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

Current use of neurotoxins for alleviating symptoms of cervical dystonia

INTRODUCTION

Cervical dystonia (CD) causes involuntary movements and postures of the head, neck, and shoulders, as well as nonmotor symptoms including pain, mood, and sleep dysfunction, and impacts quality of life. The first-line treatment for CD is botulinum neurotoxin (BoNT) injections.

AREAS COVERED

The clinical presentation and diagnosis of CD, as well as where BoNT resides in the treatment landscape, is reviewed first. Next, the mechanism of action and the pharmacological differences in the available preparations of BoNT products are explained. The evidence base for motor and nonmotor efficacy and safety of the available BoNT formulations is reviewed, with attention to duration of benefit as a driver of patient satisfaction. Practical determinants of BoNT efficacy are reviewed including muscle selection, accurate muscle injection, factors related to poor or deteriorating response, and immunogenicity.

EXPERT OPINION

BoNT represents a significant advancement in the treatment of CD. More accurate diagnosis, muscle selection and targeting, and dosing can improve outcomes with existing BoNT formulations. Further refinement of BoNT potency, duration of action, safety, and immunogenicity will help reduce unmet needs in the magnitude and duration of benefit. Additional validation of DBS and MRI-guided focused ultrasound may expand options for patients with toxin nonresponse.

Low-Dose Neubotulinum Toxin A versus Low-Dose Abobotulinum Toxin A Injection for the Treatment of Cervical Dystonia: A Multicenter, 48-Week, Prospective, Double-Blinded, Randomized Crossover Design Study

Various types of botulinum toxin (BoNT) have been studied to treat cervical dystonia (CD). Although high-dose BoNT has proven efficacy, it increases the risk of adverse events. For this reason, this study was planned to identify the non-inferiority efficacy, tolerability, and safety of low-dose neubotulinum toxin A (Neu-BoNT-A) versus low-dose abobotulinum toxin A (Abo-BoNT-A) in CD treatment. The 48-week, prospective, randomized, controlled crossover design study of CD treatment, with 50-unit Neu-BoNT-A and 250-unit Abo-BoNT-A injections at 12-week intervals, was conducted over a 24-week treatment period. This study used the following standardized rating scales to assess the efficacy of BoNT: the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS); health-related quality of life (HRQoL); the Cervical Dystonia Impact Profile (CDIP-58); the Short Form 36 health survey questionnaire (SF-36); and, for the depressive symptoms of CD patients, the Center for Epidemiological Studies-Depression Scale (CES-D) and the Patient Health Questionnaire-9 (PHQ-9). Fifty-two CD patients were enrolled from October 2019 to January 2021. The mean scores of the TWSTRS total at the post-treatments in both Neu-BoNT-A and Abo-BoNT-A had a significant reduction from baseline (p = 0.008 and 0.002, respectively). However, the mean changes of the TWSTRS total at the 12- and 24-week treatments between the two treatment groups were not significantly different (p = 0.284 and 0.129, respectively). The mean scores of the HRQoL questionnaires (the CIDP-58 and the SF-36) and the depressive symptoms (the CES-D and the PHQ-9) in both treated groups at the post-treatments did not significantly decrease from baseline and were comparable. Two patients treated with Abo-BoNT-A (250 units) reported cervical tension and benign paroxysmal positional vertigo (BPPV). There were no serious adverse events reported. Though both low-dose BoNT-As were effective at improving clinical symptoms without significant side effects, both treatments did not predict change in quality of life and depression. With the non-inferiority criteria, low-dose Neu-BoNT-A has a similar efficacy, safety, and tolerability to Abo-BoNT-A.

Efficacy of single-photon emission computed tomography aided botulinum toxin injection in cervical dystonia: A double-blind, randomized study

BACKGROUND

Although single-photon emission computed tomography (SPECT/CT) could help to predetermine dystonic muscles in patients with cervical dystonia (CD), its efficacy in aiding botulinum toxin injection is undetermined. This randomized, double-blinded study aimed to assess the efficacy of SPECT/CT aided botulinum toxin injection in CD.

METHODS

Patients were randomized into study group (candidate muscles selected by SPECT/CT and clinical evaluation) or control group (clinical evaluation). Follow-ups were done at two weeks (T1), one (T2), three (T3) and six months (T4). The primary outcomes included symptom improvement assessed using Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and Tsui score at T2.

RESULTS

A total of 122 patients were enrolled and 108 patients accomplished the study. For primary outcomes, the study group had significantly better symptom improvement at T2 (TWSTRS: β, -4.86 [95%CI -9.40 to -0.32; P = 0.036]; Tsui: β, -1.65 [95%CI -2.77 to -0.54; P = 0.004]). For secondary outcomes, the study group also showed better outcomes at T1 (TWSTRS: β, -6.33 [95%CI -10.17 to -2.49; P = 0.001]; Tsui: β, -1.42 [95%CI -2.48 to -0.37; P = 0.008]) and T3 (TWSTRS: β, -6.05 [95%CI -11.09 to -1.01; P = 0.019]; Tsui: β, -1.24 [95%CI -2.40 to -0.08; P = 0.037]). The interval of re-injection was significantly longer in the study group than the control group (159.1 ± 28.6 versus 141.8 ± 51.0 days, P = 0.032).

CONCLUSIONS

SPECT/CT could improve the efficacy of botulinum toxin in CD. It could become a useful tool to aid botulinum toxin injection.

Management of Secondary Poor Response to Botulinum Toxin in Cervical Dystonia: A Multicenter Audit

Background

Botulinum toxin A (BoNT‐A) is an effective treatment for cervical dystonia. Nevertheless, up to 30% to 40% patients discontinue treatment, often because of poor response. The British Neurotoxin Network (BNN) recently published guidelines on the management of poor response to BoNT‐A in cervical dystonia, but adherence to these guidelines has not yet been assessed.

Objectives

To assess adherence to and usefulness of BNN guidelines in clinical practice.

Methods

We undertook a retrospective medical notes audit of adherence to the BNN guidelines in 3 United Kingdom tertiary neurosciences centers.

Results

Of 76 patients identified with poor response, 42 (55%) had a suboptimal response and, following BNN recommendations, 25 of them (60%) responded to adjustments in BoNT dose, muscle selection or injection technique. Of the remaining 34 (45%) patients with no BoNT response, 20 (59%) were tested for immune resistance, 8 (40%) of whom showed resistance. Fourteen (18%) of all patients were switched to BoNT‐B, and 27 (36%) were referred for deep brain stimulation surgery. In those not immune to BoNT‐A, clinical improvement was seen in 5 (41%) after adjusting their dose and injection technique.

Conclusion

Our audit shows that optimizing BoNT dose or injection strategy largely led to improvements in those with suboptimal response and in those reporting no response without resistance. It would be helpful to standardize investigations of potential resistance in those with no therapeutic response.

Ultrasound Study to Validate the Anterior Cervical Approach to the Longus Colli Muscle Using Electromyography Control Alone

Background:

One of the main difficulties in the treatment of dystonic anterocollis is the injection of the deep flexor muscles of the neck such as Longus Colli (LCo). The injection of the LCo has been regarded as difficult and potentially dangerous; since we published our anterior median approach, a number of questions about the precision and the safety of our technique have been raised by colleagues.

Methods:

7 patients with anterocollis were injected, using our injection technique and when the needle was deemed to be in place, we used the ultrasound probe to determine what the needle had passed through, the depth of the tip of the needle and if the identified muscle was indeed LCo.

Results:

On the ultrasound section the LCo muscle is between 24 and 28 mm deep in the patients examined in this study. The location of the needle was confirmed by ultrasound and in most cases the needle was placed in the right axis but sometimes not deep enough. The EMG control made it possible to correct the depth in all cases. In most of the injections the needle traversed the thyroid. No acute incident occurred by this route of injection. Injections were performed between 22 and 28 mm deep.

Discussion:

From this study and based on a review of complications over 9 years experience with injecting LCo under EMG control using an anterior approach, we conclude that this technique is precise, safe and well tolerated.

Summary (Highlights):

The injection of the Longus Coli muscle for anterocollis has been regarded as difficult and potentially dangerous. This study showed, using ultrasound to determine the needle trajectory, that the anterior approach using EMG control is a precise, safe and well tolerated technique.

[Cervical dystonia: ways to improve the effectiveness of botulinum therapy]

Cervical dystonia is one of the most complex movement disorders, in which type A botulinum toxin (BTA) preparations are used. A significant number of types of dystonic installation of the head and neck determines a large number of different muscle patterns, sometimes with outwardly similar manifestations. Objective difficulties in choosing the actual pathological muscle pattern for subsequent injection in some cases determine the low effectiveness of botulinum therapy. Given this situation, it is necessary to adapt the anatomical approach to the correct choice of dystonic muscles in order to improve the results of botulinum therapy of cervical dystonia.

Association Between Secondary Botulinum Toxin A Treatment Failure in Cosmetic Indication and Anti-Complexing Protein Antibody Production

Introduction

Botulinum toxin A (BoT/A) treatment failure (BTF) affects patients subjected to repeated BoT/A exposure for cosmetic indications. BoT/A’s general formulation contains core BoT/A and complexing proteins. BTF may be caused by antibody-induced treatment failure. Antibodies against core BoT/A can occur; however, anti-complexing protein antibodies have never been demonstrated, and tools for anti-complexing protein antibody detection have not been developed. The aim of this study was to evaluate immune involvement in BoT/A-nonresponsive patients.

Methods

Patients suspected of nonresponsiveness to BoT/A for cosmetic indications were recruited. All volunteers were categorized as BoT/A-responsive or BoT/A-tolerant according to frontalis testing with onabotulinumtoxinA (onaA). Twenty-two BoT/A-tolerant volunteers were recruited separately for frontalis testing with incobotulinumtoxinA (incoA). Anti-BoT/A and anti-complexing protein antibodies were quantified by special ELISA using sera from blood sampled before and after frontalis testing.

Results

Significantly higher levels of IgG against complexing protein were detected in onaA-tolerant sera but not in onaA-responders, leading to proposals that anti-complexing protein antibodies could cause onaA unresponsiveness. Some onaA-tolerant patients according to frontalis test with incoA were responsive to incoA. Newly developed absorption ELISA confirmed that incoA-responsive sera predominantly contained IgG against complexing proteins, whereas incoA-tolerant sera contained significant levels of IgG against core BoT/A. The presence of anti-complexing protein antibodies higher than 90.75% in sera of onaA-tolerant patients could respond to incoA. The ELISA technique might be employed as a tool to predict incoA responsiveness. Our frontalis testing after incoA treatment showed that anti-incoA IgG levels were not increased by incoA.

Conclusions

BoT/A-exposed patients may develop antibodies against core botulinum toxin and complexing proteins. Our study is the first to demonstrate that anti-complexing protein antibodies cause BTF. High levels of antibodies against complexing proteins can cause onaA unresponsiveness, although some patients were still incoA-responsive. Our developed ELISA to detect anti-complexing protein antibodies can determine whether onaA-tolerant patients respond to incoA without incoA frontalis testing.

Development of inhibition ELISA to detect antibody-induced failure of botulinum toxin a therapy in cosmetic indications

Secondary treatment failure (STF) of botulinum toxin A (BoNT/A) therapy in cosmetic indication has been postulated as production of antibody against active sites of BoNT/A in unresponsive patients. To prove of concept, detection of anti-BoNT/A antibody is required, however, current enzyme-linked immunosorbent assay (ELISA) detects human IgGs against whole BoNT/A molecule. We developed an inhibition ELISA to quantify antibodies bound to the active sites of BoNT/A using three mouse monoclonal antibodies targeting translocation domain, receptor binding site and catalytic domain of BoNT/A prior to processing ELISA to detect human IgG (hIgG) against BoNT/A. Adults naïve to BoNT/A, or treated and responsive (toxin-response), or treated but unresponsive (toxin-tolerance) were recruited. Detection of hIgG revealed that naïve volunteers had basal level of hIgG against whole BoNT/A, whereas its level was significantly lower than those hIgG in BoNT/A-exposed cohorts. Higher anti-BoNT/A levels in sera from volunteers ever-exposed to BoNT/A indicates that BoNT/A may provoke immune responses in BoNT/A-treated cohorts. Inhibition ELISA demonstrated that levels of BoNT/A-specific hIgG in tolerance patients had a dramatic decrease in mouse monoclonal antibody blockage, suggesting presence of hIgG specific to BoNT/A's three active sites in STF patients. Therefore, our ELISA detected hIgG against whole BoNT/A protein and BoNT/A active sites suggesting that human antibodies may cause STF. To compare with frontalis test, our inhibition ELISA provided good accuracy at 83.1% (50% sensitivity and 89.9% specificity). Our test may help clinicians to diagnose possibility of STF and also to monitor immune status against BoNT/A.

Cervical dystonia: Injecting botulinum neurotoxin into semispinalis capitis improves goose-neck posture

We describe a patient with goose-neck posture as the presenting form of cervical dystonia. In our case, the bilateral semispinalis capitis muscles were hypertrophic, thick, and overactive while both splenius capitis and sternocleidomastoid muscles were normal. In this single case experience, we demonstrated that the semispinalis capitis muscle may play a primary role in causing a goose-neck posture and the observed forward sagittal shift may be a compensatory or overflow activity of neck flexor muscles. Therefore, botulinum toxin injection to the semispinalis capitis muscles can be considered in the management of patients with goose-neck posture.

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.

Pharmacological differences and clinical implications of various botulinum toxin preparations: a critical appraisal

Three different type A botulinum neurotoxins (BoNTAs) - onabotulinumtoxinA, abobotulinumtoxinA and incobotulinumtoxinA) - are currently marketed in Europe to treat several conditions. Differences between BoNTA preparations, which depend on their specific biotypes and manufacturing processes, lead to clinically relevant pharmacotherapeutic dissimilarities. All three available products are separately recognized and reviewed in American Academy of Neurology guidelines. The neurotoxin load/100U is likewise different among the different BoNTAs, with the result that the specific potency of the 150kD BoNTA neurotoxin is calculated as 137 units/ng for onabotulinumtoxinA, 154 units/ng for abobotulinumtoxinA, and 227 units/ng for incobotulinumtoxinA. It is important for clinicians to have all three BoNTAs available in order to choose the most suitable preparation for the specific indication in the single patient. Commercially available BoNTAs must be recognized as different from one another, and therefore as non-interchangeable. The essential experience of the clinician is of the utmost importance in choosing the most appropriate treatment.

Management of cervical dystonia with botulinum neurotoxins and EMG/ultrasound guidance

Purpose of review

We provide a practical guide on the use of electromyography (EMG) and ultrasound (US) to assist botulinum neurotoxin (BoNT) treatment in patients with cervical dystonia (CD).

Recent findings

US and EMG guidance improve BoNT treatment in CD. Their use is particularly valuable for targeting deep neck muscles and managing complex cases. There is also evidence that adverse events are reduced when superficial or intermediate layer muscles are injected with assisted guidance.

Summary

A structured clinical approach, based on functional neck anatomy, guides CD assessment and BoNT treatment. Muscles are selected according to clinical, EMG and US findings. US provides anatomical visualization, while EMG complements by detecting muscle activity. We review here the current practice for assisted treatment of CD through BoNT cycles. We also describe how to recognize and manage the main adverse events.

Spectrum of practice in the routine management of cervical dystonia with abobotulinumtoxinA: findings from three prospective open-label observational studies

Background

Cervical dystonia is a heterogeneous disorder with several possible presentations, for which first-line therapy is often botulinum toxin (BoNT). In routine clinical practice the success of each BoNT injection is dependent on several variables, including individual presentation and injection technique. Large multicenter, observational studies provide important information on individualized administration strategies that cannot be otherwise ascertained from controlled clinical trials. In this meta-analysis of patient level data, we aimed to evaluate the clinical characteristics of patients with cervical dystonia undergoing routine treatment with botulinum toxin, specifically abobotulinumtoxinA. We also aimed to characterize current abobotulinumtoxinA injection techniques and parameters and to explore international differences in patient presentation and treatment.

Methods

This was a meta-analysis of baseline data from three prospective, international, multicenter, observational studies (NCT01314365, NCT00833196 and NCT01753349) of botulinum toxin treatment for the routine management of adult cervical dystonia.

Results

Data presented illustrate the significant heterogeneity of CD presentation in routine practice. Most subjects presented with a complex pattern of dystonic movements and the majority had additional components of shoulder elevation, tremor and/or jerk. Dosing was generally in accordance with that recommended in the abobotulinumtoxinA prescribing information, although the range of dosing also indicates that injections are tailored to individual presentation. Sub-group analyses at the country level revealed distinct differences in injection practice.

Conclusions

This meta-analysis is based on the largest dataset of subjects with cervical dystonia studied to date. The heterogeneity revealed in our baseline findings support the need to develop consistent, practical and comprehensive best practice guidelines.

Personalized botulinum toxin type A therapy for cervical dystonia based on kinematic guidance

BACKGROUND

Botulinum toxin type A (BoNT-A) injections is the accepted first-line therapy for cervical dystonia (CD), however, numerous patients discontinue treatment early due to perceived sub-optimal relief. To improve BoNT-A therapy for CD, proper assessment of neck motion and selection of relevant muscles and dosing must be met. Kinematic technology may improve treatment outcomes by guiding physicians to better tailor muscle selection and BoNT-A dosing for CD therapy.

METHODS

28 CD participants were placed into either group: expert injector determined injection patterns by visual assessment ("vb") versus injection patterns based on kinematics interpreted by an expert injector ("kb"). Injections occurred at weeks 0, 16 and 32 with follow-ups at weeks 6, 22 and 38. Kinematics utilized four sensors to capture the severity of multiaxial, static neck posturing (e.g., torticollis) and dynamic, spasmodic/tremor movements while participants were seated. Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) score changes were evaluated over 38 weeks.

RESULTS

For the "kb" participants, there was a significant 28.8% (- 11.25 points) reduction in TWSTRS total score at week 6, as well as significant reduction in severity and disability TWSTRS sub-scores (parts I and II) with maintained improvement at subsequent visits. As for the "vb" participants had a significant reduction in total TWSTRS score by 28.5% (- 9.84 points) after week 22. Disability score for the "vb" group trended towards improvement over 38 weeks.

CONCLUSION

Clinical judgement guided by kinematic analysis of CD biomechanics can result in faster optimal muscle selections and minimize use of higher BoNT-A doses as compared to visual determination, thereby achieving comparable and potentially better treatment outcomes.

[Botulinum toxin for treatment of the focal dystonia]

Dystonia is defined as a movement disorder characterized by sustained or intermittent muscles contraction causing abnormal, often repetitive, movements, postures, or both. Dystonic movements are typically patterned and twisting, and may be tremulous. The precis diagnosis of dystonia is difficult for physicians because neurological brain imaging does not provide enough practical information. The diagnosis is depend on clinical experience of physicians. Botulinum toxin treatment is the accepted standard of care for patients with focal dystonia. Botulinum toxin treatment results in significant improvement of decreasing the symptom of dystonia. The success of treatment is dependent on muscle selection for treating involved muscles. Usually performance of botulinum toxin treatment is injected according to clinical experience of surface anatomy or clinical location method. However, the benefit of guidance of botulinum toxin treatment is improve outcome in dystonia. Injection techniques with ultra sound echogram or EMG guidance to identify dystonic muscles can be more benefit for patients.

Key Parameters for the Use of AbobotulinumtoxinA in Aesthetics: Onset and Duration

Time to onset of response and duration of response are key measures of botulinum toxin efficacy that have a considerable influence on patient satisfaction with aesthetic treatment. However, there is no overall accepted definition of efficacy for aesthetic uses of botulinumtoxinA (BoNT-A). Mechanical methods of assessment do not lend themselves to clinical practice and clinicians rely instead on assessment scales such as the Frontalis Activity Measurement Standard, Frontalis Rating Scale, Wrinkle Severity Scale, and Subject Global Assessment Scale, but not all of these have been fully validated. Onset of activity is typically seen within 5 days of injection, but has also been recorded within 12 hours with abobotulinumtoxinA. Duration of effect is more variable, and is influenced by parameters such as muscle mass (including the effects of age and sex) and type of product used. Even when larger muscles are treated with higher doses of BoNT-A, the duration of effect is still shorter than that for smaller muscles. Muscle injection technique, including dilution of the toxin, the volume of solution injected, and the positioning of the injections, can also have an important influence on onset and duration of activity. Comparison of the efficacy of different forms of BoNT-A must be made with the full understanding that the dosing units are not equivalent. Range of equivalence studies for abobotulinumtoxinA (Azzalure; Ipsen Limited, Slough UK/Galderma, Lausanne CH/Dysport, Ipsen Biopharm Limited, Wrexham UK/Galderma LP, Fort Worth, TX) and onabotulinumtoxinA (Botox; Allergan, Parsippany, NJ) have been conducted, and results indicate that the number of units of abobotulinumtoxinA needs to be approximately twice as high as that of onabotulinumtoxinA to achieve the same effect. An appreciation of the potential influence of all of the parameters that influence onset and duration of activity of BoNT-A, along with a thorough understanding of the anatomy of the face and potency of doses, are essential to tailoring treatment to individual patient needs and expectations.