Factors influencing response to Botulinum toxin type A in patients with idiopathic cervical dystonia: results from an international observational study

Update on Non-Interchangeability of Botulinum Neurotoxin Products

The growing use of botulinum neurotoxins (BoNTs) for medical and aesthetic purposes has led to the development and marketing of an increasing number of BoNT products. Given that BoNTs are biological medications, their characteristics are heavily influenced by their manufacturing methods, leading to unique products with distinct clinical characteristics. The manufacturing and formulation processes for each BoNT are proprietary, including the potency determination of reference standards and other features of the assays used to measure unit potency. As a result of these differences, units of BoNT products are not interchangeable or convertible using dose ratios. The intrinsic, product-level differences among BoNTs are compounded by differences in the injected tissues, which are innervated by different nerve fiber types (e.g., motor, sensory, and/or autonomic nerves) and require unique dosing and injection sites that are particularly evident when treating complex therapeutic and aesthetic conditions. It is also difficult to compare across studies due to inherent differences in patient populations and trial methods, necessitating attention to study details underlying each outcome reported. Ultimately, each BoNT possesses a unique clinical profile for which unit doses and injection paradigms must be determined individually for each indication. This practice will help minimize unexpected adverse events and maximize efficacy, duration, and patient satisfaction. With this approach, BoNT is poised to continue as a unique tool for achieving individual goals for an increasing number of medical and aesthetic indications.

Botulinum Toxin Injections to the Obliquus Capitis Inferioris Muscle for Dynamic Cervical Dystonia Improves Subjective Patient Outcomes

The obliquus capitis inferioris (OCI) muscle is a significant driver of cervical dystonia with torticaput movements and a no-no head tremor. Limited data are available on the efficacy of OCI injections on patient outcomes. Our study aims to determine whether the botulinum toxin injection into OCI improves subjective patient quality of life in those with dystonic head tremors. A retrospective chart review was performed for 25 patients receiving injections into the OCI for a dystonic head tremor at the London Movement Disorders Clinic between January 2020 and January 2022. Toronto Western Spasmodic Torticollis Scale-2 (TWSTRS-2) subscale scores for disability and pain, TWSTRS-PSYCH scores, and the global impression of severity were extracted. The average TWSTRS-2 disability subscale change was -2.8 points (p < 0.003). The average TWSTRS-2 pain subscale change was -4.6 points (p < 0.003). The average TWSTRS-PSYCH score prior to injection was 5.6. After injection, the average score was 3.7 (p < 0.004). The patient self-reported average global impression of severity before injection was 7.0; after this, it was 4.2 (p < 0.0003). The OCI injection showed significant improvement in retrospective patient self-reported outcomes; it should be considered early in the treatment plan for cervical dystonia with a no-no head tremor.

Deep Brain Stimulation for Focal or Segmental Craniocervical Dystonia in Patients Who Have Failed Botulinum Neurotoxin Therapy-A Narrative Review of the Literature

(1) Background: The first-line treatment for patients with focal or segmental dystonia with a craniocervical distribution is still the intramuscular injection of botulinum neurotoxin (BoNT). However, some patients experience primary or secondary treatment failure from this potential immunogenic therapy. Deep brain stimulation (DBS) may then be used as a backup strategy in this situation. (2) Methods: Here, we reviewed the current study literature to answer a specific question regarding the efficacy and safety of the use of DBS, particularly for cervical dystonia (CD) and Meige syndrome (MS) in patients with documented treatment failure under BoNT. (3) Results: There are only two studies with the highest level of evidence in this area. Despite this clear limitation, in the context of the narrowly defined research question of this paper, it is possible to report 161 patients with CD or MS who were included in studies that were able to show a statistically significant reduction in dystonic symptoms using DBS. Safety and tolerability data appeared adequate. However, much of the information is based on retrospective observations. (4) Conclusions: The evidence base in this area is in need of further scientific investigation. Most importantly, more randomized, controlled and double-blind trials are needed, possibly including a head-to-head comparison of DBS and BoNT.

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.

Pivotal role of obliquus capitis inferior in torticaput revealed by single-photon emission computed tomography

Torticaput is the most common primary form of cervical dystonia (CD). Obliquus capitis inferior (OCI) plays a major role in ipsilateral rotation of the head. The present study aimed to use single-photon emission computed tomography (SPECT/CT) to determine the involvement of OCI in torticaput and in torticaput associated with no-no tremor. We retrospectively analyzed the SPECT/CT images of 60 patients with torticaput as the main abnormal posture and ranked the affected muscles. The affected muscles in patients with no-no tremor were also ranked. The correlation between the radioactivity of OCI and the thickness of OCI measured by ultrasonography was analyzed. The agreement between SPECT/CT and electromyography in detecting OCI was also analyzed. After sternocleidomastoid muscle (81.7%), OCI was the second most affected muscle (70.0%) in torticaput, followed by splenius capitis (63.3%). In 23 patients with no-no tremor, OCI (78.3%) and sternocleidomastoid muscle (78.3%) were the most frequently affected muscles, followed by splenius capitis (69.6%). Furthermore, bilateral muscle involvement was commonly seen in patients with no-no tremor, especially for OCI (12/23) and sternocleidomastoid muscle (11/23). A positive correlation was found between the radioactivity and thickness of OCI (r = 0.330, P < 0.001). The total agreement rate between SPECT/CT and electromyography in the diagnosis of OCI excitement was 94.0%, with kappa value = 0.866 (P < 0.001). OCI plays a critical role in torticaput and no-no tremor. SPECT/CT could be a practical tool to help clinicians detect abnormally excited OCI.

The cost-effectiveness of abobotulinumtoxinA (Dysport) and onabotulinumtoxinA (Botox) for managing spasticity of the upper and lower limbs, and cervical dystonia

OBJECTIVE

To evaluate the costs and benefits associated with the use of abobotulinumtoxinA (aboBoNT-A) and onabotulinumtoxinA (onaBoNT-A) for lower limb spasticity in children, upper and lower limb spasticity in adults, and cervical dystonia in adults.

METHODS

This pharmacoeconomic analysis compared aboBoNT-A with onaBoNT-A. A decision tree model with a 1-year time horizon was conducted from a UK National Health Service (NHS) perspective using data from a variety of sources: randomized controlled trials (RCTs), network meta-analyses (NMAs), observational studies, and a physician survey investigating treatment patterns and resource utilization. Four patient populations were included: pediatric patients with lower limb spasticity (PLL), and adults with upper limb spasticity (AUL), lower limb spasticity (ALL), and cervical dystonia (CD). Outcomes included costs, quality-adjusted life years (QALYs) gained, cost per responder, and incremental cost per QALY gained. The effectiveness of each treatment was evaluated as a response to treatment. The base case assumption was that all patients in the model continued to receive botulinum toxin type A (BoNT-A) treatments at regular intervals regardless of treatment response status. Scenario analysis evaluated the impact of discontinuing BoNT-A for patients without a response to the first injection.

RESULTS

The model found that aboBoNT-A resulted in greater quality-of-life and lower costs compared with onaBoNT-A for the management of spasticity and CD in all included indications. Across populations, cost savings ranged from £304 to £3,963 and QALYs gained ranged from 0.010 to 0.02 over a 1-year time horizon. Results were robust to scenario analyses and were driven by the impact of treatment response on health-related quality-of-life.

CONCLUSIONS

AboBoNT-A was associated with higher treatment response, improved quality-of-life, and reduced costs in spasticity and CD versus onaBoNT-A. These findings could help deliver more effective and efficient healthcare in the NHS.

Does ultrasound-guidance improve the outcome of botulinum toxin injections in cervical dystonia?

PURPOSE

Ultrasound-guided injections of botulinum neurotoxin in cervical dystonia have a number of theoretical advantages. However, their action has never been compared to that of non-guided injections. The objectives of the study were to compare the outcome of botulinum neurotoxin type A treatment in patients with idiopathic, focal cervical dystonia, according to two methods: inspection and palpation of anatomical landmarks (non-guided group) or ultrasound guidance (ultrasound-guided group).

METHODS

We included consecutive patients in this single-center, prospective, real-life, non-randomized study. The outcomes were evaluated one month after the injections: Cervical Dystonia Impact Profile 58 (main outcome), Toronto Western Spasmodic Torticollis Rating Scale-2 (pain and disability subscores), Toronto Western Spasmodic Torticollis Rating Scale-PSYCH, patient-rated Clinical Global Impression - Improvement and adverse events. We used propensity score methods for statistical analysis; ten predefined confounding factors were used to build the propensity score.

RESULTS

Sixty-three patients were included in the non-guided group, and 60 other patients in the ultrasound-guided group. We found no difference in main and secondary outcomes between the two study groups.

CONCLUSION

This is the first direct comparison between ultrasound-guided and non-guided botulinum neurotoxin type A injections in patients with cervical dystonia. We hypothesize that ultrasound guidance made it possible to obtain the same results in the most severe (or the most demanding) patients as in the best responders. Further studies are still needed to assess the impact of botulinum neurotoxin injections into deep cervical muscles.

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.

Unilateral pallidotomy as a potential rescue therapy for cervical dystonia after unsatisfactory selective peripheral denervation

OBJECTIVE

Selective peripheral denervation (SPD) is a widely accepted surgery for medically refractory cervical dystonia (CD), but when SPD has failed, the available approaches are limited. The authors investigated the results from a cohort of CD patients treated with unilateral pallidotomy after unsatisfactory SPD.

METHODS

The authors retrospectively analyzed patients with primary CD who underwent unilateral pallidotomy after SPD between April 2007 and August 2019. The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) was used to evaluate symptom severity before surgery, 7 days postsurgery, 3 months postsurgery, and at the last follow-up. TWSTRS subscores for disability and pain and the 24-item Craniocervical Dystonia Questionnaire (CDQ-24) were used to assess quality of life.

RESULTS

At a mean final follow-up of 5 years, TWSTRS severity subscores and total scores were significantly improved (n = 12, mean improvement 57.3% and 62.3%, respectively, p = 0.0022 and p = 0.0022), and 8 of 12 patients (66.7%) were characterized as responders (improvement ≥ 25%). Patients with rotation symptoms before pallidotomy showed greater improvement in TWSTRS severity subscores than those who did not (p = 0.049). The most common adverse event was mild upper-limb weakness (n = 3). Patients' quality of life was also improved.

CONCLUSIONS

Unilateral pallidotomy seems to offer an effective and safe option for patients with CD who have otherwise experienced limited benefits from SPD.

Long-term Safety and Dosing of OnabotulinumtoxinA: A Prospective, Observational Study

BACKGROUND

Although therapeutic treatments are intended to help alleviate symptoms associated with disease, safety must be carefully considered and monitored to confirm continued positive benefit/risk balance. The objective of MOBILITY was to study the long-term safety of onabotulinumtoxinA for treatment of various therapeutic indications.

METHODS

A prospective, multicenter, observational, Phase IV Canadian study in patients treated with onabotulinumtoxinA for a therapeutic indication. Dosing was determined by the participating physician. Adverse events (AEs) were recorded throughout the study.

RESULTS

Patients (n = 1372) with adult focal spasticity, blepharospasm, cerebral palsy, cervical dystonia, hemifacial spasm, hyperhidrosis, or "other" diagnoses were enrolled into the safety cohort. Eighty-three patients (6%) reported 209 AEs; 44 AEs in 24 patients (2%) were considered treatment-related AEs. Seventy-two serious AEs were reported by 38 patients (3%); 10 serious AEs in 5 patients (0.4%) were considered treatment related. Most commonly reported treatment-related AEs were muscular weakness (n = 7/44) and dysphagia (n = 6/44).

CONCLUSIONS

In patients with follow-up for up to six treatments with onabotulinumtoxinA, treatment-related AEs were reported in <2% of the safety population over the course of nearly 5 years. Our findings from MOBILITY provide further evidence that onabotulinumtoxinA treatment is safe for long-term use across a variety of therapeutic indications.

Use of AbobotulinumtoxinA in Adults with Cervical Dystonia: A Systematic Literature Review

Cervical dystonia (CD) is a neurological movement disorder characterized by sustained involuntary muscle contractions. First-line therapy for CD is intramuscular injections of botulinum neurotoxin (e.g., abobotulinumtoxinA) into the affected muscles. The objective of this systematic literature review is to assess the clinical evidence regarding the effects of abobotulinumtoxinA for treatment of CD in studies of safety, efficacy, patient-reported outcomes, and economic outcomes. Using comprehensive electronic medical literature databases, a search strategy was developed using a combination of Medical Subject Heading terms and keywords. Results were reviewed by two independent reviewers who rated the level of evidence. The search yielded 263 publications, of which 232 were excluded for being duplicate publications, not meeting the selection criteria, or failing to meet predefined eligibility criteria, leaving a total of 31 articles. Clinical efficacy, patient-reported outcomes, and safety data were in 6 placebo-controlled trials (8 articles), 6 active-controlled trials, and 16 observational studies (17 articles). Data on health economic outcomes were provided in one of the clinical trials, in two of the observational studies, and in one specific cost-analysis publication. This review demonstrated that the routine use of abobotulinumtoxinA in CD is well-established, effective, and generally well-tolerated, with a relatively low cost of treatment.

Anatomy-guided injections of botulinum neurotoxin in neck muscles: how accurate is needle placement?

BACKGROUND AND PURPOSE

In cervical dystonia, the accuracy of botulinum neurotoxin (BoNT) injections may influence the response to the treatment.

METHODS

We used ultrasound to evaluate the accuracy of anatomy-guided injections of BoNT in the neck muscles.

RESULTS

A total of 56 consecutive patients and 332 injections were evaluated. The overall accuracy was 76.6%. The lowest accuracy (67.9%) was observed for the splenius capitis muscle.

CONCLUSIONS

Anatomic guidance of BoNT injections in the neck muscles is often inaccurate. Imaging guidance may improve the accuracy of BoNT injections in cervical dystonia.

Tremor in Idiopathic Cervical Dystonia - Possible Implications for Botulinum Toxin Treatment Considering the Col-Cap Classification

Background

Tremor is an important phenotypic feature of dystonia. Using the new concept (Col-Cap) of classification we examined the frequency of tremor in cervical dystonia (CD) patients, their main subtypes and muscles injected.

Methods

In this large study conducted at multiple movement disorder centres in Europe and India, between January and June 2019, we examined 293 patients with idiopathic CD who were all treated with botulinum toxin (BTX).

Results

The dystonic head tremor (DHT+) was present in 57.6 % of CD patients and they had a significantly longer duration of symptoms than patients without head tremor (DHT-). In DHT+ patients torticaput was the most common subtype and the majority (63.3%) had one or two subtypes only. There was no significant difference between the number of unilateral injections for any of the muscles in the DHT+ and DHT- groups, while the number of patients receiving bilateral injections in splenius capitis (78 vs 25; p = 0.00001), sternocleidomastoid (31 vs 6; p = 0.0005), trapezius (28 vs 9; p = 0.01), and obliquus capitis inferior (15 vs 2; p = 0.008) were significantly more in the DHT+ group. The mean doses of all three types of BTX/A were not significantly different between the two groups.

Conclusions

The frequency of head tremor was 57.6% in our CD patients and torticaput was the most common dystonic subtype associated with tremor. Simple forms of CD seemed more likely associated with head tremor, than complex forms of CD. Most of the DHT+ patients received bilateral injections. The use of 'Col-Cap' classification was helpful in the identification of muscles likely to be involved in tremor in CD patients.

Impact of abobotulinumtoxinA on the clinical features of cervical dystonia in routine practice

INTRODUCTION

The efficacy and safety of abobotulinumtoxinA in the management of cervical dystonia has been established in randomized, controlled trials that use a selected trial population. In this meta-analysis of observational data, we evaluated the real-life effectiveness of abobotulinumtoxinA as delivered in routine clinical practice.

METHODS

Meta-analysis of patient-level data for adult patients with cervical dystonia treated with abobotulinumtoxinA from three prospective, multicenter, observational studies (NCT01314365, NCT00833196 and NCT01753349).

RESULTS

We report data for patients treated with abobotulinumtoxinA over one injection cycle at 181 neurology centers in 35 countries. CD clinical features as assessed by Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) Total scores (N = 920) significantly reduced by a mean [95%CI] of -12.9 [-13.9, -11.8] points at Week 4 (N = 449) and -3.2 [-3.8, -2.7] points at the end of the injection cycle (N = 890). All three TWSTRS domains (symptom severity, disability and pain) contributed to the overall improvement. Patients were generally content with symptom control at peak effect of the treatment cycle, with 86% reporting overall satisfaction.

CONCLUSION

Findings from this meta-analysis of observational studies confirm the effectiveness of abobotulinumtoxinA in routine practice. Despite inclusion of a broader population sample, the magnitude of improvements observed is consistent with that seen in the pivotal, randomized controlled trials.

Economic evaluation of AbobotulinumtoxinA vs OnabotulinumtoxinA in real-life clinical management of cervical dystonia

Background

Botulinum neurotoxins type A (BoNT-As) are commonly used treatments for cervical dystonia (CD). Clinical trials have demonstrated the benefits of them in these patients, but data from real-life clinical practice as well as comparative data on the cost and outcome of different BoNT-A formulations are limited. The aim of this study was to compare abobotulinumtoxinA (aboBoNT-A) and onabotulinumtoxinA (onaBoNT-A) on their clinical outcomes and drug costs in real-life clinical practice.

Methods

This analysis included 356 adult patients with idiopathic CD treated with aboBoNT-A (n = 253) or onaBoNT-A (n = 103) from 38 centres across Europe and Australia (NCT00833196). The clinical outcome measures were treatment responses, changes in TWSTRS scores and changes in health utility scores from baseline to study visit 2 and 3. Health utility score was mapped from the TWSTRS total scale, using a previous publication. Costs included drug cost for France.

Results

The aboBoNT-A treated group had 2.06 (95% CI: 1.15 to 3.69) times higher odds of achieving treatment response than the onaBoNT-A treated group. The adjusted mean change in TWSTRS total score from baseline to visit 3 were - 6.42 (95% CI: - 7.52 to - 5.33) for aboBoNT-A and - 3.94 (95% CI: - 5.68 to - 2.2) for onaBoNT-A, with a difference of - 2.48 (95% CI: - 4.57 to - 0.39). The corresponding difference in the adjusted mean change for health utility score was 0.008 (95% CI: 0.001 to 0.014). Mean treatment costs for aboBoNT-A and onaBoNT-A were 314.1 (95% CI: 299.1 to 329.0) and 346.6 (95% CI: 322.9 to 370.4) Euros, respectively.

Conclusions

This comparative analysis indicated that treatment with aboBoNT-A may be less costly and lead to improved clinical outcomes when compared with onaBoNT-A, from a French healthcare system perspective. Additional comparative clinical data from larger patient cohorts, as well as more information about cost consequences of an improvement in clinical outcome would be of value to further confirm the findings.

Maladaptive striatal plasticity and abnormal reward-learning in cervical dystonia

In monogenetic generalized forms of dystonia, in vitro neurophysiological recordings have demonstrated direct evidence for abnormal plasticity at the level of the cortico-striatal synapse. It is unclear whether similar abnormalities contribute to the pathophysiology of cervical dystonia, the most common type of focal dystonia. We investigated whether abnormal cortico-striatal synaptic plasticity contributes to abnormal reward-learning behavior in patients with focal dystonia. Forty patients and 40 controls performed a reward gain and loss avoidance reversal learning task. Participant's behavior was fitted to a computational model of the basal ganglia incorporating detailed cortico-striatal synaptic learning rules. Model comparisons were performed to assess the ability of four hypothesized receptor specific abnormalities of cortico-striatal long-term potentiation (LTP) and long-term depression (LTD): increased or decreased D1:LTP/LTD and increased or decreased D2: LTP/LTD to explain abnormal behavior in patients. Patients were selectively impaired in the post-reversal phase of the reward task. Individual learning rates in the reward reversal task correlated with the severity of the patient's motor symptoms. A model of the striatum with decreased D2:LTP/ LTD best explained the patient's behavior, suggesting excessive D2 cortico-striatal synaptic depotentiation could underpin biased reward-learning in patients with cervical dystonia. Reversal learning impairment in cervical dystonia may be a behavioral correlate of D2-specific abnormalities in cortico-striatal synaptic plasticity. Reinforcement learning tasks with computational modeling could allow the identification of molecular targets for novel treatments based on their ability to restore normal reward-learning behavior in these patients.

Pallidal neurostimulation versus botulinum toxin injections in the treatment of cervical dystonia: protocol of a randomized, sham-controlled trial (StimTox-CD)

Background

Selective peripheral denervation via botulinum neurotoxin injections into dystonic muscles is the first-line treatment for cervical dystonia. Pallidal neurostimulation is a potent alternative, but currently restricted to patients failing on neurotoxin therapy. As botulinum neurotoxin is partially effective but often unsatisfactory in a relevant proportion of patients, earlier neurostimulation might be advantageous in providing stable symptom control and preventing disability. This trial intends to demonstrate, that pallidal neurostimulation is superior to neurotoxin injections in best clinical practice for controlling the symptoms of cervical dystonia and that it is safe in patients with a partial therapy response to peripheral denervation. We hypothesize a better outcome in everyday functioning and health-related quality of life of neurostimulated patients.

Methods

We aim to recruit 66 cervical dystonia patients into a double-blind comparison of pallidal neurostimulation versus botulinum neurotoxin type A. Eligible patients need ≥25% motor symptom reduction 4 weeks after a neurotoxin test injection, but are willing to undergo DBS surgery due to unsatisfactory symptom control. All participants will be implanted with a DBS system, and randomized into 2 groups: First group will receive effective neurostimulation and saline injections into dystonic muscles. Second group is treated with regular neurotoxin injections and undergoes a sham-stimulation. Primary outcome is the change in TWSTRS total score between baseline and 6 months of therapy. Secondary outcome parameters are corresponding changes in TWSTRS motor score, Tsui score, CDQ-24 and SF-36. Safety will be assessed by frequency and severity of reported adverse events. Statistical analysis includes intention-to-treat and per protocol populations, analysis based on imputation of missing values and analysis adjusting for differences in baseline TWSTRS. After 6 months of blinded treatment all patients will receive open-label neurostimulation and neurotoxin treatment as needed, and are followed up 48 weeks after randomization.

Perspective

We will assess if pallidal neurostimulation is a safe and effective alternative to selective peripheral denervation by botulinum toxin injections in cervical dystonia, which may be offered earlier in the course of disease based on patient preference. A positive study outcome would influence future treatment guidelines of cervical dystonia.

Trial registration

EudraCT registration number: 2016-001378-13.

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.

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.

Randomised controlled trial of escitalopram for cervical dystonia with dystonic jerks/tremor

OBJECTIVE

Trials for additional or alternative treatments for cervical dystonia (CD) are scarce since the introduction of botulinum neurotoxin (BoNT). We performed the first trial to investigate whether dystonic jerks/tremor in patients with CD respond to the selective serotonin reuptake inhibitor (SSRI) escitalopram.

METHODS

In a randomised, double-blind, crossover trial, patients with CD received escitalopram and placebo for 6 weeks. Treatment with BoNT was continued, and scores on rating scales regarding dystonia, psychiatric symptoms and quality of life (QoL) were compared. Primary endpoint was the proportion of patients that improved at least one point on the Clinical Global Impression Scale for jerks/tremor scored by independent physicians with experience in movement disorders.

RESULTS

Fifty-threepatients were included. In the escitalopram period, 14/49 patients (29%) improved on severity of jerks/tremor versus 11/48 patients (23%) in the placebo period (P=0.77). There were no significant differences between baseline and after treatment with escitalopram or placebo on severity of dystonia or jerks/tremor. Psychiatric symptoms and QoL improved significantly in both periods compared with baseline. There were no significant differences between treatment with escitalopram and placebo for dystonia, psychiatric or QoL rating scales. During treatment with escitalopram, patients experienced slightly more adverse events, but no serious adverse events occurred.

CONCLUSION

In this innovative trial, no add-on effect of escitalopram for treatment of CD with jerks was found on motor or psychiatric symptoms. However, we also did not find a reason to withhold patients treatment with SSRIs for depression and anxiety, which are common in dystonia.

TRIAL REGISTRATION NUMBER

NTR2178.

Longitudinal studies of botulinum toxin in cervical dystonia: Why do patients discontinue therapy?

BACKGROUND

Numerous studies have established botulinum toxin (BoNT) to be safe and effective for the treatment of cervical dystonia (CD). Despite its well-documented efficacy, there has been growing awareness that a significant proportion of CD patients discontinue therapy. The reasons for discontinuation are only partly understood.

METHODS

This summary describes longitudinal studies that provided information regarding the proportions of patients discontinuing BoNT therapy, and the reasons for discontinuing therapy. The data come predominantly from un-blinded long-term follow-up studies, registry studies, and patient-based surveys.

RESULTS

All types of longitudinal studies provide strong evidence that BoNT is both safe and effective in the treatment of CD for many years. Overall, approximately one third of CD patients discontinue BoNT. The most common reason for discontinuing therapy is lack of benefit, often described as primary or secondary non-response. The apparent lack of response is only rarely related to true immune-mediated resistance to BoNT. Other reasons for discontinuing include side effects, inconvenience, cost, or other reasons.

DISCUSSION

Although BoNT is safe and effective in the treatment of the majority of patients with CD, approximately one third discontinue. The increasing awareness of a significant proportion of patients who discontinue should encourage further efforts to optimize administration of BoNT, to improve BoNT preparations to extend duration or reduce side effects, to develop add-on therapies that may mitigate swings in symptom severity, or develop entirely novel treatment approaches.

Minimal clinically important change in the Toronto Western Spasmodic Torticollis Rating Scale

OBJECTIVES

To characterize the minimal clinically important change (MCIC) after treatment in cervical dystonia patients using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS).

METHODS

Changes in the TWSTRS from an observational study of abobotulinumtoxinA in the routine management of cervical dystonia (NCT01314365) were analyzed using the Patient Global Impression of Change (PGIC) as anchor.

RESULTS

For the overall population (N = 304, baseline TWSTRS-Total score 43.4 ± 19.4), the MCIC for the TWSTRS Total score was -11.9 (95%CI: -13.9, -10.0; p < 0.0001). However, thresholds ranged from -3.2 to -18.0 dependent on baseline severity. TWSTRS-Total scores improved linearly by 3 points for every one-point PGIC increase. There was similar linearity between the graded PGIC categories and TWSTRS subscale scores (severity, disability, and pain).

CONCLUSIONS

A 3-point change is the minimal clinically important change after treatment using TWSTRS as endpoint with higher cutoffs for greater baseline disease severity. For an average trial population (TWSTRS-total: 40-45), a 12-point decrease is clinically meaningful.

INTEREST IN CD2, a global patient-centred study of long-term cervical dystonia treatment with botulinum toxin

BACKGROUND

Longitudinal cohort studies provide important information about the clinical effectiveness of an intervention in the routine clinical setting, and are an opportunity to understand how a population presents for treatment and is managed.

METHODS

INTEREST IN CD2 (NCT01753349) is a prospective, international, 3-year, longitudinal, observational study following the course of adult idiopathic cervical dystonia (CD) treated with botulinum neurotoxin type A (BoNT-A). The primary objective is to document long-term patient satisfaction with BoNT-A treatment. Here we report baseline data.

RESULTS

This analysis includes 1036 subjects (67.4% of subjects were female; mean age was 54.7 years old; mean TWSTRS Total score was 31.7). BoNT-A injections were usually given in line with BoNT-A prescribing information. The most commonly injected muscles were splenius capitis (87.3%), sternocleidomastoid (82.6%), trapezius (64.3%), levator scapulae (40.9%) and semispinalis capitis (26.9%); 35.5% of subjects were injected using a guidance technique. Most subjects (87.8%) had been previously treated with BoNT-A (median interval between last pre-study injection and study baseline was 4 months); of these 84.8% reported satisfaction with BoNT-A treatment at peak effect during their previous treatment cycle and 51.5% remained satisfied at the end of the treatment. Analyses by geographical region revealed heterogeneity in the clinical characteristics and BoNT-A injection practice of CD subjects presenting for routine treatment.

CONCLUSIONS

These baseline analyses provide sizeable data regarding the epidemiology and clinical presentation of CD, and demonstrate an international heterogeneity of clinical practice. Future longitudinal analyses of the full 3-year study will explore how these factors impact treatment satisfaction.

Motor Cortical Plasticity Relates to Symptom Severity and Clinical Benefit From Deep Brain Stimulation in Cervical Dystonia

OBJECTIVE

To investigate the relationship between motor cortical plasticity, intracortical inhibition, and clinical response to pallidal deep brain stimulation (DBS) in patients with cervical dystonia (CD).

MATERIALS AND METHODS

Response to paired associative stimulation (PAS) and short interval intracortical inhibition (SICI) were assessed in patients with CD before and after three months of DBS and correlated with severity of dystonic symptoms as assessed by Toronto-Western-Spasmodic Torticollis Rating Scale (TWSTRS) severity score. Relations of electrophysiological parameters with clinical improvement were explored with correlation analysis.

RESULTS

Patients with higher levels of plasticity before surgery showed higher symptom severity (R = 0.83, p = 0.008) but had also the larger clinical benefit following DBS (R = 0.88, p = 0.003). This correlation was independent from preoperative (preOP) TWSTRS motor score as revealed by partial correlation analysis. Intracortical inhibition was not altered in CD and not related to clinical outcome after DBS.

CONCLUSIONS

Our findings indicate that a high degree of preOP plasticity is associated with higher symptom severity, underlining the role of abnormal plasticity in the pathophysiology of dystonia. At the same time individual degree of plasticity may drive reestablishment of normal motor programs, leading to better clinical outcome with DBS. The latter suggests that individual PAS-response may indicate the susceptibility for neuromodulatory processes as an important factor for clinical DBS effects. It might therefore serve as a neurophysiological marker to predict outcome and guide patient selection.

Involvement of obliquus capitis inferior muscle in dystonic head tremor

INTRODUCTION

Head tremor is a common feature in cervical dystonia (CD) and often less responsive to botulinum neurotoxin (BoNT) treatment than dystonic posturing. Ultrasound allows accurate targeting of deeper neck muscles.

METHODS

In 35 CD patients with dystonic head tremor the depth and thickness of the splenius capitis (SPL), semispinalis capitis and obliquus capitis inferior muscles (OCI) were assessed using ultrasound. Ultrasound guided EMG recordings were performed from the SPL and OCI.

RESULTS

Burst-like tremor activity was present in both OCI in 25 and in one in 10 patients. In 18 patients, tremor activity was present in one SPL and in 2 in both SPL. Depth and thickness of OCI, SPL and semispinalis capitis muscles were very variable.

CONCLUSION

Muscular activity underlying tremulous CD is most commonly present in OCI. Due to the variability of muscle thickness, we suggest ultrasound guided BoNT injections into OCI.

Botulinum toxin treatment failures in cervical dystonia: causes, management, and outcomes

Botulinum toxin (BoNT) is highly effective in the treatment of cervical dystonia (CD), yet a significant proportion of patients report low levels of satisfaction following treatment and fail to follow up for repeated treatments. The goal of this study was to determine the reasons that some patients have unsatisfactory responses. A total of 35 subjects who came to our center requesting alternative treatments due to unsatisfactory responses following BoNT treatment for CD were evaluated. Included were 26 women and 9 men with an average age of 57.1 years (range 25-82 years), and an average duration of illness of 12.5 years (range 1-55 years). Details of unsatisfactory BoNT treatments were methodically collected by a movement specialist using a standardized intake form, including provider subspecialty, product used, the number of satisfactory or unsatisfactory trials, doses given, specific muscles treated, the use of electromyographic guidance, side effects, and tests of resistance. The specialist then provided repeat treatments if indicated, and followed each case until the reasons for unsatisfactory outcomes could be determined. Multiple reasons for unsatisfactory outcomes were found. They included suboptimal BoNT doses, suboptimal muscle targeting, intolerable side effects, complex movement patterns, discordant perceptions, and incorrect diagnoses. Only one patient was functionally resistant to BoNT. Of 32 subjects who received repeat BoNT treatments, 25 (78 %) achieved satisfactory responses after revision of the original treatment plan. These results indicate that the majority of unsatisfactory responses to BoNT treatment of CD were caused by correctible factors and imply a need for improved education regarding optimal treatment methods.

A randomized trial of specialized versus standard neck physiotherapy in cervical dystonia

BACKGROUND

Anecdotal reports suggested that a specialized physiotherapy technique developed in France (the Bleton technique) improved primary cervical dystonia. We evaluated the technique in a randomized trial.

METHODS

A parallel-group, single-blind, two-centre randomized trial compared the specialized outpatient physiotherapy programme given by trained physiotherapists up to once a week for 24 weeks with standard physiotherapy advice for neck problems. Randomization was by a central telephone service. The primary outcome was the change in the total Toronto Western Spasmodic Torticollis Rating (TWSTR) scale, measured before any botulinum injections that were due, between baseline and 24 weeks evaluated by a clinician masked to treatment. Analysis was by intention-to-treat.

RESULTS

110 patients were randomized (55 in each group) with 24 week outcomes available for 84. Most (92%) were receiving botulinum toxin injections. Physiotherapy adherence was good. There was no difference between the groups in the change in TWSTR score over 24 weeks (mean adjusted difference 1.44 [95% CI -3.63, 6.51]) or 52 weeks (mean adjusted difference 2.47 [-2.72, 7.65]) nor in any of the secondary outcome measures (Cervical Dystonia Impact Profile-58, clinician and patient-rated global impression of change, mean botulinum toxin dose). Both groups showed large sustained improvements compared to baseline in the TWSTR, most of which occurred in the first four weeks. There were no major adverse events. Subgroup analysis suggested a centre effect.

CONCLUSION

There was no statistically or clinically significant benefit from the specialized physiotherapy compared to standard neck physiotherapy advice but further trials are warranted.

AbobotulinumtoxinA in the management of cervical dystonia in the United Kingdom: a budget impact analysis

BACKGROUND

Cervical dystonia (CD) can be effectively managed by a combination of botulinum neurotoxin A (BoNT-A) and conventional therapy (skeletal muscle relaxants and rehabilitative therapy), but the costs of different interventions in the UK vary.

METHODS

A budget impact model was developed from the UK payer perspective with a 5-year time horizon to evaluate the effects of changing market shares of abobotulinumtoxinA, onabotulinumtoxinA, and incobotulinumtoxinA, and best supportive care from the UK payer perspective. Epidemiological and resource use data were retrieved from the published literature and clinical expert opinion. Deterministic sensitivity analyses were performed to determine the parameters most influential on the budgetary findings under base case assumptions.

RESULTS

Under base case assumptions, an increased uptake of abobotulinumtoxinA showed an accumulated savings of £2,250,992 by year 5. Treatment per patient per year with onabotulinumtoxinA and incobotulinumtoxinA costs more when compared to treatment with abobotulinumtoxinA. One-way sensitivity analyses showed that the prevalence of CD, dose per injection of each of the BoNT-As, and time to reinjection of incobotulinumtoxinA and abobotulinumtoxinA influenced the base case findings most.

CONCLUSION

There is potential for cost savings associated with the greater use of abobotulinumtoxinA rather than other BoNT-A treatments, permitting more patients to benefit more from effective BoNT-A treatment with a fixed budget.

Practical guidance for CD management involving treatment of botulinum toxin: a consensus statement

Cervical dystonia is a neurological movement disorder causing abnormal posture of the head. It may be accompanied by involuntary movements which are sometimes tremulous. The condition has marked effects on patients’ self-image, and adversely affects quality of life, social relationships and employment. Botulinum neurotoxin (BoNT) is the treatment of choice for CD and its efficacy and safety have been extensively studied in clinical trials. However, current guidelines do not provide enough practical information for physicians who wish to use this valuable treatment in a real-life setting. In addition, patients and physicians may have different perceptions of what successful treatment outcomes should be. Consequently, an international group of expert neurologists, experienced in BoNT treatment, met to review the literature and pool their extensive clinical experience to give practical guidance about treatment of CD with BoNT. Eight topic headings were considered: the place of BoNT within CD treatment options; patient perspectives and desires for treatment; assessment and goal setting; starting treatment with BoNT-A; follow-up sessions; management of side effects; management of non-response; switching between different BoNT products. One rapporteur took responsibility for summarising the current literature for each topic, while the consensus statements were developed by the entire expert group. These statements are presented here along with a discussion of the background information.

Factors influencing secondary non-response to botulinum toxin type A injections in cervical dystonia

BACKGROUND

The development of secondary non-response (SNR) to botulinum neurotoxin type-A (BoNT-A) is considered a key issue in the management of cervical dystonia (CD). This case-controlled study was performed to systematically identify factors influencing SNR during BoNT-A therapy.

METHODS

This was a retrospective, international, non-interventional study of CD patients. Patients with SNR were matched with up to three responder patients (control) on the basis of duration of therapy and number of injection cycles. Factors influencing the development of SNR were screened using a univariate logistic regression model and confirmed using a multivariate conditional logistic regression model.

RESULTS

216 patients were enrolled, and 201 (SNR = 52; responder = 149) were matched and subdivided into blocks (doublets, triplets or quadruplets). At baseline, a significantly higher proportion of SNR patients had received previous or concomitant therapies (p = 0.038) and surgery for CD (p = 0.007) compared with controls. Although disease severity at onset was similar between groups, a significantly higher proportion of SNR patients experienced severe CD at the time of SNR compared with controls at the last documented visit. Multivariate analyses identified five factors that were significantly associated in predicting SNR (odds ratio [OR] > 1 indicated higher chances for being SNR): previous surgical procedure for CD (OR 9.8, p = 0.013), previous BoNT-A related severe adverse event (AE) (OR 5.6 p = 0.027), physical therapy (OR 4.6, p = 0.028), neuroleptic use (OR 3.3, p = 0.019) and average BoNT-A dose (OR 2.7, p = 0.010).

CONCLUSIONS

These findings suggest that SNR may not reflect true pharmacological resistance to BoNT-A therapy, but may be related to underlying disease severity.

Assessing the burden of illness from cervical dystonia using the Toronto Western Spasmodic Torticollis Rating Scale scores and health utility: a meta-analysis of baseline patient-level clinical trial data

PURPOSE

This study aimed to explore the burden of illness associated with cervical dystonia (CD), including possible demographic and humanistic correlates of baseline disease severity.

METHODS

The analysis involved the five multinational randomized, placebo-controlled clinical trials that had evaluated the efficacy and safety of Dysport® in patients with CD, including assessment using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). Patient-level TWSTRS scores from the individual studies were meta-analysed to estimate disease severity at baseline. One of the studies had reported Short Form-36 (SF-36) Health Survey quality-of-life measures, and these data were used to investigate whether the severity of CD was associated with humanistic outcomes, as measured by health utility. A generalized regression model was then applied to explore potential correlation between TWSTRS scores and utilities.

RESULTS

The estimated pooled mean baseline severity of CD in clinical trial entrants, as measured by TWSTRS score, was 43.23 (95% CI = 39.31-47.15). In general, disease severity was significantly greater in patients aged over 40 years (compared to the reference group aged 18-30 years). However, there was no correlation between disease severity and other demographic characteristics (e.g., weight, height, gender). Higher TWSTRS scores correlated with worse health-related quality of life as perceived by patients and was reflected in health utility (R(2 )= 0.133).

CONCLUSIONS

This study was able to define TWSTRS scores in patients with CD in terms of associated utility. This approach could help in capturing the disease's burden through measures that are more tangible than TWSTRS scores to patients, carers, clinicians, and healthcare payers.

Pallidal neurostimulation in patients with medication-refractory cervical dystonia: a randomised, sham-controlled trial

BACKGROUND

Cervical dystonia is managed mainly by repeated botulinum toxin injections. We aimed to establish whether pallidal neurostimulation could improve symptoms in patients not adequately responding to chemodenervation or oral drug treatment.

METHODS

In this randomised, sham-controlled trial, we recruited patients with cervical dystonia from centres in Germany, Norway, and Austria. Eligible patients (ie, those aged 18-75 years, disease duration ≥3 years, Toronto Western Spasmodic Torticollis Rating Scale [TWSTRS] severity score ≥15 points) were randomly assigned (1:1) to receive active neurostimulation (frequency 180 Hz; pulse width 120 μs; amplitude 0·5 V below adverse event threshold) or sham stimulation (amplitude 0 V) by computer-generated randomisation lists with randomly permuted block lengths stratified by centre. All patients, masked to treatment assignment, were implanted with a deep brain stimulation device and received their assigned treatment for 3 months. Neurostimulation was activated in the sham group at 3 months and outcomes were reassessed in all patients after 6 months of active treatment. Treating physicians were not masked. The primary endpoint was the change in the TWSTRS severity score from baseline to 3 months, assessed by two masked dystonia experts using standardised videos, analysed by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00148889.

FINDINGS

Between Jan 19, 2006, and May 29, 2008, we recruited 62 patients, of whom 32 were randomly assigned to neurostimulation and 30 to sham stimulation. Outcome data were recorded in 60 (97%) patients at 3 months and 56 (90%) patients at 6 months. At 3 months, the reduction in dystonia severity was significantly greater with neurostimulation (-5·1 points [SD 5·1], 95% CI -7·0 to -3·5) than with sham stimulation (-1·3 [2·4], -2·2 to -0·4, p=0·0024; mean between-group difference 3·8 points, 1·8 to 5·8) in the intention-to-treat population. Over the course of the study, 21 adverse events (five serious) were reported in 11 (34%) of 32 patients in the neurostimulation group compared with 20 (11 serious) in nine (30%) of 30 patients in the sham-stimulation group. Serious adverse events were typically related to the implant procedure or the implanted device, and 11 of 16 resolved without sequelae. Dysarthria (in four patients assigned to neurostimulation vs three patients assigned to sham stimulation), involuntary movements (ie, dyskinesia or worsening of dystonia; five vs one), and depression (one vs two) were the most common non-serious adverse events reported during the course of the study.

INTERPRETATION

Pallidal neurostimulation for 3 months is more effective than sham stimulation at reducing symptoms of cervical dystonia. Extended follow-up is needed to ascertain the magnitude and stability of chronic neurostimulation effects before this treatment can be recommended as routine for patients who are not responding to conventional medical therapy.

FUNDING

Medtronic.

Treatment of dystonia

Selecting the appropriate treatment for dystonia begins with proper classification of disease based on age, distribution, and underlying etiology. The therapies available for dystonia include oral medications, botulinum toxin, and surgical procedures. Oral medications are generally reserved for generalized and segmental dystonia. Botulinum toxin revolutionized the treatment of focal dystonia when it was introduced for therapeutic purposes in the 1980s. Surgical procedures are available for medication-refractory dystonia, markedly affecting an individual's quality of life.