Botulinum toxin type A versus botulinum toxin type B for cervical dystonia

Abstract

Background This is an update of a Cochrane review first published in 2003, and previously updated in 2009 (no change in conclusions). Cervical dystonia is the most common form of focal dystonia and is a disabling disorder characterized by painful involuntary head posturing. Botulinum toxin type A (BtA) is usually considered the first line therapy for this condition, although botulinum toxin type B (BtB) is an alternative option, with no compelling theoretical reason as to why it might not be as, or even more effective, than BtA. Objectives To compare the efficacy, safety, and tolerability of botulinum toxin type A versus botulinum toxin type B in cervical dystonia. Search methods We identified studies for inclusion in the review using the Cochrane Movement Disorders Group trials register, the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, reference lists of articles and conference proceedings, last run in October 2015. Search was unrestricted by language. Selection criteria Double-blind, parallel, randomised, placebo-controlled trials (RCTs) of BtA versus BtB in adult patients with cervical dystonia. Data collection and analysis Two independent authors assessed records, selected included studies, extracted data using a paper pro forma and evaluated the risk of bias. Disagreements were solved by consensus or by a third author. We performed one meta-analysis for the comparison BtA versus BtB. We used random-effects models in the presence of considerable heterogeneity and fixed-effect models when there was no heterogeneity. We performed no subgroup analyses. The primary efficacy outcome was overall improvement on any validated symptomatic rating scale. The primary safety outcome was the proportion of participants with any adverse event.Main results Three RCTs of low-to-moderate overall methodological quality including 270 participants with cervical dystonia were included. Two studies exclusively enrolled patients known to have a positive response to BtA treatment, therefore including an enriched population with higher probability of benefit from BtA treatment. None of the trials were independently funded. All RCTs evaluated the effect of a single Bt treatment session using doses between 100 and 250U of BtA and 5000 to 10000U of BtB. We found no difference between the two types of botulinum toxin in terms of overall efficacy and safety, as assessed by the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and the number of adverse events, respectively. However, when compared to BtA, treatment with BtB was associated with an improvement of 0.99 points (95% CI: 0.12 to 1.85; I2=0%) on the TWSTRS pain sub-scale at weeks 2-4 after injection, as well as with an increased risk of treatment-related dysphagia with a risk ratio (RR) of 0.49, favouring the BtA group (95% CI: 0.32 to 0.75, I2=27%) and sore throat/dry mouth, with a RR of 0.42 favouring the BtA group (95% CI: 0.31 to 0.57, I2=77%). The two types of botulinum toxin were otherwise shown to be clinically non-distinguishable in all the remaining outcomes. Authors' conclusions A single treatment session of BtA and a single treatment session of BtB are equally effective and well tolerated in the treatment of adults with certain types of cervical dystonia. Treatment with BtB causes a greater decrease disease-associated pain whilst also increasing the rate of dysphagia and sore throat/dry mouth when compared to treatment with BtA. Overall, there is no clinical evidence to support or not support the preferential use of one form of botulinum toxin over another. There is no evidence from RCTs neither regarding comparative development of secondary non-responsiveness to botulinum toxin nor regarding quality of life domains with either treatment.

A distonia cervical compreende uma patologia neurológica pouco frequente com impacto negativo na qualidade de vida dos doentes. O tratamento de primeira linha é com efetuado com recuro a injecções intramusculares de toxina botulínica, que está disponível comercialmente em dois tipos: a toxina botulínica tipo A e a toxina botulínica tipo B. Esta revisão sistemática Cochrane visa comparar estes dois compostos em relação à sua eficácia e segurança no tratamento da distonia cervical. Após um processo de pesquisa sistemática para ensaios aleatorizados sobre o tema, extração de dados e combinação dos mesmos com recurso a técnicas de combinação por meta-análise, demonstrou-se que não existem diferenças nos perfis de eficácia e segurança entre ambas as formulações de toxina botulínica, com as exepções de uma subescala de doença (avaliador dor) e a proporção de doentes com efeitos adversos específicos.