Causes of Botulinum Toxin Treatment Failure

Immunogenicity of Botulinum Toxin A: Insights

BACKGROUND

Botulinum toxin A (BoNT-A) is widely used in treating dystonia and spasticity to managing chronic migraine and cosmetic applications. However, its immunogenic potential presents challenges, such as the development of neutralizing antibodies that lead to diminished therapeutic efficacy over time, known as secondary nonresponse.

OBJECTIVE

This review aims to bridge the knowledge gap regarding the immunogenic mechanisms of BoNT-A and to explore effective management strategies to mitigate these immune responses.

MATERIALS AND METHODS

The authors conducted a systematic search in databases including PubMed, Embase, and Web of Science, using keywords related to BoNT-A's immunogenicity. The selection process refined 157 initial articles down to 23 relevant studies, which underwent analysis to investigate the underlying mechanisms of immunogenicity and the factors influencing it.

RESULTS

The analysis revealed that both the neurotoxin component and the neurotoxin-associated proteins could elicit an immune response. However, only antibodies against the core toxin influence therapeutic outcomes. Various patient-specific factors such as genetic predispositions and prior immune experiences, along with treatment-related factors such as dosage and frequency, play crucial roles in shaping these responses.

CONCLUSION

Understanding the specific immunogenic triggers and responses to BoNT-A is critical for optimizing treatment protocols and improving patient outcomes.

Effectiveness of Extracorporeal Shock Wave Therapy after Botulinum Toxin Injection for Post-Stroke Upper Extremity Spasticity: A Randomized Controlled Study

Post-stroke spasticity is a common complication that limits the functional performance of patients. Botulinum toxin (BTx) is an effective treatment for spasticity. Numerous researchers have applied extracorporeal shock wave therapy (ESWT) to address post-stroke spasticity, yielding positive clinical outcomes. We aimed to clarify the add-on effects of ESWT on BTx therapy for spasticity in patients with post-stroke. Sixteen eligible patients with upper extremity spasticity after stroke were recruited for this study. They were randomized to either a BTx with focused ESWT treatment group or a BTx alone group. Spasticity, measured using the modified Ashworth score (MAS) and modified Tardieu scale (MTS), showed statistically significant improvements in the elbow and wrist flexor muscles in both BTx + ESWT group and BTx alone groups. However, no significant differences were observed between the two groups with time flow. The BTx + ESWT group showed significantly decreased MAS of the finger flexors at follow-up and increased R1 (MTS) of the finger flexors at 3 weeks after treatment, which was not observed in the BTx alone group. This is the first study to identify the add-on effect of ESWT on BTx injections to improve post-stroke upper limb spasticity.

Office-based facial plastics procedures: Neuromodulators

Botulinum toxin is a potent neuromodulator commonly used for cosmetic applications in the clinic. In this article, we reviewed the various formulations of botulinum toxin type A commercially available in the United States, as well as clinical pearls for preprocedural planning, common in-office injections, and management of complications.

Assessment of Patients Receiving Short-Interval Botulinum Toxin Chemodenervation Treatment for Laryngeal Dystonia and Essential Tremor of the Vocal Tract

Importance

The gold-standard treatment for laryngeal dystonia (LD) and essential tremor of the vocal tract (ETVT) is botulinum toxin (BoNT) chemodenervation. Although safe and effective, it is not curative, and periodic injections are required. Some medical insurance companies only cover injections at a 3-month interval, though some patients benefit from injections more frequently.

Objective

To determine the proportion and characteristics of patients who receive BoNT chemodenervation treatment in intervals shorter than 90 days.

Design, Setting, and Participants

This retrospective cohort study across 3 quaternary care neurolaryngology specialty practices in Washington and California recruited patients who underwent at least 4 consecutive laryngeal BoNT injections for LD and/or ETVT in the past 5 years. Data were collected from March through June 2022 and analyzed from June through December 2022.

Exposure

Laryngeal BoNT treatment.

Main Outcomes and Measures

Biodemographic and clinical variables, injection characteristics, evolution during the 3 interinjection intervals, and lifetime laryngeal BoNT treatment data were collected from patient medical records. Logistic regression was used to assess association to the short-interval outcome, defined as an average injection interval shorter than 90 days.

Results

Of 255 patients included from the 3 institutions, 189 (74.1%) were female, and the mean (SD) age was 62.7 (14.3) years. The predominant diagnosis was adductor LD (n = 199 [78.0%]), followed by adductor dystonic voice tremor (n = 26 [10.2%]) and ETVT (n = 13 [5.1%]). Seventy patients (27.5%) received short-interval injections (<90 days). The short-interval group was younger than the long-interval group (≥90 days), with a mean (SD) age of 58.6 (15.5) years and 64.2 (13.5) years, respectively, and a mean difference of -5.7 years (95% CI, -9.6 to -1.8 years). There were no patient-related differences between the short- and long-interval groups in terms of sex, employment status, or diagnosis.

Conclusions and Relevance

This cohort study demonstrated that while insurance companies often mandate a 3-month or greater interval for BoNT chemodenervation financial coverage, there is a considerable subset of patients with LD and ETVT who receive short-interval treatment to optimize their vocal function. Short-interval chemodenervation injections demonstrate a similar adverse effect profile and do not appear to predispose to resistance through antibody formation.