Adverse Event Profiles of High Dose Botulinum Toxin Injections for Spasticity

Safety and Real-World Dosing of OnabotulinumtoxinA for the Treatment of Adult Spasticity: Post Hoc Analysis of the Adult Spasticity International Registry Study

OBJECTIVE

The aim of the study is to evaluate the safety of onabotulinumtoxinA treatment for spasticity across dose ranges in real-world practice.

DESIGN

Adult Spasticity International Registry was a multicenter, prospective, observational study (NCT01930786) of onabotulinumtoxinA treatment for adult spasticity over 2 yrs. Adverse events, serious adverse events, treatment-related adverse events, and serious treatment-related adverse events were sorted into five categories (≤200, 201-400, 401-600, 601-800, ≥801 U) based on cumulative dose per session.

RESULTS

In 3103 treatment sessions ( T ), 730 patients received ≥1 dose of onabotulinumtoxinA. Dose categories included the following: ≤200 U ( n = 312, T = 811), 201-400 U ( n = 446, T = 1366), 401-600 U ( n = 244, T = 716), 601-800 U ( n = 69, T = 149), and ≥801 U ( n = 29, T = 61). Of these patients, 261 reported 827 adverse events, 94 reported 195 serious adverse events, 20 reported 23 treatment-related adverse events, and 2 patients treated with 201-400 U onabotulinumtoxinA reported 3 serious treatment-related adverse events. Treatment-related adverse events reported included ≤200 U (8/811, 0.9%), 201-400 U (7/1366, 0.5%), 401-600 U (6/716, 0.8%), 601-800 U (1/149, 0.7%), and ≥801 U (1/61, 1.6%).

CONCLUSIONS

In this post hoc analysis, most treatment sessions were performed with 201-400 U onabotulinumtoxinA. Patients treated with 201-400 U onabotulinumtoxinA had an adverse event profile consistent with onabotulinumtoxinA package inserts globally (e.g., United States, European Union, United Kingdom, Canada). No new safety signals were identified.

Botulinum Toxin-A High-Dosage Effect on Functional Outcome and Spasticity-Related Pain in Subjects with Stroke

Stroke patients can develop spasticity and spasticity-related pain (SRP). These disorders are frequent and can contribute to functional limitations and disabling conditions. Many reports have suggested that higher doses than initially recommended of BTX-A can be used effectively and safely, especially in the case of severe spasticity; however, whether the treatment produces any benefit on the functional outcome and SRP is unclear. Studies published between January 1989 and December 2022 were retrieved from MEDLINE/PubMed, Embase, and Cochrane Central Register. Only obabotulinumtoxinA (obaBTX-A), onabotulinumtoxinA, (onaBTX-A), and incobotulinumtoxinA (incoBTX-A) were considered. The term "high dosage" indicates ≥600 U. Nine studies met the inclusion criteria. Globally, 460 subjects were treated with BTX-A high dose, and 301 suffered from stroke. Studies had variable method designs, sample sizes, and aims. Only five (55.5%) reported data about the functional outcome after BTX-A injection. Functional measures were also variable, and the improvement was observed predominantly in the disability assessment scale (DAS). SRP pain was quantified by visual analog scale (VAS) and only three studies reported the BTX-A effect. There is no scientific evidence that this therapeutic strategy unequivocally improves the functionality of the limbs. Although no clear-cut evidence emerges, certain patients with spasticity might obtain goal-oriented improvement from high-dose BTX-A. Likewise, data are insufficient to recommend high BTX dosage in SRP.

Effectiveness of Botulinum Toxin Injection on Bruxism: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE

The present study compiled evidence on the efficacy of botulinum toxin A (BTX) for management of bruxism.

METHODS

A literature review that included randomized control, cohort, as well as observational studies published between January 2000 and November 2022 was conducted. All studies related to BTX injections administered into the masseters of patients with bruxism were included. Primary outcomes were measured by performing a meta-analysis of changes in maximal biting forces and pain severity and meta-regression of the effects of the BTX dose.

RESULTS

Ten studies were included for quantitative analysis. The analysis of the maximal biting force after BTX injections demonstrated a significant reduction at 1 month or less compared with both oral splints (P < 0.000001) and saline injections (P = 0.01). BTX continued to outperform oral splinting (P = 0.001) and saline placebos (P = 0.03) at 3 months. Between 3 and 6 months, a significantly higher maximal biting strength was observed in the BTX group than the oral splinting group (P < 0.00001). No significant differences in the maximal biting force were observed between the BTX and saline placebo groups (P = 0.50). A similar trend was observed in the analysis of pain reduction after botulinum treatment. Additionally, for every unit increase in the BTX dose, pain severity decreased by 0.0831 points (P = 0.0011).

CONCLUSION

BTX is effective in reducing biting strength and pain severity. BTX effects are evident at less than 4 weeks, peak between 5 and 8 weeks, and last for up to 24 weeks. Higher BTX doses result in greater improvement in pain. Although BTX benefits manifest earlier, they gradually diminish, and oral splinting exerts a more enduring effect, especially after 9-12 weeks. BTX injections into masseters are recommended as management options for bruxers, especially for those having difficulties complying with wearing oral splints or those seeking earlier symptom relief. However, future studies should determine BTX effects beyond 24 weeks and after repetitive injections and how bruxers of different ages or genders respond to treatment.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Botulinum toxin for motor disorders

Botulinum neurotoxins are a group of biological toxins produced by the gram-negative bacteria Clostridium botulinum. After intramuscular injection, they produce dose-related muscle relaxation, which has proven useful in the treatment of a large number of motor and movement disorders. In this chapter, we discuss the utility of botulinum toxin treatment in three major and common medical conditions related to the dysfunction of the motor system, namely dystonia, tremor, and spasticity. A summary of the existing literature is provided along with different techniques of injection including those recommended by the authors.

A consensus statement on the use of botulinum toxin in pediatric patients

Botulinum toxin has been used in medicine for the past 30 years. However, there continues to be controversy about the appropriate uses and dosing, especially in the pediatric population. A panel of nine pediatric physiatrists from different regions and previous training programs in the United States were nominated based on institutional reputation and botulinum toxin (BoNT) experience. Based on a review of the current literature, the goal was to provide the rationale for recommendations on the administration of BoNT in the pediatric population. The goal was not only to review safety, dosing, and injection techniques but also to develop a consensus on the appropriate uses in the pediatric population. In addition to upper and lower limb spasticity, the consensus also provides recommendations for congenital muscular torticollis, cervical dystonia, sialorrhea, and brachial plexus palsies.

Botulinum Toxin Services for Neurorehabiliation: Recommendations for Challenges and Opportunities during the COVID-19 Pandemic

The COVID-19 pandemic severely impacted the function of medical facilities and rehabilitation services worldwide, including toxin services delivering Botulinum toxin treatments for neuromuscular conditions such as spasticity, dystonia, and sialorrhea. The aim of this paper is to understand how toxin services have dealt with the situation and what strategies have been adopted to continue services. The recommendations are based on a virtual round table held with toxin services experts from different European countries who shared their experiences and discussed the best practices. The challenges for toxin services were reviewed based on the experts' experiences and on relevant literature from 2020 and 2021. A set of recommendations and best practices were compiled, focusing firstly on guidance for clinical practice, including assessing patients' health and risk status and the urgency of their treatment. Secondly, it was discussed how patients on botulinum toxin therapy can be cared for and supported during the pandemic, and how modern technology and tele-medicine platforms can be generally used to optimize effectiveness and safety of toxin treatments. The technological advances prompted by the COVID-19 crisis can result in better and more modern patient care in the future.

Ultrasound-Guided Injection of the Sternocleidomastoid Muscle: A Cadaveric Study with Implications for Chemodenervation

BACKGROUND

Ultrasound guidance may improve the accuracy of botulinum toxin injection, but studies of its potential for cervical dystonia treatment are lacking.

OBJECTIVE

To determine the accuracy of ultrasound-guided injection in the sternocleidomastoid muscle (SCM).

DESIGN

Observational study.

SETTING

Tertiary care university hospital.

PARTICIPANTS

Eighteen embalmed cadavers.

INTERVENTIONS

In total, 36 SCMs from 18 embalmed cadavers were examined. One physician performed ultrasound scans to divide each SCM into quarters and evaluated its cross-sectional area (CSA) and thickness at each of three meeting points between adjacent quarters. Under ultrasound guidance, another experienced physician injected methylene blue solution at one of the three points, using the in-plane technique (12 specimens per point; right SCM 3 mL, left SCM 5 mL). One anatomist dissected all cadavers and measured the distance of dye dispersion along the longitudinal axis of each muscle. Dispersion ratio was calculated as longitudinal dye dispersion divided by SCM length.

MAIN OUTCOME MEASURES

SCM thickness and CSA; dye dispersion patterns (dispersion distance and dispersion ratio).

RESULTS

SCM thickness and CSA were greatest at the middle injection point (mean ± SD of 6.6 ± 2.0 mm and 1.4 ± 0.6 cm² , respectively). All injections were successful, except in one case where the SCM was thin and the dye reached the omohyoid muscle. Mean longitudinal dye dispersion and dispersion ratio were significantly greater when the volume was 5 mL. There were no statistically significant differences in dispersion patterns among the three injection points.

CONCLUSIONS

Ultrasound-guided intramuscular injection can be performed with good accuracy in the SCM, as ultrasound can be used to evaluate SCM thickness and CSA. Higher volumes of injection solution appear to diffuse better, but further clinical studies are required to determine optimal injection volume.

High Dosage of Botulinum Toxin Type A in Adult Subjects with Spasticity Following Acquired Central Nervous System Damage: Where Are We at?

Spasticity is a common disabling disorder in adult subjects suffering from stroke, brain injury, multiple sclerosis (MS) and spinal cord injury (SCI). Spasticity may be a disabling symptom in people during rehabilitation and botulinum toxin type A (BTX-A) has become the first-line therapy for the local form. High BTX-A doses are often used in clinical practice. Advantages and limitations are debated and the evidence is unclear. Therefore, we analysed the efficacy, safety and evidence for BTX-A high doses. Studies published from January 1989 to February 2020 were retrieved from MEDLINE/PubMed, Embase, Cochrane Central Register. Only obabotulinumtoxinA (obaBTX-A), onabotulinumtoxinA (onaBTX-A), and incobotulinumtoxinA (incoBTX-A) were considered. The term “high dosage” indicated ≥ 600 U. Thirteen studies met the inclusion criteria. Studies had variable method designs, sample sizes and aims, with only two randomised controlled trials. IncoBTX-A and onaBTX-A were injected in three and eight studies, respectively. BTX-A high doses were used predominantly in treating post-stroke spasticity. No studies were retrieved regarding treating spasticity in MS and SCI. Dosage of BTX-A up to 840 U resulted efficacious and safety without no serious adverse events (AEs). Evidence is insufficient to recommend high BTX-A use in clinical practice, but in selected patients, the benefits of high dose BTX-A may be clinically acceptable.

A pragmatic approach to Botulinum Toxin safety

Botulinum Toxin (BoNT) is widely used to treat hypertonia in pediatric patients. Although serious adverse events (AEs) occur infrequently, they can lead to significant patient morbidity and mortality. This paper will discuss potential safety risks that may affect outcomes, medical comorbidities, medication dosing, targeting techniques, and muscle morphology. It is the responsibility of the physician to discuss risks and benefits regarding the use of BoNT and mitigate risks of AEs while maximizing the effectiveness of the medication.