Single fiber EMG evaluation in denervation and reinnervation

SFEMG can be used to follow the course of reinnervation. The parameters of fiber density, mean jitter and percent blocking must each be followed and related to the type of injury to determine the stage of reinnervation. The few reported cases in the literature of SFEMG recordings followed over time after nerve compromise are reviewed and an additional case is presented by the author. Mean jitter values can return to normal approximately 1 1/2 years postonset of reinnervation. Some individual recordings may remain abnormal permanently.     

Single fiber macro versus concentric trigger macro EMG: a comparison of methods.

The values obtained from two different macro EMG methods were compared, and found to be different. Normally, macro electromyography (EMG) is performed with a modified single fiber (SF) needle using the SF potential as a trigger; a new method recommends a modified concentric needle and triggers on the concentric EMG signal. The concentric macro EMG has a 40% to 50% smaller amplitude and area values than data obtained with a SF macro EMG needle. The different values are the result of variant spatial relationships of the respective needles to the motor unit under study, and may be due to a recruitment-dependent bias resulting from different trigger properties of the two methods. The concentric macro EMG needle can be used to estimate motor unit size, to scan the unit, and to investigate its different concentric EMG signals.     

Macro EMG follow-up study in post-poliomyelitis patients

We investigated the muscle strength and motor unit (MU) territory of five patients with postpolio syndrome (PPS), six stable patients with prior poliomyelitis, and five healthy volunteers. The MU territory was assessed by measuring amplitudes of motor unit potentials (MUPs) recorded by the macro EMG technique. The investigations were repeated after 11–20 months (mean 15.6). The macro MUP amplitudes in both patient groups were markedly increased (P = 0.02). However, no statistical difference was found between the two groups in the initial amplitude values. Macro MUP amplitudes obtained on repeated examinations did not differ significantly from the initial macro MUP amplitudes in any of the three groups. In three individual PPS patients, a decline in muscle strength on the follow-up study was documented, providing the diagnosis of post-poliomyelitis muscular atrophy (PPMA). The three PPMA patients had the highest initial macro MUPs. Two of them showed a decrease in macro MUP amplitudes on follow-up. These findings suggest that a later breakdown of oversized MUs may play a role in the pathogenesis of PPMA.     

An 8-year longitudinal study of muscle strength,muscle fiber size,and dynamic electromyogram in individuals with late polio

Twenty-one subjects with polio 24 to 51 years prior to the first examination were studied on three occasions, each 4 years apart with measurements of muscle strength and endurance for knee extension, macro EMG, and muscle biopsy from vastus lateralis. On average the muscle strength decreased during the 8-year follow-up by 9–15%. Endurance decreased during the observation period. The muscle fiber area was markedly increased in most subjects. There was a decrease in the capillarization during the follow-up. Macro EMG was increased in all subjects (range 3–42 times control) and increased in 20 legs during the 8-year follow-up, but showed a decrease in 8 of 9 legs with an approximative breakpoint when macro MUPs were around 20 times the normal size. Thus, evidence of on-going denervation/reinnervation as well as of failing capacity to maintain large motor units was demonstrated. SFEMG showed a moderate degree of disturbed neuromuscular transmission. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21: 1428–1437, 1998     

The spectrum of concentric macro EMG correlations. Part I. Normal subjects.

Using a concentric macro electrode, both the concentric and macro action potentials of a motor unit were analyzed for duration, area, and amplitude. Eighty-six different motor units were analyzed from the tibialis anterior muscle in 10 normal subjects. The aim of this work was to compare concentric and macro action potential measurements of the same motor unit. The study revealed significant correlations between concentric and macro samples, with the concentric potential's area correlating better with the macro potential than its amplitude. This shows that the 10 to 15 muscle fibers studied by the concentric electrode serve as a good sample of the motor unit as a whole. We briefly review the technique used in concentric macro EMG, as well as describe the methods used for collecting and comparing both concentric and macro action potentials.     

Single fibre EMG in 6 cases of botulism

ABSTRACT- In 6 cases of mild botulinum intoxication, conventional EMG and single fibre EMG (SFEMG) were performed on admission to our ward (about 15 days after ingestion of the toxin) and 4, 8 and 14 weeks after admission.
In 4 cases, conventional EMG resulted in abnormal findings; and they normalized 4 weeks later. On the first examination, SFEMG revealed in all cases but one the occurrence of potential pairs with abnormal jitter (above 50 μs). The % of the potential pairs with abnormal jitter ranged in different cases from 17% to 44%. Some of the potential pairs with abnormal jitter showed blockings; the occurrence of blockings was not strictly related to jitter value. Mean jitter value and % of potential pairs with abnormal jitter became progressively reduced with increasing time after intoxication. Nevertheless, in 4 cases slightly abnormal findings were still present after 4 months.
The data obtained in the basal condition are in agreement with those reported by others. SFEMG findings relate fairly well to conventional EMG data and clinical status. SFEMG has proved to be a very sensitive method for studying the neuromuscular transmission defect in botulism and in obtaining further information on the course of the syndrome.     

The spectrum of concentric macro EMG correlations. Part II. Patients with diseases of muscle and nerve.

In the second part of this study we investigate the correlations between the concentric and conmac action potentials in motor units of individuals with diseases of muscle and nerve. We studied 86 myopathic and 86 neurogenic motor units and compared their concentric and conmac action potentials. In the patients with myopathy, we found that the concentric motor unit action potential's (MUAP) area correlates strongly with the conmac potential, even better than in normals, while its amplitude correlates less. In the neurogenic group, we found that both the concentric MUAP's area and amplitude correlated very well with their conmac counterpart, more so than in normals. Thus, in pathology, as in normals, measuring the concentric MUAP's area in addition to its amplitude adds to the diagnostic sensitivity of motor unit potential measurements. These findings are discussed in light of the known dynamic and architectural motor unit changes which take place in the myopathic and neurogenic motor unit.     

Single fiber EMG and cardiovascular reflexes in botulism: a follow-up study

A patient with botulism was studied at different times after intoxication using various autonomic tests of the cardiovascular reflexes, and by single fiber EMG (SFEMG). The control of heart rate and blood pressure appeared markedly impaired in the early stage of the disease as well as SFEMG. Autonomic function recovered more slowly as neuromuscolar transmission. Monitoring autonomic derangement in botulism may give the opportunity to select patients at risk for cardiac or respiratory arrest.

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Sommario Un paziente affetto da botulismo è stato studiato a vari intervalli di tempo dall'intossicazione mediante tests di esplorazione vegetativa ed elettromiografia di singole fibre. Si è osservata nella prima fase della malattia una marcata compromissione del controllo della pressione arteriosa e della frequenza cardiaca, oltrechè una notevole anormalità funzionale della placca motrice. La ripresa della funzionalità vegetativa è apparsa più lenta di quella della trasmissione neuromuscolare. Il monitoraggio delle alterazioni vegetative nel botulismo può permettere di selezionare i pazienti a rischio per un improvviso arresto cardiaco o respiratorio.

     

Comparison of sensitivities of macro EMG and concentric needle EMG in L4 radiculopathy

Abstract. The purpose of this study was to compare the sensitivities of macro EMG (mEMG) and concentric needle EMG (cnEMG) in showing abnormality in L4 radiculopathy. We evaluated 23 patients with clinically and radiologically proven L4 root lesions. Among these patients, 21 (92%) had cnEMG abnormalities. Out of 21 patients with cnEMG abnormality, 3 (14%) had fibrillations and positive sharp waves, 8 (38%) had interference pattern abnormality and all of them had motor unit potential (MUP) abnormality on quantitative MUP analysis. Seventeen patients (74%) had mEMG abnormality. Diagnostic yield of cnEMG is higher than mEMG in L4 radiculopathy. mEMG may not contribute much to the diagnosis of lumbar radiculopathy.Presented in part at the 18th Annual Meeting of the Turkish Clinical Neurophysiology EEG-EMG Society, June 2002, Turkey.     

Comparison between concentric needle EMG and macro EMG in patients with a history of polio.

OBJECTIVES: Acute poliomyelitis causes degeneration of anterior horn cells, followed by denervation. Reinnervation and muscle fibre hypertrophy are mechanisms that compensate this loss of neurones. Concentric needle EMG (CNEMG) and macro EMG are two methods to assess the magnitude of initial involvement and the compensatory reinnervation. The aim of this study is to explore the difference between CNEMG and macro EMG describing the status of the motor unit in patients previously affected by polio. METHODS: Macro and concentric needle EMG investigations were performed in 261 muscles in 121 patients with a remote history of polio. RESULTS: CNEMG was abnormal in 211 muscles, macro EMG was abnormal in 246 muscles. The macro amplitude was 3-4 times 'more abnormal' than CNEMG amplitude relative to the reference values. CNEMG duration was less abnormal and showed only weak correlation with macro amplitudes. The most likely explanation for the difference in magnitude of deviation from reference values for CNEMG and macro EMG, is a more pronounced 'phase cancellation' between single fibre action potentials in CNEMG. This is supported by simulation studies reported here. CONCLUSIONS: In conclusion macro EMG better reflects the size of the motor unit than the CNEMG. For detection of concomitant disorders, CNEMG is the method of choice.     

Guidelines for single fiber EMG

This document is the consensus of international experts on the current status of Single Fiber EMG (SFEMG) and the measurement of neuromuscular jitter with concentric needle electrodes (CNE – CN-jitter). The panel of authors was chosen based on their particular interests and previous publications within a specific area of SFEMG or CN-jitter. Each member of the panel was asked to submit a section on their particular area of interest and these submissions were circulated among the panel members for edits and comments. This process continued until a consensus was reached. Donald Sanders and Erik Stålberg then edited the final document.     

Pyridostigmine treatment of post-polio syndrome fatigue: a single fibre EMG study

Electrophysiological data suggest that impairment of neuromuscular junctions transmission (NMT) may be in part responsible for the fatigability affecting the majority of patients suffering with post-poliomyelitic syndrome (PPS). The effect of the anticholinesterase medication pyridostigmine in PPS patients was evaluated by means of voluntary activation single fibre electromyography (VA-SFEMG), a technique that is very sensitive in revealing neuromuscular transmission disturbances. Fourteen patients fulfilling the clinical criteria for PPS were included in the study. Muscle strength assessment and VA-SFEMG were performed in basal conditions and 1 week after oral administration of pyridostigmine bromide (MESTINON) 60 mg tablet every 8 h. The treatment induced a statistically significant improvement of neuromuscular junction transmission in most PPS patients, including patients with only musculoskeletal symptoms and with post-poliomyelitis progressive muscular atrophy. Pyridostigmine medication also produced an improvement of reported fatigue in about 70% of fatigued patients.     

Prognostic value of EMG genioglossus involvement in amyotrophic lateral sclerosis

ObjectiveTo evaluate the prognostic value of needle electromyography (EMG) genioglossus involvement in patients with amyotrophic lateral sclerosis (ALS) at diagnosis.MethodsWe separately explored the prognostic value of clinical bulbar lower motor neuron (LMN) signs and EMG genioglossus involvement using Cox proportional hazard models adjusted for age, gender, diagnostic delay, presence of bulbar upper motor neuron (UMN) signs, EMG cervical and lumbosacral region involvement, ALSFRS-R score and C9Orf72 gene status. Then, we compared the prognostic value of EMG masseter and genioglossus abnormalities in a subset of patients in whom both muscles were analysed.Results103 ALS patients were included in the study. Neurophysiological genioglossus involvement was associated with a shorter survival (p = 0.002), a shorter time to moderate dysphagia (p = 0.0001) and to severe dysarthria (p = 0.012). Its prognostic value was still evident in patients without clinical bulbar LMN signs. Bulbar clinical LMN signs were only associated with an earlier onset of moderate dysphagia (p = 0.0001). EMG masseter abnormalities did not reach statistical significance with regard to all the clinical milestones.ConclusionsGenioglossus EMG at diagnosis could provide important information about ALS progression rate. The masseter muscle seems to be less involved in ALS.SignificanceEMG genioglossus involvement is a prognostic factor in ALS.     

Distant effects of locally injected botulinum toxin: a double-blind study of single fiber EMG changes

We used single fiber electromyography (SFEMG) to study 42 patients who had enrolled in a double-blind, placebo-controlled trial undertaken to assess the efficacy of botulinum toxin (BTX) injection of neck muscles to treat torticollis. SFEMG in a limb muscle was performed before treatment, 2, and 12 weeks after injection of placebo or BTX. Before treatment, the mean jitter was 26.8 microsec in patients who were to receive BTX, and 25.7 microsec in the placebo group. Two weeks after injection, mean jitter in the group receiving BTX was 43.6 microsec. In the placebo group, it was 26.5 microsec (P = less than .05). Twelve weeks after injection, mean jitter in the BTX group was 35.5; for the placebo group it was 24.5. Fiber density did not change in any patient during the study. There were no remote clinical effects of BTX. Injection of BTX into muscles affected with focal dystonia is a promising and safe treatment, but there are subclinical effects on uninjected muscles.     

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

Introduction: 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. Methods: ConMac needles were used to record the electrode cannula MUAP and measure its amplitude and area during weak, moderate, and strong muscle contractions. Results: 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. Conclusions: 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. Muscle Nerve 48 : 551–556, 2013     

Single fiber EMG in a neurological department

The use of the method with examination of jitter and fiber density is mentioned. Some patients (one with polyneuritis, one with dystrophia musculorum progressiva and three with myasthenia gravis) are presented, with demonstration of the jitter (the variability of the interpotential interval).
Jitter examinated in musculus extensor digitorum communis was prolonged (over 55 microsec) in patients with myasthenia gravis and dystrophia musculorum progressiva.     

EMG evaluation of motor neuron sprouting in amyotrophic lateral sclerosis

Collateral sprouting has been evaluated in amyotrophic lateral sclerosis (ALS) patients on the basis of: 1) Motor Unit action potential (M.U.A.P.) parameters evaluated by simultaneous EMG recordings using concentric needle electrodes and surface electrodes and 2) Motor Action Potential (M.A.P.) activated by graded electrical stimulation of nerve and recorded with the same electrodes. Mean values of duration and amplitude were calculated in 40 normal age-matched controls, 42 ALS patients in the early phase of the disease and in 5 muscles of three ALS patients during the whole course of the disease including the last paralytic phase. Percentage of M.U.A.P.s with linked potentials and highest amplitude was also calculated. The study confirms previous suggestions on collateral sprouting occurring in the early, middle and advanced phases of the disease and it shows, at variance with some recent claims, that it fails in the latest phase of paralysis.

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Sommario è stato valutato lo sprouting collaterale in pazienti con Sclerosi Laterale Amiotrofica (SLA), studiando: 1) i parametri di unità motoria mediante registrazioni EMGrafiche sia ad ago che di superficie e 2) la risposta M ottenuta con stimolazioni graduate del nervo. I valori medi di durata, ampiezza e la percentuale di potenziali linked sono stati misurati in 40 soggetti normali di controllo, 42 pazienti con SLA nella fase iniziale della malattia e in 5 muscoli di 3 pazienti con SLA seguiti fino allo stadio finale paralitico della malattia. Lo studio conferma che lo sprouting collaterale avviene nelle fasi iniziali, medie e avanzate della malattia, mentre avviene meno nella fase terminale paralitica, a differenza di alcune recenti osservazioni.

     

The demonstration of the size principle in humans using macro electromyography and precision decomposition

We set out to study the relationship between a motor unit's size and firing rates and its recruitment threshold and recruitment order. The data were collected from the first dorsal interosseous muscle of 11 normal subjects and analyzed using the precision decomposition and macro electromyography techniques. Our study showed that the recruitment order of a motor unit varies directly with its recruitment threshold (P < 0.00005) and that there is a progressive increase in the macro potential size of successively recruited motor units (P = 0.002). The firing rates of motor units vary inversely with their recruitment order (P = 0.006), the smaller, earlier recruited units consistently reaching higher firing rates than the larger, later recruited units. This study confirms the existence of a size principle of motor unit recruitment in humans and reveals the interactions between a motor unit's size and its firing rate properties. © 1996 John Wiley & Sons, Inc.     

Motor unit characteristics in healthy subjects and those with postpoliomyelitis syndrome: a high-density surface EMG study

The purpose of this study was to identify optimal ways to detect neurogenic changes with high-density surface electromyography (HD-sEMG). For this purpose, we searched for the variables that most clearly discriminated between postpoliomyelitis and healthy subjects. We obtained HD-sEMG from the quadriceps muscle at different force levels in nine subjects with postpoliomyelitis syndrome and in matched healthy controls. Single motor unit action potentials (MUAPs), extracted from the HD-sEMG signal and the raw signal itself, were analyzed. Areas under the curve of the extracted MUAP waveform, indicating motor unit size, perfectly separated both groups. Raw signal analysis showed significant differences between groups for the monopolarly recorded amplitude up to 60% of maximal force and for the level of interference at higher force levels (40-100% force). We conclude that with HD-sEMG it is possible to detect neurogenic motor unit changes noninvasively, both by analysis of the raw signal itself and by analysis of extracted single MUAPs. The diagnostic yield of the single MUAP analysis is clearly higher. These findings point toward applications for clinical practice and invite further studies exploring the diagnostic value of HD-sEMG.