Time course of distant effects of local injections of botulinum toxin

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.

Botulinum Toxin-Induced Parotitis: A Postoperative Complication Following Masseter Muscle Injection

Botulinum toxin (BTX) injection is a common treatment for bruxism, but there is no literature on potential salivary gland complications. This paper presents a case of acute parotitis in a 60-year-old female following BTX injections to the masseter muscle. This case highlights the possible salivary gland complications after injection of BTX into the masticatory muscles. An electronic search of PubMed and Embase databases was conducted to create a literature review in order to delve into the etiology behind the presented case and suggest potential preventive measures to avoid salivary gland complications. Thirty-one articles are reviewed and discussed. Currently, there is no consensus on the causes of the mentioned complication. However, various factors have been proposed, encompassing anatomical, physiological, biological, and physical aspects. Several methods have been recommended for the safe injection of BTX, which, along with better medical training and knowledge, are warranted to achieve predictable results.

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.

Coordination of the upper and lower extremities during walking in children with cerebral palsy

BACKGROUND

Children with cerebral palsy indicate poor continuous gait inter-limb coordination compared to typically developing children. Limited research exists in the understanding of the coordinative relationship between the arms and legs of these children and if the phasing relationships between limbs can be improved.

RESEARCH QUESTION

Which motor control factors impact coordination in children with cerebral palsy and can coordination improve with intervention?

METHODS

This literature review provides a comprehensive overview of the current knowledge of continuous coordination in a pediatric, pathologic population with an emphasis on inter-limb coordination. Peer-reviewed research articles related to inter-limb coordination, with a focus on gait, were reviewed to identify relevant research and any gaps in the literature which could inform future study design. Consideration of the most appropriate analysis for evaluation of such movement is also presented.

RESULTS

The coordinative difficulties experienced by children with cerebral palsy may originate from the deficits in motor control, muscle tone, and weakness caused by damage to the central nervous system, which is vital in motor control of inter-limb coordination. Continuous inter-limb coordination in children with cerebral palsy may be improved with enhanced function of the upper extremities through intensive motor-learning based rehabilitation or botulinum toxin injection of the more-affected arm. Importantly, analysis of limb movements should include continuous measures of relative phase, as it provides a more detailed description of coordination compared to discrete measures.

SIGNIFICANCE

Improved upper extremity function may produce a positive change in the phasing relationship between the arms and legs. This type of coordination should be analyzed using relative phase analysis, as this type of analysis can provide more information compared to traditional spatiotemporal parameters. However, more research is required to fully understand the connection between improved upper extremity function and its positive impact on gait coordination in children with cerebral palsy.

Peri-operative Botulinum Neurotoxin injection to improve outcomes of surgeries on spastic limbs: A systematic review

Our objective was to systematically review literature regarding the rationale and current evidence for peri-operative Botulinum Neurotoxin (BoNT) injection to improve outcomes of surgeries on spastic limbs. We conducted a systematic search of databases MEDLINE, EMBASE, and Cochrane Central Register of Controlled until March 2020, using the PRISMA guidelines. After assessing all titles and abstracts against inclusion criteria, full texts were reviewed for studies of potential interest. The inclusion criteria were studies on humans with any study design, published in all languages. Participants had to have underlying limb spasticity and be scheduled to undergo surgery on one or more spastic limb(s). BoNT had to be administered peri-operatively to improve surgical outcomes and not solely for the purpose of alleviating spasticity. The risk of bias was evaluated using the Physiotherapy Evidence Database (PEDro) scoring system for randomized controlled trials (RCTs) and the Downs and Black tool for RCTs and non-randomized trials. Further, the level of evidence was evaluated using a five-level scale (simplified form of Sackett). Five studies met our inclusion criteria comprising a total of 90 participants, of both pediatric and adult age groups, with underlying limb spasticity, who received BoNT perioperatively to improve outcomes of the surgeries performed on spastic limbs. Interventions were intramuscular BoNT injection prior to, at the time of, or after surgery on a spastic limb for the purpose of improving surgical outcomes, and not solely for alleviating muscle spasticity. Outcome measures were surgical success/failure, post-operative pain and analgesic use, sleep quality, adverse events, spasticity control e.g. Modified Ashworth Scale. Our literature search yielded 5 articles that met the inclusion criteria. Current evidence supports peri-operative injection of BoNT to improve outcomes of surgeries performed on spastic limbs. There is level 1 evidence that BoNT administered pre-operatively is effective for reducing pain, spasticity, and analgesic use in pediatric patients with cerebral palsy (CP). This is supported by level 4 evidence from a retrospective case series. Level 5 evidence from case reports highlights the potential for the use of BONT in the peri-operative period. There is level 1 evidence that BoNT administered intra-operatively is not effective for reducing pain and analgesic use in pediatric patients with CP. This lack of benefit may reflect sub-optimal timing of injections, different methods of injection, different timing of the primary outcome measure, and/or differences in adjunctive therapies, but further research is required.

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.

Pathomechanisms and Clinical Implications of Myasthenic Syndromes Exacerbated and Induced by Medical Treatments

Myasthenic syndromes are typically characterized by muscle weakness and increased fatigability due to an impaired transmission at the neuromuscular junction (NMJ). Most cases are caused by acquired autoimmune conditions such as myasthenia gravis (MG), typically with antibodies against the acetylcholine receptor (AChR). Different drugs are among the major factors that may complicate pre-existing autoimmune myasthenic conditions by further impairing transmission at the NMJ. Some clinical observations are substantiated by experimental data, indicating that presynaptic, postsynaptic or more complex pathomechanisms at the NMJ may be involved, depending on the individual compound. Most robust data exist for the risks associated with some antibiotics (e.g., aminoglycosides, ketolides, fluoroquinolones) and cardiovascular medications (e.g., class Ia antiarrhythmics, beta blockers). Apart from primarily autoimmune-mediated disorders of the NMJ, de novo myasthenic manifestations may also be triggered by medical treatments that induce an autoimmune reaction. Most notably, there is growing evidence that the immune checkpoint inhibitors (ICI), a modern class of drugs to treat various malignancies, represent a relevant risk factor to develop severe and progressive medication-induced myasthenia via an immune-mediated mechanism. From a clinical perspective, it is of utmost importance for the treating physicians to be aware of such adverse treatment effects and their consequences. In this article, we aim to summarize existing evidence regarding the key molecular and immunological mechanisms as well as the clinical implications of medication-aggravated and medication-induced myasthenic syndromes.

A review on iatrogenic botulism

Background:

With the flourishing application of botulinum toxin cosmetically and therapeutically is the emergence of iatrogenic botulism, a new type of botulism in addition to the traditional ones.

Objectives:

We aim at a comprehensive review of the clinical characteristics of iatrogenic botulism. Methods: The available publications are retrieved and studied.

Results:

Botulinum toxin blocks cholinergic transmission in the neuromuscular junctions and autonomic ganglia. The blockade can spread from the site of tissue injection to adjacent or sometimes far off structures, resulting in inadvertent disabling or even lethal effects. On literature review, weakness and dysphagia are the commonest complications of iatrogenic botulism, whereas ophthalmological and oropharyngeal symptoms are more prevalent in the cosmetic group and dyspnea in the therapeutic group. Antitoxin therapy is required in about 20% of the patients. Diagnosis of iatrogenic botulism is primarily clinical and should not be confused with the neurological diagnoses possessing similar clinical manifestations. Vigilance to the drug formulation, dosage, and administration during botulinum toxin injection are part of the preventive measures in minimizing the occurrence of iatrogenic botulism.

Conclusion:

While overlapping with the traditional types of botulism, iatrogenic botulism carries its unique clinical characteristics.

Wearing Off Effect of OnabotulinumtoxinA Near the End of Treatment Cycle for Chronic Migraine: A 4-Year Clinical Experience

INTRODUCTION

The injection interval for onabotulinumtoxinA (BoNTA) in the management of chronic migraine (CM) is 12 weeks (78-84 days). The aim of this study was to review patient-reported wearing off effect (WOE) of the therapeutic benefit of BoNTA near the end of the treatment cycle. We intended to describe the demographics of patients at baseline and compare groups of patients with multiple episodes of WOE.

METHODS

We conducted a retrospective review of patients with CM who received uninterrupted BoNTA therapy from January 2014 to March 2018. The data from patient-reported WOE (worsening headache variables and neck pain) that occurred during the 4 weeks (28 days) prior to the scheduled re-injection of BoNTA for treatment cycles with injection interval ≤13 weeks and without obvious confounding factors were reviewed.

RESULTS

We identified 98 eligible patients and analyzed 471 treatment cycles. Forty-three unique patients reported at least 1 occurrence of WOE. About 24/43 patients reported 1 WOE event and 19/43 patients reported ≥2 WOE events. Between the 2 groups, anxiety disorder and opioid use for headache were statistically significantly different. In the former group, the median interquartile range (IQR) dose of BoNTA was 165 (155, 175) units and the median IQR duration of the antinociceptive effect of BoNTA was 66.5 (63, 71.5) days. In the latter group, the median IQR dose of BoNTA was 167 (155, 173.3) units and the median IQR duration of the antinociceptive effect of BoNTA was 65.3 (62.5, 68.8) days. Up to 32% of these patients reported an increase in the use of abortive therapies to manage the symptoms of WOE.

DISCUSSION

The primary goal of BoNTA in the treatment of CM is to mitigate the development of central sensitization. Since the 12-week injection paradigm may not provide sustained antinociceptive effect in all patients, it may account for the failure of response to BoNTA. Repeated occurrences of the WOE can potentially lead to medication overuse and impact quality of life.

Cosmetic Injection of Botulinum Toxin Unmasking Subclinical Myasthenia Gravis: A Case Report and Literature Review

Cosmetic or therapeutic use of botulinum toxin type A (BoNT-A) is usually safe but can rarely cause iatrogenic botulism. Iatrogenic botulism and myasthenia gravis (MG) share similar clinical features, because both BoNT-A and anti-acetylcholine receptorantibodies impair neuromuscular transmission. We report a patient who underwent cosmetic BoNT-A injection and later developed serious local and systemic adverse reactions. The peculiarity of this case is that a latent seropositive MG was eventually discovered, suggesting that both iatrogenic botulism and MG contributed to the clinical picture. This patient is one of the less than 10 reported cases worldwide in whom MG was unmasked by BoNT-A injection. He is the first to be assessed in detail by single-fiber electromyography. This case emphasizes the risk associated with BoNT-A injection in patients with subclinical impairment of neuromuscular transmission and prompts the search for MG in case of exaggerated response.

Co-Expression Network Approach to Studying the Effects of Botulinum Neurotoxin-A

Botulinum Neurotoxin A (BoNT-A) is a potent neurotoxin with several clinical applications. The goal of this study was to utilize co-expression network theory to analyze temporal transcriptional data from skeletal muscle after BoNT-A treatment. Expression data for 2000 genes (extracted using a ranking heuristic) served as the basis for this analysis. Using weighted gene co-expression network analysis (WGCNA), we identified 19 co-expressed modules, further hierarchically clustered into five groups. Quantifying average expression and co-expression patterns across these groups revealed temporal aspects of muscle's response to BoNT-A. Functional analysis revealed enrichment of group 1 with metabolism; group 5 with contradictory functions of atrophy and cellular recovery; and groups 2 and 3 with extracellular matrix (ECM) and non-fast fiber isoforms. Topological positioning of two highly ranked, significantly expressed genes-Dclk1 and Ostalpha-within group 5 suggested possible mechanistic roles in recovery from BoNT-A induced atrophy. Phenotypic correlations of groups with titin and myosin protein content further emphasized the effect of BoNT-A on the sarcomeric contraction machinery in early phase of chemodenervation. In summary, our approach revealed a hierarchical functional response to BoNT-A induced paralysis with early metabolic and later ECM responses and identified putative biomarkers associated with chemodenervation. Additionally, our results provide an unbiased validation of the response documented in our previous work.

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.

Therapeutic use of botulinum toxin in pain treatment

Botulinum toxin is one of the most potent molecule known to mankind. A neurotoxin, with high affinity for cholinergic synapse, is effectively capable of inhibiting the release of acetylcholine. On the other hand, botulinum toxin is therapeutically used for several musculoskeletal disorders. Although most of the therapeutic effect of botulinum toxin is due to temporary skeletal muscle relaxation (mainly due to inhibition of the acetylcholine release), other effects on the nervous system are also investigated. One of the therapeutically investigated areas of the botulinum neurotoxin (BoNT) is the treatment of pain. At present, it is used for several chronic pain diseases, such as myofascial syndrome, headaches, arthritis, and neuropathic pain. Although the effect of botulinum toxin in pain is mainly due to its effect on cholinergic transmission in the somatic and autonomic nervous systems, research suggests that botulinum toxin can also provide benefits related to effects on cholinergic control of cholinergic nociceptive and antinociceptive systems. Furthermore, evidence suggests that botulinum toxin can also affect central nervous system (CNS). In summary, botulinum toxin holds great potential for pain treatments. It may be also useful for the pain treatments where other methods are ineffective with no side effect(s). Further studies will establish the exact analgesic mechanisms, efficacy, and complication of botulinum toxin in chronic pain disorders, and to some extent acute pain disorders.

Pyridostigmine for the Reversal of Severe Adverse Reactions to Botulinum Toxin in Children

Therapeutic botulinum toxin injections are commonly performed in pediatric otolaryngology. Aerodigestive complications from botulinum toxin injections, although rare, may be serious. Oral pyridostigmine is effective in the symptomatic treatment of these complications. We report 2 cases of aerodigestive complications arising from injection of botulinum toxin that were successfully treated with pyridostigmine.

Botulinum Neurotoxins: Biology, Pharmacology, and Toxicology

The study of botulinum neurotoxins (BoNT) is rapidly progressing in many aspects. Novel BoNTs are being discovered owing to next generation sequencing, but their biologic and pharmacological properties remain largely unknown. The molecular structure of the large protein complexes that the toxin forms with accessory proteins, which are included in some BoNT type A1 and B1 pharmacological preparations, have been determined. By far the largest effort has been dedicated to the testing and validation of BoNTs as therapeutic agents in an ever increasing number of applications, including pain therapy. BoNT type A1 has been also exploited in a variety of cosmetic treatments, alone or in combination with other agents, and this specific market has reached the size of the one dedicated to the treatment of medical syndromes. The pharmacological properties and mode of action of BoNTs have shed light on general principles of neuronal transport and protein-protein interactions and are stimulating basic science studies. Moreover, the wide array of BoNTs discovered and to be discovered and the production of recombinant BoNTs endowed with specific properties suggest novel uses in therapeutics with increasing disease/symptom specifity. These recent developments are reviewed here to provide an updated picture of the biologic mechanism of action of BoNTs, of their increasing use in pharmacology and in cosmetics, and of their toxicology.

Improvement of upper trunk posture during walking in hemiplegic patients after injections of botulinum toxin into the arm

BACKGROUND

It has been hypothesized that altered trunk movements during gait in post-stroke patients or children with cerebral palsy are compensatory to lower limb impairment. Improvement of trunk movements and posture after injections of botulinum toxin into the affected arm would be at variance with this hypothesis and hint towards a multifactorial trunk control deficit.

PATIENTS AND METHODS

Clinical gait analysis was performed in 11 consecutively recruited hemiplegic patients immediately before and 4weeks after a botulinum toxin type A-injection into the affected arm. Kinematic data were collected using an 8 camera optical motion-capturing system and reflective skin-markers were attached according to a standard plug-in-gait model. Deviation of the trunk in lateral and forward direction and the trajectory of the C7-marker in a sacrum-fixed horizontal plane were analyzed in addition to classical gait parameters. The Wilson-signed-rank test was used for pre/post-botulinum toxin comparisons.

FINDINGS

After botulinum toxin injections a significant improvement of forearm flexion scores from 2.57 to 2.0 (p<0.014), and a reduced lateral deviation of the upper trunk from 3.5degrees to 2.5degrees (p<0.014) were observed. Free-walkers tended to walk faster (p<0.046, 1-sided), with reduced pre-swing duration of both legs and an increased step length of the non-affected leg. The C7-marker trajectory was shifted towards the midline.

INTERPRETATION

Injections of botulinum toxin into the affected arm of hemiplegic patients improve abnormal trunk lateral flexion. This shift of the center of mass of the upper body towards the midline improves various gait parameters including gait speed.

Effects of onabotulinumtoxinA on cardiac function following intradetrusor injections

OnabotulinumtoxinA intradetrusor injections are considered a highly effective localized therapy for refractory detrusor overactivity. However, despite evidence for distant systemic effects of onabotulinumtoxinA, little is known on potential systemic side effects following intradetrusor injections. Given that onabotulinumtoxinA is a highly potent toxin this is an important safety issue specifically with regard to repeat injections and parallel treatments with botulinum toxin. Hence, it was the purpose of this prospective study to investigate, using heart rate variability (HRV) analysis, whether onabotulinumtoxinA causes systemic effects on cardiac function following intradetrusor injections. Patients with neurogenic detrusor overactivity (NDO) and age-matched healthy controls were recruited. Concomitant medication and diseases affecting the cardio-vascular system were exclusion criteria. A 3-channel resting electrocardiogram (ECG) was recorded in supine position for 15min during four consecutive visits: 1) 2weeks prior onabotulinumtoxinA intradetrusor injections, 2) 10min prior injections, 3) 30min after injections, and 4) 6weeks after injections. NDO patients received intradetrusor injections (300units Botox®) between visits 2 and 3. The control group had no intervention. Short-term (5min) HRV analysis included assessment of frequency and time domain parameters. Statistical analysis was performed using ANOVA with repeated measures and the t-test. Due to multiple comparisons, α was corrected to 0.0125 (Bonferroni method). Twelve healthy volunteers (5♀, 7♂; 46±12years old) and 12 NDO patients (5♀, 7♂; 46±13years old) completed all measurements. Comparing both groups, resting heart rate was significantly higher in the patients group at visit 4 only. No further significant differences in time and frequency domain parameters were discovered. Within the NDO group, standard deviation of the normal to normal intervals (SDNN) in the ECG demonstrated a significant decrease (1.70 to 1.53ms, p=0.003) from visit 3 to 4, whereas the total power (TP) significantly increased (3.05 to 3.29ms², p=0.009) from visit 2 to 3. This increase subsided until visit 4.

STUDY LIMITATIONS

single treatment investigation under resting conditions only. In conclusion, onabotulinumtoxinA intradetrusor injections do not seem to affect resting state cardiac function. Short-term changes such as total power might rather result from natural cardio-vascular responses to the procedure itself (e.g. discomfort, stress). Further detailed investigations also under physical stress and repeated injections are necessary to fully exclude systemic cardiac side effects of onabotulinumtoxinA intradetrusor injections.

Adverse Clinical Effects of Botulinum Toxin Intramuscular Injections for Spasticity

OBJECTIVE

The adverse events (AEs) with botulinum toxin type-A (BoNTA), used for indications other than spasticity, are widely reported in the literature. However, the site, dose, and frequency of injections are different for spasticity when compared to the treatment for other conditions and hence the AEs may be different as well. The objective of this study was to summarize the AEs reported in Canada and systematically review the AEs with intramuscular botulinum toxin injections to treat focal spasticity.

METHODS

Data were gathered from Health Canada (2009-2013) and major electronic databases.

RESULTS

In a 4 year period, 285 AEs were reported. OnabotulinumtoxinA (n=272 events): 68% females, 53% serious, 18% hospitalization, and 8% fatalities. The type of AEs reported were - muscle weakness (19%), oropharyngeal (14%), respiratory (14%), eye related (8%), bowel/bladder related (8%), and infection (5%). IncobotulinumtoxinA (n=13): 38% females, 62% serious, and 54% hospitalization. The type of AEs reported were - muscle weakness (15%), oropharyngeal (15%), respiratory (38%), eye related (23%), bowel/bladder related (15%), and infection (15%). Commonly reported AEs in the literature were muscle weakness, pain, oropharyngeal, bowel/bladder, blood circulation, neurological, gait, and respiratory problems.

CONCLUSION

While BoNTA is useful in managing spasticity, future studies need to investigate the factors that can minimize AEs. A better understanding of the underlying mechanisms of the AEs can also improve guidelines for BoNTA administration and enhance outcomes.

A clinically relevant BTX-A injection protocol leads to persistent weakness, contractile material loss, and an altered mRNA expression phenotype in rabbit quadriceps muscles

Botulinum toxin type-A (BTX-A) injections have become a common treatment modality for patients suffering from muscle spasticity. Despite its benefits, BTX-A treatments have been associated with adverse effects on target muscles. Currently, application of BTX-A is largely based on clinical experience, and research quantifying muscle structure following BTX-A treatment has not been performed systematically. The purpose of this study was to evaluate strength, muscle mass, and contractile material six months following a single or repeated (2 and 3) BTX-A injections into the quadriceps femoris of New Zealand white rabbits. Twenty three skeletally mature rabbits were divided into four groups: experimental group rabbits received 1, 2, or 3 injections at intervals of 3 months (1-BTX-A, 2-BTX-A, 3-BTX-A, respectively) while control group rabbits received volume-matched saline injections. Knee extensor strength, quadriceps muscle mass, and quadriceps contractile material of the experimental group rabbits were expressed as a percentage change relative to the control group rabbits. One-way ANOVA was used to determine group differences in outcome measures (α=0.05). Muscle strength and contractile material were significantly reduced in experimental compared to control group rabbits but did not differ between experimental groups. Muscle mass was the same in experimental BTX-A and control group rabbits. We concluded from these results that muscle strength and contractile material do not fully recover within six months of BTX-A treatment.

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.

Botulinum toxin A, brain and pain

Botulinum neurotoxin type A (BoNT/A) is one of the most potent toxins known and a potential biological threat. At the same time, it is among the most widely used therapeutic proteins used yearly by millions of people, especially for cosmetic purposes. Currently, its clinical use in certain types of pain is increasing, and its long-term duration of effects represents a special clinical value. Efficacy of BoNT/A in different types of pain has been found in numerous clinical trials and case reports, as well as in animal pain models. However, sites and mechanisms of BoNT/A actions involved in nociception are a matter of controversy. In analogy with well known neuroparalytic effects in peripheral cholinergic synapses, presently dominant opinion is that BoNT/A exerts pain reduction by inhibiting peripheral neurotransmitter/inflammatory mediator release from sensory nerves. On the other hand, growing number of behavioral and immunohistochemical studies demonstrated the requirement of axonal transport for BoNT/A's antinociceptive action. In addition, toxin's enzymatic activity in central sensory regions was clearly identified after its peripheral application. Apart from general pharmacology, this review summarizes the clinical and experimental evidence for BoNT/A antinociceptive activity and compares the data in favor of peripheral vs. central site and mechanism of action. Based on literature review and published results from our laboratory we propose that the hypothesis of peripheral site of BoNT/A action is not sufficient to explain the experimental data collected up to now.

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 toxin for the treatment of movement disorders

After botulinum toxin was initially used to treat strabismus in the 1970s, others started using it to treat movement disorders including blepharospasm, hemifacial spasm, cervical dystonia, spasmodic dysphonia, and oromandibular dystonia. It was discovered that botulinum toxin can be an effective treatment for focal movement disorders with limited side effects. Over the past three decades, various formulations of botulinum toxin have been developed and the therapeutic use of these toxins has expanded in movement disorders and beyond. We review the history and mechanism of action of botulinum toxin, as well as describe different formulations available and their potential therapeutic uses in movement disorders.

Contralateral weakness following botulinum toxin for poststroke spasticity

INTRODUCTION

We describe 2 patients who received botulinum toxin A (BoNT) for poststroke spasticity and developed contralateral limb weakness.

METHODS

Both patients received high doses of BoNT with large dilution volumes and injection in the proximal upper extremity muscles, and developed weakness of the contralateral upper limb. These patients then underwent electrodiagnostic testing of the affected limb.

RESULTS

Repetitive nerve stimulation of the axillary and spinal accessory nerves revealed decrements of 23% and 16%, respectively. EMG revealed abnormal spontaneous activity and small polyphasic motor unit potentials with reduced recruitment. These findings indicated blockade of the neuromuscular junction. Both patients improved.

CONCLUSIONS

Isolated weakness of the contralateral limb after BoNT injection for poststroke spasticity suggests diffusion of toxin through tissue planes from proximal upper extremity muscles, across the midline, to contralateral muscles. High doses of botulinum toxin, high dilution volumes, and injection of proximal upper extremity muscles appear to be risk factors for this adverse effect.

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.

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.

The role of botulinum toxin in management of pain: an evidence-based review

PURPOSE OF REVIEW

In the present review we discuss the role of botulinum neurotoxins (BoNTs) in the management of different pain conditions, with evidence-based data on the toxins' efficacy on pain and its mechanisms.

RECENT FINDINGS

Experimental in-vitro studies have reported promising results of a novel recombinant chimera of BoNT A and E that inhibits the calcitonin gene-related peptide exocytosis from brainstem sensory neurons. Animal studies in neuropathic pain rat models have reported an analgesic effect of BoNT A given after the neuropathic procedure and a bilateral antinociceptive effect to the unilateral noxious stimuli. There is a growing body of evidence that BoNTs are effective in myofascial pain syndrome, neuropathic pain, and joint pain. The pre-existing evidence that BoNTs are ineffective in migraine or other headache disorders has not yet been challenged. In other pain syndromes, studies published in the last review year have not contributed significantly in either demonstrating or invalidating the research that has so far proved inconclusive.

SUMMARY

The role of BoNTs in management of pain is not yet well established. Larger studies in neuropathic pain, joint pain, and myofascial pain syndrome are needed to fully ascertain the role for BoNT therapy in those areas.

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.

The use of botulinum toxin for the treatment of muscle spasticity in the first 2 years of life

Although there are sound theoretical reasons for the use of botulinum toxin (Btx) as early as possible in the management of severe childhood muscle spasticity, the experience with its safety in children younger than 2 years of age is limited and information about its possible effects on the development and maturation of the human motor system is still scarce. This study discusses the rationale and the potential pitfalls of the use of Btx in the first 2 years of the child's life. It also reviews the currently available evidence on the efficacy and safety of Btx in this age group. It concludes by suggesting a framework for studies of the optimal time to start treatment of childhood spasticity with Btx.

Changes in contractile properties of muscles receiving repeat injections of botulinum toxin (Botox)

Botulinum toxin type A (BTX-A) is a frequently used therapeutic tool to denervate muscles in the treatment of neuromuscular disorders. Although considered safe by the US Food and Drug Administration, BTX-A can produce adverse effects in target and non-target muscles. With an increased use of BTX-A for neuromuscular disorders, the effects of repeat injections of BTX-A on strength, muscle mass and structure need to be known. Therefore, the purpose of this study was to investigate the changes in strength, muscle mass and contractile material in New Zealand White (NZW) rabbits. Twenty NZW rabbits were divided into 4 groups: control and 1, 3 and 6 months of unilateral, repeat injections of BTX-A into the quadriceps femoris. Outcome measures included knee extensor torque, muscle mass and the percentage of contractile material in the quadriceps muscles of the target and non-injected contralateral hindlimbs. Strength in the injected muscles was reduced by 88%, 89% and 95% in the 1, 3 and 6 months BTX-A injected hindlimbs compared to controls. Muscle mass was reduced by 50%, 42% and 31% for the vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM), respectively, at 1 month, by 68%, 51% and 50% at 3 months and by 76%, 44% and 13% at 6 months. The percentage of contractile material was reduced for the 3 and 6 months animals to 80-64%, respectively, and was replaced primarily by fat. Similar, but less pronounced results were also observed for the quadriceps muscles of the contralateral hindlimbs, suggesting that repeat BTX-A injections cause muscle atrophy and loss of contractile tissue in target muscles and also in non-target muscles that are far removed from the injection site.

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.

Hemifacial spasm non-motor and motor-related symptoms and their response to botulinum toxin therapy

Hemifacial spasm (HFS) is a chronic movement disorder which presents as clonic and/or tonic facial muscle contractions frequently accompanied by many other sensory (visual or auditory disturbances, pain), motor (facial weakness, trismus, bruxism, dysarthria) and/or autonomic (lacrimation, salivation) symptoms. The aim of the study was to assess the occurrence of HFS non-motor and motor-related symptoms and their responsiveness to botulinum toxin type A (BTX-A) therapy. 56 HFS patients were included in the open-label design study. Patients were examined three times: before BTX-A injection, and 2 and 12 weeks later. The occurrence of non-motor and motor-related symptoms was assessed by a special questionnaire, and the severity of HFS was rated by the Clinical Global Impression-Severity scale (CGI-S) and depression symptoms by the Beck Depression Inventory (BDI). Over 81% of the patients before BTX-A therapy reported HFS non-motor and motor-related symptoms. Almost 50% of the patients reported more than three symptoms. The most frequent symptoms were: tearing (44.5%), eye irritation (39.3%), facial paraesthesia (26.8%) and hearing of a "clicking" sound (25.0%). 2 weeks after BTX-A injection 75% of the patients did not report any symptoms and 20% reported only one or two. 3 months later the number of symptoms had increased again, with 57% of patients reporting at least one. The number of HFS non-motor and other symptoms did not correlate with the patients' age, disease duration and the presence of neuro-vascular conflict, but were positively correlated with the CGI-S and BDI scores. This study showed that muscle contractions in HFS patients are commonly accompanied by non-motor and other motor-related symptoms and most of them are reduced following BTX-A treatment.

Central origin of the antinociceptive action of botulinum toxin type A

Here we provide behavioural evidence for an axonal transport and the central origin of the antinociceptive effect of botulinum toxin type A (BTX-A). In rats we investigated the effectiveness of BTX-A on "mirror pain" induced by unilateral repeated intramuscular acidic saline injections (pH 4.0). Since experimental evidence suggest that bilateral pain induced by acidic saline is of central origin, peripheral application of BTX-A should have no effect on this type of pain. However, here we demonstrated that the unilateral subcutaneous BTX-A (5U/kg) application diminished pain on the ipsilateral, and on the contralateral side too. When injected into the proximal part of a distally cut sciatic nerve, BTX-A still reduced pain on the contralateral side. Colchicine, an axonal transport blocker, when injected into the ipsilateral sciatic nerve, prevented the effect of the peripheral BTX-A injection on both sides. Additionally, when BTX-A (1U/kg) was applied intrathecally in the lumbar cerebrospinal fluid, the bilateral hyperalgesia was also reduced. The results demonstrate the necessity of retrograde axonal transport and involvement of the central nervous system for the antinociceptive activity of BTX-A.

CENTRAL EFFECT OF BOTULINUM TOXIN TYPE A IN HUMANS

This study investigated the changes in the cortical excitability with a paired-pulse transcranial magnetic stimulation (TMS) model after a botulinum toxin type A (BTA) injection in normal humans. Ten healthy subjects were enrolled in the study, which involved applying paired TMS to the motor cortex and recording the motor evoked potentials (MEP) before and after the BTA injection. BTA (2.5 mouse units) was injected into the right extensor digitorum brevis muscle. The amplitudes of MEP during rest and the cortical silent period (CSP) for the period of the tonic muscle contraction were measured at an interstimulus interval (ISI) of 3 ms and 20 ms. One month and three months after BTA injection, the level of intracortical inhibition increased significantly at an ISI of 3 ms and the intracortical facilitation decreased at an ISI of 20 ms. The duration of CSP shortened significantly at an ISI of 3 ms 1 month after BTA injection, which was also shortened significantly at an ISI of 20 ms. These findings were maintained until 3 months after the injection. It was concluded that cortical excitability could be modified by BTA injection in normal humans.

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.