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.     

Single fiber EMG in a congenital myasthenic syndrome associated with facial malformations

Six patients with a newly described genetic syndrome in Iraqi and Iranian Jews of congenital myasthenia associated with facial malformations were studied with voluntary and stimulation single fiber EMG (SFEMG). Voluntary SFEMG revealed abnormal jitter in all patients in both extensor digitorum communis (EDC) and orbicularis oculi (OOC) muscles, though much smaller in the clinically unaffected EDC. SFEMG study of OOC muscle by axonal stimulation at rates from 1 to 48 Hz showed the most increased jitter at the highest stimulation frequencies in the majority of end-plates, one-third of which showed maximal jitter at intermediate rates. These results may suggest a postsynaptic abnormality as the underlying cause for the neuromuscular transmission defect, and demonstrate the usefulness of SFEMG in the diagnosis of congenital myasthenia. © 1993 John Wiley & Sons, Inc.     

Muscle fiber conduction velocity changes with length

While recording activity from individual muscle fibers by single fiber EMG (SFEMG), stimulated either through their axons or directly, the length of the recorded muscle fiber was changed—stretched or made shorter—by manipulating the recording needle or by passive joint movements. This resulted in significant changes of latency corresponding to an increase in propagation velocity on shortening of the muscle fiber and to a slowing of its lengthening. The maximum increase in velocity was estimated to 33% and slowing to about 22%. These lengthdependent changes of muscle fiber propagation velocity are suggested to contribute to the supernormal phase of propagation velocity recovery function and to be responsible for an important part of the myogenic, interdischarge interval-dependent, jitter. © 1993 John Wiley & Soncs, Inc.     

Single fiber EMG reference values: A collaborative effort

Single fiber electromyography (SFEMG) measurements of fiber density and jitter are used in the diagnosis of a variety of peripheral nervous system disorders. However, the normal values of these measurements for most muscles and age groups are not well documented in the literature. We present a retrospective and prospective multicenter collection of SFEMG jitter and fiber density data from control subjects obtained for the purpose of defining reference values for many muscles and different ages. The data and calculated upper limits for fiber density, individual pair jitter, and mean jitter are presented for each muscle in tabular and graphical format, for different age groups.     

The utility of EMG interference pattern analysis in botulinum toxin treatment of torticollis: A randomised, controlled and blinded study

Objective

The significance of electromyography (EMG) guidance in botulinum toxin (BT) treatment has been much debated. The aim of this study was to evaluate if EMG guidance in the treatment of torticollis in BT-naive patients had a better outcome than treatment after clinical evaluation alone.

Methods

Twenty-six patients with torticollis were included and treated for 1 year in this prospective, blinded study. Quantitative EMG was performed simultaneously in the four most frequently affected muscles: the sternocleidomastoid muscles and the posterior neck muscles on both sides. EMGs were analysed for turns per second. Clinical ratings were performed by an experienced neurologist (A). Injections were given by another neurologist (B), who was blinded to the ratings. In group 1, the results of the EMG were available to the treating neurologist B, whereas in group 2, neurologist B was blinded. In group 1, treatment with BT was given when turns per second were higher than 100.

Results

In patients treated guided by EMG, clinical outcome, evaluated by objective ratings, was better than in patients treated based on clinical judgement alone (p = 0.05). In group 2, 105 muscles were treated with BT. Of these, 37 did not show dystonic EMG activity.

Conclusions

Treatment with BT guided by EMG results in better clinical outcome than treatment without EMG and reduces the amount of BT used.

Significance

EMG guidance by interference pattern analysis may optimise BT treatment in torticollis by a more precise injection and may reduce side effects and the risk of development of antibodies to BT.     

Single fiber EMG in the frontalis muscle in ocular myasthenia: specificity and sensitivity.

Patients (n = 41) with isolated weakness of the eyelids or extraocular muscles, who had been referred for single fiber electromyography (SFEMG), were followed up after 4 to 24 months, At follow-up the patients were classified as "definite ocular myasthenia gravis" (MG), "definite other diagnosis," or "no definite diagnosis" on the basis of the completed investigations and subsequent course. The original SFEMG findings in the frontalis muscle were then reviewed. The specificity and sensitivity of SFEMG for "definite ocular MG" could be maximized by using as criteria for abnormality greater than 8/20 pairs with jitter greater than 45 microseconds, or a mean jitter of 20 pairs of greater than 50 microseconds. Patients with abnormal SFEMG according to these criteria have MG, and are likely to require treatment in the immediate future. Patients who have normal SFEMG according to these criteria (and no other demonstrated disorder) may have MG, but it is so mild that they are unlikely to require treatment. Two patients whose final diagnosis was progressive external ophthalmoplegia had normal SFEMG according to these criteria.     

Botulinum neurotoxin‐A does not spread to distant muscles after intragastric injection: A double‐blind single‐fiber electromyography study

The purpose of this study was to perform a careful neurophysiological examination to identify subclinical signs of botulinum toxin spread distant to the injection site following intragastric injection for obesity treatment. Single‐fiber electromyography of extensor digitorum communis and repetitive stimulation of abductor digiti minimi were performed before and 8 days after multiple intragastric injections of botulinum toxin A (Botox, 200 U per patient) or placebo. The study was performed in a randomized double‐blind fashion. No patient in either group displayed results indicative of neuromuscular dysfunction either before or after the treatment. No significant change in muscle jitter was observed when comparing baseline with the after‐treatment evaluation in either group, and no significant differences between groups were observed. After intragastric botulinum toxin injection no subclinical sign of distant spread was observed. Muscle Nerve, 2010     

Concentric and single fiber needle electrodes yield comparable jitter results in myasthenia gravis

The single fiber needle electrode (SFNE), which is designed to isolate single muscle fiber action potentials, has played an important role in the diagnosis of myasthenia gravis (MG). However, the concentric needle electrode (CNE) has been recently adopted by some workers to study neuromuscular instability in MG, and reference data have also been obtained in healthy subjects. In this study we wanted to establish whether data acquired using the SFNE is comparable to that obtained using the CNE when studying patients with MG. We established reference data for our laboratory using the CNE for orbicularis oculi (OO) and extensor digitorum communis (EDC). We compared data from 24 MG patients using both SFNE and CNE and found no significant differences in mean jitter values for either muscles. We correlated the neurophysiological data obtained by either electrode with various clinical assessments, the ice pack test, OO and EDC strength measurement, and MGFA classification of disease, and we found no significant relation. We compared discomfort scores for the two needle electrodes for each muscle and found that the discomfort scores for CNE are significantly lower (P = 0.0004). We conclude that the CNE is a useful alternative electrode for studying single fiber potentials, but more reference data from normal control subjects is desirable. Muscle Nerve, 2008     

Placebo-controlled double-blind cross-over study of botulinum A toxin in hemifacial spasm

The evaluation of the efficacy of botulinum A toxin injection for hemifacial spasm has never previously been done in a double-blind study in spite of its use as a treatment. We thus conducted a double-blind cross-over study of botulinum A toxin use in hemifacial spasm in 55 patients at Siriraj Hospital, Mahidol University, Bangkok, Thailand. Thirteen patients decided to withdraw from the study due to a lack of efficacy, all of them were subsequently found to be in the saline injection group. The remaining 42 patients, in the botulinum A toxin injection (30 mouse units) group, reported the responses as: excellent (34 patients; 80.95%), moderate patients; 2.38%). In contrast, when given the saline injection they reported no excellent outcome, 1 patient (2.38%) with moderate improvement, 5 patients (11.90%) with mild improvement and, 36 patients (85.71%) with no response. Side effects of botulinum toxin injections were found in 14.29% of patients compared with 9.5% of the saline injection group. The side effects of botulinum toxin injection were mild transient facial weakness (7.14%), local pain (4.76%) and excessive lacrimation (2.38%).

We concluded that botulinum A toxin injection was a simple and effective out-patient treatment for the management of hemifacial spasm.     

Efficacy and safety of botulinum type A toxin (Dysport) in cervical dystonia: results of the first US randomized, double-blind, placebo-controlled study.

Botulinum toxin type A (Dysport) has been shown in European studies to be a safe and effective treatment for cervical dystonia. This multicenter, double-blind, randomized, controlled trial assessed the safety and efficacy of Dysport in cervical dystonia patients in the United States. Eighty patients were randomly assigned to receive one treatment with Dysport (500 units) or placebo. Participants were followed up for 4 to 20 weeks, until they needed further treatment. They were assessed at baseline and weeks 2, 4, 8, 12, 16, and 20 after treatment. Dysport was significantly more efficacious than placebo at weeks 4, 8, and 12 as assessed by the Toronto Western Spasmodic Torticollis Rating Scale (10-point vs. 3.8-point reduction in total score, respectively, at week 4; P < or = 0.013). Of participants in the Dysport group, 38% showed positive treatment response, compared to 16% in the placebo group (95% confidence interval, 0.02-0.41). The median duration of response to Dysport was 18.5 weeks. Side effects were generally similar in the two treatment groups; only blurred vision and weakness occurred significantly more often with Dysport. No participants in the Dysport group converted from negative to positive antibodies after treatment. These results confirm previous reports that Dysport (500 units) is safe, effective, and well-tolerated in patients with cervical dystonia.     

Use of single fiber EMG and macro EMG in study of reinnervation

The use of single fiber EMG and macro EMG in studies of reinnervation is discussed. SFEMG gives information about changes in the topography of the motor unit and in function of transmission in terminal nerve, motor endplate and muscle fiber. Dynamics of reinnervation may be studied with this technique. The amount of reinnervation is obtained from macro EMG studies. The capacity for reinnervation is discussed for a few conditions as well as factors that limit the reinnervation process.     

Single fiber EMG as a prognostic tool in myasthenia gravis

Introduction: Single fiber electromyography (SFEMG) is the most sensitive diagnostic tool for diagnosis of myasthenia gravis (MG). Its prognostic value is not known. Methods: We retrospectively analyzed the clinical course of 232 MG patients who presented with only mild symptoms and had SFEMG of the orbicularis oculi muscle. We correlated their SFEMG results with the severity of their later clinical course. Results: During the observation period 39 patients (17%) developed severe disease exacerbations, and 193 (83%) remained stable. Patients with severe disease exacerbation had a significantly higher mean jitter value (P < 0.0001), a greater percentage of fibers with increased jitter (P < 0.0001), and/or impulse blocking (P < 0.0001) on SFEMG. Conclusions: The extent of the SFEMG abnormalities in this study correlated with the later clinical course of MG. Muscle Nerve 54 : 1034–1040, 2016     

Side-effects of intradermal injections of botulinum A toxin in the treatment of palmar hyperhidrosis: a neurophysiological study

Focal palmar hyperhidrosis can be effectively abolished by intradermal injections with botulinum toxin. Muscle weakness of finger grip has been reported as a reversible side-effect of this new treatment. The objective of this work was to measure muscular side-effects after treatment of palmar hyperhidrosis with botulinum toxin. As botulinum toxin has been used in the treatment of pain, we studied whether the toxin might influence afferent thin-fibre function by measuring temperature perception thresholds. Thirty-seven patients treated with botulinum toxin (Botox, Allergan Pharmaceuticals, Irvine, CA, USA) showed a decrease in compound muscle action potential (CMAP) for both abductor pollicis brevis (APB) and abductor digiti minimi (ADM) compared with pre-injection values on average by 64 and 36%, respectively, at 3 weeks which returned nearly to normal at 37 weeks. Muscle power for both finger abduction and finger opposition decreased to a lesser extent. Repetitive nerve stimulation and single fibre electromyography (EMG) showed a disturbed neuromuscular transmission. Thus, despite careful technique with small doses of botulinum toxin injected intradermally, the toxin diffuses to underlying muscles. With regard to the present results, one should be careful in using higher doses of Botox than 0.8 mU/cm(2) in the palmar skin above intrinsic muscles. No influence on thin-fibre function was seen.     

Pharmacology of botulinum toxin: differences between type A preparations

Different types of botulinum neurotoxin (BoNT) block different proteins of the soluble N‐ethylmaleimide sensitive factor attachment protein receptor (SNARE) protein complex within cholinergic nerve terminals, producing blockade of cholinergic neuromuscular and autonomic synapses. Animal studies indicate the longest duration of action for BoNT type A (BoNTA) followed by types B, F, and E. Diffusion to adjacent and remote muscles may be related to protein composition, dilutions, volume, target muscle selection, and injection technique. A review of head‐to‐head, randomized, controlled trials of BoNTA preparations (Botox® and Dysport®) suggests that Dysport® tends to have higher efficacy, longer duration, and higher frequency of adverse effects. Conversion factors between the preparations varied, however, and remain controversial. In clinical settings, a Botox®:Dysport® conversion ratio of 1:3 may be appropriate. Animal studies suggest a conversion ratio of 1:2.5–3. When therapeutic effects between these preparations are attempting to be equalized, Dysport® seems to produce more adverse effects. In mice, Botox® appears to have a better safety margin than Dysport® and BoNTB. In rats, diffusion margins are similar for Botox® and Dysport®. Jitter derived from stimulation single‐fiber EMG of injected and remote muscles show no differences between Botox® and Dysport®. Atrophy of extrafusal muscle fibers of injected and remote muscles do not differ between the BoNTA preparations.     

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.     

Secondary nonresponsiveness to botulinum toxin A in cervical dystonia: the role of electromyogram-guided injections, botulinum toxin A antibody assay, and the extensor digitorum brevis test.

We studied 20 patients with cervical dystonia who had started to respond poorly to botulinum toxin A (BTXA) injections after an initial good response. All patients had extensor digitorum brevis (EDB) tests performed in addition to BTXA immunoprecipition assay (IPA) and mouse bioassay (MBA) antibody testing. The patients were reexamined and then treated with carefully placed electromyogram (EMG)-guided BTXA. Nine patients had a good clinical response to EMG-guided injections and all of these patients showed an obvious decrement on the EDB test. All were BTXA blocking antibodies (Abs)-negative via IPA and MBA (apart from one patient who had low BTXA antibodies titers using IPA but no antibodies by MBA). In the other 11 patients, there was a poor clinical response to EMG-guided BTXA injections. Seven of these 11 had small EDB decrement and BTXA antibodies using IPA, suggesting resistance to BTXA. Of the remaining four patients, two had obvious EDB decrement and low antibody titers via IPA (one of them had no antibodies via MBA), while the other two patients showed obvious decrement on the EDB test and no antibodies via IPA. This study shows that the EDB test correlates better with the clinical response than the antibody assays and that EDB decrement does not always correlate quantitatively with the BTXA antibody titers. In patients with secondary nonresponsiveness, it is recommended that an EDB test is the initial investigation of choice. In those patients where the EDB test does not demonstrate resistance to BTXA, a reexamination of the patients and carefully placed injections under EMG guidance may improve results.     

Subcutaneous histamine versus botulinum toxin type A in migraine prophylaxis: a randomized, double-blind study

Objectives:  To compare the efficacy and tolerability of the subcutaneous administration of histamine and botulinum toxin type A (BoNTA) in migraine prophylaxis.
Background:  Histamine has a selective affinity for H3 receptors and it may specifically inhibit the neurogenic edema response involved in migraine pathophysiology.
Methods:  One hundred patients with migraine were selected in a 12-week double-blind controlled clinical trial to evaluate the efficacy of subcutaneous administration of histamine (1–10 ng twice a week) n  = 50, compared with administration of 50 U of BoNTA (one injection cycle) n  = 50.
Results:  The data collected during the 4th week of treatment revealed a significant decrease in all parameters studied, in histamine and BoNTA ( P  < 0.001). After 4 weeks of treatment, but one injection cycle of 50 U BoNTA had only a 40-day period of efficacy.
Conclusions:  This randomized study demonstrated that both histamine and BoNTA are similarly effective and well tolerated in reducing or eliminating headache in migraine prophylaxis. Low doses of histamine applied subcutaneously may represent a novel and effective therapeutic alternative in migraine patients and lay the clinical and pharmacological groundwork for the use of H3 agonist in migraine prophylaxis.     

Serial SFEMG studies of orbicularis oculi muscle after the first administration of botulinum toxin

Serial single fiber electromyography (SFEMG) examinations of orbicularis oculi muscle in patients with blepharospasm or hemifacial spasm treated with botulinum toxin injections were performed. The aim of the study was to evaluate the impairment of neuromuscular transmission, to follow reinnervation after botulinum toxin administration and to find out whether there was a relationship between SFEMG parameters and clinical symptoms. Examinations were performed before injection, during early and late remission of symptoms, and after recurrence of the involuntary movement. Severe impairment of neuromuscular transmission, as revealed by increased jitter and increased presence of abnormal potential pairs and pairs with blocking, was found in early remission, but fiber density remained unchanged when compared with pretreatment values. In late remission, increased fiber density was registered for the first time. The recurrence of involuntary movements was related to the further increase of fiber density and tendency to normalization of jitter parameters. The study therefore suggests that formation of new neuromuscular junctions and their functional maturation is responsible for muscle recovery after botulinum toxin administration.