Treatment algorithm
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intramuscular botulinum toxin
The intramuscular administration of botulinum toxin provides the best proven efficacy in acquired torticollis.
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Sustained efficacy in reduction of dystonia severity has been demonstrated after 7 years of repeated injections with onabotulinumtoxinA.[25] Botulinum toxin injections are considered as first-line therapy for acquired torticollis by the European Federation of Neurological Societies and are recommended by the American Academy of Neurology.[18][26]
Botulinum toxin types A and B have been shown to provide significant benefit in placebo-controlled trials.[33][54]
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The unit doses are not equivalent/interchangeable. Botulinum toxin has also been found to be significantly more beneficial than oral trihexyphenidyl.[26][27][28][29][30][31] No significant differences in efficacy of botulinum toxin type A and botulinum toxin type b have been demonstrated.[24][32][33] Dry mouth was more frequent adverse event with botulinum toxin type B.[33]
The American Academy of Neurology states that abobotulinumtoxinA and rimabotulinumtoxinB are established effective treatments for cervical dystonia and and should be offered, and onabotulinumtoxinA and incobotulinumtoxinA are probably effective and should be considered.[26]
Technical considerations for its use include: injection into dystonic muscles which serves to block acetylcholine release into the neuromuscular junction resulting in partial denervation; clinical effect typically lasts 3 to 4 months;[35] injections are typically repeated every 3 to 4 months;[35] some clinicians advocate the use of electromyography to localise muscles for injection; electromyography is particularly useful in injecting deep or small muscles. Limited evidence suggests that using electromyography guidance may improve outcomes.[36] Ultrasound imaging is also sometimes used to guide injections.[37]
Side effects of therapy with intramuscular botulinum toxin are related to induced muscle weakness and can include significant dysphagia (when injected into cervical muscles) or systemic uptake of toxin resulting in mild botulism (of which difficulty swallowing is an early symptom). When compared with placebo, patients treated with rimabotulinumtoxinB were at increased risk of dry mouth and dysphagia.[31] Ultrasound-guided injections into the sternocleidomastoid are being investigated as a way to reduce the risk of dysphagia.[38]
Neutralising antibody development occurs in 2% of patients and may manifest as loss of efficacy, although some patients with demonstrated antibodies to abobotulinumtoxinA continue to have a clinical response to injection.[40] Risk can be reduced by using the lowest effective dose of botulinum toxin and temporally spacing injections by at least 3 months.[39]
The US Food and Drug Administration (FDA) posted an early communication in February 2008 warning of potential botulism with local infection of botulinum toxin.[42] These products now come with a boxed warning highlighting the risk of potential distant spread of toxin effects resulting in systemic symptoms with local injection. Most cases occurred in children treated for spasticity in the setting of cerebral palsy.[42]
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Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups. See disclaimer
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