of fibers and the spatial distribution of the motor units but determination of its onset and termination is difficult. For this reason, some derivate parameters had been developed. qEMG although takes extra time, improves the sensitivity of the EMG evaluation, but special care is required to correct automatic marking errors.

The study of sleep disorder factors in patients with Guillain–Barré syndrome

In this study, we explore the sleep disorders and its associated factors in patients with Guillain–Barré syndrome (GBS), so as to work out appropriate interventions to promote early recovery of the patients. This study subjects included 49 patients with GBS who had been admitted to the Department of Neurology at The Affiliated Hospital of Hebei University, fulfilling National Institute of Neurological and Communicative Diseases and Stroke (NINCDS) criteria for GBS; 37 cases were male and 12 female (age: 27–68 years). Patients were evaluated once daily for two consecutive weeks. By using Wong and Baker Face Scale (WBFS) to evaluate the numbness and pain in patients, 0 points representing completely no pain and 10 points represents the most severity of the pain reactions; the same applies for numbness. The GBS Disability Scale (GBS DS) is used to evaluate the severity of GBS. The Hospital Anxiety and Depression Scale (HADS) is used to evaluate the anxiety and depression the patient is experiencing. All patients take routine EMG and sleep EEG. The sleep quality of the subjects was evaluated by the Pittsburgh Sleep Quality Index Scale (PSQI) and Richard Campbell Sleep Rating Scale. This study found that the application of ventilators, numbness, anxiety and severe limb movement disorders are the main factors causing sleep disorders. Cerebrospinal fluid (CSF) protein concentration is also associated with sleep disorders. But, no obvious abnormalities were found in sleep EEG. The application of the ventilator, numbness, anxiety and severe limb movement disorder are main factors causing sleep disorders. CSF protein concentration is also associated with sleep disorders.

Sleep scoring made easy—Semi-automated sleep analysis software and manual rescoring tools for basic sleep research in mice

Studying sleep behavior in animal models demands clear separation of vigilance states. Pure manual scoring is time-consuming and commercial scoring software is costly. We present a LabVIEW-based, semi-automated scoring routine using recorded EEG and EMG signals. This scoring routine is•designed to reliably assign the vigilance/sleep states wakefulness (WAKE), non-rapid eye movement sleep (NREMS) and rapid eye movement sleep (REMS) to defined EEG/EMG episodes.•straightforward to use even for beginners in the field of sleep research.•freely available upon request.Chronic recordings from mice were used to design and evaluate the scoring routine consisting of an artifact-removal, a scoring- and a rescoring routine. The scoring routine processes EMG and different EEG frequency bands. Amplitude-based thresholds for EEG and EMG parameters trigger a decision tree assigning each EEG episode to a defined vigilance/sleep state automatically. Using the rescoring routine individual episodes or particular state transitions can be re-evaluated manually. High agreements between auto-scored and manual sleep scoring could be shown for experienced scorers and for beginners quickly and reliably. With small modifications to the software, it can be easily adapted for sleep analysis in other animal models.

Long-term evaluation of clinical outcome after microvascular decompression for trigeminal neuralgia – Langzeitauswertung der klinischen Ergebnisse nach mikrovaskulärer Dekompression bei Trigeminusneuralgie

The treatment of trigeminal neuralgia using microvascular decompression (MVD) is still challenging regarding postoperative outcome. According to the literature a considerable recurrence rate has been observed. In order to support the quality of the clinical outcome, 3D visualization of the MRI data has been used for our preoperative planning to achieve a detailed understanding of the complex neurovascular relationships at the surface of the brainstem as well as routine intraoperative BAEP and EMG monitoring has been applied to avoid neurological deficits during surgery. The achieved results were analyzed in a current study in the short- and long-term follow-up.

Motor unit potential change with contraction level: A concentric macro electromyography study

Motor unit action potential (MUAP) reference values are usually given per muscle and age group. Our aim was to evaluate the change in MUAP size at different contraction levels using the concentric macro (ConMac) EMG technique. ConMac needles were used to record the electrode cannula MUAP and measure its amplitude and area during weak, moderate, and strong muscle contractions. MUAP area and amplitude gradually increased from weak to strong contraction levels in all muscles studied. MUAP amplitudes were larger in distal than in proximal muscles, likely because of a higher fiber density distally. MUAP normal values in the literature per muscle do not take into account the contraction level at which they were recorded and can misrepresent the interpretation of normal. Concentric macro EMG is a simple and useful complement to routine EMG studies and yields additional information on MUAP neurophysiology.

Diurnal fluctuations of human nerve conduction velocity.

In 14 normal subjects, sensory conduction velocity (SCV), determined at constant skin temperature, displayed diurnal fluctuations which were related to similar variations in rectal temperature. Control of surface limb temperature in routine EMG does not completely obviate the variations induced by the body temperature cycle. Diurnal fluctuations should be taken into account when performing serial CV determinations in the same individual.

The Fourth Dorsal Interosseus Pedis Muscle: A Useful Muscle in Routine Electromyography

The aim of the study was to assess the utility of needle examination of the fourth dorsal interosseus pedis (FDIP) muscle in routine EMG. FDIP is an easily accessible muscle and may be less prone to blunt trauma as compared with the other foot muscles but despite its potential utility in electrophysiology, little if any data are available on the FDIP muscle. Detailed neurologic examination, nerve conduction, and needle EMG studies were performed in 118 individuals referred to the EMG laboratory of a tertiary referral center. The FDIP was studied by inserting a needle obliquely at an angle of about 30 degrees immediately proximal to the fourth and fifth metatarsal heads. In 44 subjects (patients/volunteers) with normal studies, <5% had increased insertional activity (IA) in the FDIP, but none had sustained spontaneous activity (SA). Among 32 patients with mixed sensorimotor polyneuropathy, FDIP showed abnormal SA in >90%. In patients with S1 root compromise, 66% had sustained SA in FDIP but none with involvement of L3, L4, or L5 nerve root alone. Two of the four patients with tibial and one of five with peroneal neuropathies had increased SA in this muscle; none with other lower limb focal neuropathies. In patients with lumbosacral plexopathy, FDIP showed denervation potentials with diffuse plexus involvement but not with upper plexopathy. Almost all patients tolerated the FDIP needle examination well. End plates were frequently encountered in the FDIP muscle. We concluded that in normal feet, the FDIP muscle has a low incidence of sustained SA. Abnormal SA in FDIP correlates well with the overall neurologic condition, and it may be a useful muscle to include in routine electrodiagnostic evaluation.

P32.2 Tracking and measuring the compensatory response of neuromuscular systems to disease in routine EMG

P32.2 Tracking and measuring the compensatory response of neuromuscular systems to disease in routine EMG

FC13.2 Assessment and optimization of the number of turns as an alternative to fiber density measurements during routine EMG studies

FC13.2 Assessment and optimization of the number of turns as an alternative to fiber density measurements during routine EMG studies

Multi‐motor unit action potential analysis (MMA)

We have developed an algorithm, called multi-motor unit action potential analysis (MMA), to aid quantification in routine needle EMG examination. In only 5-8 min, it was possible to extract, analyze, and validate 20 motor unit action potentials (MUAPs). In the biceps muscle of normal subjects, the MUAP measurements are compared with measurements using manual, triggered averaging, automatic decomposition, and other MMA algorithms described in the literature. The mean values of MUAP features by MMA fell between the extreme limits obtained from the amplitude-triggered method and the manual method described in the literature. In patients, the results are consistent with routine EMG and similar to those results described in the literature. Fast acquisition and analysis of MUAPs as well as interference pattern (IP) analysis make this technique useful to document EMG abnormalities in routine needle examination.

PS-1-6 Recruitment order in routine EMG

PS-1-6 Recruitment order in routine EMG

Multi-MUP EMG analysis — a two year experience in daily clinical work

A new quantitative motor unit potential (MUP) analysis method, called multi-MUP analysis, is described. Multi-MUP analysis is a type of decomposition analysis of the EMG signal. At each site 6 different MUPs may be recorded during an epoch of 4.8 sec. Calculation time is about 3 sec. A study of 20–30 MUPs including editing takes 4–8 min. Compared to many earlier MUP analysis methods it is faster and more user friendly, therefore it can be used in daily routine EMG analysis. The accuracy and reliability of the method are good. The differences from methods based on manual analysis, spike triggered averaging, template matching and decomposition are discussed. The main advantages of multi-MUP analysis are: (1) quick acquisition of many MUPs; (2) simultaneous collection of several MUPs at one recording site; (3) possibility to analyze not only low threshold MUPs; (4) less bias in the selection of MUPs; and (5) the reproducibility of the results that allow the same reference values to be used in different laboratories. So far we have successfully used this method for 2 years on more than 2000 patients.

Can the size principle be detected in conventional emg recordings?

According to Henneman's size principle, small motor units are recruited before large ones. It is commonly believed that this can be detected in routine conventional EMG recordings even among the earliest recruited motor units. That is, the MUP amplitude, area, and thickness should increase with recruitment order. We studied the first four motor unit potentials (MUPs) recruited within the pickup area of the electrodes. Data were obtained from 179 different sites in monopolar recordings and in 153 concentric recordings from 5 health subjects. In the pooled material, amplitude, area, and thickness increased slightly between consecutively recruited MUPs. However, at individual recording sites the size of consecutively recruited MUPs varied considerably. At some recording sites the first recruited MUP had the largest amplitude and the later MUPs has successively smaller amplitudes. We conclude that, at individual recording sites, the size principle cannot be detected in low threshold motor units with monopolar or concentric EMG electrodes. The reason for this is the small uptake area of these electrodes in relation to the motor unit territory.

Guillain-Barré syndrome: a model of random conduction block.

In the Guillain-Barré syndrome clinical deficit is caused by failure of conduction in nerve fibres. Immunological mechanisms are generally held responsible, but the mechanism has not yet been elucidated. A recent longitudinal analysis of the distribution of lesions along the nerve trunks suggested two main patterns. In one of them, motor conduction block dispersed over the length of the nerve trunk was found, whereas sensory fibres were usually spared. For further pathogenetic studies of this subgroup, it is important to know whether conduction block occurs randomly or at preferred sites. As a tool to establish this, a model for conduction block is presented, based on a random distribution of lesions in the peripheral nerves. It is applicable to compound muscle action potentials (CMAP) obtained in routine EMG studies. Comparison of predicted and measured CMAPs in a first group of seven Guillain-Barré patients with evidence of conduction block supports the concept of a random distribution of lesions in this subgroup.

Painful shoulder in hemiplegic patients: a study of the suprascapular nerve.

The etiology of painful shoulder in hemiplegic patients has not been fully explained. Since it has been shown that a suprascapular nerve lesion can be associated with "frozen shoulder," we have investigated the possibility that a similar lesion may exist in the painful contracted shoulder of hemiplegic patients. Thirty hemiplegic men with shoulder pain were examined and latencies determined for the suprascapular nerve from the supraclavicular fossa to the supra- and infraspinatus muscles on both sides. Routine EMG was also done for the same muscles. Patients' ages ranged from 45 to 85 (means 67 years) and the duration of hemiplegia from 1 month to 13 years (means 30.9 months). Mean latencies of the noninvolved side were 3.2 +/- 0.5 (SD) and 4.2 +/- 0.7 ms to the supraspinatus and the infraspinatus muscles, respectively. Three patients had latencies greater by two SD on the hemiplegic side than on the noninvolved side. Suprascapular nerve block did not relieve the shoulder pain completely in these patients. Excluding these three, mean latencies on the hemiplegic side were 3.1 +/- 0.4 ms to the supraspinatus muscle and 4.1 +/- 0.6 ms to the infraspinatus muscle. It is concluded that a lesion of the suprascapular nerve is not responsible for the painful contracted shoulder of the hemiplegic patient although such a lesion may exist incidentally.

Measurement of rise time of averaged muscle action potential in normal subjects and patients with myopathy.

As a result of diminution of the number of muscle fibers in patients with myopathy, the rise time of the fast negative phase of the spike potentials in the EMG becomes shorter. By using a small special purpose computer (averager) a mean action potential is obtained from which the rise time of the "spike" is determined. In normal muscles the mean value is 509 microseconds (SD 118). Myopathic muscles show a mean value of 225 microseconds (SD 76). There is a slight overlap and uncertainty between 280 and 370 microseconds. Because of the short time needed to examine the muscle for this parameter many muscles may be examined during one routine EMG.

Double discharges in neuromuscular diseases

Double discharges (doublets) of motor units were examined in routine EMG. The material consisted of 132 patients suffering from different neuromuscular diseases and 34 controls in whom the examined muscles were intact. Only m. tibialis anterior and biceps brachii were examined. Activity from at least 10 different motor units per muscle were recorded and analyzed off-line. Modified criteria were used in determining doubling units. Applying the modified criteria no doubling units were found in controls. In myopathies doublets occurred only in myotonic dystrophy and in one case of polymyositis in remission. In neuropathies, the occurrence of doublets was most common in proximal neuropathies. In polyneuropathies and root syndromes doubling units were relatively common, but none were found in exclusively distal neuropathies. It is concluded that doublets have a definite diagnostic value in routine EMG examination.