Approach
The primary goal of treatment is to lessen the severity of dystonia. This often leads to:
Improved function (e.g., ability to turn head easily when driving)
Relief of pain
Enhanced quality of life.
Secondary goals include:
Reduction of psychological distress (through patient education about the condition, management of expectations related to treatment and treatment of accompanying anxiety or depression)
Reduced social stigma.
Treatment is indicated when symptoms impair function or cause a significant degree of patient distress. If patients present with a chief complaint of acquired torticollis, this criterion has usually been met. However, acquired torticollis that is noted incidentally by the clinician may not require treatment.
Oral medications
Treatment solely with oral medicines seldom leads to satisfactory results. However, there are legitimate reasons to attempt oral therapy first line (in lieu of botulinum toxin injections):
A small number of patients may achieve adequate relief with oral medicines alone and thereby avoid recurrent expensive and invasive therapy
In the clinical setting of a more widespread or generalised dystonia, administration of botulinum toxin to all affected muscles is impossible, so oral medicines are typically the basis of therapy.
Anticholinergics (e.g., trihexyphenidyl), baclofen, tizanidine, and clonazepam are the most widely used medicines.[19]
General principles applicable to all agents include:
Limited efficacy, especially at tolerable dosing
Central side effects (e.g., fatigue, confusion) that are usually dose limiting
All agents should be started at low doses and increased to efficacy or until tolerability limits dose.
Physiotherapy
While a robust evidence base for physiotherapy in cervical dystonia is lacking, physiotherapy can be helpful for some patients and does not carry significant risk of harm.[20][21] It is thus reasonable to consider physiotherapy as part of any treatment plan.
One small randomised study (26 patients with initial sub-optimal response to botulinum toxin treatment) found physiotherapy as an adjunct to botulinum toxin treatment to be superior to botulinum toxin treatment alone measured by change from baseline in the Toronto Western spasmodic torticollis rating scale.[22]
Botulinum toxin
Botulinum toxin acts by inhibiting pre-synaptic release of acetylcholine, blocking neuromuscular transmission. The mechanism of clinical efficacy in acquired torticollis is incompletely understood, and may involve the interruption of sensory (muscle spindle) as well as motor transmission. Seven subtypes of botulinum toxin have been identified; only subtypes A and B are currently used therapeutically. No convincing data have been presented demonstrating superiority of any particular formulation.[23][24] It is important for both the treating and referring clinician to realise that dosing between different formulations are not equivalent.
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 botulinum toxin type A.[25] Botulinum toxin injections are considered 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. Botulinum toxin has also been found to be significantly more beneficial than oral trihexyphenidyl.[26][27][28][29][30][31]
According to the American Academy of Neurology, abobotulinumtoxinA and rimabotulinumtoxinB are established effective treatments for cervical dystonia and should be offered, while onabotulinumtoxinA and incobotulinumtoxinA are probably effective and should be considered.[26]
Head-to-head randomised trials have compared botulinum toxin type A to botulinum toxin type B. No significant differences in efficacy have been demonstrated.[24][32][33] Dry mouth was a more frequent adverse event with botulinum toxin type B.
A Cochrane review found that a single botulinum toxin type A injection session led to improvement in cervical dystonia-related impairment and pain compared with placebo; however, data were insufficient to evaluate efficacy of repeated injections.[33]
A Cochrane review found no significant difference in efficacy of botulinum toxin type B versus type A; however, there was an increased risk of sore throat/dry mouth with type B.[23]
Although most evidence for the efficacy of botulinum toxin injections comes from trials of idiopathic isolated cervical dystonia, a small trial of cervical dystonia in people with cerebral palsy has shown similar efficacy.[34]
Technical considerations in the use of intramuscular botulinum toxin include the following:
Botulinum toxin is injected into dystonic muscles and serves to block release of acetylcholine into the neuromuscular junction, resulting in partial chemical denervation.
The 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. This technique 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]
A Cochrane review found insufficient evidence to evaluate the benefits of electromyography guidance techniques.[33]
Side effects of therapy with intramuscular botulinum toxin are related to induced muscle weakness and can include significant dysphagia via diffusion to pharyngeal musculature 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 botulinum toxin type B 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]
Although there has been concern about neutralising antibodies to botulinum toxin, the rate of antibody development is low (<2%). Using the lowest effective dose of botulinum toxin and temporally spacing injections by at least 3 months may reduce the risk of antibody formation.[39] When present, antibody formation may manifest as lost efficacy of toxin injections. However, some patients with demonstrated antibodies to botulinum toxin type A continue to have a clinical response to injection.[40]
In a randomised crossover trial, the addition of an exercise programme and biofeedback was found to be more effective than botulinum toxin alone.[24][32][41]
Following reports of severe adverse events associated with the use of botulinum toxin in children with cerebral palsy in 2008, the US Food and Drug Administration (FDA) reviewed the safety of botulinum toxin products.[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.
Treatment of refractory acquired torticollis
Therapy for refractory acquired torticollis includes deep brain stimulation, radiofrequency ablation, selective surgical denervation, chemical denervation by phenol injections, and intrathecal baclofen.[18]
Deep brain stimulation of the globus pallidus pars interna (GPi) is a confirmed treatment for generalised dystonia and has been shown to provide benefit to patients with medically refractory acquired torticollis.[18][43] However, a Cochrane Review rated current clinical evidence for deep brain stimulation in cervical dystonia as low quality.[44] In a randomised sham-controlled trial, GPi deep brain stimulation significantly reduced severity of torticollis compared with sham stimulation at 3 months.[45] Stimulation of bilateral GPi has been shown to have a durable effect at 3 years.[46] Another series showed significant improvement in dystonia severity at a median of 30 months in a blinded evaluation.[47] A positive effect was also reported for deep brain stimulation of the bilateral subthalamic nucleus in 9 patients with refractory cervical dystonia.[48]
Significant and durable improvement in symptoms has been reported in 70% of patients undergoing radiofrequency ablation and post-procedure physiotherapy.[49]
Case series of selective surgical denervation have shown significant reductions in disease severity scores.[50] A single institution series found similar results with selective peripheral denervation compared with deep brain stimulation.[51] There are limited but positive published data regarding combining deep brain stimulation and selective denervation in refractory cases.[52]
Injections of 2% phenol have been shown to be effective.[53] Electromyography or motor stimulation may be used to localise the motor end plate. Adverse effects include pain, swelling, tissue necrosis, and thrombosis.
Intra-thecal baclofen administered via an implanted pump has been used for the treatment of severe or refractory acquired torticollis. This may be particularly useful in patients with comorbid spasticity. There is no high-quality evidence to provide comparative data on efficacy.[18]
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