Botulinum toxin for treatment of dystonia

Neurotoxins Acting at Synaptic Sites: A Brief Review on Mechanisms and Clinical Applications

Neurotoxins generally inhibit or promote the release of neurotransmitters or bind to receptors that are located in the pre- or post-synaptic membranes, thereby affecting physiological functions of synapses and affecting biological processes. With more and more research on the toxins of various origins, many neurotoxins are now widely used in clinical treatment and have demonstrated good therapeutic outcomes. This review summarizes the structural properties and potential pharmacological effects of neurotoxins acting on different components of the synapse, as well as their important clinical applications, thus could be a useful reference for researchers and clinicians in the study of neurotoxins.

Meta-Analysis of Effectiveness and Safety of Botulinum Toxin in the Treatment of Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) is characterized by pain, limited range of motion, swelling, skin changes, vasomotor instability, and patchy bone demineralization. Conservative management strategies for CRPS include physical and occupational therapy, psychosocial and behavioral therapy, and pharmacotherapy. However, some patients still experience CRPS symptoms after receiving conventional treatments. Therefore, botulinum toxin (BoNT) has been applied to patients with CRPS in several trials considering its analgesic effect in musculoskeletal and neuropathic pain; however, the results were controversial. We conducted the study to explore the effectiveness and safety of BoNT in patients with complex regional pain syndrome (CRPS). A search was performed using the following electronic databases up to 19 October 2022: PubMed, Embase, and Cochrane Library. We included both randomized controlled trials and nonrandomized controlled studies involving patients with complex regional pain syndrome managed with botulinum toxin. Cochrane risk-of-bias tool and Joanna Briggs Institute Critical Appraisal Checklist were used for quality assessment for randomized controlled trials and quasi-experimental studies. Only randomized controlled trials entered the meta-analysis. The primary outcome was the visual analogue scale of pain presented as a weighted mean difference (WMD) and 95% confidence interval (CI). The secondary outcome was the risk of adverse events presented as an odds ratio (OR) with 95% CI. We analyzed eight articles with 176 patients, including three randomized controlled trials with 62 participants. The age of the patients ranged from 23.8 to 51 years old. The duration of the disease ranged from 2.2 to 11.8 years. The proportion of females ranged from 16.6% to 100%. The route of administration of BoNT included: (1) lumbar sympathetic block (LSB), (2) intramuscular injection, (3) subcutaneous or intradermal injection (SC/ID). Improvement in pain was revealed in six studies, and adverse events were all self-limited and temporary. Meta-analysis revealed a significant reduction in pain at the first follow-up between 3 weeks to 1 month after intervention (WMD, -1.036, 95% CI, -1.673 to -0.400) but not at the second follow-up between 2 to 3 months after treatment (WMD, -0.895, 95% CI, -2.249 to 0.458). Subgroup analyses between LSB and SC/ID were nonsignificant at both follow-up periods (p = 0.422, 0.139). The risk of adverse events was similar between the BoNT and control group (OR, 0.698, 95% CI, 0.136 to 3.581). In conclusion, BoNT may be effective and safe for alleviating pain in patients with CRPS. However, we could not draw definite conclusions due to small sample size and high between-study heterogeneity. The limited number of participants may conceal the possibility of serious adverse events. Further large-scale randomized controlled trials are warranted to delineate the role of BoNT in CRPS.

The Effectiveness and Safety of Botulinum Neurotoxin in Obstetric Brachial Plexus Injury: A Systematic Review and Meta-Analysis

Obstetric brachial plexus injury, also known as neonatal brachial plexus injury, is not unusual in newborns. Given the lack of a comprehensive synthesis of the available data on the effectiveness of botulinum neurotoxin (BoNT) in treating children with obstetric brachial plexus injury, we conducted a systematic review and meta-analysis. We searched PubMed, Embase, Web of Science, and Cochrane databases from inception to 25 November 2022. Outcomes were function of the shoulder and elbow joints, muscle power of the deltoid, biceps brachii and triceps brachii, and the recurrence rate of subluxation or dislocation after reduction of the shoulder joint after BoNT application. Meta-regression was conducted to assess the moderator effect of age. We included 11 case series and 2 cohort studies. Passive range of motion of shoulder external rotation (standardized mean difference [SMD], 0.678; 95% confidence interval [95%CI], 0.423 to 0.934), Active Movement Scale for shoulder external rotation (SMD, 0.47; 95%CI, 0.131 to 0.808), and active range of motion of elbow extension (SMD, 2.445; 95%CI, 1.556 to 3.334) increased significantly after BoNT. However, the modified Gilbert scale for shoulder abduction (SMD, 1.239; 95% CI, -0.2 to 2.678), the Toronto score for active elbow flexion (SMD, 1.099; 95% CI, -0.053 to 2.252), muscle power of deltoid (SMD, 0.675; 95% CI, -0.599 to 1.949), biceps brachii (SMD, 0.225; 95% CI, -0.633 to 1.083), and triceps brachii (SMD, 1.354; 95% CI, -1.493 to 4.202) did not reach statistical significance. The moderator effect of age was not significant (p = 0.88). Meta-analysis was not done for recurrence rate of subluxation or dislocation due to insufficient data. In conclusion, our data support BoNT use in patients with obstetric brachial plexus injury. However, definite conclusions cannot be drawn due to small sample size and the lack of randomized controlled trials. More research is warranted to clarify the effectiveness of BoNT in patients with obstetric brachial plexus injury by using standardized injection protocols and outcome measurements.

Effectiveness of Botulinum Neurotoxin in Treatment of Scoliosis among Children and Adolescents: A Systematic Review and Meta-Analysis

Scoliosis refers to a three-dimensional deviation in the axis of the spine. Muscle imbalance is believed to play a role in scoliosis. Botulinum neurotoxin (BoNT) can reduce muscle overactivity and may have the potential to ameliorate spinal scoliosis. This study investigated the effectiveness of intramuscular BoNT injection in vertebral curve correction and reviewed the possible influencing factors. PubMed, Medline, Cochrane Central Register of Controlled Trials, Web of Science, Airiti Library, and Index of the Taiwan Periodical Literature System databases were searched from inception until 7 September 2022 for eligible studies. The main outcome was the change in Cobb angle after BoNT application. Subgroup analysis was conducted according to differences in study designs, etiology of scoliosis, and methods used for target muscle selection. We enrolled three studies including 31 participants aged between 2 and 18 years. The meta-analysis revealed no significant reduction in the Cobb angle after BoNT injection (standardized mean difference, −0.783, 95% CI, −2.142 to 0.576). Study designs (p = 0.011) and methods used for target muscle selection (p = 0.017) but not etiology of scoliosis (p = 0.997) reached statistical significance between subgroups. In conclusion, the current meta-analysis does not support the application of BoNT in children and adolescents with scoliosis. However, a decisive conclusion could not be made due to high between-study heterogeneity and small sample size. More randomized controlled trials with appropriate target muscle selection and standard outcome measurement should be conducted to examine the efficacy of botulinum neurotoxin in treating scoliosis. INPLASY ID: INPLASY202290031.

Efficacy and safety of botulinum toxin type A in distraction osteogenesis of the lower extremities: a meta-analysis of randomized controlled trials

Background

To explore the efficacy and safety of botulinum toxin in patients who received distraction osteogenesis of the lower extremities.

Methods

We searched the PubMed, Medline, Cochrane Library, and Web of Science databases for randomized controlled trials that administered botulinum toxin to individuals who underwent distraction osteogenesis of the lower limbs. The final search was conducted on July 6, 2021. Quality assessments were conducted using the Cochrane risk of bias tool and the Jadad scale. We performed random-effects meta-analysis to calculate the standardized mean differences (SMDs) and confidence intervals (CIs) of the pooled effect sizes, and subgroup analysis and meta-regression were performed for potential moderators.

Results

Our analysis of four randomized controlled trials, which enrolled a total of 257 participants, revealed that the difference in pain during the distraction phase was not statistically significant between groups (SMD, − 0.165; 95% CI, − 0.379 to 0.050, p = 0.133, I² = 0.0%). The meta-regression analyses did not find any influence on the effect size, considering age (β = − 0.0092; p = 0.61) and the amount of lengthening (β = 0.0023; p = 0.99). Subgroup analysis did not reveal difference between different doses of botulinum toxin and single or multi-site study design. An analysis of two randomized controlled trials enrolling a total of 177 individuals demonstrated a limited effect of botulinum toxin in reducing postoperative pain (SMD, − 0.239; 95% CI, − 0.641 to 0.162, p = 0.24, I² = 37.6%), total adverse events (SMD, − 0.207; 95% CI, − 0.505 to 0.090, p = 0.17, I² = 0.0%), and infection of pin site (SMD, − 0.131; 95% CI, − 0.428 to 0.165, p = 0.39, I² = 0.0%). No botulinum toxin–related adverse events were reported.

Conclusions

The current evidence does not support the administration of botulinum toxin in patients who receive distraction osteogenesis of the lower limbs. However, we were unable to draw decisive conclusions because of the limitations of our meta-analysis. Future well-designed, large-scale randomized controlled trials are necessary to confirm our conclusions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05175-2.

Classification of Dystonia

Dystonia is a hyperkinetic movement disorder characterized by abnormal movement or posture caused by excessive muscle contraction. Because of its wide clinical spectrum, dystonia is often underdiagnosed or misdiagnosed. In clinical practice, dystonia could often present in association with other movement disorders. An accurate physical examination is essential to describe the correct phenomenology. To help clinicians reaching the proper diagnosis, several classifications of dystonia have been proposed. The current classification consists of axis I, clinical characteristics, and axis II, etiology. Through the application of this classification system, movement disorder specialists could attempt to correctly characterize dystonia and guide patients to the most effective treatment. The aim of this article is to describe the phenomenological spectrum of dystonia, the last approved dystonia classification, and new emerging knowledge.

Pallidal versus subthalamic deep-brain stimulation for meige syndrome: a retrospective study

Deep-brain stimulation (DBS) is an effective treatment for patients with Meige syndrome. The globus pallidus interna (GPi) and the subthalamic nucleus (STN) are accepted targets for this treatment. We compared 12-month outcomes for patients who had undergone bilateral stimulation of the GPi or STN. Forty-two Asian patients with primary Meige syndrome who underwent GPi or STN neurostimulation were recruited between September 2017 and September 2019 at the Department of Neurosurgery, Peking University People's Hospital. The primary outcome was the change in motor function, including the Burke-Fahn-Marsden Dystonia Rating Scale movement (BFMDRS-M) and disability subscale (BFMDRS-D) at 3 days before DBS (baseline) surgery and 1, 3, 6, and 12 months after surgery. Secondary outcomes included health-related quality of life, sleep quality status, depression severity, and anxiety severity at 3 days before and 12 months after DBS surgery. Adverse events during the 12 months were also recorded. Changes in BFMDRS-M and BFMDRS-D scores at 1, 3, 6, and 12 months with DBS and without medication did not significantly differ based on the stimulation target. There were also no significant differences in the changes in health-related quality of life (36-Item Short-Form General Health Survey) and sleep quality status (Pittsburgh Sleep Quality Index) at 12 months. However, there were larger improvements in the STN than the GPi group in mean score changes on the 17-item Hamilton depression rating scale (- 3.38 vs. - 0.33 points; P = 0.014) and 14-item Hamilton anxiety rating scale (- 3.43 vs. - 0.19 points; P < 0.001). There were no significant between-group differences in the frequency or type of serious adverse events. Patients with Meige syndrome had similar improvements in motor function, quality of life and sleep after either pallidal or subthalamic stimulation. Depression and anxiety factors may reasonably be included during the selection of DBS targets for Meige syndrome.

Clinical Practice: Evidence-Based Recommendations for the Treatment of Cervical Dystonia with Botulinum Toxin

Cervical dystonia (CD) is the most frequent form of focal dystonia. Symptoms often result in pain and functional disability. Local injections of botulinum neurotoxin are currently the treatment of choice for CD. Although this treatment has proven effective and is widely applied worldwide, many issues still remain open in the clinical practice. We performed a systematic review of the literature on botulinum toxin treatment for CD based on a question-oriented approach, with the aim to provide practical recommendations for the treating clinicians. Key questions from the clinical practice were explored. Results suggest that while the beneficial effect of botulinum toxin treatment on different aspects of CD is well established, robust evidence is still missing concerning some practical aspects, such as dose equivalence between different formulations, optimal treatment intervals, treatment approaches, and the use of supportive techniques including electromyography or ultrasounds. Established strategies to prevent or manage common side effects (including excessive muscle weakness, pain at injection site, dysphagia) and potential contraindications to this treatment (pregnancy and lactation, use of anticoagulants, neurological comorbidities) should also be further explored.

Treatment for dysphagia (swallowing difficulties) in hereditary ataxia

BACKGROUND

Hereditary ataxias are a heterogeneous group of disorders resulting in progressive inco-ordination. Swallowing impairment, also known as dysphagia, is a common and potentially life threatening sequel of disease progression. The incidence and nature of dysphagia in these conditions is largely unknown. The loss of an effective and safe swallow can dramatically affect the health and well-being of an individual. Remediation of difficulties of eating and drinking is an important goal in the clinical care of people with hereditary ataxia.

OBJECTIVES

To assess the effects of interventions for swallowing impairment (dysphagia) in people with hereditary ataxias.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL Plus, PsycINFO, and the Education Resources Information Center (ERIC) on 14 September 2015. We also searched Linguistics and Language Behavior Abstracts (LLBA), Dissertation Abstracts, and Trials Registries on 24 September 2015.

SELECTION CRITERIA

We considered all randomised controlled trials (RCTs) and quasi-RCTs that compared treatments for hereditary ataxia with placebo or no treatment. We only included studies measuring dysphagia.

DATA COLLECTION AND ANALYSIS

Three review authors (ES, KJ, MK) independently screened all titles and abstracts. In the event of any disagreement or uncertainty over the inclusion of a particular paper, the review authors planned to meet and reach consensus.

MAIN RESULTS

We identified no RCTs from the 519 titles and abstracts screened. We excluded papers primarily for not including participants with a hereditary ataxia (that is, being focused on other neurological conditions), being theoretical reviews rather than intervention studies, or being neither randomised nor quasi-randomised trials.We identified five papers of various design that described treatment for dysphagia, or improvement to swallow as a by-product of treatment, in people with hereditary ataxia. None of these studies were RCTs or quasi-RCTs.

AUTHORS' CONCLUSIONS

There is an absence of any significant evidence supporting the use of any dysphagia intervention in hereditary ataxia. The lack of evidence highlights the critical need for well-controlled treatment trials in the field.

Botulinum toxin B increases intrinsic muscle activity in organotypic spinal cord-skeletal muscle co-cultures

In organotypic spinal cord-skeletal muscle co-cultures, motoneurons are driven by locomotor commands and induce contractions in surrounding muscle fibres. Using these co-cultures, it has been shown that effects of organophosphorus compounds on neuromuscular synapses can be determined in vitro. In the present study we aimed to extend this in vitro tool for pharmacologic testing of botulinum toxin B. This neurotoxin is widely used for the treatment of dystonia. Besides its effects on the neuromuscular junction, botulinum toxins may also act at centrally located synapses. Incubation with botulinum toxin B (Neurobloc(®)) induced a significant increase in muscular activity after 24, 48 and 72h. Application of the NMDA- and AMPA-receptor antagonists AP5 (20μM) and CNQX (15μM) induced a similar augmentation of muscle activity after 48 and 72h, respectively. Administration of the glycine- and GABA(A)-receptor antagonists strychnine (1μM) and bicuculline (100μM) did not alter intrinsic muscle activity. In contrast, application of a non-depolarizing muscle relaxant rocuronium bromide reduced the muscle activity in a dose-dependent manner. Our findings suggest that glutamatergic synapses in the spinal cord are more sensitive to botulinum toxin B than synaptic contacts between spinal motoneurons and muscle fibres.

A practical approach to management of focal hand dystonia

Dystonia can be focal, segmental, multifocal, generalized, or hemidystonia. Focal dystonia is localized to a specific part of the body. Overall upper limb is more commonly involved in focal dystonia than lower limb and since it starts from hand, focal hand dystonia (FHD) is a more accepted terminology. Writer's cramp and musician dystonia are commonest types of FHD. Typically this dystonia is task specific, but in some patients this specificity may be lost over a period of time. Segmental or generalized dystonia may also start as FHD, so a detailed clinical assessment is required, which should be supplemented by relevant investigations. Treatment includes oral medications, injection botulinum toxin, neurosurgery including neurostimulation, and rehabilitation. Role of injection botulinum toxin has been extensively studied in writer's cramp patients and found to be effective; however, selection of muscles and techniques of injection are crucial in getting best results.

A Beautician’s Dystonia: Long-Lasting Effect of Botulinum Toxin

Treatment options for dystonia are not curative but symptomatic; the treatment of choice for focal dystonias is repeated botulinum toxin injections. Here, we present the case of a 46-year-old beautician with focal dystonia in her left hand that affected her ability to work. Pharmacological treatment with clonazepam and gabapentin failed to resolve her symptoms and was discontinued due to side effects (sleepiness, gastrointestinal disorders). Intramuscular injection of botulinum toxin (incobotulinumtoxinA, Xeomin) into the extensor digitorum communis (35 U), flexor carpi radialis (35 U), and flexor digitorum superficialis (30 U) muscles resulted in complete resolution of symptoms at clinical assessments at 1, 3, 6, and 10 months after the injections, confirmed by the results of surface electromyography 10 months after treatment. The patient was able to work again 1 month after treatment. No reinjection has been necessary at the last evaluation (12 months after treatment). In conclusion, botulinum toxin is an effective treatment for focal dystonia that can have long-lasting effects and can improve patients' ability to work and quality of life.

Long-term efficacy and safety of incobotulinumtoxinA injections in patients with cervical dystonia

INTRODUCTION

Previously, controlled trials have demonstrated the efficacy and tolerability of fixed doses of incobotulinumtoxinA (Xeomin, NT 201, botulinum toxin type A free from complexing proteins) to treat cervical dystonia (CD). To explore the clinical relevance of these findings, this study evaluated long-term use of flexible dosing regimens of incobotulinumtoxinA in a setting close to real-life clinical practice.

METHODS

Patients with CD received five injection sessions of incobotulinumtoxinA using flexible intervals (10-24 weeks) and dosing (≤300 Units) based on patients' needs. Outcome measures included Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS), the Dystonia Discomfort Scale (DDS), Investigator Global Assessment of Efficacy (IGAE) and Patient Evaluation of Global Response (PEGR).

RESULTS

Of 76 patients enrolled (men: 34%; naïve to botulinum toxin: 25%), 64 completed the study, receiving treatment over a duration of 49.3-114.1 weeks (total maximum duration: 121 weeks). Mean TWSTRS-Total and DDS scores significantly improved from study baseline to 4 weeks after each injection session (ranges of improvement: TWSTRS-Total: -11.7 to -14.3; DDS: -20.2 to -23.0). Up to 81.6% of investigators rated the efficacy as 'good' or 'very good' (IGAE) and up to 78.9% of patients rated the treatment response as 'improved' (PEGR). The most common adverse events were dysphagia, nasopharyngitis and headache.

CONCLUSIONS

In this long-term study, incobotulinumtoxinA was administered using more flexible dosing regimens than those permitted in previous controlled trials. Repeated injections of highly purified incobotulinumtoxinA are effective and well tolerated for the treatment of CD in a setting close to real-life clinical practice.

IGF-1 antibody prolongs the effective duration time of botulinum toxin in decreasing muscle strength

Botulinum toxin type-A (Btx-A), a powerful therapeutic tool in various medical specialties, requires repeated injections to maintain its effect. Therefore, novel methods to prolong the effective duration time of Btx-A are highly needed. Rats were assigned to three major groups: control group (n = 30), Btx-A group (n = 30), and IGF-1 Ab groups. IGF-1 Ab groups were composed by sub-groups A1-A5 (each has 25 rats) for the subsequent IGF-1Ab dose-effect study. Muscle strength was determined by a survey system for rat lower limbs nerve and muscle function. Muscle-specific receptor tyrosine kinase (MuSK), Insulin-like growth factor binding protein-5 (IGFBP5), and growth-associated protein, 43-kDa (GAP43) were determined by real-time polymerase chain reactions (PCRs) and Western blot. We found that Btx-A decreased the muscle strength, with a paralysis maintained for 70 days. IGF-1Ab prolonged the effective duration time of Btx-A. Real-time PCRs and Western blot showed that IGF-1Ab delayed the increase of MuSK and IGFBP5 after Btx-A injection, without affecting GAP43. These results indicate that IGF-1Ab might prolong the effective duration time of Btx-A on muscle strength through delaying the increase of MuSK. It would be interesting to determine whether IGF-1Ab can be used as an auxiliary measure to the Btx-A treatment in the future.

Botulinum toxin physiology in focal hand and cranial dystonia

The safety and efficacy of botulinum toxin for the treatment of focal hand and cranial dystonias are well-established. Studies of these adult-onset focal dystonias reveal both shared features, such as the dystonic phenotype of muscle hyperactivity and overflow muscle contraction and divergent features, such as task specificity in focal hand dystonia which is not a common feature of cranial dystonia. The physiologic effects of botulinum toxin in these 2 disorders also show both similarities and differences. This paper compares and contrasts the physiology of focal hand and cranial dystonias and of botulinum toxin in the management of these disorders.

Severe Spastic Trismus without Generalized Spasticity after Unilateral Brain Stem Stroke

A 62-year-old female patient diagnosed with left brain stem stroke 2 months ago was admitted to our clinic for rehabilitation. She had no generalized spasticity on both extremities, but could open her mouth only approximately 2 mm between her upper and lower teeth due to severe trismus. On needle electromyography, the left masseter muscle showed paradoxically increased muscle activity during mouth opening. We injected 50 units of type A botulinum toxin (Botox®) into the left masseter muscle, and 20 units into the left temporalis muscle with guidance of ultrasonography. The interincisal distance increased to 8 mm on the 3(rd) day after injection, and 9 mm on the 4(th) day. One month later, the interincisal distance increased to 14 mm. The increased interincisal distance was maintained for 13 months after injection, and the quality of hygienic care and compliance of oral stimulation therapy also improved.

Botulinum toxins in the treatment of primary focal dystonias

Focal dystonia, such as cervical dystonia, blepharospasm, oromandibular dystonia, laryngeal dystonia, and limb dystonia, is often observed in adult-onset primary dystonia syndromes that affect a specific area of the body and tend to have little or no spread. This review will examine the past, present, and future approaches to the treatment of focal dystonia. Botulinum toxin (BoNT) has emerged as the treatment of choice for the majority of focal dystonias. Currently four products are widely available commercially, three of BoNT/A type and one of BoNT/B type. Each has important pharmacological differences that give rise to markedly different dosing recommendations. The four approved BoNTs are safe and effective for treating focal dystonias, including long-term treatment. Adverse events are limited and transient and, for the most part, mild in severity. Potential problems with the use of BoNT agents are diffusion and neutralizing antibody formation; the latter can lead to treatment resistance. Because each BoNT product is developed from distinct purification and manufacturing procedures and has varying toxin complex size and structures, physicians need to be aware of these differences when choosing an agent.

Compositional differences among commercially available botulinum toxin type A

PURPOSE OF REVIEW

Since the advent of botulinum neurotoxin (BoNT) in the facial cosmetic field, it has become the leading nonsurgical cosmetic procedure in the USA, and several different formulations are currently in use. The aim of this study is to review the major 'players' in order to help the physician understand the clinically relevant dissimilarities between the products and by that promote treatment efficacy and patient satisfaction.

RECENT FINDINGS

The different available formulations can be classified into two groups by the existence of absence of complexing proteins. Most of the influence that was previously attributed to these proteins has been found to be less relevant clinically, the immune response being the only remaining issue with supporting evidence in the literature.

SUMMARY

Botulinum toxin type A is widely utilized in the cosmetic field, and it seems that all available and approved formulations are both well tolerated and effective in treating facial rhytids. The treating physician must be familiar with the differences between all the products, especially the fact that they are not interchangeable in respect to their recommended dosage.

Prospective analysis of neutralising antibody titres in secondary non-responders under continuous treatment with a botulinumtoxin type A preparation free of complexing proteins--a single cohort 4-year follow-up study

OBJECTIVES

In long-term botulinum neurotoxin treatment, loss of therapeutic efficacy may occur due to neutralising antibody formation. Preliminary results with incobotulinumtoxinA, a preparation free of complexing/accessory proteins, have indicated a low antigenicity. We hypothesised that continuous treatment with this botulinum neurotoxin preparation would not result in an increase in neutralising antibody titres (NABTs) in patients with pre-existing NABTs.

DESIGN

Prospective, blinded cohort study.

SETTING

Single centre in Germany.

PARTICIPANTS

Thirty-seven cervical dystonia patients with NABTs and partial secondary non-responsiveness to their previous botulinum neurotoxin type A treatment.

INTERVENTION

Three-monthly intramuscular injections of incobotulinumtoxinA with a constant dose of 200 MU per injection during the first year; thereafter up to 500 MU for the next 36 months.

PRIMARY OUTCOME MEASURE

number of patients in whom NABTs declined below the initial titre after 48 months of incobotulinumtoxinA treatment or in whom titres had become negative within the 48 months.

SECONDARY OUTCOME MEASURE

steepness of changes in NABT. NABTs were determined by mouse hemidiaphragm assay. Findings were compared to long-term data from 24 cervical dystonia patients who had developed NABTs and in whom treatment had been discontinued.

RESULTS

Following a transient increase in the first 24 months under incobotulinumtoxinA treatment in some patients, NABTs declined well below the initial titre in the majority of patients. Test assay results were negative in most of the patients followed for more than 36 months. NABTs seemed to decline into the negative detection range as rapidly under incobotulinumtoxinA treatment as after cessation of botulinum neurotoxin therapy.

CONCLUSIONS

The reduction of NABTs despite continuous treatment with incobotulinumtoxinA indicates low antigenicity of incobotulinumtoxinA. This might have implications on restrictions such as minimum injection intervals of ≥10 weeks currently in place for maintaining successful long-term application of botulinum neurotoxin.

Profile of Xeomin® (incobotulinumtoxinA) for the treatment of blepharospasm

Even though conventional botulinum neurotoxin (BoNT) products have shown successful treatment results in patients with benign blepharospasm (BEB), the main, potential long-term side effect of BoNT use is the development of immunologic resistance due to the production of neutralizing antibody to the neurotoxin after repeated injections. Xeomin^® (incobotulinumtoxinA), a unique botulinum neurotoxin type A (BoNT/A) drug free of complexing proteins otherwise contained in all conventional BoNT/A drugs, was recently approved by US Food and Drug Administration for the treatment of cervical dystonia or blepharospasm in adults. The newly approved BoNT/A drug may overcome this limitation of previous conventional products, since it contains pure neurotoxin (150 kDa) through a manufacturing process that separates it from complexing proteins such as hemagglutinins produced by fermentation of Clostridium botulinum. Many studies have also shown that Xeomin^® has the same efficacy and safety profile as complexing protein-containing products such as Botox^® and is exchangeable with Botox^® using a simple 1:1 conversion ratio. Xeomin^® represents a new treatment option for the repeated treatment of patients with blepharospasm in that it may reduce antibody-induced therapy failure. But, long-term comparative trials in naïve patients between Xeomin^® and conventional BoNT/A drugs are required to confirm the low immunogenicity of Xeomin^®.