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

Contribution of Single-Fiber Evaluation on Monitoring Outcomes Following Injection of Botulinum Toxin-A: A Narrative Review of the Literature

Botulinum toxin-A (BoNT-A) blocks acetylcholine release at the neuromuscular junction (NMJ) and is widely used for neuromuscular disorders (involuntary spasms, dystonic disorders and spasticity). However, its therapeutic effects are usually measured by clinical scales of questionable validity. Single-fiber electromyography (SFEMG) is a sensitive, validated diagnostic technique for NMJ impairment such as myasthenia. The jitter parameter (µs) represents the variability of interpotential intervals of two muscle fibers from the same motor unit. This narrative review reports SFEMG use in BoNT-A treatment. Twenty-four articles were selected from 175 eligible articles searched in Medline/Pubmed and Cochrane Library from their creation until May 2020. The results showed that jitter is sensitive to early NMJ modifications following BoNT-A injection, with an increase in the early days’ post-injection and a peak between Day 15 and 30, when symptoms diminish or disappear. The reappearance of symptoms accompanies a tendency for a decrease in jitter, but always precedes its normalization, either delayed or nonexistent. Increased jitter is observed in distant muscles from the injection site. No dose effect relationship was demonstrated. SFEMG could help physicians in their therapeutic evaluation according to the pathology considered. More data are needed to consider jitter as a predictor of BoNT-A clinical efficacy.

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.

Assessing the immediate impact of botulinum toxin injection on impedance of spastic muscle

This study aimed to investigate the immediate impacts of Botulinum Toxin A (BoNT-A) injections on the inherent electrical properties of spastic muscles using a newly developed electrical impedance myography (EIM) technique. Impedance measures were performed before and after a BoNT-A injection in biceps brachii muscles of 14 subjects with spasticity. Three major impedance variables, resistance (R), reactance (X) and phase angle (θ) were obtained from three different configurations, and were evaluated using the conventional EIM frequency at 50kHz as well as multiple frequency analysis. Statistical analysis demonstrated a significant decrease of resistance in the injected muscles (Multiple-frequency: R_pre=25.17±1.94Ohm, R_post=23.65±1.63Ohm, p<0.05; 50kHz: R_pre=29.06±2.16Ohm, R_post=27.7±1.89Ohm, p<0.05). Despite this decrease, there were no substantial changes in the reactance, phase angle, or anisotropy features after a BoNT-A injection. The significant changes of muscle resistance were most likely associated with the liquid injection of the BoNT-A-saline solution rather than the immediate toxin effects on the muscle. This study demonstrated high sensitivity of the EIM technique in the detection of alterations to muscle composition.

Hemifacial spasm: The past, present and future

Hemifacial spasm is characterised by unilateral contractions of the facial muscles. Though considered to be benign by many people, it can lead to functional blindness and a poor quality of life due to social embarrassment for the suffering individual. Botulinum toxin therapy is an excellent noninvasive tool to treat this condition. However, surgical decompression of the aberrant vessel is also an upcoming approach to therapy for this condition.

Effect of botulinum neurotoxin treatment in the lateral spread monitoring of microvascular decompression for hemifacial spasm

INTRODUCTION

Botulinum neurotoxin (BtNtx) treatment for hemifacial spasm (HFS) prior to microvascular decompression (MVD) is hypothesized to be a factor in the variability of intraoperative neurophysiological monitoring (IONM) during this procedure.

METHODS

We analyzed 282 MVDs performed at the University of Pittsburgh Medical Center between January 1, 2000 and December 31, 2007. We retrospectively compared the lateral spread response (LSR) in the mentalis muscle when stimulus-triggered electromyography (EMG) was elicited from the facial nerve. Previous BtNtx treatment was the grouping factor.

RESULTS

Baseline LSR amplitudes during MVD (prior BtNtx: mean = 341.47 μV; no BtNtx: mean = 241.81 μV) were significantly different between groups (df = 1,281; t = -2.463; P = 0.014). Comparisons of latency and current threshold at baseline, as well as HFS disappearance or LSR persistence after the procedure, did not achieve statistical significance.

CONCLUSIONS

HFS patients treated with BtNtx prior to MVD demonstrated higher LSR baseline amplitudes during IONM. This could be related to muscle poly-reinnervation after recovery from repeated BtNtx use.

Prospective, randomized, double-blind study, comparing botulinum toxins type a botox and prosigne for blepharospasm and hemifacial spasm treatment

Botulinum toxin A (BTA) is considered an effective treatment of blepharospasm and hemifacial spasm, but there are few studies to permit a comparison of its different formulations. This prospective, randomized, double-blind study compared Prosigne, a BTA of Chinese origin, with Botox to establish safety, efficacy, and equivalence of doses between those 2 formulations in blepharospasm and hemifacial spasm treatment. Fifty-seven patients participated in this study: 21 blepharospasm (from whom 11 were treated with Botox; and 10, with Prosigne) and 36 hemifacial spasm patients (17 were treated with Botox; and 19, with Prosigne). All patients were similar in age, disease time span, number of previous shots, and time elapsed since the last BTA application. Pain and burning during the injection and the result of the treatment were similar in both groups. There were no systemic adverse events, and the local ones were observed with similar intensity and frequency for both groups. The mean effect time length was similar for both blepharospasm (11.3 weeks for both toxins) and hemifacial spasm patients (12.8 weeks for Botox and 12.9 weeks for Prosigne). In both blepharospasm groups, only the 36-Item Short-Form Health Survey emotional aspects domain showed improvement from baseline after 16 weeks. There were no differences between the 36-Item Short-Form Health Survey scores before and after the treatment of all hemifacial spasm patients. Therefore, it has been concluded that Botox and Prosigne have similar efficacy, safety, and tolerability profiles, so that a dose equivalence of 1:1 may be considered for blepharospasm and hemifacial spasm treatments.

Botulinum toxins in neurological disease

Botulinum toxins are among the most potent neurotoxins known to humans. In the past 25 years, botulinum toxin has emerged as both a potential weapon of bioterrorism and as a powerful therapeutic agent, with growing applications in neurological and non-neurological disease. Botulinum toxin is unique in its ability to target peripheral cholinergic neurons, preventing the release of acetylcholine through the enzymatic cleavage of proteins involved in membrane fusion, without prominent central nervous system effects. There are seven serotypes of the toxin, each with a specific activity at the molecular level. Currently, serotypes A (in two preparations) and B are available for clinical use, and have been shown to be safe and effective for the treatment of dystonia, spasticity, and other disorders in which muscle overactivity gives rise to symptoms. This review focuses on the pharmacology, electrophysiology, immunology, and application of botulinum toxin in selected neurological disorders.

Single Fiber EMG as an Outcome Measure in Myasthenia Gravis: Results from a Double-Blind, Placebo-Controlled Trial

In a placebo-controlled, therapeutic, pilot trial of mycophenolate mofetil (MM) in autoimmune myasthenia gravis (MG), the authors compared pretreatment and posttreatment single fiber electromyography (SFEMG) jitter measurements performed on the same muscle in a total of 11 patients. The mean jitter value decreased (improved) by an average of 15.4 micros in patients receiving MM (n = 6), compared to an increase (worsening) in mean jitter of 4.0 micros in patients receiving placebo (n = 5). This difference was statistically significant (P = 0.030). In most patients, the change in SFEMG measurements correlated with the change in clinical state as measured by quantitative testing of muscle function. The authors conclude that immunomodulation by MM improves neuromuscular junction function in MG and that SFEMG may be a useful marker of early response in future therapeutic trials in autoimmune MG.

Local injection of botulinum toxin type A for hemifacial spasm

The preliminary experience of botulinum toxin treatment for hemifacial spasm is reported in this study. Five patients were treated with 10 injections of botulinum toxin in total. Botulinum toxin had a good to excellent effect in all cases. Improvement was observed 2 weeks to 1 month after the injection. The duration of improvement was 0-9 months (mean 4.2 months). The peak rank tended to decrease and the duration of improvement increased after several treatments. Hemifacial spasm caused by the anterior inferior cerebellar artery tended to subside easily. In contrast, compression by the vertebral artery was more refractory. Continuous facial spasm caused by operative trauma subsided after the injection, but paroxysmal spasm still occurred when eating or laughing. Spasm caused by trauma disappeared 4.5 months after the injection. The complications, which were facial nerve paresis in two cases (3 injections, 30%) and diplopia in one case (1 injection, 10%), were transient and subsided in 2 weeks.