Evaluating the Duration and Efficacy of Botulinum Toxin Treatment in Cervical Dystonia: Anna Castagna, MD

WATCH TIME: 7 minutes

"There is currently no consensus on how to assess the duration of effect in patients with cervical dystonia, which is crucial to avoid the 'yo-yo effect' and maintain treatment efficacy."

For those with cervical dystonia, treatment with botulinum toxin, a first-line therapy, usually requires injections every 3 to 4 months for as long as their symptoms continue which in some instances can persist for the patient’s whole lifetime. The duration of botulinum toxin effect can influence patients’ quality of life since it is critical that efficacy is consistent during an injection cycle to avoid fluctuations of effect following each injection. Currently, there is no consensus for clinicians on how to evaluate the duration of botulinum toxin effect among patients with cervical dystonia in the clinical setting.

Newly published in Parkinsonism & Related Disorders, a scoping review conducted by lead author Anna Castagna, MD, and colleagues, summarized available evidence from phase 3 clinical trials of botulinum toxin in cervical dystonia and interpreted the reported duration of its effect.¹ Authors analyzed the available evidence in the context of clinical experience and real-world treatment practices of cervical dystonia. Across the publications, methods for the estimation of duration of effect varied although most were based on artificial constructs developed for clinical trials and were not appropriate to apply for the clinical setting.

In the review, studies also showed that clinical trial outcomes in cervical dystonia were not assessed objectively, and did not prioritize the needs of patients or focus on factors that impacted their daily living activities and quality of life. Therefore, authors noted that there is a need for better evidence and consistency of reports for duration of effect for botulinum toxin in cervical dystonia to guide clinicians on when reinjection is likely to be essential. Researchers also noted that the goal would be to keep patient's symptom-free as long as possible, with flexible reinjection intervals tailored to their needs.

The results from the review were also presented at the recently concluded 3rd Annual Advanced Therapeutics in Movement and Related Disorders (ATMRD) Congress, held by the PMD Alliance from June 22-25, 2024, by Castagna, a consultant neurologist at Fondazione Don Carlo Gnocchi ONLUS in Milan, Italy. Not long after the Congress, Castagna sat down with NeurologyLive^® to discuss key factors that influence the variability in the duration of botulinum toxin's effect in patients with cervical dystonia. She also talked about how different studies in the review measured the efficacy and optimal timing for reinjection of botulinum toxin. Furthermore, she spoke about the implications of the "yo-yo effect" on the quality of life for patients with cervical dystonia.

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REFERENCES
1. Castagna A, Jinnah HA, Albanese A. Duration of botulinum toxin efficacy in cervical dystonia clinical trials: A scoping review. Parkinsonism Relat Disord. 2024;125:107011. doi:10.1016/j.parkreldis.2024.107011