Clinical presentation and management of antibody-induced failure of botulinum toxin therapy

"Pseudo"-Secondary Treatment Failure Explained via Disease Progression and Effective Botulinum Toxin Therapy: A Pilot Simulation Study

BACKGROUND

The objective of this study was to provide evidence from a simple simulation. In patients with focal dystonia, an initial good response to botulinum neurotoxin (BoNT) injections followed by a secondary worsening does not necessarily arise from an antibody-induced secondary treatment failure (NAB-STF), but may stem from a "pseudo"-secondary treatment failure (PSEUDO-STF).

METHODS

The simulation of the outcome after BoNT long-term treatment was performed in four steps: 1. The effect of the first single BoNT injection (SI curve) was displayed as a 12-point graph, corresponding to the mean improvement from weeks 1 to 12. 2. The remaining severity of the dystonia during the nth injection cycle was calculated by subtracting the SI curve (weighted by the outcome after n - 1 cycles) from the outcome after week 12 of the (n - 1)th cycle. 3. A graph was chosen (the PRO curve), which represents the progression of the severity of the underlying disease during BoNT therapy. 4. The interaction between the outcome during the nth BoNT cycle and the PRO curve was determined.

RESULTS

When the long-term outcome after n cycles of BoNT injections (applied every 3 months) was simulated as an interactive process, subtracting the effect of the first cycle (weighted by the outcome after n - 1 cycles) and adding the progression of the disease, an initial good improvement followed by secondary worsening results. This long-term outcome depends on the steepness of the progression and the duration of action of the first injection cycle. We termed this response behavior a "pseudo"-secondary treatment failure, as it can be compensated via a dose increase.

CONCLUSION

A secondary worsening following an initial good response in BoNT therapy of focal dystonia might not necessarily indicate neutralizing antibody induction but could stem from a "PSEUDO"-STF (a combination of good response behavior and progression of the underlying disease). Thus, an adequate dose adaptation must be conducted before diagnosing a secondary treatment failure in the strict sense.

Mechanism and clinical use of botulinum neurotoxin in head and facial region

PURPOSE

Botulinum neurotoxin (BoNT) is a biological toxin produced by Clostridium botulinum. BoNT is a potent toxin extensively used in therapeutic interventions. This review provides an updated overview of the mechanisms of action and clinical applications of BoNT in head and facial region.

STUDY SELECTION

MEDLINE/PubMed searches were conducted using the terms "botulinum neurotoxin" and "dentistry" along with a combination of other related terms. In addition, studies were manually selected from reference lists of the selected articles.

RESULTS

The Food and Drug Administration in the United States initially approved BoNT to treat strabismus, blepharospasm, and hemifacial spasms. The use of BoNT in dermatology and cosmetics has been widely established and has created a revolution in these fields. Over the years, its applications in various medical specialties have expanded widely. Owing to its safety, efficacy, and long duration of action, it is well-accepted by patients. BoNT/A and BoNT/B are widely used in clinical practice. Several off-label uses of BoNT in the dental fraternity have yielded promising results. We have elaborated on the speculated mechanism of action, dosage, effective sites of injection, and adverse effects of each therapeutic application. The various clinical indications for BoNT include bruxism, myofascial pain, temporomandibular joint dislocation, hemifacial pain, orofacial dystonia, facial paralysis, chronic migraine, and trigeminal neuralgia.

CONCLUSIONS

BoNT is a safe treatment that can be used effectively, provided that the clinician has adequate knowledge regarding the mechanism, injection techniques, and local and systemic side effects and that it is administered cautiously and purposefully.

Exploring the Interplay between the Clinical and Presumed Effect of Botulinum Injections for Cervical Dystonia: A Pilot Study

BACKGROUND

Repetitive intramuscular injections of botulinum neurotoxin type A (BoNT/A) are the treatment of choice in patients with cervical dystonia (CD). As soon as BoNT therapy is initiated, the natural course of CD cannot be observed anymore. Nevertheless, the present study focuses on the "presumed" course of disease severity under the assumption that no BoNT therapy had been performed. The "experienced" benefit is compared with the "presumed" worsening.

METHODS

Twenty-seven BoNT/A long-term-treated CD patients were recruited. They had to assess the remaining severity of CD in percent of its severity at the start of BoNT therapy (RS-%). Then, they had to draw the course of severity from the onset of symptoms to the start of BoNT/A therapy (CoDB graph), as well as the course of severity from the start of BoNT/A therapy until the day of recruitment (CoDA graph). Then, they were instructed to presume the development of CD severity from the day of the start of BoNT/A therapy until the day of recruitment under the assumption that no BoNT/A therapy had been performed, and to assess the maximal severity they could presume in percent of the severity at the start of BoNT therapy (IS-%). Then, they had to draw the "presumed" development of CD severity (CoDI graph). The "experienced" change in disease severity and the "presumed" change since the start of BoNT/A therapy were compared and correlated with a variety of demographical and treatment-related data, including the actual severity of CD at the day of recruitment, which was assessed using the TSUI score and the actual dose per session (ADOSE).

RESULTS

No CD patients expected an improvement without BoNT therapy. "Presumed" worsening ((IS-%)-100) was about 50% in the mean and did not correlate with the "experienced" benefit (100-(RS-%)). However, IS-% was significantly correlated with ATSUI and ADOSE.

CONCLUSION

Obviously, CD patients have the opinion that their CD would have further progressed and worsened if no BoNT/A therapy had been performed. Thus, the total benefit of BoNT/A therapy for a patient with CD is a combination of the "experienced" benefit under BoNT/A therapy and the prevented worsening of CD that the patient expects to occur without BoNT/A therapy.

Addressing the Real-World Challenges of Immunoresistance to Botulinum Neurotoxin A in Aesthetic Practice: Insights and Recommendations from a Panel Discussion in Hong Kong

With increasing off-label aesthetic indications using higher botulinum neurotoxin A (BoNT-A) doses and individuals starting treatment at a younger age, particularly in Asia, there is a greater risk of developing immunoresistance to BoNT-A. This warrants more in-depth discussions by aesthetic practitioners to inform patients and guide shared decision-making. A panel comprising international experts and experienced aesthetic practitioners in Hong Kong discussed the implications and impact of immunoresistance to BoNT-A in contemporary aesthetic practice, along with practical strategies for risk management. Following discussions on a clinical case example and the results of an Asia-Pacific consumer study, the panel concurred that it is a priority to raise awareness of the possibility and long-term implications of secondary non-response due to immunoresistance to BoNT-A. Where efficacy and safety are comparable, a formulation with the lowest immunogenicity is preferred. The panel also strongly favored a thorough initial consultation to establish the patient's treatment history, explain treatment side effects, including the causes and consequences of immunoresistance, and discuss treatment goals. Patients look to aesthetic practitioners for guidance, placing an important responsibility on practitioners to adopt risk-mitigating strategies and adequately communicate important risks to patients to support informed and prudent BoNT-A treatment decisions.

No Secondary Treatment Failure during Incobotulinumtoxin-A Long-Term Treatment Demonstrated by the Drawing of Disease Severity

The aim of this study was to detect clinical hints regarding the development of secondary treatment failure (STF) in patients with focal dystonia who were exclusively treated with incobotulinumtoxin/A (incoBoNT/A). In total, 33 outpatients (26 with idiopathic cervical dystonia, 4 with Meige syndrome and 3 with other cranial dystonia) who were treated with repeated injections of incoBoNT/A for a mean period of 6.4 years without interruptions were recruited to draw the course of their disease severity (CoD) from the onset of symptoms to the onset of BoNT therapy (CoDB graph) and from the onset of BoNT therapy to recruitment (CoDA graph). At the time of recruitment, the patients assessed the change in severity as a percentage of the severity at the onset of BoNT therapy. Blood samples were taken to test the presence of neutralizing antibodies (NABs) using the mouse hemidiaphragm assay (MHDA). Patients reported an improvement of about 70% with respect to the mean. None of the patients tested positive for MHDA. Three different types of CoDB and three different types of CoDA graphs could be distinguished. The patients with different CoDB graphs reported different long-term outcomes, but there was no significant difference in long-term outcomes between patients with different CoDA graphs. None of the patients produced a CoDA graph with an initial improvement and a secondary worsening as a hint for the development of STF. A primary non-response was not observed in any of the patients. During long-term treatment with BoNT/A, NABs and/or STF may develop. However, in the present study on patients with incoBoNT/A long-term monotherapy, no hints for the development of NABs or STF could be detected, underlining the low antigenicity of incoBoNT/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.

Improving the Efficacy of Botulinum Toxin for Cervical Dystonia: A Scoping Review

Cervical dstonia (CD) is a chronic disorder with a significant detrimental impact on quality of life, requiring long-term treatment. Intramuscular injections of botulinum neurotoxin (BoNT) every 12 to 16 weeks have become the first-line option for CD. Despite the remarkable efficacy of BoNT as a treatment for CD, a significantly high proportion of patients report poor outcomes and discontinue the treatment. The reasons that drive sub-optimal response or treatment failure in a proportion of patients include but are not limited to inappropriate muscle targets and/or BoNT dosing, improper method of injections, subjective feeling of inefficacy, and the formation of neutralizing antibodies against the neurotoxin. The current review aims to complement published research focusing on the identification of the factors that might explain the failure of BoNT treatment in CD, highlighting possible solutions to improve its outcomes. Thus, the use of the new phenomenological classification of cervical dystonia known as COL-CAP might improve the identification of the muscle targets, but more sensitive information might come from the use of kinematic or scintigraphic techniques and the use of electromyographic or ultrasound guidance might ensure the accuracy of the injections. Suggestions are made for the development of a patient-centered model for the management of cervical dystonia and to emphasize that unmet needs in the field are to increase awareness about the non-motor spectrum of CD, which might influence the perception of the efficacy from BoNT injections, and the development of dedicated rehabilitation programs for CD that might enhance its effectiveness.

Botilinum toxin in the treatment of strabismus

Introduction: Strabismus is an oculomotor imbalance that occurs in 0.5 to 5% of the population. There are various etiopathogenetic theories and several modalities of treatment. One of these modalities is the application of botulinum toxin intramuscularly. This chemodenervation causes temporary muscle paresis which acts as a recession while its antagonist contracts. This achieves a temporary correction of strabismus. However, further research is needed. The aim of the paper was evaluation of published research studies on botulinum toxin as a treatment option in strabismus, as a primary and adjuvant therapy and as a preventive therapy in patients with abducens nerve palsy. For this purpose, we searched the major databases of the medical publications Medline and Pubmed, using keywords: strabismus, botulinum toxin. We found more than 50 articles related to our search for the last 30 years, 30 of which have been used for this review. In this review paper we have presented the most important insights from the literature, as well as our opinions and insights on the topic. Although further studies are needed regarding dosing as well as avoiding side effects, botulinum toxin has been shown to be a good alternative and adjunctive therapy to strabismus surgery, with the downside being that the effect is temporary. Positive effects and faster recovery have also been shown in patients with abducens nerve palsy.

Functional Deimmunization of Botulinum Neurotoxin Protease Domain via Computationally Driven Library Design and Ultrahigh-Throughput Screening

Botulinum neurotoxin serotype A (BoNT/A) is a widely used cosmetic agent that also has diverse therapeutic applications; however, adverse antidrug immune responses and associated loss of efficacy have been reported in clinical uses. Here, we describe computational design and ultrahigh-throughput screening of a massive BoNT/A light-chain (BoNT/A-LC) library optimized for reduced T cell epitope content and thereby dampened immunogenicity. We developed a functional assay based on bacterial co-expression of BoNT/A-LC library members with a Förster resonance energy transfer (FRET) sensor for BoNT/A-LC enzymatic activity, and we employed high-speed fluorescence-activated cell sorting (FACS) to identify numerous computationally designed variants having wild-type-like enzyme kinetics. Many of these variants exhibited decreased immunogenicity in humanized HLA transgenic mice and manifested in vivo paralytic activity when incorporated into full-length toxin. One variant achieved near-wild-type paralytic potency and a 300% reduction in antidrug antibody response in vivo. Thus, we have achieved a striking level of BoNT/A-LC functional deimmunization by combining computational library design and ultrahigh-throughput screening. This strategy holds promise for deimmunizing other biologics with complex superstructures and mechanisms of action.

Botulinum toxin antibody titres: measurement, interpretation, and practical recommendations

Botulinum toxin (BT) therapy may be blocked by antibodies (BT-AB) resulting in BT-AB induced therapy failure (ABF). BT-AB may be detected by the mouse lethality assay (MLA), the mouse diaphragm assay (MDA) and the sternocleidomastoid test (SCMT). For the first time, we wanted to compare all three BT-AB tests and correlate them to subjective complaint of complete or partial secondary therapy failure in 37 patients with cervical dystonia (25 females, 12 males, age 51.2 ± 11.4 years, disease duration 12.4 ± 6.3 years). Complaint of therapy failure was not correlated with any of the BT-AB tests. MDA and MLA are closely correlated, indicating that the MDA might replace the MLA as the current gold standard for BT-AB measurement. The SCMT is closely correlated with MDA and MLA confirming that BT-AB titres and BT's paretic effect are in a functional balance: low BT-AB titres are reducing BT's paretic effect only marginally, whereas high BT-AB titres may completely block it. When therapy failure is classified as secondary and permanent, BT-AB evaluation is recommended and any BT-AB test may be applied. For MDA > 10 mU/ml, MLA > 3 and SCMT < 25%, ABF is highly likely. MDA < 0.6 mU/ml are therapeutically irrelevant. They are neither correlated with pathologic MLA nor with pathologic SCMT. They should not be the basis for treatment decisions, such as switching dystonia therapy to deep brain stimulation. All other results are intermediate results. Their interactions with therapy efficacy is unpredictable. In these cases, BT-AB tests should be repeated or one or two additional test methods should be applied.

Botulinum toxin in the management of myalgia in temporomandibular disorders: are all injections equal?

Botulinum toxin (BTX) is becoming widely used as an adjunct to conservative management of myalgia-predominant temporomandibular disorders (TMDs) with reports of improved quality of life. There is, however, no consensus on the optimal dosage. Based on previous studies, dose regimens vary between clinicians, and we know of no standard dose protocol for the administration of BTX for the purpose of TMD management. A survey was sent to members of the British Association of Oral and Maxillofacial Surgeons (BAOMS) Temporomandibular Joint Sub-Specialty Interest Group (TMJ SSIG) and an international mailing list of high-volume TMJ surgeons (the TMJ Internetwork) to ascertain variations in dose regimens between different clinicians. The survey found that 41 respondents offered BTX to patients. The masseter muscle group was the most commonly injected site, and the majority of respondents (34/41) used Botox® (Allergan). Brands less commonly used included Dysport® (Ipsen), and Xeomin® (Merz Pharma). Botox® doses varied between 30 and 100 units, whilst Dysport® doses ranged from 50 - 300 units/muscle. The number of injection sites/muscle also varied. This survey demonstrates the wide variation in practice amongst clinicians with respect to BTX administration. To ensure optimal dose and response titration, further studies and evidence-based research are needed to standardise its use for the treatment of TMDs.

The incidence of Frey syndrome and treatment with botulinum toxin in the Central Denmark Region

Objectives

Frey syndrome (FS) is a common complication to large salivary glands surgery. This study primarily aims to describe the incidence of FS among parotid surgery patients in the Central Denmark Region. The secondary aim is to describe predisposing characteristics to syndrome development and the effect of treatment with botulinum toxin (Botox) injection.

Methods

This is a retrospective qualitative study spanning the years 2015-2020. Data on patients diagnosed with FS after parotid surgery with symptoms severe enough to require Botox was extracted from electronic patient records. Incidence of FS development was calculated using data from all parotid gland surgeries in the same period and region.

Results

The incidence of treatment-requiring FS was 2.6% (20/775), with an annual incidence ranging from 0.8% (1/125) in 2017 to 4.5% (5/112) in 2016. Difference in FS development for men and women was not statistically significant (p = .07), although it was significantly more common after total parotidectomy compared to superficial resection (p = .003), and after malignant compared to benign diagnosis (p = .01). Complications in the postoperative period arose for 30% of FS patients. Repeated treatment with Botox was necessary after 6-12 months and at a median interval of 11 months. Forty-five percent of patients received only one injection. The average dose per injection was 48.3 IU.

Conclusion

This study revealed a rather low incidence of FS in the Central Denmark Region compared to current international literature. Total parotidectomy and malignant diagnosis predisposed to syndrome development. Botox injection had a wide-ranging effective duration but typically lasted for around 1 year.

Level of evidence

Level IV.

The Immunology of Botulinum Toxin Therapy: A Brief Summary

Like all proteins foreign to the human body, also botulinum toxin (BT) is antigenic and may stimulate an immune response with formulation of antibodies (BT-AB). Affected patients may no longer respond to BT therapy and various degrees of BT-AB related therapy failure (ABF) may result. We want to review the immunological interactions between BT and BT-AB, the prevalence, the time course and the risk factors for BT-AB formation as they are related to the treatment algorithms, the patient's immune system and to exogenic factors. Special emphasis is placed on various features of the BT drugs including the specific biological activity (SBA) as a predictor of their antigenicity. Quantitative detection of BT-AB by the mouse diaphragm assay will be demonstrated. As ABF may have serious consequences for patients affected, careful risk factor analysis is warranted to reduce them wherever possible.

A dual dopaminergic therapy with L-3,4-dihydroxyphenylalanine and chlorpromazine for the treatment of blepharospasm, a focal dystonia: Possible implications for striosomal D1 signaling

Impairment of balanced activity between dopamine D1 and D2 receptor functions in the striatum, particularly in striatal functional subdivisions (i.e., striosome and matrix compartments), has been proposed to underlie dystonia genesis. This study was undertaken to examine the therapeutic effect of dual dopaminergic modulation with L-3,4-dihydroxyphenylalanine (L-DOPA) and chlorpromazine (CPZ) in patients with blepharospasm, a focal dystonia. For this purpose, Dopacol tablets™ (L-DOPA 50 mg plus carbidopa 5 mg) and Wintermin™ (CPZ phenolphthalinate 180 mg/g) were used. Clinical evaluations were performed before and after an 8-week drug treatment interval using the Visual Analog Scale (VAS), Blepharospasm Disability Index (BSDI), modified VAS (mVAS), and Jankovic Rating Scale (JRS). The data were analyzed using non-parametric statistics. Results showed that in patients (n = 7) with blepharospasm, dystonia symptoms were significantly alleviated by the administration of both Dopacol tablets™ (one tablet × 3/day) and CPZ (5 mg × 3/day), as determined using the VAS, BSDI, mVAS, and JRS. In contrast, there was no improvement of dystonia symptoms in patients (n = 7) who ingested Dopacol tablets™ (one tablet × 3/day) alone, nor in those (n = 7) who ingested CPZ (5 mg × 3/day) alone. Thus, dual pharmacotherapy with L-DOPA and CPZ can exert a therapeutic effect on blepharospasm, suggesting that dystonia symptoms can be attenuated through dopaminergic modulation with inducing an increase in striatal D1-signals. Since dopamine D1 receptors are heavily enriched in the striosome compartment in the “human” striatum, our results also suggest that striosomal loss of D1-signaling may be important in the pathogenesis of dystonia.

Immunogenicity of botulinum toxin

Botulinum toxin treatment is the most common non-surgical cosmetic treatment. Although there are many available treatments using botulinum toxin, their effects are temporary and repeated injections are required. These frequent injections can trigger an immunological response. In addition, botulinum toxin acts as an antigen in the body; thus, its effect disappears progressively due to this immunological reaction, which may cause treatment failure. Active botulinum toxin consists of a core neurotoxin and complexing proteins, the exact effects of which remain unclear. However, the complexing proteins are closely related to the immune response and the formation of neutralizing antibodies. Since neutralizing antibodies can lead to treatment failure, their formation should be prevented. Furthermore, various methods of detecting neutralizing antibodies have been used to predict treatment failure.

Significant Long-Lasting Improvement after Switch to Incobotulinum Toxin in Cervical Dystonia Patients with Secondary Treatment Failure

Under continuous long-term treatment with abo- or onabotulinum toxin type A (BoNT/A), ~10 to 15% of patients with cervical dystonia (CD) will develop neutralizing antibodies and reduced responsiveness over an ~10-year treatment period. Among the botulinum neurotoxin type A preparations so far licensed for CD, incobotulinum toxin A (incoBoNT/A; Xeomin^®) is the only one without complex proteins. Whether CD patients with treatment failure under abo- or onaBoNT/A may still respond to incoBoNT/A is unknown. In this cross-sectional, retrospective study, 64 CD patients with secondary treatment failure after abo- or onaBoNT/A therapy who were switched to incoBoNT/A were compared to 34 CD patients exclusively treated with incoBoNT/A. The initial clinical severity of CD, best outcome during abo- or onaBoNT/A therapy, severity at the time of switching to incoBoNT/A and severity at recruitment, as well as all corresponding doses, were analyzed. Furthermore, the impact of neutralizing antibodies (NABs) on the long-term outcome of incoBoNT/A therapy was evaluated. Patients significantly improved after the switch to incoBoNT/A (p < 0.001) but did not reach the improvement level obtained before the development of partial secondary treatment failure or that of patients who were exclusively treated with incoBoNT/A. No difference between abo- and onaBoNT/A pretreatments or between the long-term outcomes of NAB-positive and NAB-negative patients was found. The present study demonstrates significant long-term improvement after a switch to incoBoNT/A in patients with preceding secondary treatment failure after abo- or onaBoNT/A therapy and confirms the low antigenicity of incoBoNT/A.

Immunogenicity to Botulinum Toxin Type A: A Systematic Review With Meta-Analysis Across Therapeutic Indications

BACKGROUND

Botulinum toxin A (BTX-A) is commonly employed as a neuromodulator in several neurological diseases and aesthetic indications. Formation of neutralizing antibodies (NAbs) after BTX-A injections may be responsible for treatment failure.

OBJECTIVES

The authors sought to quantify the prevalence of NAbs following treatment with Abobotulinumtoxin A, Incobotulinumtoxin A, and Onabotulinumtoxin A for therapeutic indications.

METHODS

An electronic systematic search (2000-2020) of PubMed, Scopus, Web of Science, and Embase was conducted. Original studies reporting prevalence of NAbs were included. Data analysis was carried out through open meta-analysis softwares.

RESULTS

Forty-three studies involving 8833 patients were included in this meta-analysis. The incidence of NAbs was 1.8% (summary estimate = 0.018, 95% CI [0.012, 0.023]); a meta-regression analysis revealed that BTX-A duration was significantly associated with increased incidence of NAbs (P = 0.007). Patients with dystonia had the highest incidence (7.4%) of NAbs against BTX-A (summary estimate = 0.074, 95% CI = [0.045, 0.103], I2 = 93.%, P < 0.00) followed by patients with spasticity (6.7%) and urological indications (6.2%). Abobotulinumtoxin A was associated with the highest incidence of NAbs (7.4%) (summary estimate = 0.074, 95% CI = [0.053, 0.096], I2 = 97.24%, P < 0.00) by the Incobotulinumtoxin A and Onabotulinumtoxin A 0.3% (summary estimate <0.003%, 95% CI = [-0.001, 0.007], P < 0.003).

CONCLUSIONS

Although the overall incidence of NAbs following BTX-A injections is relatively low, patients with secondary nonresponse to BTX-A with no apparent causes should be investigated for NAbs. A consensus needs to be developed for the optimal management of such patients.

LEVEL OF EVIDENCE: 2

Botulinum toxin in cancer therapy-current perspectives and limitations

Abstract

Different serotypes of botulinum toxins (BoNTs) act upon different types of SNARE proteins. This property is used in aesthetic medicine to treat certain eye disorders such as crossed eyes (strabismus) and uncontrolled blinking (blepharospasm), to treat muscle spasms or movement disorders, and, for the two last decades, more and more often, to provide support in cancer therapy, especially so as to obtain analgesic effects upon spastic conditions. The limited literature data also suggests that the addition of BoNTs to the culture of cancer cell lines reduces cell growth, and mitotic activity, and promotes their apoptosis. BoNTs have several advantages that can be emphasized: BoNTs act on both perfusion and oxygenation; moreover, BoNTs are considered to be safe and free of systemic side effects upon administration. Recently, advances in molecular biology techniques have allowed a wide variety of novel BoNT constructs with alternative functions. These constructs could be assessed as potential new classes of anti-cancer drugs. This creates new potential perspectives in the wider use of non-toxic modified BoNT constructs in cancer therapy. In the light of the mentioned premises and existing literature reports, the aim of this review is to summarize current data and reports considering BoNT use in cancer therapy.

Key points

•Botulinum toxin (BoNTs) may be useful in cancer treatment.

•Botulinum toxin can serve as an analgesic after cancer radiotherapy.

•Botulinum toxin has the ability to inhibit tumor growth and promote apoptosis of neoplastic cells.

Repeated onabotulinum neurotoxin A injections for drooling in children with neurodisability

AIM

To evaluate the effect of repeated onabotulinum neurotoxin A injections for the treatment of drooling in children with neurodisabilities.

METHOD

This was a retrospective cohort study, in which the first, second, and third onabotulinum neurotoxin A injection were compared within children treated between 2000 and 2020. Primary outcomes included drooling quotient, visual analogue scale (VAS), and treatment success defined as ≥50% reduction in drooling quotient and/or VAS 8 weeks after treatment. Each outcome was obtained at baseline and 8 weeks posttreatment.

RESULTS

Seventy-seven children were included (mean age at first injection: 8y 3mo, SD 3y 7mo, range 3-17y; 44 males, 33 females; 51.9% with cerebral palsy, 45.5% wheelchair-bound). The objective (drooling quotient) and subjective (VAS) effect after the second injection was lower compared to the first injection. The third injection showed less objective and significantly less subjective effect compared to the first injection. An overall success rate of 74.0%, 41.6%, and 45.8% were found for the first, second, and third injection respectively.

INTERPRETATION

Although onabotulinum neurotoxin A remained effective throughout the entire treatment course, there is less effect of subsequent onabotulinum neurotoxin A injections compared to the first. Although there might be a loss of effect after repeated injections, there is continued improvement for most children. What this paper adds Repeated injections show a diminished treatment effect after the second injection. A continued improvement is seen in most patients.

The Impact of the Course of Disease before Botulinum Toxin Therapy on the Course of Treatment and Long-Term Outcome in Cervical Dystonia

This study analyses the influence of the course of the disease of idiopathic cervical dystonia (CD) before botulinum toxin (BoNT) therapy on long-term outcomes. 74 CD-patients who were treated on a regular basis in the botulinum toxin outpatient department of the University of Düsseldorf and had received at least 3 injections were consecutively recruited after written informed consent. Patients were asked to rate the amount of change of CD in relation to the severity of CD at begin of BoNT therapy (IMPQ). Then they had to draw the course of disease of CD from onset of symptoms until initiation of BoNT therapy (CoDB-graph) on a sheet of paper into a square of 10 × 10 cm² size. Remaining severity of CD was estimated by the treating physician using the TSUI-score. Demographical and treatment related data were extracted from the charts of the patients. Depending on the curvature four different types of CoDB-graphs could be distinguished. Time to BoNT therapy, increase of dose and improvement during BoNT treatment were significantly (p < 0.05) different when patients were split up according to CoDB-graph types. The lower the age at onset of symptoms, the shorter was the time to therapy (p < 0.02). Initial dose (p < 0.04) and actual dose (p < 0.009) were negatively correlated with the age of the patients at recruitment. The course of disease of CD before BoNT therapy has influence on long-term outcome. This has implications on patient management and information on the efficacy of BoNT treatment.

Long-term stable efficacy of botulinum toxin A in facial movement disorders with no need for increasing dose

Botulinum toxin A is considered an effective treatment for involuntary facial movements. We examined whether treatment efficacy maintained or changed over time with two products, Botox and Dysport, in patients with hemifacial spasm, facial synkinesis and benign essential blepharospasm.We retrospectively investigated 87 consecutive patients (51 women, 36 men) who had undergone treatment for ≥6 years. Long-term effects, as well as side effects of Botox or Dysport local injections were evaluated. The first three treatments were considered the titration period and not taken into account when testing for dose changes.Mean treatment duration was 10 years (range 6-11, SD 1.0), 2441 treatments were administered, 1162 with Botox and 1279 with Dysport, the two brands were interchanged as needed. Good to full improvement was seen in 90% of patients both with both brands. Injection doses and treatment responses were consistent during the study with both drugs. No major side effects were reported, and relatively few minor adverse events were reported, with clear reduction from the titration period (6.1%), to the remainder of the study (3.9%).Botulinum toxin (BTX-A) is a satisfactory long-term treatment without need for dose increase over. Both Botox and Dysport were effective when used interchangeably.

Botulinum Injections for Idiopathic Cervical Dystonia: a Longitudinal Study

Botulinum toxin (BT) injections into the cervical muscles are an effective and commonly practiced treatment approach for cervical dystonia. In this retrospective longitudinal study, we collected data from the Sheba electronic medical records on consecutive patients with idiopathic cervical dystonia (ICD), treated regularly with periodic BT injections between the years 2008-2020. All treatment visits were analyzed regarding type of toxin, dose injected, and clinical outcomes. The vast majority of patients were treated with abobotulinum toxin A. Sixty-four ICD patients (51 (79.7%) females, onset at age 45.8 ± 13.7 years) were treated over 17.1 ± 13.9 (range 3 to 49) visits per patient; BT treatment efficacy increased gradually from initial treatment sessions to visit 13, when it achieved a steady state. While the subjective report of percentage improvement and its duration were around 78.9 ± 17.1% for 2.8 ± 1.0 months, respectively, the dose of BT increased significantly over the years (p = 0.006). Side effects (SE) were not rare, and commonly recurred after subsequent sessions and were usually mild and short-lasting, with dysphagia being the most common (~17.5%), followed by neck/arm weakness (11.9%) and cervical pain (8.9%). Repeated injections of BT for ICD remain beneficial for patients over several years of therapy, and despite mild SE, patients tend to adhere to a 3-4 months interval schedule.

Clinical Improvement After Treatment With IncobotulinumtoxinA (XEOMIN®) in Patients With Cervical Dystonia Resistant to Botulinum Toxin Preparations Containing Complexing Proteins

This study investigated the clinical long-term effect of incobotulinumtoxinA (incoBoNT/A) in 33 cervical dystonia (CD) patients who had developed partial secondary therapy failure (PSTF) under previous long-term botulinum toxin (BoNT) treatment. Patients were treated four times every 12 weeks with incoBoNT/A injections. Physicians assessed treatment efficacy using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) at the baseline visit, week 12 and 48. Patients rated quality of life of CD with the Craniocervical Dystonia Questionnaire (CDQ-24). Titres of neutralizing antibodies(NAB) were determined at start of the study and after 48 weeks. All patients had experienced significant and progressive worsening of symptoms in the last 6 months of previous BoNT treatment. Repeated incoBoNT/A injections resulted in a significant reduction in mean TWSTRS at week 12 and 48. Patients' rating of quality of life was highly correlated with TWSTRS but did not change significantly over 48 weeks. During the 48 weeks -period of incoBoNT/A treatment NAB titres decreased in 32.2%, did not change in 45.2%, and only increased in 22.6% of the patients. Thus, repeated treatment with the low dose of 200 MU incoBoNT/A over 48 weeks provided a beneficial clinical long-term effect in PSTF and did not booster titres of NAB.

The impact of the initial severity on later outcome: retrospective analysis of a large cohort of botulinum toxin naïve patients with idiopathic cervical dystonia

BACKGROUND

The aim of study was to demonstrate that the first three injections of botulinum neurotoxin type A (BoNT/A) appear to be less effective in botulinum toxin naïve patients with idiopathic cervical dystonia (CD) with mild symptoms and low severity scores (TSUI-scores) at onset of BoNT/A-therapy compared to patients with full-blown CD and high initial TSUI-scores.

METHODS

In 337 patients with CD who started BoNT/A-therapy in the BoNT-outpatient clinic of the university hospital in Düsseldorf during the last 12 years, demographical and treatment-related data as well as outcome measures (TSUI-scores) of the first four visits were extracted from the treatment ACCESS data bank.

RESULTS

Distribution of the severity of CD scored using the TSUI-score significantly changed with the first three injections. In patients with a high baseline severity (TSUI-score > 10), mean TSUI-score continuously decreased (p < 0.001), whereas in patients with a low initial severity (TSUI-score < 6), mean TSUI-score increased (p < 0.001) during the first three injection cycles. Individual responses varied between 100% improvement, no response at all, and even worsening. Improvement of CD at the end of an injection cycle was observed in less than 25% in the mildly affected patients, but in more than 80% in the more severely affected patients.

CONCLUSION

Clinical response to the first three BoNT/A-injections in severely affected de novo CD-patients is different from the response to BoNT/A in mildly affected de novo CD-patients. This has implications for further scientific studies and the patient management of mildly affected de novo patients with cervical dystonia.

The Extreme Ends of the Treatment Response Spectrum to Botulinum Toxin in Cervical Dystonia

Background: The response to BoNT is not uniform; a broad spectrum of responses and side-effects usually occurs. This study aimed to show special cervical dystonia cases with therapy response very different to normal treatment course which indicate the extreme ends of therapy spectrum. Patients: Clinical data and course of treatment of five long-term treated patients with cervical dystonia out of therapy response norms are presented: a patient who was supersensitive to standard dose and has required dose adjustment to lower dose of BoNT; one patient who worsened under a standard dose, but responded excellently to twice the standard dose; one insensitive patient who responded poorly for years to a dose well above the standard dose, but responded when dose was further increased; and two patients with a totally different response pattern to BoNT/A preparation 1, but the development of a neutralizing antibody induced secondary treatment failure in both cases and a totally different response after switch to BoNT/A preparation 2. Conclusions: These five patients indicate that the response of a patient to a BoNT preparation may be unexpected. Therefore, cautious onset of BoNT therapy is recommended as well as consequent dose adjustment later on and even switch to another BoNT/A preparation when a patient has already developed NABs against BoNT/A.

Botulinum Toxin A: A Review of Potential Uses in Treatment of Female Urogenital and Pelvic Floor Disorders

Background: Botulinum toxin is an injectable neuromodulator that inhibits transmission between peripheral nerve endings and muscle fibers, resulting in muscle paralysis. Botulinum toxin type A is the most common form of botulinum toxin used in clinical practice.

Methods: In this review, we examine the mechanism of action, formulations, common clinical use in the genital-urinary tract, and potential clinical use in pelvic floor disorders of botulinum toxin type A.

Results: Several aspects of botulinum toxin A make it a favorable therapeutic tool, including its accessibility, its longevity, and its impermanence and reversibility of resultant chemodenervation in a relatively short and safe manner. Although botulinum toxin A has well-established efficacy in treating refractory overactive bladder and neurogenic detrusor overactivity, its use in pelvic floor disorders is still in its infancy.

Conclusion: The efficacy of botulinum toxin A for treating pelvic pain, voiding dysfunction, muscle pain and dysfunction, and certain colorectal-related pain issues shows promise but requires additional rigorous evaluation.

Transient Improvement after Switch to Low Doses of RimabotulinumtoxinB in Patients Resistant to AbobotulinumtoxinA

Botulinum toxin type B (BoNT/B) has been recommended as an alternative for patients who have become resistant to botulinum toxin type A (BoNT/A). This study aimed to compare the clinical effect, within a patient, of four injections with low doses of rimabotulinumtoxinB with the effect of the preceding abobotulinumtoxinA (aboBoNT/A) injections. In 17 patients with cervical dystonia (CD) who had become resistant to aboBoNT/A, the clinical effect of the first four rimabotulinumtoxinB (rimaBoNT/B) injections was compared to the effect of the first four aboBoNT/A injections using a global assessment scale and the TSUI score. After the first two BoNT/B injections, all 17 patients responded well and to a similar extent as to the first two BoNT/A injections, but with more side effects such as dry mouth and constipation. After the next BoNT/B injection, the improvement started to decline. The response to the fourth BoNT/B injection was significant (p < 0.048) lower than the fourth BoNT/A injection. Only three patients developed a complete secondary treatment failure (CSTF) and five patients a partial secondary treatment failure (PSTF) after four BoNT/B injections. In nine patients, the usual response persisted. With the use of low rimaBoNT/B doses, the induction of CSTF and PSTF to BoNT/B could not be avoided but was delayed in comparison to the use of higher doses. In contrast to aboBoNT/A injections, PSTF and CSTF occurred much earlier, although low doses of rimaBoNT/B had been applied.

Clinical Implications of Difference in Antigenicity of Different Botulinum Neurotoxin Type A Preparations: Clinical Take-Home Messages from Our Research Pool and Literature

The three different botulinum toxin type A (BoNT/A) preparations being licensed in Europe and the U.S. differ in protein content, which seems to be a major factor influencing the antigenicity of BoNT/A. In the present study, several arguments out of our research pool were collected to demonstrate that the clinical response and antigenicity were different for the three BoNT/A preparations: some results of (1) a cross-sectional study on clinical outcome and antibody formation of 212 patients with cervical dystonia (CD) being treated between 2 and 22 years; 2) another cross-sectional study on the clinical aspects and neutralizing antibody (NAB) induction of 63 patients having developed partial secondary treatment under abobotulinum (aboBoNT/A) onabotulinumtoxin (onaBoNT/A) who were switched to incobotulinumtoxin (incoBoNT/A) in comparison to 32 patients being exclusively treated with incoBoNT/A. These results imply that (1) the presence of NAB cannot be concluded from the course of treatment, that (2) an increase in the dose and variability of outcome with treatment duration indicates the ongoing induction of NABs over time, that (3) the higher protein load of BoNT/A goes along with a higher incidence and prevalence of NAB induction and that (4) the best response to a BoNT/A is also dependent on the protein load of the preparation.

Antibody-induced botulinum toxin treatment failure: A review and novel management approach

BACKGROUND

Botulinum neurotoxin A (BoNT/A) has been used for cosmetic indications for many decades. Consumption of BoNT/A usage has been markedly increased for a few years. Even new formulations of BoNT/A to decrease immunogenicity have been released, repeated treatment to maintain efficacy outcome is inevitable and could finally provoke immune response. In the past, prevalence of botulinum treatment failure (BTF) in cosmetic indication was rare leading to less medical concern. Current decade, case reports on BTF, especially antibody-induced botulinum toxin treatment failure (ABTF), have been increasingly revealed and risk factors associated with ABTF have been intensively studied.

AIMS

In this article, we will review antibody-induced botulinum toxin treatment failure (ABTF), risk-associated ABTF, prevalence and recent case reports of ABTF, and new approach to deal with ABTF.

METHODS

Literature search was conducted using PubMed. The relevant literatures published between January 2000 and May 2020 concerning BTF and ABTF including investigation for ABTF were included and analyzed.

RESULTS

Possible causes of BTF were summarized. ABTF could be a tip of iceberg of BTF, its prevalence, and currently, 10-year case reports of ABTF were published evidence. Risk factors and investigation methods for ABTF were also summarized. Based on previous studies and our experience, novel approach to management of ABTF was described.

CONCLUSION

Effective management of BTF is to explore causes of treatment failure. Antibodies against BoNT/A complex could be one of many possibilities. Laboratory in vitro tests could be alternative tools to decrease adverse effect and rebooting immune responses in BTF patients.

Agrin Influences Botulinum Neurotoxin A-Induced Nerve Sprouting via miR-144-agrin-MuSK Signaling

Botulinum neurotoxin (BoNT) has become a powerful therapeutic tool, and is extensively used in aesthetic medicine and in the treatment of neurological disorders. However, its duration of effect is limited, mainly owing to nerve sprouting. Inhibition of nerve sprouting to prolong the effective duration of BoNT is therefore of great clinical interest. However, appropriate interventional strategies to accomplish this are currently unavailable. In this study, we determined the role of the neurogenic regulator agrin in BoNT type A (BoNT/A)-induced nerve sprouting in a rat model. We then determined whether agrin could be used as an interventional target for prolonging the duration of effect of BoNT/A, and made a preliminary study of the upstream and downstream regulatory mechanisms by which agrin could influence the effective duration of BoNT/A. Our results showed that agrin was involved in the regulation of BoNT/A-induced nerve sprouting, and blocking of agrin function with anti-agrin antibody temporarily could delay muscle strength recovery and prolong the duration of BoNT/A effect. Moreover, agrin influenced the duration of BoNT/A effect by regulating downstream myogenic muscle-specific receptor tyrosine kinase (MuSK), and was simultaneously regulated by upstream miR-144. In conclusion, agrin could regulate BoNT/A-induced nerve sprouting through miR-144-agrin-MuSK signaling; it influences the effective duration of BoNT/A, and could find clinical application as an interventional target for prolonging the effect of BoNT/A.

Clinical relevance of neutralizing antibodies in botulinum toxin long-term treated still-responding patients with cervical dystonia

Background:

The aim of the study was to test the clinical relevance of neutralizing antibodies (NABs) in patients with cervical dystonia (CD) still responding to repeat injections with botulinum toxin type A (BoNT/A).

Methods:

Enzyme-linked immunosorbent assay (ELISA)-test evidence from a cross-sectional study on 221 CD-patients with treatment durations of between 2 and 21 years and still responding to repeat BoNT/A-injections showed the presence of antibodies against BoNT/A in 39 patients. A mouse hemi-diaphragm (MHDA) confirmation test was performed in these 39 ELISA-positive patients, and demographic (age, sex, age at onset of CD) and treatment-related (duration of treatment, mean dose of the last 10 injections, TSUI-score, patient’s subjective scoring of the treatment effect, patient’s scoring of quality of life by means of the CDQ24-questionnaire) data from these 39 patients were compared with data from ELISA-negative patients. Paralysis time, the MHDA outcome measure, was correlated with clinical data.

Results:

The ELISA-positive CD-patients had significantly higher TSUI-scores (p < 0.015), and had been treated for significant longer (p < 0.022) and with significantly higher doses (p < 0.001). Patient’s rating of BoNT/A-treatment effect and quality of life tended to be worse in ELISA-positive compared with ELISA-negative patients. The paralysis time of ELISA-positive patients was significantly correlated with the mean dose of the last 10 injections (p < 0.027) and the pain subscore of the CDQ24 (p < 0.012).

Conclusions:

Presence of NABs is clinically relevant in CD, leading to a significantly worse head position, therapy with significantly higher BoNT/A doses, and a correlation between the CDQ24 pain-subscore and antibody titers.

Immunogenicity Associated with Botulinum Toxin Treatment

Botulinum toxin (BoNT) has been used for the treatment of a variety of neurologic, medical and cosmetic conditions. Two serotypes, type A (BoNT-A) and type B (BoNT-B), are currently in clinical use. While considered safe and effective, their use has been rarely complicated by the development of antibodies that reduce or negate their therapeutic effect. The presence of antibodies has been attributed to shorter dosing intervals (and booster injections), higher doses per injection cycle, and higher amounts of antigenic protein. Other factors contributing to the immunogenicity of BoNT include properties of each serotype, such as formulation, manufacturing, and storage of the toxin. Some newer formulations with purified core neurotoxin devoid of accessory proteins may have lower overall immunogenicity. Several assays are available for the detection of antibodies, including both structural assays such as ELISA and mouse-based bioassays, but there is no consistent correlation between these antibodies and clinical response. Prevention and treatment of antibody-associated non-responsiveness is challenging and primarily involves the use of less immunogenic formulations of BoNT, waiting for the spontaneous disappearance of the neutralizing antibody, and switching to an immunologically alternate type of BoNT.

Immunogenicity induced by botulinum toxin injections for limb spasticity: A systematic review

BACKGROUND

The imputability of neutralizing antibodies (NABs) in secondary non-response (SnR) to botulinum toxin (BoNT) injections for limb spasticity is still debated.

OBJECTIVE

This systematic literature review aimed to determine the prevalence of NABs after BoNT injections for limb spasticity and analyze their determinants and their causal role in SnR.

METHODS

We searched MEDLINE via PubMed, Cochrane and Embase databases for articles published during 1990-2018. Two independent reviewers extracted the data and assessed the quality of studies with a specific scale (according to PRISMA and STROBE guidelines). Because the techniques used to detect NABs did not influence the results, we calculated the global (all studies) sensitivity and specificity of NAB positivity to reveal SnR.

RESULTS

We included 14 articles published from 2002 to 2018 (including an epublication) describing 5 randomized controlled trials and 5 interventional and 4 observational studies. The quality was satisfactory (mean score 18/28 arbitrary units). NAB detection was the primary criterion in 5 studies and a secondary criterion in 9. In total, 1234 serum samples for 1234 participants (91% with stroke) were tested after injection. NAB prevalence was about 1%, with no significant difference among formulations. NAB positivity seemed favoured by long-duration therapy with high doses and a short interval between injections. The identification of non-response by NAB positivity had poor global sensitivity (56%) but very high specificity (99.6%). No consensual criteria were used to diagnose non-response to BoNT injection.

CONCLUSIONS

NAB prevalence is much lower after BoNT treatment for limb spasticity than cervical dystonia. Consensual criteria must be defined to diagnose non-response to BoNT injection. Because immunogenicity is not the most common cause of non-response to BoNT injection, NABs should be sought in individuals with SnR with no other cause explaining the treatment inefficacy. A test with 100% specificity is recommended. In cases for which immunogenicity is the most likely cause of non-response to BoNT injections, some biological arguments suggest trying another BoNT, but no clinical evidence supports this strategy.

Clinical Pharmacology of Botulinum Toxin Drugs

Botulinum toxin (BT) has changed from a deadly poison to a novel therapeutic principle for a large number of disorders in many medical areas.BT drugs are special in many ways: they are biologicals, their active ingredient BT is not patentable, their spectrum of clinical applications is extremely broad, their dose range is enormous, their mode of action is local and their life cycles are special.This review covers BT's therapeutic mode of action, time course of action, target tissues, pharmacological profile, adverse effects, interactions, potency labelling and antigenicity as well as BT's therapeutic preparations.

Contemporary Review and Case Report of Botulinum Resistance in Facial Synkinesis

BACKGROUND

Botulinum resistance poses significant treatment challenges for both patients and healthcare practitioners. We first present a case highlighting botulinum resistance in a patient who failed to respond to alternative formulations but who responded remarkably to incobotulinum toxinA, an identical toxin free of complexing proteins. Secondly, we provide a treatment algorithm and a review of the literature detailing clinical and immunochemical botulinum resistance.

RESULTS

Patients with botulinum resistance show a predisposition to failure on subsequent injections and possess a propensity toward neutralizing and nonneutralizing antibody development. The mechanisms of resistance are not entirely understood but thought to be secondary to an immunologic response. Risk factors for resistance include higher botulinum doses, more frequent injections, and high total lifetime dosage. Patients may still respond to other botulinum formulations or subtypes; however, this effect may be temporary.

CONCLUSION

This case report describes a patient who responded to incobotulinum toxinA after failing treatment with the identical toxin compounded with buffer proteins, ultimately supporting the possibility of immune-mediated resistance to the surrounding proteins and not the toxin itself. Often, impending treatment resistance is preceded by a poor or limited clinical response. Antibody testing is not indicated because it is neither sensitive nor specific and does not change clinical practice. Initially, higher doses of botulinum may overcome resistance without increasing treatment frequency, and side effects are far less common in those with clinical resistance. If higher dosages fail to produce a response, alternative botulinum formulations or subtypes can be considered. Laryngoscope, 129:2269-2273, 2019.

Antibody-induced failure of botulinum toxin therapy: re-start with low-antigenicity drugs offers a new treatment opportunity

Botulinum toxin (BT) can stimulate formation of BT antibodies (BTAB) thus producing Antibody-Induced Therapy Failure (ABTF). BTAB titres may drop eventually. When BT therapy is then re-started with conventional BT drugs, BTAB titres re-increase promptly. We wanted to study whether the use of the low-antigenicity BT drug incobotulinumtoxinA (INCO) can prevent this re-increase. 8 patients with cervical dystonia and ABTF with maximal BTAB titres (6 women, 2 men, age 41.4 ± 12.1 years, disease duration 6.6 ± 4.7 years) were studied. ABTF ocurred under onabotulinumtoxinA (ONA) in five patients and under abobotulinumtoxinA (ABO) in 3 after 8.8 ± 3.8 injection series and a treatment time of 962.0 ± 473.2 days. After 3881.5 ± 2468.3 days without BT, all BTAB titres had dropped to insignificant levels before BT therapy was re-started with INCO. Treatment parameters before and after re-start were as follows: single dose 219.2 ± 90.7 MU vs 252.6 ± 109.0 MU (ns), interinjection interval 119.7 ± 18.4 vs 104.5 ± 14.7 days (ns), cumulative dose 1893.8 ± 1161.6 MU vs 5130.4 ± 3602.5 MU (ns), treatment time 962.0 ± 505.9 vs 1895.4 ± 1211.4 days (ns) and number of injection series 8.8 ± 3.8 vs 19.3 ± 11.8 (ns). Repeated BTAB measurements and clinical examinations did not reveal any signs of ABTF after re-start. INCO offers a new and long-term treatment opportunity for ABTF patients when their BTAB titres have dropped. Our observations also confirm lower antigenicity of INCO compared to conventional BT drugs.

Extracorporeal Shock Waves Versus Botulinum Toxin Type A in the Treatment of Poststroke Upper Limb Spasticity: A Randomized Noninferiority Trial

OBJECTIVE

To investigate whether extracorporeal shock wave therapy (ESWT) is noninferior to botulinum toxin type A (BoNT-A) for the treatment of poststroke upper limb spasticity.

DESIGN

Randomized noninferiority trial.

SETTING

Referral medical center.

PARTICIPANTS

Patients (N=42) with chronic stroke (28 men; mean age, 61.0±10.6y).

INTERVENTIONS

Patients received either ESWT or BoNT-A. During the study period, all patients continued their regular rehabilitation.

MAIN OUTCOME MEASURES

Assessments were performed at baseline and at 1, 4, and 8 weeks after the intervention. The primary outcome was the change from baseline of the modified Ashworth scale (MAS) score of the wrist flexors at week 4. Secondary outcomes included the change of the MAS scores, Tardieu angles of the wrist and elbow flexors, wrist and elbow passive range of motion (PROM), and upper extremity Fugl-Meyer Assessment (UE-FMA) score during the study period, as well as the treatment response rate.

RESULTS

The primary outcome result in the ESWT group (-0.80±0.41) was similar to that in the BoNT-A group (-0.90±0.44), with a higher confidence limit (0.4) for the difference between groups within the prespecified margin of 0.5, indicating the noninferiority of ESWT to BoNT-A. The response rate was not significantly different between the 2 groups. Both groups showed significant improvement in secondary outcomes relative to baseline; however, the ESWT group yielded greater improvement in wrist and elbow PROM and UE-FMA score.

CONCLUSION

Our results suggest that ESWT is a noninferior treatment alternative to BoNT-A for poststroke upper limb spasticity. ESWT and BoNT-A caused similar reduction in spasticity of the wrist and elbow flexors; however, ESWT yielded greater improvement in wrist and elbow PROM and UE-FMA score.

Comparison of 2 Operative Methods for Treating Laterocollis and Torticollis Subtypes of Spasmodic Torticollis: Follow-Up of 121 Cases

OBJECTIVE

The aim of this study was to compare the effects and complications of microvascular decompression (MVD) and neurectomy of spinal accessory nerve in the treatment of laterocollis and torticollis subtypes spasmodic torticollis (ST).

METHODS

Clinical data were retrospectively collected from 121 patients with laterocollis and torticollis subtypes of ST from January 1, 2012 to January 1, 2016. Among all the patients, 80 were treated by MVD and 41 were treated by neurectomy of spinal accessory nerve. The effect of the surgery was evaluated by the reduction in the Toronto Western spasmodic torticollis rating scale total scores before and after the operation. The mean duration of the postoperative follow-up period was 18.7 months (range, 12-27 months).

RESULTS

At the final follow-up, the Toronto Western spasmodic torticollis rating scale total score in the MVD group and in the neurectomy group was lowered by 50.43% ± 20.3% and 30.23% ± 19.4%, respectively, compared with the preoperative status (P < 0.05). In the MVD group, 25 (31.25%) patients achieved excellent relief, 44 (55%) patients improved moderate spasm, and 11 (13.75%) showed no relief. In the neurectomy group, 6 (14.63%) patients improved with excellent outcome, 7 (17.07%) had moderate relief, and 28 (68.29%) had no relief. There was no mortality or severe complication postoperatively, with the exception of hoarseness, shoulder numbness, and weakness.

CONCLUSIONS

MVD for ST of laterocollis and torticollis subtypes can provide satisfactory and lasting improvements without nerve impairment. MVD is to be preferred to neurectomy of accessory nerve in treating ST of laterocollis and torticollis subtypes.

Safety and Patient Satisfaction of AbobotulinumtoxinA for Aesthetic Use: A Systematic Review

A systematic review of the published literature (from January 2000 to January 2016) to ascertain the safety of, and patient satisfaction with, the aesthetic use of abobotulinumtoxinA was conducted. In addition to the licensed indications, other special populations were considered for discussion. The potential impact of neutralizing antibodies and systemic toxicity were also addressed. A total of 364 papers were screened and 86 were found to be relevant to the population, intervention(s), and outcomes stipulated in the protocol. The safety and patient satisfaction data from these publications are discussed in this review.

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.

Safety of botulinum toxin short interval therapy using incobotulinumtoxin A

The therapeutic efficacy of botulinum toxin (BT) can be completely blocked by formation of BT antibodies (BTAB), thus producing antibody-induced therapy failure (ABTF). One of the risk factors for this is the interval between two subsequent injection series. To prevent BTAB formation it is universally recommended not to use interinjection intervals of less than 12 weeks. However, BT's therapeutic efficacy may be considerably shorter than this interval, thus causing substantial reduction of quality of life. We wanted to study whether BT therapy with interinjection intervals of less than 12 weeks (short interval therapy, SIT) would be immunologically and otherwise safe. To minimise the risk of BTAB formation we used incobotulinumtoxin A which has a particularly low antigenicity. Altogether 30 patients (age 59.2 ± 13.5 years. 19 females, 11 males) with different dystonias were included in this study. They received SIT with incobotulinumtoxinA (Xeomin^®, Merz Pharmaceuticals, Frankfurt/M, Germany) at interinjection intervals of 69.0 ± 8.1 days (equal 9.9 weeks or 2.2 months, min 48.9 ± 2.4 days) for 14.3 ± 2.9 injection series (equal 906 ± 169 days or 2.5 ± 0.5 years) in a dose of 259 ± 159 MU (max 670 ± 144.4 MU). None of the patients showed signs of ABTF, unusual BT effects or increased adverse effects. Information provided by this study confirms safety of SIT. With a considerable percentage of patients hitherto undertreated for prolonged periods of time with BT therapy applying 12 weeks intervals, SIT may substantially improve the quality of life for those patients. Whether SIT is also safe with other BT drugs needs to be tested.

Neutralizing Antibody and Botulinum Toxin Therapy: A Systematic Review and Meta-analysis

The formation of neutralizing antibodies (NAbs) directed specifically against the active neurotoxin part of the botulinum neurotoxin (BoNT) complex is often cited as a major cause of secondary non-responsiveness (SnR) to treatment. This systematic and meta-analytic review evaluates the frequency of NAbs among patients treated with BoNT therapy for any clinical indication. A comprehensive database search strategy was designed to retrieve relevant clinical data from the published literature up to April 2013. All English-language publications that analyzed NAbs prevalence in more than ten patients were included, regardless of BoNT formulation, assay method, and study design. For the meta-analysis, patients were divided into three categories: secondary nonresponse (SnR) patients, clinically responding patients and all patients, independently of BoNT responsiveness. The meta-analysis included 61 studies reporting data for 8525 patients; 4972 dystonic patients, 1170 patients with spasticity, 294 patients with urologic indications, 396 patient with hyperhidrosis, 1659 patients with glabellar line, and 34 patients with hypersalivation. Among the ‘‘all patients’’ group NAbs frequency was 20%for dystonia, 5.9%for spasticity, and 2.7% for urologic patients and 1.1% for other conditions. The prevalence of NAbs was lower (3.5%) among clinically responding patients and higher in 53.5%SnR patients. About a half of patients with SnR do not have NAbs. NAbs was high among patients treated with RIMA but it was not associated with clinical non-responsiveness. Meta-analysis of the frequency of NAbs and SnR are limited by the heterogeneity of study design and reported outcomes. Indeed the analysis of several factors that can influence the development of NAbs, i.e.,MHCof patients, frequency and site of injection, injection technique, cumulative dose, and toxin denaturation, was not specifically evaluated due to the paucity and heterogeneity of data. The identification of all these missing data should be taken into account in order to improve the methodology of future studies.

High Botulinum Toxin-Neutralizing Antibody Prevalence Under Long-Term Cervical Dystonia Treatment

BACKGROUND

The aim of this study was to determine the prevalence of neutralizing antibodies in a large cohort of long-term treated patients with cervical dystonia (CD) still responding to repetitive injections with botulinum toxin (BoNT).

METHODS

Consecutively recruited CD patients (n = 221) under long-term BoNT treatment (≥2-21 years) underwent a clinical examination at the same time blood samples were taken for neutralizing antibody determination. Collected data included demographics, mean dose of the last 10 botulinum injections, treatment duration, Tsui score for CD severity, and patients' subjective impression of treatment effect. Blood samples were screened for antibody presence by ELISA; positive samples were further analyzed by mouse hemidiaphragm test. The two laboratories performing antibody testing were blinded to the coded samples.

RESULTS

Antibody status could be determined for 212 patients; 39 (18.4%) were ELISA positive and 31 (14.6%) additionally positive in the mouse hemidiaphragm test. Patients with positive neutralizing antibody titers had significantly higher Tsui scores and were treated for a significantly longer time with significantly higher doses. There were no differences between male and female patients and between onabotulinumtoxinA- and abobotulinumtoxinA-treated patients. When BoNT preparations had been switched during the last 10 injections, a significantly higher proportion of neutralizing antibody-positive patients was detected.

CONCLUSIONS

Neutralizing antibody prevalence in long-term treated, still responding CD patients is substantially higher than suggested by follow-up studies with a shorter time frame. It should therefore be emphasized that antigenicity of BoTN preparations is still a relevant problem and should be taken into account in long-term treatment decisions.

Long-Term Botulinum Toxin Dose Consistency for Treatment of Adductor Spasmodic Dysphonia

Objectives:

Botulinum toxin (BTX) injection is currently the primary and most common treatment for adductor spasmodic dysphonia (ADSD). A variety of injection strategies and dosage regimens have been described. This study reports on our experience with the dosage schedule and dosing consistency of BTX for the treatment of ADSD.

Methods:

We retrospectively reviewed our laryngeal BTX database for the period 1991 to 2005. Our strict inclusion requirements limited our selection to 13 patients who had received a minimum of 6 injections (average, 11.5; range, 6 to 19) of BTX for ADSD.

Results:

The average total dose of BTX to the larynx for each treatment episode was 3.9 units (range, 1.5 to 7.5). The total dose administered tended to trend downward among patients who began treatment from 1991 to 1998, indicating that the initial dose (usually 2.5 units per side) may have been high. Those patients who began from 1999 onward had a more stable dose, indicating that the initial dose (usually 1.5 units per side) was more suitable. The subjects underwent an average of 2.2 injections (range, 1 to 5) before reaching their optimal BTX dose. The total number of treatments performed in this group of patients was 150, of which 145 were successful (96.7%).

Conclusions:

The BTX dose for the optimal treatment of ADSD usually remains consistent over time, as does the treatment interval. An initial dose of 1.5 units per side or less appears to improve dosing stability, indicating that the initial dosing of 2.5 units per side in our study was often greater than required. The optimal BTX dose was usually ascertained by the second or third injection. In our patient population, the long-term dosing consistency of BTX confirmed that neither tachyphylaxis nor increasing sensitivity to BTX occurred during the course of treatment for ADSD.

British Neurotoxin Network recommendations for managing cervical dystonia in patients with a poor response to botulinum toxin

Botulinum toxin (BoNT) injections are an effective treatment for cervical dystonia. Approximately 20% of patients eventually stop BoNT treatment, mostly because of treatment failure. These recommendations review the different therapeutic interventions for optimising the treatment in secondary poor responder patients. Immunoresistance has become less common over the years, but the diagnosis has to be addressed with a frontalis test or an Extensor Digitorum Brevis test. In case of immunoresistance to BoNT-A, we discuss the place the different therapeutic options (BoNT-A holidays, BoNT-B injections, alternative BoNT-A injections, deep brain stimulation). When poor responders are not immunoresistant, they benefit from reviewing (1) injections technique with electromyography or ultrasound guidance, (2) muscles selection and (3) dose of BoNT. In addition, in both scenarios, a holistic approach including drug treatment, retraining and psychological support is valuable in the management of these complex and severe cervical dystonia.

Pharmaceutical, biological, and clinical properties of botulinum neurotoxin type A products

Botulinum neurotoxin injections are a valuable treatment modality for many therapeutic indications and have revolutionized the field of aesthetic medicine so that they are the leading cosmetic procedure performed worldwide. Studies show that onabotulinumtoxinA, abobotulinumtoxinA, and incobotulinumtoxinA are comparable in terms of clinical efficacy. Differences between the products relate to the botulinum neurotoxin complexes, specific biological potency, and their immunogenicity. Protein complex size and molecular weight have no effect on biological activity, stability, distribution, or side effect profile. Complexing proteins and inactive toxin (toxoid) content increase the risk of neutralizing antibody formation, which can cause secondary treatment failure, particularly in chronic disorders that require frequent injections and long-term treatment. These attributes could lead to differences in therapeutic outcomes, and, given the widespread aesthetic use of these three neurotoxin products, physicians should be aware of how they differ to ensure their safe and effective use.

Clinical differences between botulinum neurotoxin type A and B

In humans, the therapeutic use of botulinum neurotoxin A (BoNT/A) is well recognized and continuously expanding. Four BoNTs are widely available for clinical practice: three are serotype A and one is serotype B: onabotulinumtoxinA (A/Ona), abobotulinumtoxinA (A/Abo) and incobotulinumtoxinA (A/Inco), rimabotulinumtoxinB (B/Rima). A/Abo, A/Inco, A/Ona and B/Rima are all licensed worldwide for cervical dystonia. In addition, the three BoNT/A products are approved for blepharospasm and focal dystonias, spasticity, hemifacial spasm, hyperhidrosis and facial lines, with remarkable regional differences. These toxin brands differ for specific activity, packaging, constituents, excipient, and storage. Comparative literature assessing the relative safety and efficacy of different BoNT products is limited, most data come from reports on small samples, and only a few studies meet criteria of evidence-based medicine. One study compared the effects of BoNT/A and BoNT/B on muscle activity of healthy volunteers, showing similar neurophysiological effects with a dose ratio of 1:100. In cervical dystonia, when comparing the effects of BoNT/A and BoNT/B, results are more variable, some studies reporting roughly similar peak effect and overall duration (at a ratio of 1:66, others reporting substantially shorter duration of BoNT/B than BoNT/A (at a ratio 1/24). Although the results of clinical studies are difficult to compare for methodological differences (dose ratio, study design, outcome measures), it is widely accepted that: BoNT/B is clinically effective using appropriate doses as BoNT/A (1:40-50), injections are generally more painful, in most of the studies on muscular conditions, efficacy is shorter, and immunogenicity higher. Since the earliest clinical trials, it has been reported that autonomic side effects are more frequent after BoNT/B injections, and this observation encouraged the use of BoNT/B for sialorrhea, hyperhidrosis and other non-motor symptoms. In these indications the efficacy of toxins A and B are comparable and dose ratio is 1:25-30.