Neuromuscular effects distant from the site of botulinum neurotoxin injection

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.

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.

Electrophysiological abnormalities in iatrogenic botulism: Two case reports and review of the literature

Therapeutic use of botulinum neurotoxin type A (BoNT/A) is effective, and generally safe. Nevertheless, iatrogenic botulism (IB) is rarely reported as a result of systemic spread of the BoNT/A, causing general weakness, bulbar symptoms and dysautonomia. Suggestive clinical feature are decisive to raise the diagnostic suspicion, which however needs a confirmation in the electrodiagnostic (EDX) study, above all to exclude other treatable diseases. In this study, we report 2 patients who developed IB after receiving therapeutic doses of BoNT/A, assessing the EDX changes, and reviewing the literature on EDX in IB. Although there is not enough data to draw solid conclusions we propose that, in a subject with suggestive clinical features and recent exposure to BoNT/A, the absence of a decremental or incremental response to repetitive nerve stimulation in muscles showing acute denervation changes, is a suggestive finding for the diagnosis of IB.

Assessing adverse effects of intra-articular botulinum toxin A in healthy Beagle dogs: A placebo-controlled, blinded, randomized trial

OBJECTIVE

To investigate the clinical, cytological, and histopathological adverse effects of intra-articularly injected botulinum toxin A in dogs and to study whether the toxin spreads from the joint after the injection.

METHODS

A longitudinal, placebo-controlled, randomized clinical trial was conducted with six healthy laboratory Beagle dogs. Stifle joints were randomized to receive either 30 IU of onabotulinum toxin A or placebo in a 1:1 ratio. Adverse effects and spread of the toxin were examined by evaluating dynamic and static weight-bearing of the injected limbs, by assessing painless range of motion and pain on palpation of joints, and by performing synovial fluid analysis, neurological examination, and electrophysiological recordings at different examination time-points in a 12-week period after the injections. The dogs were then euthanized and autopsy and histopathological examination of joint structures and adjacent muscles and nerves were performed.

RESULTS

Intra-articular botulinum toxin A did not cause local weakness or injection site pain. Instead, static weight-bearing and painless range of motion of stifle joints decreased in the placebo limbs. No clinically significant abnormalities associated with intra-articular botulinum toxin A were detected in the neurological examinations. Electrophysiological recordings showed low compound muscle action potentials in two dogs in the botulinum toxin A-injected limb. No significant changes were detected in the synovial fluid. Autopsy and histopathological examination of the joint and adjacent muscles and nerves did not reveal histopathological adverse effects of the toxin.

CONCLUSION

Intra-articular botulinum toxin A does not produce significant clinical, cytological, or histopathological adverse effects in healthy dogs. Based on the electrophysiological recordings, the toxin may spread from the joint, but its clinical impact seems to be low.

Focal treatment of spasticity using botulinum toxin A in cerebral palsy cases of GMFCS level V: evaluation of adverse effects

OBJECTIVE

To report on the experience of injections of botulinum toxin A (BTA) in a series of patients with cerebral palsy of Gross Motor Function Classification System (GMFCS) level V.

METHODS

This was a retrospective case series study on 33 patients with cerebral palsy of GMFCS level V who received 89 sessions of BTA application (of which 84 were Botox(®) and five were other presentations), in which the basic aim was to look for adverse effects.

RESULTS

The mean number of application sessions per patient was three, and the mean age at the time of each injection was 4 + 6 years (range: 1.6-13 years). The muscles that most frequently received injections were the gastrocnemius, hamstrings, hip adductors, biceps brachii and finger flexors. The mean total dose was 193 U and the mean dose per weight was 12.5 U/kg. Only one patient received anesthesia for the injections and no sedation was used in any case. No local or systemic adverse effects were observed within the minimum follow-up of one month.

CONCLUSION

The absence of adverse effects in our series was probably related to the use of low doses and absence of sedation or anesthesia. According to our data, BTA can be safely used for patients with cerebral palsy of GMFCS level V, using low doses and preferably without sedation or anesthesia.

Employment of higher doses of botulinum toxin type A to reduce spasticity after stroke

Spasticity is a common disabling symptom for several neurological conditions. Botulinum toxin type A injection represents the gold standard treatment for focal spasticity with efficacy, reversibility, and low prevalence of complications. Current guidelines suggest a dose up to 600 units (U) of onabotulinumtoxinA/incobotulinumtoxinA or up to 1,500 U of abobotulinumtoxinA to treat post-stroke spasticity to avoid important adverse effects. However, recently, higher doses of botulinum toxin type A were employed, especially in case of upper and lower limb severe spasticity. With searches of US National Library of Medicine databases, we identified all studies published from December 1989 to July 2014 concerning the use of higher doses of this neurotoxin for spasticity treatment with at least a dose of 600 U of onabotulinumtoxinA and incobotulinumtoxinA or 1,800 U of abobotulinumtoxinA. The cumulative body of evidence coming from the eight studies selected suggested that higher doses of botulinum toxin type A appeared to be efficacious in reducing spasticity of the upper and lower limbs after stroke, with adverse effects generally mild. However, further investigations are needed to determine the safety and reproducibility in larger case series or randomized clinical trials of higher doses of botulinum toxin type A also after repeated injections.

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.

Influence of injection of Chinese botulinum toxin type A on the histomorphology and myosin heavy chain composition of rat gastrocnemius muscles

BACKGROUND AND OBJECTIVE

Botulinum toxin type A (BoNT/A) is a metalloprotease that blocks synaptic transmission via the cleavage of a synaptosomal-associated protein of 25 kDa (SNAP-25). It has gained widespread use as a treatment for cerebral palsy and skeletal muscle hypertrophy. In China, Chinese botulinum toxin type A (CBTX-A), a type of BoNT/A, is in widespread clinical use. However, the changes in the morphological and biochemical properties of treated muscles and in remote muscles from the CBTX-A injection site are relatively unknown. Therefore, we investigated the changes in histomorphology and myosin heavy chain (MyHC) isoform composition and distribution in rat gastrocnemius muscles after intramuscular injection of CBTX-A.

METHODS

The weakness of the injected muscles was assessed periodically to identify their functional deficiency. Muscle slices were stained with hematoxylin-eosin (HE) and adenosine triphosphatase (ATPase). MyHC isoform composition was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to uncover changes in morphological and biochemical properties.

RESULTS

Our findings demonstrate that following injection of CBTX-A 5 U into rat gastrocnemius muscles, shifts in MyHC isoform composition emerged on the third day after injection and peaked in the fourth week. The composition remained distinctly different from that of the control group after the twelfth week. More specifically, there was a decrease in the proportion of the type IIb isoform and an increase in the proportions of type IIx, type IIa, and type I isoforms.

CONCLUSIONS

Data revealed that CBTX-A led to a shift in MyHC composition towards slower isoforms and that the MyHC composition remained far from normal six months after a single injection. However, no noticeable remote muscle weakness was induced.

Onabotulinum toxin a (botox®) in the treatment of neurogenic bladder overactivity

Botulinum toxin (BT) is a potent presynaptic neuromuscular blocking agent which induces selective, reversible muscle weakness for months when injected intramuscularly. During recent years BT has revolutionized the treatment of previously intractable symptoms of detrusor overactivity. Based on a systematic search of the PubMed database, a review of the current literature on the use of onabotulinum toxin A (Botox®) in the treatment of neurogenic detrusor overactivity is presented.

Onabotulinum toxin A proved to be highly effective in the majority of studies, even though a wide range of injection techniques and dosages were described. The onset of the effect usually appeared before 2 weeks, and reached a peak within 2-6 weeks, with the clinical effect being maintained for approximately 6-8 months, or even longer. Depending on the dose, a number of patients developed high residual volume and clean intermittent self/helper catheterization (CIC) may become necessary. Only a few side effects were described, and intravesical onabotulinum toxin A injection seems to be well tolerated. However, details on injection technique, dose interval between injections, etc. are still under debate and only a few randomized, placebo controlled studies have been published.

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.

On muscle spindles, dystonia and botulinum toxin

Dystonia may produce co-contractions and constant strain in numerous muscle fibers, including those of the muscle spindles. As proprioceptors, muscle spindles detect dynamic or static changes in muscle length and their afferent projections to the spinal cord play a central role in control of antagonistic muscles. Their parallel arrangement with extrafusal muscle fibers and association with the earlier recruited oxidative motor units allow them to conveniently sample the activity of all motor units and effectively modulate movement. At the same time, fusimotor muscle spindle innervation contracts the striated polar portions of the intrafusal muscle fibers and prevents their slackening during extrafusal muscle contractions. Botulinum toxin remains the most efficient therapy of dystonia. Its muscular mechanism of action is hinged on cholinergic blockade not only of extrafusal, but also of intrafusal muscle fibers. Besides being a targeted muscular therapy, the alteration of the corresponding sensory input following an effect of botulinum toxin on the intrafusal muscle fibers is pivotal in modulating loss of pre-synaptic inhibition in dystonia, including suppression of the tonic vibration reflex. Whether or not trans-synaptic botulinum toxin migration occurs, a modification of the central motor programming is bound to happen in dystonia, with botulinum toxin acting either as another 'sensory trick' or as a form of 'short-term plasticity'. Knowledge of the muscle spindle anatomy and function is key to unify our understanding of abnormal movements and of effects of botulinum toxin therapy. Thus, in dystonia, overactivity of muscles and increased spindle sensitivity are germane to botulinum toxin targets of action.

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.

Clinical consequences of reinnervation disorders after focal peripheral nerve lesions

Axonal regeneration and organ reinnervation are the necessary steps for functional recovery after a nerve lesion. However, these processes are frequently accompanied by collateral events that may not be beneficial, such as: (1) Uncontrolled branching of growing axons at the lesion site. (2) Misdirection of axons and target organ reinnervation errors, (3) Enhancement of excitability of the parent neuron, and (4) Compensatory activity in non-damaged nerves. Each one of those possible problems or a combination of them can be the underlying pathophysiological mechanism for some clinical conditions seen as a consequence of a nerve lesion. Reinnervation-related motor disorders are more likely to occur with lesions affecting nerves which innervate muscles with antagonistic functions, such as the facial, the laryngeal and the ulnar nerves. Motor disorders are better demonstrated than sensory disturbances, which might follow similar patterns. In some instances, the available examination methods give only scarce evidence for the positive diagnosis of reinnervation-related disorders in humans and the diagnosis of such condition can only be based on clinical observation. Whatever the lesion, though, the restitution of complex functions such as fine motor control and sensory discrimination would require not only a successful regeneration process but also a central nervous system reorganization in order to integrate the newly formed peripheral nerve structure into the prepared motor programs and sensory patterns.

Botulinum toxin type B (Myobloc, NeuroBloc): a new choice in cervical dystonia

Botulinum toxin has dramatically improved the treatment of cervical dystonia. Prior to the use of botulinum toxin for many neurologic disorders, patients had few effective therapeutic options. Botulinum toxin type B (Myobloc, NeuroBloc) is a new antigenically distinct botulinum toxin with a unique structure and mechanism of action. Preclinical studies have demonstrated that im. injections of botulinum toxin type B effectively induce a dose-dependent paralysis. Controlled clinical trials have shown that it is safe and effective in alleviating symptoms associated with cervical dystonia. Given its efficacy and safety profile, the clinical use of type B toxin is anticipated to expand into other therapeutic areas.

Vaginismus: results of treatment with botulin toxin

In view of the long-term therapy necessary to cure vaginismus and specially persistent cases, we considered using botulin toxin (BT) injections for the treatment of such cases. Eight women (mean age 26.6 +/- 1.2 years) with vaginismus were treated with BT. Another five women with vaginismus, matching the eight patients in age, acted as controls. The patients in the study group were injected with BT (25 IU diluted in 1 ml saline) into each of the two bulbospongiosus muscles. Control patients were injected with saline. Mean follow-up was 10.2 +/- 3.3 months. All the patients injected with BT improved. The couples could achieve satisfactory intromission. No patient was in need of re-injection and there was no recurrence during the follow-up period. Control subjects did not improve with the saline injection into the bulbospongiosus muscle. In conclusion, BT injection effected cure in all of the vaginismus patients with no complications or recurrence. The technique is simple, easy, cost-effective, not time-consuming and can be achieved on an outpatient basis.

Undesirable distant effects following botulinum toxin type a injection

OBJECTIVES

To study the incidence of clinical signs linked to botulinum toxin type A (BoNTA) spread from the injection site.

METHODS

Single-center, retrospective, cohort study. All patients who received BoNTA injections for spasticity treatment were assessed 1 month postinjection. Adverse effects indicative of BoNTA treatment were systematically sought. Any patient with adverse effects possibly due to BoNTA spread underwent further clinical examination and single-fiber electromyography. One patient underwent neuromuscular biopsy.

RESULTS

Between January and September 2005, 266 BoNTA injection sessions (187 patients) were performed (233 BOTOX, 33 Dysport). Five patients presented with clinical signs of toxin spread. Four of these underwent single-fiber electromyography, which showed increased jitter. Neuromuscular biopsy detected signs of recent denervation without signs of reinnervation.

CONCLUSIONS

Diffusion diagnosis of BoNTA from the injection site depends on clinical, temporal, and electromyographic factors. Clinical expression of spread varies widely, with mechanisms remaining largely unknown, and further prospective, randomized clinical trials are required.

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.

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.

Iatrogenic botulism due to therapeutic botulinum toxin a injection in a pediatric patient

Botulinum toxin A is commonly used to reduce spasticity and dystonia in children with cerebral palsy. We report a pediatric patient who developed systemic botulism as a result of a severe overdose of the injected toxin (40 U/kg). This case highlights the importance of physicians having adequate knowledge of primate and human literature on the lethal dose, 50% of botulinum toxin A before injecting children.

Abnormal surface EMG during clinically normal wrist movement in cervical dystonia

We investigated whether patients with cervical dystonia (CD) have abnormal muscle activation in non-dystonic body parts. Eight healthy controls and eight CD patients performed a flexion-extension movement of the right wrist. Movement execution was recorded by surface electromyography (EMG) from forearm muscles. Although patients had no complaints concerning wrist movement and had no apparent difficulty in executing the task, they demonstrated lower mean EMG amplitude (flexor: 0.32 mV and extensor: 0.61 mV) than controls (flexor: 0.67 mV; P = 0.021 and extensor: 1.18 mV; P = 0.068; borderline significant). Mean extensor muscle contraction was prolonged in patients (1860 ms) compared with controls (1334 ms; P = 0.026). Variation in mean EMG amplitude over movements tended to be higher in patients (flexor: 43% and extensor: 35%) than controls (flexor: 34%; P = 0.072 and extensor: 26%; P = 0.073). These results suggest that CD patients also have abnormal muscle activation in non-dystonic body parts at a subclinical level. This would support the concept that in dystonia, non-dystonic limbs are in a 'pre-dystonic state'.

Electrodiagnostic studies of the facial nerve in peripheral facial palsy and hemifacial spasm

Electrodiagnostic (EDX) assessment is one of the most important aspects in the evaluation of the two most common disorders of the facial nerve: facial palsy and hemifacial spasm. Facial palsy is usually an acute disorder that resolves in a few weeks but, in a number of cases, leads to a postparalytic facial syndrome featuring muscle synkinesis, myokymia, and involuntary mass contractions of muscles on the affected side. Hemifacial spasm is usually a chronic disorder characterized by paroxysms of involuntary, clonic, and synchronous twitching of all facial muscles on the affected side. EDX studies provide information on lesion location and severity, pathophysiology underlying the two disorders, and differential diagnosis between syndromes presenting with abnormal facial muscle activity. This monograph is intended to describe the most relevant EDX findings in the two disorders and the most appropriate timing for the examinations in order to provide useful information for prognosis and therapeutic decision-making.

Quantitative EMG of facial muscles in myasthenia patients with MuSK antibodies

OBJECTIVE

Our aim was to study the pathophysiological process leading to facial muscle atrophy in 13 patients with MuSK antibody positive myasthenia gravis (MuSK-MG), and to compare with findings from 12 acetylcholine receptor antibody positive myasthenia patients (AChR-MG), selected because they suffered from the same degree of disease severity and required similar treatment.

METHODS

Motor unit action potential (MUAP) and interference pattern analysis from orbicularis oculi (O oculi) and orbicularis oris (O oris) muscles were studied using a concentric needle electrode, and compared with findings in 20 normal subjects, 6 patients receiving botulinum toxin injections (representing a neurogenic model) and 6 patients with a muscle dystrophy (representing a myopathic model). The techniques and control data have been reported previously.

RESULTS

The mean MUAP durations for O oculi and O oris were significantly reduced (p<0.001) in both MG cohorts when compared with healthy subjects, and were similar to those in the myopathic control group. They were significantly different from those obtained from the neurogenic control group (p<0.001 for both O oculi and O oris). The MUAP findings in O oculi occurred independently from neuromuscular blocking on single fibre EMG (SFEMG) in the same muscle. On turns amplitude analysis (TAA), 50% of MuSK-MG patients and 42% of AChR-MG patients had a pattern in O oculi which was similar to that in the myopathic control group, and 62% of MuSK-MG patients and 50% of AChR-MG patients had a pattern in O oris that was also similar to that in the myopathic control group. The TAA findings for O oculi and O oris in both MG cohorts were different from those obtained from the neurogenic control group.

CONCLUSIONS

Facial muscle atrophy in MuSK-MG patients is not neurogenic and the pathophysiological changes are akin to a myopathic process. The selected AChR-MG patients also show evidence of a similar pathophysiological process in the facial muscles albeit to a lesser degree.

SIGNIFICANCE

We propose that muscle atrophy in MuSK-MG is a myopathic process consisting of either muscle fibre shrinkage or loss of muscle fibres from motor units. The duration of disease and long-term steroid treatment may be further contributory factors.

Using translational medicine to understand clinical differences between botulinum toxin formulations

When using botulinum toxin-based products, the physician must decide the optimal location and dose required to alleviate symptoms and improve the patient's quality of life. To deliver effective treatment, the physician needs to understand the importance of accurate target muscle selection and localization and the implications of each product's migration properties when diluted in different volumes. Pre-clinical mouse models of efficacy and safety have been utilized to compare local and distal muscle relaxation effects following defined intramuscular administration. Data from the model allow the products to be ranked based on their propensity for local efficacy versus their distal migration properties. Using standardized dilutions, the non-parallel dose-response curves for the various formulations demonstrate that they have different efficacy profiles. Distal effects were also noted at different treatment doses, which are reflected in the different safety and/or therapeutic margins. Based on these pre-clinical data, the safety and therapeutic margin rankings are ordered, largest to smallest, as BOTOX, Dysport and Myobloc. The results of subsequent clinical trials are variable and dose comparisons are inconclusive, thus supporting the regulatory position that the dose units of the individual preparations are unique and cannot be simply converted between products.

Severe Dysphagia After Botulinum Toxin B Injection to the Lower Limbs and Lumbar Paraspinal Muscles

We report a case of severe dysphagia in a 29-yr-old woman with cerebral palsy after she was injected with botulinum toxin B to her lower limbs and lumbar paraspinal muscles. Four days after the treatment, she developed difficulty swallowing, more severe for solid foods than for liquids, accompanied by dry mouth, blurred vision, and voice hoarseness. Fifteen days after the injection, with worsening of her dysphagia, she was hospitalized. A laryngoscopic evaluation revealed bilateral vocal cord paresis, and a modified barium swallow test demonstrated delayed oral initiation, upper airway penetration, and no reflexive cough. In the following days, she improved spontaneously and was discharged 12 days later when she re-acquired the ability to swallow solid foods. Her symptoms resolved completely only 75 days after the injection. Although dysphagia is a common side effect of botulinum injection in the neck, to our knowledge, this is the first reported case of severe dysphagia after injection in a distant anatomic site.

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.

Adverse events after botulinum A toxin injection for neurogenic voiding disorders

OBJECTIVES

To review the side effects of local injections of botulinum A toxin (BTX-A).

METHODS

A medline search for publications about adverse events after injection of BTX-A for lower urinary tract dysfunctions.

RESULTS

We found four publications that report generalised side effects after BTX-A injection for detrusor overactivity (two) and detrusor-sphincter dyssynergia (two). The causes of generalised adverse events are not clear, but spread outside the target organ and into the systemic circulation may contribute. The dose used, the injection volume and the injection technique can all play a role.

CONCLUSION

Generalised side effects after BTX-A injection for voiding disorders are rare but they can be very disabling for spinal cord-injured patients. Although no long-term side effects are reported so far, urologists should be aware that these effects of BTX-A injections are unknown.

[Botulinum toxin and medical liability: is the patient sufficiently informed?]

INTRODUCTION

The use of botulinum toxin injection therapy is soaring significantly today, with an ever-wider field of applications despite well-known side effects of the treatment. This article aims at analysing the medicolegal practices of practitioners who use this therapy, especially the information given to patients and finding a common practice for providing that information.

METHODS

We sent a questionnaire to 340 practitioners who might use the therapy (physiatrists, neurologists, ophthalmologists, ENT specialists, plastic surgeons) working in hospitals and in physical therapy and rehabilitation centres in France. Besides mentioning the possible side effects of the therapy, the questionnaire focused on how such information was transmitted before the injection.

RESULTS

Data collection and analysis were performed by use of a spreadsheet software programme. A total of 124 questionnaires were analysed. We did not analyse the items dealing with side effects. Sixty-five percent of the responders said they did not seek statutory authorisation for injections. Only 31% provided written, detailed information and 12% required a signed consent form. Complaints were rare, approximately 12%, were written or verbal, and were always dismissed.

DISCUSSION

Side effects after botulinum toxin injection are clearly described in the medical literature. Therefore, it is of utmost importance for this product to be used therapeutically and only by experienced therapists who will carefully respect the product's standard rules of use and inform their patients to the best of their ability. Issuing a detailed letter of information describing all the side effects seems necessary. We suggest a model information letter such as that provided to the patients in our facility.

CONCLUSION

Botulinum toxin is a very worthwhile product for numerous abnormalities but has side effects, often brief, at the site of the injection. Therefore it is our duty to inform patients effectively.

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 for lower limb spasticity in children with cerebral palsy: a single-blinded trial comparing dilution techniques

OBJECTIVE

To compare the effect of equivalent doses of botulinum toxin type A given in high-volume or low-volume injections on lower limb spasticity in children with cerebral palsy.

DESIGN

A total of 17 subjects whose modified Ashworth scale scores in the calf flexors bilaterally ranged from 2 to 3 were enrolled. The right gastrocnemius was injected with botulinum toxin type A using a high-volume preparation (100 IU/4 ml), and the left gastrocnemius was injected with a low-volume preparation (100 IU/1 ml). The amplitude and area of the compound muscle action potential for both medial gastrocnemius muscles, the dynamic muscle range, static muscle range, modified Ashworth scale for both ankles, and the Gross Motor Functional Classification System were assessed before and after treatment.

RESULTS

Spasticity was reduced in both legs. There was no significant difference in the changes in the amplitude and area of compound muscle action potential (P = 0.74 and 0.30, respectively), dynamic muscle range (P = 0.7), static muscle range (P = 0.65), and modified Ashworth scale (P = 1) in the right vs. left legs after botulinum toxin type A injection. The high-volume preparation did not cause more pain.

CONCLUSIONS

A higher volume preparation with a 4-fold dilution of botulinum toxin type A does not yield better results than a low-volume preparation.

Movement disorders in patients with peripheral facial palsy

Acute unilateral facial paralysis is usually a benign neurological condition that resolves in a few weeks. However, it can also be the source of a transient or long-lasting severe motor dysfunction, featuring disorders of automatic and voluntary movement. This review is organized according to the two most easily recognizable phases in the evolution of facial paralysis: (1). Just after presentation of facial palsy, patients may exhibit an increase in their spontaneous blinking rate as well as a sustained low-level contraction of the muscles of the nonparalyzed side, occasionally leading to blepharospasm-like muscle activity. This finding may be due to an increase in the excitability of facial motoneurons and brainstem interneurons mediating trigeminofacial reflexes. (2). If axonal damage has occurred, axonal regeneration beginning at approximately 3 months after the lesion leads inevitably to clinically evident or subclinical hyperactivity of the previously paralyzed hemifacial muscles. The full-blown postparalytic facial syndrome consists of synkinesis, myokymia, and unwanted hemifacial mass contractions accompanying normal facial movements. The syndrome has probably multiple pathophysiological mechanisms, including abnormal axonal branching after aberrant axonal regeneration and enhanced facial motoneuronal excitability. Although the syndrome is relieved with local injections of botulinum toxin, fear of such uncomfortable contractions may lead the patients to avoid certain facial movements, with the implications that this behavior might have on their emotional expressions.

Complications with the use of botulinum toxin

This article discusses complications with the use of botulinum toxin. The following topics are explored: conditions caused by muscle spasms, resistance to botulinum toxin, cosmetic use of botulinum toxin, complications in treating hyperhidrosis, treatment of migraine headaches, and informed consent.

Comparison of botulinum toxins A and B in the treatment of facial rhytides

Facial rhytides of the upper one third of the face are common aesthetic concerns, and are caused principally by overactivity of the underlying facial musculature. Botulinum toxin, which acts by causing flaccid paralysis of facial mimetic muscles, has become a treatment of choice for the management of these hyperfunctional facial lines. Two antigenically distinct serotypes have been developed and are currently available for commercial use in the United States. There are major differences between the two toxins in terms of pharmacology and formulation that account for clinical differences, and precise interconversion is not well-established. Nevertheless, in these preliminary studies, Myobloc seems to have a faster onset of action and potentially a more even and smoother paralysis. The shorter duration of action of Myobloc seems to be dose-related. It is clear that both agents safely and effectively reduce dynamic facial rhytides. Based on individual efficacy, safety, diffusion pattern, onset, and duration, ultimately, with further trials and clinical experience, it is conceivable that each toxin will have its own set of indications.

Intraparotid Injection of Botulinum Toxin A as a Treatment to Control Sialorrhea in Children with Cerebral Palsy

OBJECTIVE

To determine the efficacy of botulinum toxin A in the management of drooling (sialorrhea) in children and young adults with cerebral palsy.

DESIGN

Twenty-one children were enrolled in an open-label, nonblinded prospective study. Subjective and objective measures were used to determine the effect of botulinum toxin A on drooling and saliva production. Subjective measures included visual scales to document the child's severity and frequency of drooling. Objective measures included the number of bibs used per day and salivary secretion. At the initial visit, subjective and objective measures established the child's baseline drooling and saliva production. Fifteen units of botulinum toxin A was injected into each parotid glans. At each fellow-up visit of telephone survey, subjective and objective measures were recorded to monitor the child's drooling and saliva production. A postinjection questionnaire evaluated overall effect and caregiver satisfaction.

RESULTS

The visual analog scales and number of bibs used per day demonstrated statistically significant reduction in severity and frequency of drooling at 2 wks, 1 mo and 2 mos. Salivary production was significantly reduced at 1-mo fellow-up. Eighty-nine percent of the caregivers reported and improvement of their child's drooling after botulinum toxin A injection. Severity-nine percent of caregivers were satisfied with the treatment and would perform the treatment again.

CONCLUSION

Intraparotid injections of botulinum toxin A are efficacious in decreasing severity and frequency of drooling, the number of bibs used per day, and the production of saliva in children with cerebral palsy. The injections are relatively safe and adverse effects were observed in this study.

Contraindications and complications with the use of botulinum toxin

Cosmetic use of BTX has skyrocketed in recent years, especially since the approval of BTX-A for treatment of glabellar lines. Complications and adverse reactions can easily arise, particularly for the novice injector. This paper provides insights from an experienced physician on how to avoid these complications, and how to treat them when and if they occur. The main cosmetic uses for BTX are analyzed for possible complications and adverse events. Injection techniques are discussed. Comparisons between BTX-A and BTX-B are given to point out the need for different injection techniques based on the product being used. Treatment recommendations for the Glabella, Brow, Crow's Feet, Upper Lip Wrinkling/Lines, Depressor Anguli Oris, Nasolabial Folds, Mentalis, Neck and Hyperhidrosis are discussed, as well as systemic complications. It is important for the injecting physician to be familiar with these potential complications, even though the use of BTX has been safe and generally well tolerated, because it will lead to even greater success with the use of BTX.

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.