Botulinum toxin for blepharospasm: single-fiber EMG studies

Clinical neurophysiology in the treatment of movement disorders: IFCN handbook chapter

In this review, different aspects of the use of clinical neurophysiology techniques for the treatment of movement disorders are addressed. First of all, these techniques can be used to guide neuromodulation techniques or to perform therapeutic neuromodulation as such. Neuromodulation includes invasive techniques based on the surgical implantation of electrodes and a pulse generator, such as deep brain stimulation (DBS) or spinal cord stimulation (SCS) on the one hand, and non-invasive techniques aimed at modulating or even lesioning neural structures by transcranial application. Movement disorders are one of the main areas of indication for the various neuromodulation techniques. This review focuses on the following techniques: DBS, repetitive transcranial magnetic stimulation (rTMS), low-intensity transcranial electrical stimulation, including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), and focused ultrasound (FUS), including high-intensity magnetic resonance-guided FUS (MRgFUS), and pulsed mode low-intensity transcranial FUS stimulation (TUS). The main clinical conditions in which neuromodulation has proven its efficacy are Parkinson's disease, dystonia, and essential tremor, mainly using DBS or MRgFUS. There is also some evidence for Tourette syndrome (DBS), Huntington's disease (DBS), cerebellar ataxia (tDCS), and axial signs (SCS) and depression (rTMS) in PD. The development of non-invasive transcranial neuromodulation techniques is limited by the short-term clinical impact of these techniques, especially rTMS, in the context of very chronic diseases. However, at-home use (tDCS) or current advances in the design of closed-loop stimulation (tACS) may open new perspectives for the application of these techniques in patients, favored by their easier use and lower rate of adverse effects compared to invasive or lesioning methods. Finally, this review summarizes the evidence for keeping the use of electromyography to optimize the identification of muscles to be treated with botulinum toxin injection, which is indicated and widely performed for the treatment of various movement disorders.

Single fiber electromyography and measuring jitter with concentric needle electrodes

This monograph contains descriptions of the single fiber electromyography (SFEMG) method and of the more recently implemented method of recording jitter with concentric needle electrodes (CNEs). SFEMG records action potentials from single muscle fibers (SFAPs), which permits measuring fiber density (FD), a sensitive measure of reinnervation, and jitter, a sensitive measure of abnormal neuromuscular transmission (NMT). With voluntary activation, jitter is measured between two SFAPs with acceptable amplitude and rise time. With activation by axon stimulation, jitter is measured between the stimulus and individual SFAPs. Pitfalls due to unstable triggers and inconstant firing rates during voluntary activation and subliminal stimulation during axon stimulation should be identified and avoided. In CNE recordings, spikes with shoulders or rising phases that are not parallel are produced by summation of SFAPS; these should be excluded and reference values for CNE jitter should be used. CNE and SFEMG have similar and very high sensitivity in detecting increased jitter, as in myasthenia gravis and other myasthenic conditions. However, jitter is also seen in ongoing reinnervation and some myopathic conditions. With SFEMG, these can be identified by increased FD; however, FD cannot be measured with CNE, and conventional electromyography should be performed in muscles with increased jitter to detect neurogenic or myogenic abnormalities. Jitter is abnormal after injections of botulinum toxin, even in muscles remote from the injection site, and can persist for 6 mo or more. This can complicate the detection or exclusion of abnormal NMT.

Single fiber EMG and measuring jitter with concentric needle electrodes

This monograph contains descriptions of the single-fiber electromyography (SFEMG) method and of the more recently implemented method of recording jitter with concentric needle electrodes (CNE). SFEMG records action potentials from single muscle fibers (SFAPs), which permits measuring fiber density (FD), a sensitive measure of reinnervation, and jitter, a sensitive measure of abnormal neuromuscular transmission (NMT). With voluntary activation, jitter is measured between two SFAPs with acceptable amplitude and rise time. With activation by axon stimulation, jitter is measured between the stimulus and individual SFAPs. Pitfalls due to unstable triggers and inconstant firing rates during voluntary activation and subliminal stimulation during axon stimulation should be identified and avoided. In CNE recordings, spikes with shoulders or rising phases that are not parallel are produced by summation of SFAPS; these should be excluded and reference values for CNE jitter should be used. CNE and SFEMG have similar and very high sensitivity in detecting increased jitter, as in myasthenia gravis and other myasthenic conditions. However, jitter is also seen in ongoing reinnervation and some myopathic conditions. With SFEMG, these can be identified by increased FD; however, FD cannot be measured with CNE, and conventional EMG should be performed in muscles with increased jitter to detect neurogenic or myogenic abnormalities. Jitter is abnormal after injections of botulinum toxin, even in muscles remote from the injection site, and can persist for 6 mo or more. This can complicate the detection or exclusion of abnormal NMT.

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.

Soft Nanomembrane Sensors and Flexible Hybrid Bioelectronics for Wireless Quantification of Blepharospasm

Blepharospasm (BL) is characterized by involuntary closures of the eyelids due to spasms of the orbicularis oculi muscle. The gold standard for clinical evaluation of BL involves visual inspection for manual rating scales. This approach is highly subjective and error prone. Unfortunately, there are currently no simple quantitative systems for accurate and objective diagnostics of BL. Here, we introduce a soft, flexible hybrid bioelectronic system that offers highly conformal, gentle lamination on the skin, while enabling wireless, quantitative detection of electrophysiological signals. Computational and experimental studies of soft materials and flexible mechanics provide a set of key fundamental design factors for a low-profile bioelectronic system. The nanomembrane soft electrodes, mounted around the eyes, are capable of accurately measuring clinical symptoms, including the frequency of blinking, the duration of eye closures during spasms, as well as combinations of blinking and spasms. The use of a deep-learning, convolutional neural network, with the bioelectronics offers objective, real-time classification of key pathological features in BL. The wearable bioelectronics outperform the conventional manual clinical rating, as shown by a pilot study with 13 patients. In vivo demonstration of the bioelectronics with these patients indicates the device as an easy-to-use solution for objective quantification of BL.

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.

Application of botulinum toxin in pregnancy and its impact on female reproductive health

Introduction: Botulinum toxin (BoNT) is a protein secreted by the anaerobic Gram-negative bacterium Clostridium botulinum. Among the seven known subtypes, type A is the most commonly used in women to treat diseases. It primarily blocks presynaptic release of acetylcholine at the neuromuscular junction, resulting in temporary muscle paralysis; thus, it is suitable for treating dystonia and other systemic diseases. BoNT is used widely for treating diseases that persist throughout, and may worsen during, pregnancy, such as cervical dystonia and achalasia. Thus, it is important to investigate whether BoNT injection during pregnancy causes side effects in pregnant women, fetuses, or newborns.Areas covered: This review highlights the efficiency and safety of BoNT injection in pregnancy. and assessed current literature with respect to the use of BoNT for disease treatment during pregnancy.Expert opinion: BoNT injection does not increase the risk of complications in pregnant women and fetuses. However, the use of BoNT to treat disease during pregnancy requires fully informed consent from patients. In addition, further research is needed to determine how to reduce the side effects of BoNT injection during pregnancy (e.g., by improving drug composition, or adjusting the amount of BoNT or the injection interval).

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.

Myasthenia Gravis and Lambert-Eaton Myasthenic Syndrome

PURPOSE OF REVIEW

This article discusses the pathogenesis, diagnosis, and management of autoimmune myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS).

RECENT FINDINGS

Recognition of new antigenic targets and improved diagnostic methods promise to improve the diagnosis of MG, although the clinical phenotypes associated with newer antibodies have not yet been defined. Future therapies might specifically target the aberrant immune response. The apparent increase in the prevalence of MG is not fully explained. Results of a long-awaited trial of thymectomy support the practice of performing a thymectomy under specific conditions.

SUMMARY

The current treatment options are so effective in most patients with MG or LEMS that in patients with refractory disease the diagnosis should be reconsidered. The management of MG is individualized, and familiarity with mechanisms, adverse effects, and strategies to manage these commonly used treatments improves outcome. Patient education is important. LEMS, frequently associated with an underlying small cell lung cancer, is uncommon, and the mainstay of treatment is symptomatic in most patients.

Neurophysiological Measures of Efficacy and Safety for Botulinum Toxin Injection in Facial and Bulbar Muscles: Special Considerations

Botulinum toxin (BoNT) injections into facial and bulbar muscles are widely and increasingly used as medical treatments for cervical and facial dystonia, facial hemispasm, correction of facial palsy, hyperhidrosis, as well as cosmetic treatment of glabellar lines associated with grief and anger. Although BoNT treatment is generally considered safe, the diffusion of the toxin to surrounding muscles may result in complications, including difficulties swallowing, in a dose-dependent manner. The sensitivity of clinical examination for detecting adverse events after BoNT treatment is limited. Few reports have highlighted the potential effects on other muscles in the facial area due to the spreading of the toxin. The possibilities of spreading and thus unknown pharmacological BoNT effects in non-targeted muscles emphasise the importance of correct administration of BoNT in terms of dose selection, injection points, and appropriate effect surveillance. In this review article, we will focus on novel objective measures of efficacy and safety regarding BoNT treatment of facial muscles and the reasons why this is important.

Single-fiber electromyography analysis of botulinum toxin diffusion in patients with fatigue and pseudobotulism

OBJECTIVE

To characterize electromyographic abnormalities according to symptoms (asymptomatic, fatigue, pseudobotulism) reported 1 month after botulinum toxin injection.

DESIGN

Retrospective, single-center study comparing single-fiber electromyography (SFEMG) in the extensor digitorum communis (EDC) or orbicularis oculi (OO) muscles.

SETTING

Hospital.

PARTICIPANTS

Four groups of adults treated for spasticity or neurologic bladder hyperactivity (N=55): control group (asymptomatic patients: n=17), fatigue group (unusual fatigue with no weakness: n=15), pseudobotulism group (muscle weakness and/or visual disturbance: n=20), and botulism group (from intensive care unit of the same hospital: n=3).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Mean jitter, percentage of pathologic fibers, and percentage of blocked fibers were compared between groups.

RESULTS

SFEMG was abnormal for 17.6% of control patients and 75% of patients in the pseudobotulism group. There were no differences between the control and fatigue groups. Mean jitter, percentage of pathologic fibers, and percentage of blocked fibers of the EDC muscle were significantly higher in the pseudobotulism group than in the fatigue and control groups. There were no differences between groups for the OO muscle. The SFEMG results in the botulism group were qualitatively similar to those of the pseudobotulism group.

CONCLUSIONS

SFEMG of the EDC muscle confirmed diffusion of the toxin into muscles distant from the injection site in the pseudobotulism group. SFEMG in the OO muscle is not useful for the diagnosis of diffusion. No major signs of diffusion of botulinum toxin type A were found away from the injection site in patients with fatigue but no motor weakness. Such fatigue may be related to other mechanisms.

Diffusion, spread, and migration of botulinum toxin

Botulinum toxin (BoNT) is an acetylcholine release inhibitor and a neuromuscular blocking agent used for the treatment of a variety of neurologic and medical conditions. The efficacy and safety of BoNT depends on accurate selection and identification of intended targets but also may be determined by other factors, including physical spread of the molecule from the injection site, passive diffusion, and migration to distal sites via axonal or hematogenous transport. The passive kinetic dispersion of the toxin away from the injection site in a gradient-dependent manner may also play a role in toxin spread. In addition to unique properties of the various BoNT products, volume and dilution may also influence local and systemic distribution of BoNT. Most of the local and remote complications of BoNT injections are thought to be due to unwanted spread or diffusion of the toxin's biologic activity into adjacent and distal muscles. Despite widespread therapeutic and cosmetic use of BoNT over more than three decades, there is a remarkable paucity of published data on the mechanisms of distribution and its effects on clinical outcomes. The primary aim of this article is to critically review the available experimental and clinical literature and place it in the practical context.

Botulinum toxins: mechanisms of action, antinociception and clinical applications

Botulinum toxin (BoNT) is a potent neurotoxin that is produced by the gram-positive, spore-forming, anaerobic bacterium, Clostridum botulinum. There are 7 known immunologically distinct serotypes of BoNT: types A, B, C1, D, E, F, and G. Clostridum neurotoxins are produced as a single inactive polypeptide chain of 150kDa, which is cleaved by tissue proteinases into an active di-chain molecule: a heavy chain (H) of ∼100 kDa and a light chain (L) of ∼50 kDa held together by a single disulfide bond. Each serotype demonstrates its own varied mechanisms of action and duration of effect. The heavy chain of each BoNT serotype binds to its specific neuronal ecto-acceptor, whereby, membrane translocation and endocytosis by intracellular synaptic vesicles occurs. The light chain acts to cleave SNAP-25, which inhibits synaptic exocytosis, and therefore, disables neural transmission. The action of BoNT to block the release of acetylcholine botulinum toxin at the neuromuscular junction is best understood, however, most experts acknowledge that this effect alone appears inadequate to explain the entirety of the neurotoxin's apparent analgesic activity. Consequently, scientific and clinical evidence has emerged that suggests multiple antinociceptive mechanisms for botulinum toxins in a variety of painful disorders, including: chronic musculoskeletal, neurological, pelvic, perineal, osteoarticular, and some headache conditions.

The effects of electrical stimulation exercise on muscles injected with botulinum toxin type-A (botox)

Botulinum toxin type A (BTX-A) is a frequently used treatment modality for a variety of neuromuscular disorders. It acts by preventing acetylcholine release at the motor nerve endings, inducing muscle paralysis. Although considered safe, studies suggest that BTX-A injections create adverse effects on target and non-target muscles. We speculate that these adverse effects are reduced by direct electrical stimulation (ES) exercising of muscles. The aims were to determine the effects of ES exercise on strength, mass, and contractile material in BTX-A injected muscles, and to investigate if BTX-A injections affect non-target muscles. Seventeen New Zealand White (NZW) rabbits were divided into three groups: (1) Control group received saline injections; (2) BTX-A group received monthly BTX-A (3.5 U/kg) injections into the quadriceps for six months and (3) BTX-A+ES group received monthly BTX-A injections and ES exercise three times a week for six months. Outcome measures included knee extensor torque, muscle mass, and contractile material percentage area in injected and contralateral, non-injected quadriceps. Glycogen depletion and direct muscle stimulation were used to assess possible muscle inhibition in non-injected quadriceps. ES exercise partially prevented muscle weakness, atrophy, and contractile material loss in injected muscles, and mostly prevented muscle degeneration in contralateral, non-injected muscles. Non-injected muscles of BTX-A+ES group showed higher force with direct muscle compared to nerve stimulation, and retained glycogen following the depletion protocol, suggesting that BTX-A inhibited activation in non-target muscles. We conclude that ES exercise provides some protection from degeneration to target and non-target muscles during BTX-A treatments.

Intra-prostatic injection of botulinum toxin type A in treatment of dogs with spontaneous benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a common, naturally developing, age-related condition in dogs. The pathogenesis of BPH is not completely known; however, DHT is a hormone involved in enlargement of the prostate. Recently, the effect of botulinum toxin A (BT-A) was investigated in the rat and human prostate and has shown to induce atrophy of the gland on the canine prostate. This study investigated the effect of BT-A in the canine prostate and on the semen. Eight sexually intact male dogs with BPH (detected radiographically and ultrasonographically), and with clinical signs of BPH (e.g. hematuria or tenesmus) were used. Each lobe of the prostate received an injection of 125 U of BT-A with one-needle pass under transabdominal ultrasound guidance. The clinical results were evaluated at baseline and after treatment. No local complications or systemic adverse effects were reported. At 4 weeks, the mean prostate volume (PV) was not significantly changed after BT-A (from 17.70 ± 6.34 to 16.48 ± 5.98 cm(3)). At 8 weeks the PV had further decreased to 16.04 ± 5.80 cm(3), reaching its maximum effect, but that change was not significant. The results were maintained at 16 weeks. All dogs had normal libido, erection, and ejaculation during semen collection. No significant difference was observed in all seminal parameters. Results suggest that the administration of 250 U of BT-A do not contribute to PV reduction and do not adversely affect the semen quality of dogs with BPH.

Botulinum neurotoxin A: a review

Despite its ubiquity in cosmetic circles and broad general awareness, a literature search of botulinum neurotoxin in JPRAS and BJPS yielded a mere 4 articles germane to cosmesis. A pair each detailing its application in masseteric hypertrophy(1,2) and the use of cryoanalgesia.(3,4) Given that botulinum neurotoxin A is the most commonly used cosmetic treatment, with American figures being most accurate,(5) a review of the background, development and scientific evidence would be perhaps useful, if not overdue, as Plastic Surgeons increasingly incorporate non-surgical interventions into their practices as part of a comprehensive facial rejuvenation strategy.

Pilot study evaluating the safety of intradetrusor injections of botulinum toxin type A: investigation of generalized spread using single-fiber EMG

AIMS

Intradetrusor botulinum toxin type-A injections are a novel therapy for treatment of neurogenic overactive bladder resistant to parasympatholytic treatment. In rare cases, however, it may be associated with generalized muscle weakness. Single-fiber electromyographic (SFEMG) analysis of neuromuscular jitter (NJ) was used to study OnabotulinumtoxinA (BOTOX®) migration to striated muscle.

METHODS

This study comprised a prospective, single-center investigation of 21 spinal cord injured patients receiving intradetrusor OnabotulinumtoxinA. Clinical tolerance was assessed through muscle testing and para-clinical tolerance by systematic analysis of NJ in muscles distant from the bladder.

RESULTS

Twenty-one patients (13 males, 8 females) received one intradetrusor injection of 300  U OnabotulinumtoxinA. Mean age was 42.1  ±  14.4 and mean number of injections prior to study inclusion was 2.6  ± 1.7. Clinical and para-clinical assessments were performed on average 26 days  ±  8 days post-OnabotulinumtoxinA injection. Seven patients had abnormal NJ results on SFEMG, but no patient had evidence of blocking. Four patients complained of tiredness (one with NJ abnormalities).

CONCLUSIONS

Patients showed good tolerance to intradetrusor OnabotulinumtoxinA injections. Tiredness was not associated with generalized muscle weakness since testing remained unchanged and NMJ was normal in three of four patients. NJ analysis was abnormal in 7 of 21 patients, but this was not considered serious and there was no evidence of muscle fiber block. These results support the safety of bladder injections of OnabotulinumtoxinA and suggest that, although migration of OnabotulinumtoxinA to other muscle groups may impair NJ function in a minority of patients, this does not correlate with symptoms of tiredness or muscle weakness.

Systemic weakness after therapeutic injections of botulinum toxin a: a case series and review of the literature

The use of intramuscular injections of Botulinum neurotoxin A (BoNT-A) is common in the treatment of hypertonicity and movement disorders. Although most side effects are mild, systemic effects, manifested by generalized weakness distant from the site of injection, have been reported. Previously reported occurrences are discussed, and 3 new cases of patients, who developed systemic weakness after administration of BoNT-A (Botox), despite having tolerated similar injections on several previous occasions, are presented. A review of the literature and reported cases indicate that risk of developing systemic effects does not seem to be related to dose based on body weight. It may be more likely that risk for systemic effects is related to total injection dose and injection frequency. The results of our 3 patients would indicate that injections of greater than 600 units of Botox with follow-up injections occurring every 3 months may lead to an increased risk. We would recommend careful consideration of reinjection frequency if injections of greater than 600 units of Botox are given. Reduction in systemic side effects may occur if reinjection frequency occurs in intervals of 4 months or greater in these individuals.

Muscle changes can account for bone loss after botulinum toxin injection

Studies to date have assumed that botulinum toxin type A (BTX) affects bone indirectly, through its action on muscle. We hypothesized that BTX has no discernable effect on bone morphometry, independent of its effect on muscle. Therefore, we investigated whether BTX had an additional effect on bone when combined with tenotomy compared to tenotomy in isolation. Female BALB/c mice (n = 73) underwent one of the following procedures in the left leg: BTX injection and Achilles tenotomy (BTX-TEN), BTX injection and sham surgery (BTX-sham), Achilles tenotomy (TEN), or sham surgery (sham). BTX groups were injected with 20 μL of BTX (1 U/100 g) in the posterior lower hindlimb. At 4 weeks, muscle cross-sectional area (MCSA) and tibial bone morphometry were assessed using micro-CT. Each treatment, other than sham, resulted in significant muscle and bone loss (P < 0.05). BTX-TEN experienced the greatest muscle loss (23-45% lower than other groups) and bone loss (20-30% lower bone volume fraction than other groups). BTX-sham had significantly lower MCSA and bone volume fraction than TEN and sham. After adjusting for differences in MCSA, there were no significant between-group differences in bone properties. We found that BTX injection resulted in more adverse muscle and bone effects than tenotomy and that effects were amplified when the procedures were combined. However, between-group differences in bone could be accounted for by MCSA. We conclude that any independent effect of BTX on bone morphometry is likely small or negligible compared with the effect on muscle.

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.

Neurophysiological effects of botulinum toxin type a

Botulinum toxin type A (BoNT-A) acts peripherally by inhibiting acetylcholine release from the presynaptic neuromuscular terminals, thus weakening muscle contraction, and its clinical benefit depends primarily on the toxin's peripheral action. In addition to acting directly at the neuromuscular junction, the toxin alters sensory inputs to the central nervous system, thus indirectly inducing secondary central changes. Some of the long-term clinical benefits of BoNT-A treatment may also reflect plastic changes in motor output after the reorganization of synaptic density.

Therapeutic uses of botulinum toxin: from facial palsy to autonomic disorders

BACKGROUND

The therapeutic uses of botulinum toxin have been expanding due to deeper knowledge of its molecular behaviour and different mechanisms of action.

OBJECTIVE

To present suggested doses of Botox and Dysport for controlling the muscle hyperkinetic activity in facial palsy in the perioral area and to review other uses.

METHODS

An extensive updated literature review on the success and limits of the botulinum neurotoxin (BoNT) therapeutic treatments.

RESULTS/CONCLUSION

BoNT can be considered to be the preferred single method for many disorders; it has substituted for some conventional surgical methods and it can be associated with other therapies to increase overall treatment performance. Depending on the disorder, the lack of permanent effect causes no major inconvenience.

Prospective study examining remote effects of botulinum toxin a in children with cerebral palsy

We examined the remote effects on muscle strength and functional decline of lower-extremity botulinum toxin A injections in children with cerebral palsy. This prospective study enrolled 34 children (19 boys, 15 girls; mean age, 7.7 years) diagnosed with spastic cerebral palsy. Patients were examined at baseline and 1 month to determine if they experienced a change in upper-extremity strength (handheld dynamometry) or function (Pediatric Outcomes Data Collection Instrument). Subjects were analyzed in aggregate and by dosing group (low dose, 0-10 U/kg body weight; high dose, 11-25 U/kg) to determine if injection dose was associated with a change in remote muscle strength or function. We measured baseline and 1-month postinjection strength in shoulder flexor, shoulder abductor, elbow flexor, elbow extensor, and finger flexor muscles. None of these remote muscle groups was significantly weaker at 1 month after injection. No correlation was evident between change in muscle strength and toxin dose. These findings indicate that doses of botulinum toxin A in the lower extremities, at up to 21 U/kg, do not affect upper-extremity strength. This information can help guide dosages of botulinum toxin A in the management of spasticity in children with cerebral palsy.

Autonomic cardiovascular function and baroreflex sensitivity in patients with cervical dystonia receiving treatment with botulinum toxin type A

OBJECTIVE

To investigate possible changes in autonomic cardiovascular regulation and cardiopulmonary baroreflex sensitivity in patients with primary cervical dystonia receiving chronic treatment with botulinum toxin type A.

METHODS

Short-term power spectral analysis of heart rate and systolic blood pressure variability, high-frequency and low-frequency oscillations of heart rate variability, low frequency/high frequency ratio and baroreflex sensitivity (alpha index) were measured in 12 patients with cervical dystonia before and 2-4 weeks after botulinum toxin type A injection and compared with normative data.

RESULTS

Before treatment, at rest, patients had significantly lower high frequency power than healthy subjects (p < 0.01), whereas no differences were found in low frequency power. Botulinum toxin injection in patients induced no changes in either power frequency. In patients before treatment and healthy subjects the low frequency oscillatory components increased similarly from rest to tilt (p < 0.01), but tilt induced lower low frequency values in patients than in healthy subjects (p < 0.01). In patients before treatment, the high frequency variations from rest to tilt remained unchanged, whereas in healthy subjects they decreased significantly (p < 0.01). Botulinum toxin type A injection in patients induced no changes in low frequency or high frequency powers. In patients before treatment the low frequency/high frequency ratio increased slightly from rest to tilt, but in healthy subjects increased significantly (p < 0.01). Botulinum toxin type A left the pretreatment low frequency/high frequency ratio unchanged. The alpha-index measured at rest in patients before treatment was lower than in healthy subjects (p<0.05), whereas during tilt was similar in both groups. The alpha-index measured after botulinum toxin injection in patients remained unchanged at rest and during tilt.

CONCLUSIONS

Patients with cervical dystonia receiving treatment with botulinum toxin type A have mild, subclinical abnormalities in autonomic cardiovascular regulation and cardiopulmonary baroreflex sensitivity. These changes do not worsen after acute botulinum toxin type A injection.

Pharmakologische Aspekte therapeutischer Botulinum-Toxin-Präparationen

Therapeutic preparations of botulinum toxin (BT) consist of botulinum neurotoxin (BNT), complexing proteins, and excipients. Depending on the target tissue, BNT can block cholinergic neuromuscular innervation of intra- and extrafusal muscle fibres or cholinergic autonomic innervation of sweat, lacrimal, and salival glands and smooth muscles. Indirect CNS effects are numerous; direct ones have not been reported after intramuscular application. Botulinum toxin type A is distributed as Botox, Dysport, Xeomin, Hengli/CBTX-A, and Neuronox and BT type B as NeuroBloc/Myobloc. Differences in potency labelling of therapeutic BT preparations can be corrected by introduction of a conversion factor of 1:3 between Botox and Dysport, of 1:1 between Botox and Xeomin, and of 1:40 between Botox and NeuroBloc/Myobloc. Acute adverse effects of BT can be obligate, local or systemic. Adverse effect profiles of the different preparations are similar. However, BT type B frequently produces additional autonomic systemic adverse effects. Long-term application does not produce additional adverse effects. BNT can be partially or completely blocked by antibodies. Risk factors include the amount of BNT applied at each injection series, the interval between injection series, and the specific biological potency (SBP) of the BT preparation used. The SBP is 5 equivalent mouse units/ng BNT for NeuroBloc, 60 for Botox, 100 for Dysport, and 167 for Xeomin. Xeomin should therefore have a particularly low antigenicity. Clinical confirmation of this predicition, however, is lacking.

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.

Botulinum toxin A during pregnancy: a survey of treating physicians

Botulinum toxin A (btxA) is widely used for cosmetic purposes, headaches, dystonia, spasticity, pain and other on and off label uses. Despite the widespread use of btxA in women of childbearing potential, there are few data on the effects of this drug on pregnant women and the fetus. The goal of this study was to survey physicians who use btxA, to determine their experience with pregnant women. We surveyed 900 physicians who used commercially available btxA. The questionnaire asked treating physicians if they had knowingly or unknowingly injected pregnant women and what was the outcome of each pregnancy. In total, 396 physicians (44%) returned questionnaires, of whom only 12 physicians reported injecting pregnant women with btxA. Sixteen pregnant women were injected, mostly in the first trimester, and only one patient, who had prior spontaneous abortions, suffered a miscarriage. Another woman had a therapeutic abortion. All other pregnancies went to term and there were no fetal malformations. Based on this limited survey of treating physicians in the USA, btxA appears to be relatively safe for both expectant mother and fetus. We need further data, however, and we would recommend that physicians and patients carefully consider the risks and benefits before using btxA in pregnant women.

Botulinum toxin-physiology and applications in head and neck disorders

This article is structured around a literature review that was carried out using Ovid and Medline with the key words "botulinum," "toxin," and "ENT." Botulinum toxin has been used safely in humans for more than 20 years. The effects are transient, such that treatments are required to be repeated at intervals. Its application to ENT provides a useful tool to treat dystonia, autonomic dysfunction, facial nerve paresis, and hyperfunctional lines. It may also be of benefit in laryngeal rebalancing and the treatment of headaches. Further research is being carried out and new indications for treatment with botulinum toxin may include sialorrhea and rhinorrhea.

The therapeutic use of botulinum toxin

Since Alan Scott's research, botulinum toxin (BoNT) has been used in several diseases or conditions characterised by muscular overactivity. BoNT acts on either neuromuscular or autonomic cholinergic junctions. Seven different serotypes are known, with antigenic specificity and different therapeutic profiles. BoNT is made up of a heavy chain, involved in binding and membrane translocation, and a light chain, involved in blocking neuroexcytosis. Each serotype shares a specific acceptor on the presynaptic membrane of a cholinergic junction. The available BoNT preparations differ in toxicity, purity and stability. Injection of the neurotoxin produces several modifications at a neuromuscular junction. Axonal sprouting, muscular fibre atrophy, and new end-plates are the most evident histological events after BoNT treatment. They appear to be reversible in untreated muscles. Diffusion can occur at first by haematogeneous or local BoNT spread. Several factors, such as dose, volume, site of injection, muscle size, and muscular fascia, can influence the amount of diffusion and possible side-effects. After prolonged BoNT treatment patients can become unresponsive. Antibodies directed against BoNT have been observed with ELISA or mouse bioassay. Different serotypes have been used to treat non-responder patients. Novel toxins with lower immunogenicity and prolonged clinical efficacy are required for more effective treatment.

Botulinum Toxin for the Treatment of Temporomandibular Joint Disk Disfigurement: Clinical Experience

Type A botulinum toxin was used for the treatment of symptoms of 26 patients (40 joints) with temporomandibular joint disk disfigurement. In all patients, 0.5 ml (12.5 U) was injected into the lateral pterygoid muscle. The temporalis, medial pterygoid, and masseter muscles were injected if severe tenderness was noted. The data were compared using the Wilcoxon signed rank test and the McNemar test. With the exception of clicking of the right joint, all mean outcome measures showed a significant difference between the preinjection and postinjection assessments. There was a significant difference between the preinjection and postinjection pain scores of the right joint (P=0.0019) and the left joint (P=0.000). Postinjection values of the mouth opening (P=0.002), subjective functional dysfunction (P=0.065), and clicking of the left joint (P=0.001) also showed a statistically significant difference from the preinjection values. In addition, the severity and frequency of headache were reduced after botulinum toxin-A injection into the lateral pterygoid muscle.

Botulinum toxin: mechanisms of action

This review describes therapeutically relevant mechanisms of action of botulinum toxin (BT). BT's molecular mode of action includes extracellular binding to glycoproteine structures on cholinergic nerve terminals and intracellular blockade of the acetylcholine secretion. BT affects the spinal stretch reflex by blockade of intrafusal muscle fibres with consecutive reduction of Ia/II afferent signals and muscle tone without affecting muscle strength (reflex inhibition). This mechanism allows for antidystonic effects not only caused by target muscle paresis. BT also blocks efferent autonomic fibres to smooth muscles and to exocrine glands. Direct central nervous system effects are not observed, since BT does not cross the blood-brain-barrier and since it is inactivated during its retrograde axonal transport. Indirect central nervous system effects include reflex inhibition, normalisation of reciprocal inhibition, intracortical inhibition and somatosensory evoked potentials. Reduction of formalin-induced pain suggests direct analgesic BT effects possibly mediated through blockade of substance P, glutamate and calcitonin gene related peptide.

Botulinum toxin A for the treatment of cervical dystonia

Idiopathic cervical dystonia (ICD) is the most common adult-onset focal dystonia. It is characterised by relatively sustained, involuntary contractions of neck muscles. Injections of botulinum toxin (BTX)-A are safe and effective for the treatment of ICD, and have substantially improved its treatment. BTX-A is manufactured by Allergan Pharmaceuticals in the US and Ireland, and is distributed as Botox. In Europe, BTX-A is manufactured and distributed by Ipsen Pharmaceuticals as Dysport. Success rates for BTX-A injections for ICD ranges 64-90%, with 76-93% of injected patients experiencing pain reduction. Side effects are generally mild and include dysphagia and neck weakness.

Botulinum toxin: mechanisms of action

Botulinum toxin (BT) has been perceived as a lethal threat for many centuries. In the early 1980s, this perception completely changed when BT's therapeutic potential suddenly became apparent. We wish to give an overview over BT's mechanisms of action relevant for understanding its therapeutic use. BT's molecular mode of action includes extracellular binding to glycoprotein structures on cholinergic nerve terminals and intracellular blockade of the acetylcholine secretion. BT affects the spinal stretch reflex by blockade of intrafusal muscle fibres with consecutive reduction of Ia/II afferent signals and muscle tone without affecting muscle strength (reflex inhibition). This mechanism allows for antidystonic effects not only caused by target muscle paresis. BT also blocks efferent autonomic fibres to smooth muscles and to exocrine glands. Direct central nervous system effects are not observed, since BT does not cross the blood-brain barrier and since it is inactivated during its retrograde axonal transport. Indirect central nervous system effects include reflex inhibition, normalisation of reciprocal inhibition, intracortical inhibition and somatosensory evoked potentials. Reduction of formalin-induced pain suggests direct analgesic BT effects possibly mediated by blockade of substance P, glutamate and calcitonin gene-related peptide.

Botulinum toxin in children with cerebral palsy

Botulinum toxin is a neurotoxin that blocks the synaptic release of acetylcholine from cholinergic nerve terminals mainly at the neuromuscular junction, resulting in irreversible loss of motor end plates. It is being widely tried as a targeted antispasticity treatment in children with cerebral palsy. A number of studies have shown that it reduces spasticity and increases the range of motion and is particularly useful in cases with dynamic contractures. However improvement in function has not been convincingly demonstrated. It is an expensive mode of therapy and the injections need to be repeated after 3-6 months. Whereas Botulinum toxin can be a valuable adjunct in select cases, it should not be projected as a panacea for children with spastic cerebral palsy.

Time Course of Recovery of Juvenile Skeletal Muscle After Botulinum Toxin A Injection

OBJECTIVE

To study the effects of neuromuscular blockade using botulinum toxin A on juvenile muscles at a dosage of 6 units/kg body weight in a rat model.

DESIGN

A total of 34 male Sprague-Dawley rats (1-mo old) were used. A small incision was made along the posterior aspect of the left hind leg with the exposure of the gastrocnemius. Botulinum toxin A was injected at a dosage of 6 units/kg body weight in the medial and lateral heads of the muscle. An equivalent volume of saline were injected into the right gastrocnemius (control). Motor evoked action potentials, muscle force generation, and muscle mass and neuromuscular junction morphometry were analyzed at different time intervals up to 1 yr after toxin injection.

RESULTS

During the 1-2 wks after botulinum toxin A injection, muscle mass, electrophysiologic variables, and muscle force generation were significantly reduced but returned to nearly normal at 6 mos postinjection. In the study group, neuromuscular junction gutter depth became significantly shallower 2 mos after injection, then normalized at 1 yr. There was a nonsignificant trend toward larger neuromuscular junctions from the gastrocnemius injected with botulinum toxin A.

CONCLUSION

Our findings provide scientific evidence to support the clinical situation in which the interinjection interval of 3-6 mos of botulinum toxin A at a similar dosage is used.

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.

Physiological effects of botulinum toxin in spasticity

There is considerable evidence that injection of botulinum toxin (BTX) into muscles with spastic overactivity reduces resistance to passive movement in joints supplied by the injected muscles. The demonstration of improvement in active performance of the paretic limbs has been only anecdotal to date, and represents the most difficult challenge in research on BTX therapy in spastic paralysis. Data are reviewed that indicate several neurophysiological actions of BTX, other than the blocking of acetylcholine release at the neuromuscular ending: effects on the central nervous system, including retrograde axonal transport, reduced motoneuronal excitability, action on central synapses such as decreased Renshaw inhibition and increased presynaptic inhibition; action on gamma motoneuronal endings; action on most active terminals; spread of BTX to neighboring muscles; spread of BTX effects to remote muscles. Several of these neurophysiological actions are likely to contribute to improvement in active movements, as they may antagonize the primary mechanisms of functional impairment in patients with spastic paralysis: weakness, spastic cocontraction, spastic dystonia, and muscle shortening. We review the evidence for reduction of spastic cocontraction in both the injected muscle and its antagonist, and for improvement of antagonist weakness after BTX injection. The capacity of intramuscular BTX to reduce spastic dystonia and lengthen shortened muscles is also discussed based on prior literature. When injected into the more overactive of a pair of spastic antagonists around a joint, BTX should affect all the main mechanisms impairing active function around the joint.

The basic science of botulinum toxin

Understanding the basic science of botulinum toxin should serve as a fundamental first step for clinical therapy. This article endeavors to cover many aspects of basic research that also have clinical import. The two principal toxins of the clostridial family, Clostridium tetani and C botulinum, are described in detail. The five clinical manifestations of botulism poisoning are also outlined, and structural aspects and the mechanism of action of botulinum toxin are then presented. Finally, the immunologic and pharmacologic principles that define the various serotypes of botulinum toxin are set forth.