Long-term efficacy and safety of botulinum toxin treatment for cervical dystonia: a critical reappraisal

ABSTRACT

Introduction: Botulinum toxin (BoNT) injections represent the gold standard treatment for cervical dystonia (CD). Different types of BoNT have been used for the treatment of CD, but only two serotypes, BoNT type A (BoNT-A) and type B (BoNT-B), have been approved by regulatory agencies. Efficacy and safety of BoNT have been well documented by many short-term studies, but the longterm effects have been investigated only relatively recently.

Areas covered: In the present review, we aimed to critically reappraise the existing evidence on the long-term efficacy and safety of BoNT treatment in CD. The examined studies mainly explored BoNT-A serotypes. Only a few studies examined the long-term effects of BoNT-B serotypes, and only one head-to-head comparison between BoNT-A and BoNT-B was found. BoNT was consistently reported to be an effective and safe treatment for CD patients, with good outcomes and a few adverse events in the long-term. However about a third of patients still drop out from the treatment during a long-term follow-up.

Expert opinion: We conclude that BoNT is safe and effective in the long-term treatment of patients with CD. Additional studies are needed to further explore patients real-life experiences and perspectives to better understand the long-term outcomes and reasons for discontinuation of treatment.

KEYWORDS:

• Botulinum neurotoxin
• cervical dystonia
• efficacy
• long-term treatment
• safety

Article highlights

• Since the 1990s, several randomized, but short term, studies have demonstrated the efficacy and safety of botulinum neurotoxin-A in the treatment of cervical dystonia

• Cochrane reviews and meta-analyses have then confirmed the evidence supporting the efficacy and safety in the short term of both serotypes, A and B, of botulinum neurotoxin serotypes

• The four botulinum toxin products currently available for the treatment of cervical dystonia appear to have similar efficacy and safety

• In the last decade, single-center longitudinal studies and real-life observations showed long-term efficacy and safety of botulinum neurotoxin

This box summarizes key points contained in the article.

Abbreviations

aboBoNT-A abobotulinumtoxinA; AEs, adverse events; BoNT-A, Botulinum toxin type A; BoNT-B, Botulinum toxin type B; Botulinum toxin (BoNT); CD, cervical dystonia; daxiBoNT-A, daxibotulinumtoxinA; incoBoNT-A, incobotulinumtoxinA; MDS, International Parkinson and Movement Disorder Society; onaBoNT-A, onabotulinumtoxinA; rimaBoNT-B; rimabotulinumtoxin-B; SF-36, short form 36; TWSTRS, Toronto Western Spasmodic Torticollis Rating Scale;VAS, visual analog scale.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Declaration of interest

J Jankovic has received research or training grants from Allergan, Inc; Dystonia Coalition; and Revance Therapeutics, Inc. J Jankovic has served as a consultant for Aeon BioPharma; Allergan, Inc; and Revance Therapeutics. C Colosimo has received grants from Abbvie, Alfasigma, BIAL, Ipsen and Zambon unrelated to the present research, honoraria from the Movement Disorders Society, and publishing royalties Oxford University press and Cambridge University Press. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/14740338.2021.1915282

Additional information

Funding

This paper was not funded.