Use of botulinum toxin type F injections to treat torticollis in patients with immunity to botulinum toxin type A

Lessons about Botulinum Toxin A Therapy from Cervical Dystonia Patients Drawing the Course of Disease: A Pilot Study

AIM OF THE STUDY

To compare the course of severity of cervical dystonia (CD) before and after long-term botulinum toxin (BoNT) therapy to detect indicators for a good or poor clinical outcome.

PATIENTS AND METHODS

A total of 74 outpatients with idiopathic CD who were continuously treated with BoNT and who had received at least three injections were consecutively recruited. Patients had to draw the course of severity of CD from the onset of symptoms until the onset of BoNT therapy (CoDB graph), and from the onset of BoNT therapy until the day of recruitment (CoDA graph) when they received their last BoNT injection. Mean duration of treatment was 9.6 years. Three main types of CoDB and four main types of CoDA graphs could be distinguished. The demographic and treatment-related data of the patients were extracted from the patients' charts.

RESULTS

The best outcome was observed in those patients who had experienced a clear, rapid response in the beginning. These patients had been treated with the lowest doses and with a low number of BoNT preparation switches. The worst outcome was observed in those 17 patients who had drawn a good initial improvement, followed by a secondary worsening. These secondary nonresponders had been treated with the highest initial and actual doses and with frequent BoNT preparation switches. A total of 12 patients were primary nonresponders and did not experience any improvement at all. No relation between the CoDB and CoDA graphs could be detected. Primary and secondary nonresponses were observed for all three CoDB types. The use of initial high doses as a relevant risk factor for the later development of a secondary nonresponse was confirmed.

CONCLUSIONS

Patients' drawings of their course of disease severity helps to easily detect "difficult to treat" primary and secondary nonresponders to BoNT on the one hand, but also to detect "golden responders" on the other hand.

Transient Receptor Potential Channels and Botulinum Neurotoxins in Chronic Pain

Pain afflicts more than 1.5 billion people worldwide, with hundreds of millions suffering from unrelieved chronic pain. Despite widespread recognition of the importance of developing better interventions for the relief of chronic pain, little is known about the mechanisms underlying this condition. However, transient receptor potential (TRP) ion channels in nociceptors have been shown to be essential players in the generation and progression of pain and have attracted the attention of several pharmaceutical companies as therapeutic targets. Unfortunately, TRP channel inhibitors have failed in clinical trials, at least in part due to their thermoregulatory function. Botulinum neurotoxins (BoNTs) have emerged as novel and safe pain therapeutics because of their regulation of exocytosis and pro-nociceptive neurotransmitters. However, it is becoming evident that BoNTs also regulate the expression and function of TRP channels, which may explain their analgesic effects. Here, we summarize the roles of TRP channels in pain, with a particular focus on TRPV1 and TRPA1, their regulation by BoNTs, and briefly discuss the use of BoNTs for the treatment of chronic pain.

Clinical duration of action of different botulinum toxin types in humans

The Botulinum NeuroToxin (BoNT) comprises several serotypes with distinct properties, mechanisms of action, sensitivity and duration of effect in different species. The serotype A (BoNT/A) is the prevalent neurotoxin applied in human's disease. In this paper we present an overview of the current knowledge regarding the duration of effect and the neuromuscular sprouting of different BoNT serotypes in humans. Then, we report the original results of a study in healthy subjects treated with BoNT/A, B, C and F using different neurophysiological techniques. Twelve healthy volunteers (7 men, 5 women) are treated with BoNT/A, B, C and F or placebo in Abductor digiti minimi (ADM) muscle of the hand. Before and after injections, an extensive neurophysiological study is performed with the CMAP amplitude variation, Multi-Motor Unit Action Potentials (MUAPs) analysis, the Turns/Amplitude ratio of interference pattern (IP) and determination of jitter and Fiber Density (FD) at single-fiber electromyography (SFEMG), at week 2 (w2), 4 (w4), 6 (w6) and 8 (w8). A maximal neuromuscular block is obtained at w2 for all the serotypes. Afterwards, the CMAP trend appear similar for BoNT/A, B, and C while, BoNT/F shows a faster recover. Multi-MUAPs analysis and IP detect mild changes at w2 for all serotypes, except for BoNT/F that shows a greater change since w4. SFEMG have minimal changes in FD while, Jitter increase at w2 with a slower decrease over the time for all BoNTs. In conclusion, BoNT/F has earlier sprouting and complete recovery at w8. Other serotypes present a slower and similar profile. The EMG appear useful to study the functional recovery in humans, and these results should provide new evidence for assessing different serotypes. These findings improve our knowledge regarding the methods to evaluate duration of effects and dose equivalents in different serotypes, that in the future could change the clinicians strategy for disease-tailored BoNT therapies.

Novel Native and Engineered Botulinum Neurotoxins

Botulinum neurotoxins (BoNTs), produced by Clostridia and other bacteria, are the most potent toxins known. Their cleavage of the soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) proteins in neurons prevents the release of neurotransmitters, thus resulting in the muscle paralysis that is characteristic of botulism. This mechanism of action has been exploited for a variety of therapeutic and cosmetic applications of BoNTs. This chapter provides an overview of the native BoNTs, including the classical serotypes and their clinical use, mosaic BoNTs, and novel BoNTs that have been recently identified in clostridial and non-clostridial strains. In addition, the modular structure of native BoNTs, which are composed of a light chain and a heavy chain, is amenable to a multitude of novel fusions and mutations using molecular biology techniques. These novel recombinant BoNTs have been used or are being developed to further characterize the biology of toxins, to assist in vaccine production, to serve as delivery vehicles to neurons, and to be utilized as novel therapeutics for both neuronal and non-neuronal cells.

The Expanding Therapeutic Utility of Botulinum Neurotoxins

Botulinum neurotoxin (BoNT) is a major therapeutic agent that is licensed in neurological indications, such as dystonia and spasticity. The BoNT family, which is produced in nature by clostridial bacteria, comprises several pharmacologically distinct proteins with distinct properties. In this review, we present an overview of the current therapeutic landscape and explore the diversity of BoNT proteins as future therapeutics. In recent years, novel indications have emerged in the fields of pain, migraine, overactive bladder, osteoarthritis, and wound healing. The study of biological effects distal to the injection site could provide future opportunities for disease-tailored BoNT therapies. However, there are some challenges in the pharmaceutical development of BoNTs, such as liquid and slow-release BoNT formulations; and, transdermal, transurothelial, and transepithelial delivery. Innovative approaches in the areas of formulation and delivery, together with highly sensitive analytical tools, will be key for the success of next generation BoNT clinical products.

Substrate cleavage and duration of action of botulinum neurotoxin type FA ("H, HA")

Botulinum neurotoxin (BoNT) type FA is the only known naturally occurring chimeric BoNT of domains of BoNT/A and BoNT/F. BoNT/FA consists of an F5-like light chain (LC), a unique heavy chain (HC) translocation domain, and a HC receptor binding domain similar to BoNT/A1. Previous analyses of purified BoNT/FA have indicated a 5-10-fold greater potency in cultured human or rat neurons as compared to BoNT/A1 and a 400-500-fold greater potency compared to BoNT/B1. However, in vivo potency in mice was about 5-fold lower than BoNT/A1 or/B1. In this report, species specificity was examined by cell-based assays using primary neurons from mice and examining VAMP1 and 2 cleavage. The data indicated similar potency of BoNT/FA in primary mouse spinal cord neurons as previously observed in primary rat and human induced pluripotent stem cell (hiPSC) derived neuronal cell models, and equal enzymatic cleavage of mouse VAMP1 and 2 isoforms. Since the duration of action of BoNTs is due to continuous enzymatic activity of the LC in the neuronal cytosol, BoNT/FA was expected to have a short duration of action due to its F-type LC. In this report the duration of action of BoNT/FA was compared to that of BoNT/F1,/F5, and/B1 in both hiPSC derived neurons and in the in vivo mouse model. The data indicate a duration of action of BoNT/FA similar to BoNT/B1, while BoNT/F5 had a short duration of action similar to BoNT/F1.

Botulinum toxin type A versus botulinum toxin type B for cervical dystonia

BACKGROUND

This is an update of a Cochrane review first published in 2003. Cervical dystonia is the most common form of focal dystonia and is a disabling disorder characterised by painful involuntary head posturing. There are two available formulations of botulinum toxin, with botulinum toxin type A (BtA) usually considered the first line therapy for this condition. Botulinum toxin type B (BtB) is an alternative option, with no compelling theoretical reason why it might not be as- or even more effective - than BtA.

OBJECTIVES

To compare the efficacy, safety and tolerability of botulinum toxin type A (BtA) versus botulinum toxin type B (BtB) in people with cervical dystonia.

SEARCH METHODS

To identify studies for this review we searched the Cochrane Movement Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, reference lists of articles and conference proceedings. All elements of the search, with no language restrictions, were last run in October 2016.

SELECTION CRITERIA

Double-blind, parallel, randomised, placebo-controlled trials (RCTs) comparing BtA versus BtB in adults with cervical dystonia.

DATA COLLECTION AND ANALYSIS

Two independent authors assessed records, selected included studies, extracted data using a paper pro forma, and evaluated the risk of bias. We resolved disagreements by consensus or by consulting a third author. We performed meta-analyses using the random-effects model, for the comparison BtA versus BtB to estimate pooled effects and corresponding 95% confidence intervals (95% CI). No prespecified subgroup analyses were carried out. The primary efficacy outcome was improvement on any validated symptomatic rating scale, and the primary safety outcome was the proportion of participants with adverse events.

MAIN RESULTS

We included three RCTs, all new to this update, of very low to low methodological quality, with a total of 270 participants.Two studies exclusively enrolled participants with a known positive response to BtA treatment. This raises concerns of population enrichment, with a higher probability of benefit from BtA treatment. None of the trials were free of for-profit bias, nor did they provide information regarding registered study protocols. All trials evaluated the effect of a single Bt treatment session, and not repeated treatment sessions, using doses from 100 U to 250 U of BtA (all onabotulinumtoxinA, or Botox, formulations) and 5000 U to 10,000 U of BtB (rimabotulinumtoxinB, or Myobloc/Neurobloc).We found no difference between the two types of botulinum toxin in terms of overall efficacy, with a mean difference of -1.44 (95% CI -3.58 to 0.70) points lower on the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) for BtB-treated participants, measured at two to four weeks after injection. The proportion of participants with adverse events was also not different between BtA and BtB (BtB versus BtA risk ratio (RR) 1.40; 95% CI 1.00 to 1.96). However, when compared to BtA, treatment with BtB was associated with an increased risk of one adverse events of special interest, namely treatment-related sore throat/dry mouth (BtB versus BtA RR of 4.39; 95% CI 2.43 to 7.91). Treatment-related dysphagia (swallowing difficulties) was not different between BtA and BtB (RR 2.89; 95% CI 0.80 to 10.41). The two types of botulinum toxin were otherwise clinically non-distinguishable in all the remaining outcomes.

AUTHORS' CONCLUSIONS

The previous version of this review did not include any trials, since these were still ongoing at the time. Therefore, with this update we are able to change the conclusions of this review. There is low quality evidence that a single treatment session of BtA (specifically onabotulinumtoxinA) and a single treatment session of BtB (rimabotulinumtoxinB) are equally effective and safe in the treatment of adults with certain types of cervical dystonia. Treatment with BtB appears to present an increased risk of sore throat/dry mouth, compared to BtA. Overall, there is no clinical evidence from these single-treatment trials to support or contest the preferential use of one form of botulinum toxin over the other.

Botulinum toxin type B for cervical dystonia

BACKGROUND

This is an update of a Cochrane review first published in 2004, and previously updated in 2009 (no change in conclusions). Cervical dystonia is a frequent and disabling disorder characterised by painful involuntary head posturing. Botulinum toxin type A (BtA) is usually considered the first line therapy for this condition, although botulinum toxin type B (BtB) is an alternative option.

OBJECTIVES

To compare the efficacy, safety and tolerability of botulinum toxin type B (BtB) versus placebo in people with cervical dystonia.

SEARCH METHODS

We identified studies for inclusion in the review using the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, reference lists of articles and conference proceedings, last run in October 2015. We ran the search from 1977 to 2015. The search was unrestricted by language.

SELECTION CRITERIA

Double-blind, parallel, randomised, placebo-controlled trials (RCTs) of BtB versus placebo in adults with cervical dystonia.

DATA COLLECTION AND ANALYSIS

Two independent authors assessed records, selected included studies, extracted data using a paper pro forma and evaluated the risk of bias. We resolved disagreements by consensus or by consulting a third author. We performed one meta-analysis for the comparison BtB versus placebo. We used random-effects models when there was heterogeneity and fixed-effect models when there was no heterogeneity. In addition, we performed pre-specified subgroup analyses according to BtB doses and BtA previous clinical responsiveness. The primary efficacy outcome was overall improvement on any validated symptomatic rating scale. The primary safety outcome was the number of participants with any adverse event.

MAIN RESULTS

We included four RCTs of moderate overall methodological quality, including 441 participants with cervical dystonia. Three studies excluded participants known to have poorer response to Bt treatment, therefore including an enriched population with a higher probability of benefiting from Bt treatment. None of the trials were independently funded. All RCTs evaluated the effect of a single Bt treatment session using doses between 2500 U and 10,000 U. BtB was associated with an improvement of 14.7% (95% CI 9.8% to 19.5) in the patients' baseline clinical status as assessed by investigators, with reduction of 6.8 points in the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS-total score) at week 4 after injection (95% CI 4.54 to 9.01). Mean difference (MD) in TWSTRS-pain score at week 4 was 2.20 (95% CI 1.25 to 3.15). Overall, both participants and clinicians reported an improvement of subjective clinical status. There were no differences between groups in the withdrawals rate due to adverse events or in the proportion of participants with adverse events. However, BtB-treated patients had a 7.65 (95% CI 2.75 to 21.32) and a 6.78 (95% CI 2.42 to 19.05) increased risk of treatment-related dry mouth and dysphagia, respectively. Statistical heterogeneity between studies was low to moderate for most outcomes. All tested dosages were efficacious against placebo without clear-cut evidence of a dose-response gradient. However, duration of effect (time until return to baseline TWSTRS-total score) and risk of dry mouth and dysphagia were greater in the subgroup of participants treated with higher BtB doses. Subgroup analysis showed a higher improvement with BtB among BtA-non-responsive participants, although there were no differences in the effect size between the BtA-responsive and non-responsive subgroups.

AUTHORS' CONCLUSIONS

A single BtB-treatment session is associated with a significant and clinically relevant reduction of cervical dystonia impairment including severity, disability and pain, and is well tolerated, when compared with placebo. However, BtB-treated patients are at an increased risk of dry mouth and dysphagia. There are no data from RCTs evaluating the effectiveness and safety of repeated BtB injection cycles. There are no RCT data to allow us to draw definitive conclusions on the optimal treatment intervals and doses, usefulness of guidance techniques for injection, and impact on quality of life.

Current status and future directions of botulinum neurotoxins for targeting pain processing

Current evidence suggests that botulinum neurotoxins (BoNTs) A1 and B1, given locally into peripheral tissues such as skin, muscles, and joints, alter nociceptive processing otherwise initiated by inflammation or nerve injury in animal models and humans. Recent data indicate that such locally delivered BoNTs exert not only local action on sensory afferent terminals but undergo transport to central afferent cell bodies (dorsal root ganglia) and spinal dorsal horn terminals, where they cleave SNAREs and block transmitter release. Increasing evidence supports the possibility of a trans-synaptic movement to alter postsynaptic function in neuronal and possibly non-neuronal (glial) cells. The vast majority of these studies have been conducted on BoNT/A1 and BoNT/B1, the only two pharmaceutically developed variants. However, now over 40 different subtypes of botulinum neurotoxins (BoNTs) have been identified. By combining our existing and rapidly growing understanding of BoNT/A1 and /B1 in altering nociceptive processing with explorations of the specific characteristics of the various toxins from this family, we may be able to discover or design novel, effective, and long-lasting pain therapeutics. This review will focus on our current understanding of the molecular mechanisms whereby BoNTs alter pain processing, and future directions in the development of these agents as pain therapeutics.

Botulinum toxins: mechanisms of action, antinociception and clinical applications

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

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.

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.

Temporal characteristics of botulinum neurotoxin therapy

Botulinum neurotoxin is a pharmaceutical treatment used for an increasing number of neurological and non-neurological indications, symptoms and diseases. Despite the wealth of clinical reports that involve the timing of the therapeutic effects of this toxin, few studies have attempted to integrate these data into unified models. Secondary reactions have also been examined including the development of adverse events, resistance to repeated applications, and nerve terminal sprouting. Our primary intent for conducting this review was to gather relevant pharmacodynamic data from suitable biomedical literature regarding botulinum neurotoxins via the use of automated data-mining techniques. We envision that mathematical models will ultimately be of value to those who are healthcare decision makers and providers, as well as clinical and basic researchers. Furthermore, we hypothesize that the combination of this computer-intensive approach with mathematical modeling will predict the percentage of patients who will favorably or adversely respond to this treatment and thus will eventually assist in developing the increasingly important area of personalized medicine.

Clinical use of non-A botulinum toxins: botulinum toxin type C and botulinum toxin type F

Botulinum neurotoxin (BoNT) serotype A is commonly used in the treatment of focal dystonia, but some patients are primarily or become secondarily resistant to it. Consequently, other serotypes have to be used when immuno-resistance is proven. In the literature, patients with focal dystonia have been treated with BoNT serotype F with clinical benefit but with short lasting effects. Recently, BoNT serotype C has been used with positive clinical outcome. An update on the clinical use of BoNT serotype F and BoNT serotype C is provided.

Treatment of dystonia

Dystonia may be a sign or symptom, that is comprised of complex abnormal and dynamic movements of different etiologies. A specific cause is identified in approximately 28% of patients, which only occasionally results in specific treatment. In most cases, treatment is symptomatic and designed to relieve involuntary movements, improve posture and function and reduce associated pain. Therapeutic options are dictated by clinical assessment of the topography of dystonia, severity of abnormal movements, functional impairment and progression of disease and consists of pharmacological, surgical and supportive approaches. Several advances have been made in treatment with newer medications, availability of different forms of botulinum toxin and globus pallidus deep brain stimulation (DBS). For patients with childhood-onset dystonia, the majority of whom later develop generalized dystonia, oral medication is the mainstay of therapy. Recently, DBS has emerged as an effective alternative therapy. Botulinum toxin is usually the treatment of choice for those with adult-onset primary dystonia in which dystonia usually remains focal. In patients with secondary dystonia, treatment is challenging and efficacy is typically incomplete and partially limited by side effects. Despite these treatment options, many patients with dystonia experience only partial benefit and continue to suffer significant disability. Therefore, more research is needed to better understand the underlying cause and pathophysiology of dystonia and to explore newer medications and surgical techniques for its treatment.

Myobloc for the treatment of benign essential blepharospasm in patients refractory to botox

PURPOSE

A small percentage of cases with essential blepharospasm or hemifacial spasm will become resistant to botulinum toxin A (Botox). We present our experience treating these patients with botulinum toxin B (Myobloc).

METHODS

We reviewed all charts of patients in one physician's practice who received botulinum toxin B after becoming refractory to botulinum toxin A. For each treatment session, patients were evaluated for side effects, relief of spasms, and duration of treatment effect.

RESULTS

Data were collected on 16 patients and a total of 93 treatment visits. Average total dosage was 3,633 U per treatment session. Mean duration of beneficial effect was 7.3 weeks and was most commonly rated as fair to excellent. Side effects for botulinum toxin B occurred at a higher rate than is typical for botulinum toxin A. Most common side effects were pain on injection (100%), ptosis (32.3%), facial or mouth droop (22.6%), dry mouth (17.2%), dry eye (9.7%), exposure keratitis (7.5%), and blurred vision (5.4%). The rate of occurrence of side effects appears to be dose-dependent.

CONCLUSIONS

Botulinum toxin B is a useful treatment for cases that have become refractory to botulinum toxin A. The duration of beneficial effect is shorter than for type A. The side effect profile is similar to that for toxin type A except for pain on injection and the occurrence of dry mouth. Side effects occurred at a higher frequency than with botulinum toxin A, and the pattern suggests that botulinum toxin B spreads more diffusely. Side effects appear to be dosage-related.

The therapeutic use of botulinum toxin

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

The safety and tolerability of botulinum toxins for the treatment of cervical dystonia

The use of botulinum toxin to treat cervical dystonia (CD) has dramatically improved the quality of life of patients with this disabling, often painful disease. Two forms of type A toxin (BOTOX and Dysport) and one form of type B toxin (MyoBloc) are available in some parts of the world to treat patients with CD. The literature supports the efficacy of each in reducing the pain and movement of cervical dystonia. The dosing and side effects vary between the toxins. The potential availability of several forms of toxin will allow physicians to offer further treatment options to patients with CD. However, it is incumbent on the treating physicians to have a working knowledge of the different serotypes, different doses used of each formulation of each serotype, the side effect profile of each product and the potential for anti-body formation for each form of toxin.

Botulinum toxin type B for cervical dystonia

BACKGROUND

Cervical dystonia is the most common form of focal dystonia. It is characterized by involuntary posturing of the head and frequently is associated with neck pain. Disability and social withdrawal are common. Most cases of cervical dystonia are idiopathic and generally it is a life-long disorder. In recent years, Botulinum toxin type A (BtA) has become the first line therapy. However, some patients become resistant to it. This problem led to the study of another Botulinum toxin (Bt) serotype, Bt type B (BtB) to address the issues of clinical efficacy, effect size, and safety of BtB in the treatment of cervical dystonia.

OBJECTIVES

To determine whether botulinum toxin (BtB) is an effective and safe treatment for cervical dystonia.

SEARCH STRATEGY

We identified studies for inclusion in the review using the Cochrane Movement Disorders Group trials register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE; and by handsearching the Movement Disorders Journal and abstracts of international congresses on movement disorders and botulinum toxin, by communication with other researchers in the field, by searching reference lists of papers found using the above search strategies, and by contacting authors and drug manufacturers.

SELECTION CRITERIA

We considered studies eligible for inclusion in the review if they evaluated the efficacy of BtB for the treatment of cervical dystonia in randomized, placebo-controlled trials.

DATA COLLECTION AND ANALYSIS

We used a paper pro forma to collect data from the included studies with double extraction by two independent reviewers. Both reviewers assessed each trial for internal validity and settled differences by discussion. The outcome measures used included adverse events, improvement in symptomatic rating scales, subjective evaluation by patients and clinicians, changes in pain scores, changes in quality of life assessments.

MAIN RESULTS

Studies were short term (16 weeks) employing a single BtB injection session. All were multicentre and conducted in the US. All patients included had previously received BtA. The trials differed with respect to whether or not the patients were still responding to BtA but other entry criteria were similar. All studies used a dose of 10,000 Units of BtB in one group and the technique of administration was the same. Meta-analysis of three trials enrolling 308 participants showed statistically and clinically significant improvements in the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) total score at week four with a Peto odds ratio (OR) for the number of patients who had at least a 20% improvement of 4.69 (95% CI 2.06 to 10.69) and a weighted mean difference of -5.92 (95% CI -9.61 to -2.23). Subjective rating scales (Patient Global Assessment of Change, Investigator Global Assessment of Change, and Patient Analog Pain Assessment) also improved. Adverse events clearly associated with the mechanism of action of BtB included dysphagia and dry mouth and the number of patients with any adverse event were more frequent in BtB treatment groups. Subgroup analyses showed a clear dose-response relationship for subjective and objective benefit, for frequency and severity of adverse events, and a greater benefit for BtA resistant patients than BtA responders in the primary outcome. The duration of effect was about 16 weeks. We found three eligible studies enrolling 308 participants. Studies were short term (16 weeks) employing a single BtB injection session. All were multicentre and conducted in the US. All patients included had previously received BtA. The trials differed with respect to whether or not the patients were still responding to BtA but other entry criteria were similar. Patient groups were appropriately selected and well matched. From the methodological point of view these trials were probably not subjected to important selection, performance or attrition bias and all studies used an intention-to-treat analysis.The dose varied significantly between studies although all used 10,000 Units of BtB in one group and the technique of administration was the same. The primary outcome in all trials was change in TWSTRS total score at week four and other efficacy outcomes were similar between studies. The number of dropouts was small and balanced in all trials. Reasons for withdrawals were given. One randomized double-blind placebo-controlled study was excluded because data couldn't be extracted for the outcomes. Meta-analysis showed statistically and clinically significant improvements with a Peto odds ratio (OR) of 20% in TWSTRS total score at week four (OR 4.69; 95% CI 2.06 to 10.69) and a weighted mean difference of -5.92 (95% CI -9.61 to -2.23). Subjective rating scales (Patient Global Assessment of Change, Investigator Global Assessment of Change, and Patient Analog Pain Assessment) also improved. The weighted mean difference for changes in these subjective scales varied between -13% to -21%. However, for many of the outcomes, we could not combine data from all studies. Only adverse events clearly associated with the mechanism of action of BtB were more frequent in the treatment group. These included dysphagia and dry mouth. The number of patients with any adverse event was more frequent with BtB. Subgroup analyses showed a clear dose-response relationship for subjective and objective benefit and for frequency and severity of adverse events. Subgroup analyses showed a greater benefit for the BtA resistant patients than BtA responders in the primary outcome. The duration of effect was about 16 weeks. These trials did not measure quality of life nor did they establish the long term duration of effect or immunogenicity

AUTHORS' CONCLUSIONS

A single injection of BtB was effective and safe for treating cervical dystonia. Long-term uncontrolled studies suggested that further injection cycles continue to work for most patients. Future research should explore technical factors such as the optimum treatment intervals and use of image or electromyographic guidance for administration. Other issues include service delivery, quality of life, long-term efficacy and safety, and the relative indications for BtA, BtB and other treatments such as deep brain stimulation.

Botulinum toxin therapy in pain management

BTs seem to be a useful treatment in refractory MPS and headache. Presumably BTs work by breaking the spasm or pain cycle giving the patient a "window of opportunity" for traditional conservative measures to have a greater beneficial impact, but several studies suggest that a direct antinociceptive effect distinct from any reduction in muscle spasm may be at play. The major benefit of BTs compared with standard therapies is duration of response. We do not advocate that BTs be used as a first line treatment for MPS or headache. However, in refractory cases where nothing else has worked, it may offer a chance for improvement or cure not otherwise available. For now, it remains an off label, but increasingly accepted, approach in-patients with refractory myofascial pain and headache, who despite multidisciplinary approaches, continue to suffer.

Different types of botulinum toxin in humans

In humans, botulinum neurotoxin (BoNT) serotype A (BoNT/A) is a useful therapeutic tool, but different BoNT serotypes may be useful when a specific immune resistance related to BoNT/A is proved. BoNT serotype F (BoNT/F) was injected into human muscles but its effects are shorter compared to BoNT/A, whereas BoNT serotype B (BoNT/B) is effective in humans only if injected at very high doses. BoNT serotype C (BoNT/C) has a general profile of action similar to BoNT/A. Nevertheless, a comparison between these different BoNTs in human has not yet been reported. To establish the general profile of these different BoNTs in humans and the spread in near and untreated muscles we conducted an electrophysiological evaluation in 12 healthy volunteers by injecting BoNT/A (BOTOX 15MU), BoNT/B (NeuroBloc 1500MU), BoNT/F (15MU), BoNT/C (15MU) and a saline solution (placebo) in the abductor digiti minimi muscle (ADM) in a double-blind manner. The compound muscle action potential (CMAP) amplitude variation, before and at 2, 4, 6 and 8 weeks after the injections, was evaluated in the ADM, the fourth dorsal interosseus, the first dorsal interosseus and the abductor pollicis brevis APB. We detected an earlier recovery for BoNT/F when compared to the other BoNTs. No significant differences in the local or distant BoNT spread was observed among the different serotypes. We conclude that in humans, BoNT/B and BoNT/C have a general profile similar to BoNT/A and as such these serotypes could be alternative therapies to BoNT/A. BoNT/F might be useful when only a short duration of neuromuscular blockade is required.

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.

[Mode of action of botulinum neurotoxin: pathological, cellular and molecular aspect]

Several bacteria of the Clostridium genus (C. botulinum) produce 150 kDa di-chainal protein toxins referred as botulinum neurotoxins or BoNTs. They associate with non-toxic companion proteins and form a complex termed botulinum toxin or BoTx. The latter is used in clinic for therapeutic purpose. BoNTs affect cholinergic nerve terminals in periphery where they block acetylcholine release, thereby causing dysautonomia and motorparalysis (i.e. botulism). The cellular action of BoNTs can be depicted according to a three steps model: binding, internalisation and intraneuronal action. The toxins heavy chain mediates binding to specific receptors followed by endocytotic internalisation of BoNT/receptor complex. BoNT receptors may comprise gangliosides and synaptic vesicle-associated proteins as synaptotagmins. Vesicle recycling induces BoNT internalisation. Upon acidification of vesicles, the light chain of the neurotoxin is translocated into the cytosol. Here, this zinc-endopeptidase cleaves one or two among three synaptic proteins (VAMP-synaptobrevin, SNAP25, and syntaxin). As the three protein targets of BoNT play major role in fusion of synaptic vesicles at the release sites, their cleavage is followed by blockage of neurotransmitter exocytosis. The duration of the paralytic effect of the BoNTs is determined by 1) the turnover of their protein target; 2) the time-life of the toxin light chain in the cytosol, and 3) the sprouting of new nerve-endings that are retracted when the poisoned nerve terminal had recovered its full functionality.

[First use of botulinum toxin type B in ENT patients with secondary therapy failure of botulinum toxin type A]

The first botulinum toxin type B (BT-B) formulation, NeuroBloc, has been licensed in Germany for the treatment of cervical dystonia since March 2001. This allows the treatment of patients with secondary failure of botulinum type A (BT-A) injections for the first time. Three patients with such a secondary failure were successfully treated with BT-B. A total of 1,000 mouse units (MU) NeuroBloc per eye were injected in a patient with blepharospasm. The treatment was effective for 4 months. In a patient with spasmodic dysphonia, 250 MU were injected into each vocal cord. This was effective for 3.5 months. The third patient suffered from bilateral Frey's syndrome. A total of 7,500 MU were used on the right side and 6,000 MU on the left side to stop the gustatory sweating for 9 months. Overall, BT-B showed similar intervals of effectiveness as BT-A. Side effects were not seen using the above dosage regimes.

Extensor digitorum brevis test and resistance to botulinum toxin type A

We studied 22 patients with dystonia to determine the normal range of values for the extensor digitorum brevis (EDB) test, and to determine its sensitivity and specificity in detecting resistance to botulinum toxin type A (BTX-A). Three compound muscle action potentials (CMAPs) elicited by peroneal nerve stimulation were averaged before and 2 weeks after injection of 20 units of BTX-A into the EDB. Amplitude and area ratios were calculated by dividing the averaged postinjection CMAP by the averaged preinjection CMAP values. The difference in means of this ratio between clinically sensitive and resistant subjects was statistically significant (P < 0.002). A normal range of <0.45 for each ratio was determined by adding two standard deviations to the ratio mean of 14 clinically sensitive subjects. Four of five resistant patients had values outside the normal range. The EDB test is a simple quantitative method of detecting resistance to BTX-A, with a sensitivity of 80% and specificity of 94%.

Therapeutic use of botulinum toxins: background and history

The seven botulinum neurotoxin serotypes share less than 50% sequence homology and are immunologically distinct. The neurotoxins inhibit release of the neurotransmitter acetylcholine from the axon terminals of motor neurons, preganglionic sympathetic and parasympathetic neurons, and postganglionic parasympathetic nerves by a multi-step mechanism that differs slightly, but significantly, for each serotype. The inhibition is long lasting but temporary. The resulting muscle paralysis has provided the basis for therapeutic use of botulinum toxin types A and B in a variety of focal dystonias. The safety of the botulinum toxins, when administered focally, has permitted their widespread use in a number of other painful conditions.

Comparison of neuromuscular blockade and recovery with botulinum toxins A and F

Intramuscular injection of botulinum toxin A is used to treat focal dystonias. Because immunoresistance has been documented in some patients, other molecular forms of the toxin have been evaluated clinically. The present investigation compared the time course and extent of neuromuscular blockade and recovery of botulinum toxin types A and F using an electromyographic monitoring system implanted in the rat hindlimb. For a given dose, the degree and duration of blockade was more complete with type A toxin. Delayed onset of recovery in animals that received high doses of type A toxin allowed time for denervative changes to prevent a full return to baseline, as confirmed histologically. Conversely, animals receiving type F toxin fully recovered within 30 days at all dose levels. The rapid recovery with type F toxin suggested that neuromuscular transmission was restored via the original terminals rather than through functional collateral sprouting. The reversible nature of blockade with this molecular species puts in question its future clinical utility.

Botulinum toxin type A (BOTOX) for treatment of migraine

An open-label study and 2 double-blind, placebo-controlled studies have provided supporting evidence of botulinum toxin type A (BTX-A) as an effective, well-tolerated treatment for migraine. Observed durations of benefit were consistent with known properties of BTX-A. Findings suggest that response may vary by features of preinjection headaches, such as migraine frequency. The precise mechanism by which BTX-A provides pain relief is hypothesized to be related not only to acetylcholine inhibition but also to a blocking action on the parasympathetic nervous system. Additional studies that control factors likely to be related to response may lead to better understanding of the BTX-A effect on migraine and an optimal treatment protocol.

Cervical dystonia pathophysiology and treatment options

Dystonia is a syndrome of sustained involuntary muscle contractions, frequently causing twisting and repetitive movements or abnormal posturing. Cervical dystonia (CD) is a form of dystonia that involves neck muscles. However, CD is not the only cause of neck rotation. Torticollis may be caused by orthopaedic, musculofibrotic, infectious and other neurological conditions that affect the anatomy of the neck, and structural causes. It is estimated that there are between 60,000 and 90,000 patients with CD in the US. The majority of the patients present with a combination of neck rotation (rotatory torticollis or rotatocollis), flexion (anterocollis), extension (retrocollis), head tilt (laterocollis) or a lateral or sagittal shift. Neck posturing may be either tonic, clonic or tremulous, and may result in permanent and fixed contractures. Sensory tricks ('geste antagonistique') often temporarily ameliorate dystonic movements and postures. Commonly used sensory tricks by patients with CD include touching the chin, back of the head or top of the head. Patients with CD are classified according to aetiology into two groups: primary CD (idiopathic--may be genetic or sporadic) or secondary CD (symptomatic). Patients with primary CD have no evidence by history, physical examination or laboratory studies (except primary dystonia gene) of any secondary cause for the dystonic symptoms. CD is a part of either generalised or focal dystonic syndrome which may have a genetic basis, with an identifiable genetic association. Secondary or symptomatic CD may be caused by central or peripheral trauma, exposure to dopamine receptor antagonists (tardive), neurodegenerative disease, and other conditions associated with abnormal functioning of the basal ganglia. In the majority of patients with CD, the aetiology is not identifiable and the disorder is often classified as primary. Unless the aetiological investigation reveals a specific therapeutic intervention, therapy for CD is symptomatic. It includes supportive therapy and counselling, physical therapy, pharmacotherapy, chemodenervation [botulinum toxin (BTX), phenol, alcohol], and central and peripheral surgical therapy. The most widely used and accepted therapy for CD is local intramuscular injections of BTX-type A. Currently, both BTX type A and type B are commercially available, and type F has undergone testing. Pharmacotherapy, including anticholinergics, dopaminergic depleting and blocking agents, and other muscle relaxants can be used alone or in combination with other therapeutic interventions. Surgery is usually reserved for patients with CD in whom other forms of treatment have failed.

Secondary nonresponsiveness to botulinum toxin type A in patients with oromandibular dystonia

Intramuscular injection of botulinum toxin type A is the treatment of choice for most cases of oromandibular dystonia. We report on five patients with oromandibular dystonia that developed secondary nonresponsiveness to botulinum toxin type A following multiple injections over a 6-year period.

Botulinum toxin type B: a new injectable treatment for cervical dystonia

Cervical dystonia (CD) causes involuntary muscle spasms and is often associated with pain. Recently, botulinum toxin type B (BTX-B) (Myobloc, Elan South San Francisco, CA, USA) was approved for general use in the treatment of CD in the USA. In two large pivotal trials, BTX-B was found to be safe and effective in decreasing the movements, pain and disability associated with CD. Benefits were noted both in patients who no longer respond and in those who continue to respond to botulinum toxin type A (BTX-A). BTX-B offers an additional therapeutic option for patients with CD.

Botulinum toxin therapy for pain and inflammatory disorders: mechanisms and therapeutic effects

Botulinum toxin (BTX) injections are a well-recognised therapeutic modality for the treatment of regional involuntary muscle disorders and recently BTX has been used for treatment of pain and inflammatory disorders. The primary purpose of this review is to discuss the mechanism of action of therapeutic BTX in light of both the traditional understanding of BTX pharmacological effects as well as new observations. The review will deal with clinical observations and relevant animal experimentation. The data and hypotheses presented are not only relevant to botulinum toxin technology but will certainly prove important in the basic mechanisms of some of the diseases where botulinum toxin has been successfully applied. BTX used clinically comprises botulinum neurotoxin (BoNT) complexed with non-toxic proteins. The non-toxic components of the BTX complexes stabilise the labile BoNT during purification and formulation as a therapeutic. The complex proteins may also have unrecognised clinical significance such as slowing diffusion in tissues or imparting stability. The mechanisms of BTX formulations acting on SNARE proteins are briefly reviewed providing a basis for BTX clinical applications. The potential for design of improved botulinum toxins and formulations is addressed.

Botulinum toxin type A (BOTOX) for treatment of migraine

An open-label study and 2 double-blind, placebo-controlled studies have provided supporting evidence of botulinum toxin type A (BTX-A) as an effective, well-tolerated treatment for migraine. Observed durations of benefit were consistent with known properties of BTX-A. Findings suggest that response may vary by features of preinjection headaches, such as migraine frequency. The precise mechanism by which BTX-A provides pain relief is hypothesized to be related not only to acetylcholine inhibition but also to a blocking action on the parasympathetic nervous system. Additional studies that control factors likely to be related to response may lead to better understanding of the BTX-A effect on migraine and an optimal treatment protocol.

Muscle paralysis produced by botulinum toxin type A injection in treated torticollis patients compared with toxin naive individuals

We sought to determine whether the response to varying doses of botulinum toxin type A (BTX-A) injected in BTX-A-treated torticollis patients differed from the same injections given in toxin-naive individuals. We have developed a technique to objectively measure muscle weakness resulting from BTX injections in humans and have validated the technique in those not previously treated with BTX. We now examine BTX-A-treated torticollis patients to see if their response to BTX-A injection is similar to that of toxin-naive individuals. We injected 11 torticollis patients who had been receiving BTX-A injections with a standard 5-mouse unit (mu) dose into one extensor digitorum brevis (EDB) muscle and a varying dose into the other EDB, measuring muscle paralysis 2 weeks after the injection. Nine of the 11 patients were clinical and electrophysiologic responders. Two patients were non-responders. In the 9 responding patients the dose response curve to increasing doses of BTX-A was very similar to that seen in toxin-naive individuals. The mean muscle paralysis from the standard 5 mu dose was also similar to that previously reported in toxin-naive individuals. Torticollis patients who continue to respond clinically to BTX-A injections demonstrate essentially the same degree of muscle paralysis from the EDB injections as do subjects who have never been exposed to BTX-A.

The current use of botulinum toxin

Botulinum toxin is the most potent neurotoxin known, and has been in clinical use since the late 1970s. The toxin inhibits the release of acetylcholine from nerve terminals by inhibiting transport of the synaptic vesicles, thus causing functional denervation lasting up to 6 months. Our understanding of the mechanism of action of the toxin and the spectrum of diseases treatable with this agent continues to increase. Efficacy has been demonstrated in hemifacial spasm, dystonia, spasticity, hyperhidrosis and other conditions. Alternative serotypes are used in some centres, generally after the development of immunoresistance to the standard toxin (serotype A), and are likely to be in routine use in the near future. This paper reviews the history, pharmacology and current uses of botulinum toxin.

Pharmacotherapy with botulinum toxin: harnessing nature's most potent neurotoxin

Botulinum toxin (BTX), a potent biologic neurotoxin, commonly is associated with lethal outbreaks of food poisoning; however, it also plays a role as a therapeutic agent. Since the 1970s physicians have investigated BTX therapy in patients with neurologic disorders. The number of applications greatly expanded over the years to include certain focal dystonias (blepharospasm, torticollis, laryngeal dystonias, writer's cramp), strabismus, and a wide variety of other indications (gastrointestinal disorders, cosmetic wrinkle correction, spasticity, hyperhidrosis). BTX's safety and efficacy are reviewed.

The effects of tetanus toxin on the orbicularis oculi muscle

PURPOSE

Tetanus toxin can cause localized neuromuscular weakness, but it also can produce systemic tetany. The action of tetanus toxin on the orbicularis muscle has not been studied in animals immunized to prevent systemic tetany. Our objective was to determine whether tetanus toxin could be used to treat orbicularis oculi muscle spasms.

METHODS

We analyzed the clinical, electrophysiologic, and histopathologic effects of tetanus toxin injected into the orbicularis oculi muscle of rabbits with passive immunity to tetanus toxin. In six rabbits, the orbicularis oculi function in both eyes was assessed clinically, and the baseline orbicularis oculi muscle action potential was measured physiologically with electromyography (EMG). The rabbits then were immunized against tetanus toxin with tetanus immunoglobulin for immediate and definitive immunity. Tetanus toxin was injected into the left orbicularis oculi muscles, leaving the right eyes as controls. Ten days later, the rabbits were again assessed by clinical examination and with EMGs on both the injected side and the noninjected side. The animals were killed at 14 days, and the orbicularis muscle was removed from both sides. The injected and control tissues were examined microscopically for signs of neuromuscular denervation.

RESULTS

All six rabbits showed weakness in eye closure on the side injected with tetanus toxin. In addition, four rabbits developed complete ear ptosis on the tetanus toxin injected side because of spread of the toxin to adjacent ear muscles. EMGs showed both a denervation of the orbicularis oculi muscle and a poor blink potential on the side injected with tetanus toxin. Histopathologic studies of the orbicularis oculi muscle injected with tetanus toxin showed angulation of both slow and fast types of muscle fibers compatible with neuromuscular denervation.

CONCLUSIONS

Tetanus toxin can cause localized orbicularis oculi weakness, as documented clinically, physiologically, and microscopically, without producing systemic tetany in immunized rabbits. Tetanus toxin may have a potential application in the treatment of blepharospasm and hemifacial spasm.

Retention of cleaved synaptosome-associated protein of 25 kDa (SNAP-25) in neuromuscular junctions: a new hypothesis to explain persistence of botulinum A poisoning

Botulinum neurotoxins can block neurotransmitter release for several months. The molecular mechanism of these toxins' action is known, but the persistence of neuromuscular paralysis that they cause is unexplained. At frog neuromuscular junctions, application of botulinum toxin type A caused paralysis and reduced the C-terminus immunoreactivity of SNAP-25, but not that of the remaining N-terminus fragment. Botulinum toxin type C caused paralysis and reduced syntaxin immunoreactivity without affecting that of SNAP-25. Co-application of botulinum A and C reduced syntaxin immunoreactivity, and that of both C and N termini of SNAP-25. Application of hydroxylamine to de-palmitoylate SNAP-25 resulted in a slight reduction of the immunoreactivity of SNAP-25 N terminus, while it had no effect on immunoreactivity of botulinum A cleaved SNAP-25. In contrast, application of hydroxylamine to nerve terminals where syntaxin had been cleaved by botulinum C caused a considerable reduction in SNAP-25 N-terminus immunoreactivity. Hence the retention of immunoreactive SNAP-25 at the neuromuscular junction depends on its interactions with syntaxin and plasma membrane. Persistence of cleaved SNAP-25 in nerve terminals may prevent insertion of new SNAP-25 molecules, thereby contributing to the longevity of botulinum A effects.Key words: SNAP receptor, neurotoxin, dystonia, botulism, torticollis.

Botulinum toxin in motor disorders

Advances in the clinical use of botulinum neurotoxins continue. Of interest to the neurologist is the advanced practice in the treatment of focal dystonia and the new developments on other dyskinesias and on autonomic control of smooth muscle motility. New toxin serotypes are now being tested; their availability will improve clinical practice and will possibly lead to combined treatments. Indications in spasticity and in juvenile cerebral palsy are now under scrutiny. The combination of focal chemodenervation with specific rehabilitation procedures enables new development in this field.

Doxorubicin chemomyectomy as a treatment for cervical dystonia: histological assessment after direct injection into the sternocleidomastoid muscle

The sternocleidomastoid muscle (SCM) is one of the major muscles involved in producing abnormal head position in cervical dystonia patients. This study tested whether doxorubicin chemomyectomy, direct injection of doxorubicin into the SCM to permanently remove muscle fibers, has the potential to be a nonsurgical, permanent treatment for cervical dystonia. The right SCM of rabbits was injected with either 1 or 2 mg doxorubicin. Animals were sacrificed 1-2 months postinjection. The SCM was prepared for histological examination of muscle fiber loss and fiber type composition. In all cases, direct injection of doxorubicin resulted in significant decreases in total muscle cross-sectional areas ranging from 75% up to 98%. Individual myofiber cross-sectional areas were smaller than normal after 2 mg doxorubicin treatment, but similar to normal fiber size after 1 mg doxorubicin. There were increased numbers of myofibers that expressed slow and neonatal myosin heavy chain isoforms in these remaining muscle fibers compared to the untreated SCM on the contralateral side. Developmental myosin heavy chain (MHC) was also present in 53% of the remaining myofibers of the treated muscles. The fiber type composition of muscles contralateral to the doxorubicin injections was compared to the fiber type composition of SCM from normal, untreated controls; no difference was seen in the proportions of fast, slow, and neonatal MHC fiber types in these SCM muscles. In summary, the direct injection of doxorubicin into the SCM resulted in significant muscle loss. This supports the use of doxorubicin chemomyectomy as a potential permanent, nonsurgical treatment for cervical dystonia.

Further studies using higher doses of botulinum toxin type F for torticollis resistant to botulinum toxin type A

OBJECTIVE

A previous study of botulinum toxin type F (BTX-F) treatment for torticollis had shown a dose of 520 MU to be effective, but for a much shorter duration than is usual with botulinum toxin type A (BTX-A). The objective was to assess the effect of a higher dose of BTX-F.

METHODS

Four of the previously treated patients, plus an additional patient, were treated with a higher dose of 780 MU BTX-F. All were secondary nonresponders to BTX-A due to neutralising antibodies. A test injection of 40 MU BTX-F was also given into the extensor digitorum brevis muscle (EDB), to examine the time course of the biological effect of the toxin electrophysiologically. Patients were followed up at two, four, eight, and 12 weeks.

RESULTS

All patients reported subjective improvement lasting from seven to 11 (mean 8.6) weeks accompanied by a significant reduction in mean clinical severity scores at two weeks. Four patients had pain which was substantially reduced. The electrophysiological studies confirmed biological sensitivity to the toxin in all patients, showing a significant change beginning at two weeks and returning to baseline at 12 weeks. The time course of this effect paralleled roughly that of the clinical response. The four patients who had previously received 520 MU BTX-F reported that the response was better and longer in duration with 780 MU. Dysphagia was more common than reported with the lower dose.

CONCLUSION

Better results are possible with higher doses of BTX-F but the duration of benefit is still shorter than with BTX-A, seemingly due to a shorter duration of neuromuscular junction blockade.

Variability of the immunologic and clinical response in dystonic patients immunoresistant to botulinum toxin injections

Immunoresistance (Ab+) to botulinum toxin type A (BTX-A) has been a serious concern since the introduction of BTX-A in the treatment of dystonia and other disorders associated with abnormal muscle contractions. We studied seven patients who developed Ab+ and later reverted to antibody-negative (Ab-) status. These seven patients, six women (mean age, 56 years; range, 41-80 years), with an average duration of dystonia for all patients of 197 months (range, 84-360 months), received a total mean cumulative dose of 1659 units (U) (range, 810-1975 U), with an average dose of 207 U per visit. All of these patients became unresponsive to BTX-A treatment and became Ab+ as determined by mouse bioassay. Their response to BTX-A after they reverted to Ab- was analyzed. The average latency between the initial BTX-A treatment and development of Ab+ was 27 months (range, 1543 months). The average duration between the detection of Ab+ status and subsequent reversal to Ab- status was 30 months (range, 10-78 months). Six of these Ab- patients were reinjected with BTX-A, and all six benefited from repeat injections comparable with their earlier response. Three patients lost their clinical response to subsequent injections and were found to be again Ab+. Two of the five patients who became immunoresistant to BTX-A received botulinum toxin type F (BTX-F) injections and one patient received a single session of BTX-B with improvement in their symptoms. In conclusion, this unique group of patients who were Ab+ and became Ab- responded favorably to repeat BTX-A injections, but some lost the benefit with subsequent injections. These observations suggest that the anamnestic immunologic response to BTX-A can wane, but can be reactivated by repeat BTX-A treatments. The presence of antibodies did not interfere with the response to BTX-F or BTX-B injections, thus confirming the antigenic specificity of various BTX serotypes.

Botulinum neurotoxin serotype C: a novel effective botulinum toxin therapy in human

Botulinum neurotoxin (BoNT) serotype A is commonly used in the treatment of focal dystonia. Nevertheless, some patients are or become resistant to this serotype. Consequently, other different serotypes have to be used. A comparison of the neuromuscular blockade induced by BoNT type A and C in the extensor digitorum brevis muscles of voluntary subjects was studied, by evaluating the amplitude variation over the time (until 90 days) of the compound muscular action potential elicited by supramaximal electrical stimulation of the peroneal nerve at the ankle. A very similar effect and temporal profile, was observed for each serotype. On this basis, two patients with idiopathic facial hemispasm and one with blepharospasm were treated with BoNT serotype C with very beneficial long lasting effects.