Dystonia is a neurological movement disorder that causes sustained or irregular involuntary muscle contractions resulting in involuntary, abnormal twisted movements and postures which often cause pain (Albanese et al., 2013). The condition typically occurs in repetitive and patterned movements, with or without tremor in the affected region(s) of the body (Albanese et al., 2013). Dystonia can affect any region of the body, can present differently from person to person and affects individuals of any age, gender, race, or ethnic background (Grutz & Klein, 2021).
Dystonia is believed to be the result of damage or abnormalities to several areas of the brain, including the basal ganglia, cortical region and cerebellum, all of which are responsible for the coordination of movement. In dystonia, neurotransmitters from the affected part of the brain send abnormal signals, which then result in the unusual posture or position in the affected region of the body (Bautista et al., 2020).
The diagnosis of dystonia is typically made by a neurologist who specialises in movement disorders. Examinations used in the diagnosis of dystonia include a comprehensive physical assessment and medical history, laboratory tests including urine and blood samples, and genetic testing if required. Other radiological examinations such as magnetic resonance imaging (MRI) and electroencephalogram (EEG) scans may be necessary to diagnose acquired dystonia or rule out other conditions or disorders (Albanese et al., 2019).
The classification of dystonia has had a chequered past. The first use of the term dystonia, did not appear until 1911, with Oppenheim’s description of “
Dystonia comes in many forms. It can be a standalone condition, or it can be one part of many other complex diseases. Focal dystonia is the most common type of dystonia observed. For this type of dystonia, to date no cause has been established (Comella, 2018). Thus, it is referred to as
According to Albanese et al., (2013), classifying the various types of dystonia remains difficult, and there are many factors that should be considered including age of onset of dystonia, region(s) of the body affected by dystonia, the pattern of dystonia and any accompanying features.
Due to the many different factors that make classification of dystonia difficult, it is a condition that is often undiagnosed or misdiagnosed (Comella, 2018). As a result, there are no reliable statistics on the number of individuals living with dystonia in the general population of Australia at this time.
Dystonia can be drug induced. For example as seen in
Unfortunately, at the present time, there is neither cure nor disease modifying treatment that can slow down or change the course of dystonia. The focus of the treatment for dystonia is based on the concept of symptomatic management and enhancing quality of life (Bledsoe et al. 2020). Thus, the treatment of dystonia is categorised into four main areas including medications, neurotoxins, neuromodulation and rehabilitation.
Medications for the treatment of dystonia must be individualised. Dopaminergic medications used for Parkinson’s disease such as levodopa, dopamine agonists and monoamine oxidase inhibitors (MAOIs) can be effective in the treatment of dystonia particularly in types such as dopa-responsive dystonia (DRD), myoclonus dystonia or rapid-onset dystonia Parkinsonism (Pirio et al., 2017). Responses may vary depending on the condition and levodopa-induced dyskinesia may occur as a side effect (Bledsoe et al. 2020).
Tetrabenazine is a medication that is effective against tardive dystonia and anticholinergic medications, for example benzhexol and benztropine, are most effective in treating generalised dystonia (Jinnah, 2020). Baclofen, a medication more commonly used to treat spasticity, has been effective in treating idiopathic and tardive dystonia (Pirio et al., 2017). Benzodiazepines such as diazepam and clonazepam, are used as second or third -line agents for management of dystonia (Bledsoe et al. 2020).
Another agent used in the treatment of dystonia is botulinum toxin (BoNT) however, the approval for BoNT use for dystonia varies from country to country. In Australia, BoNT has been approved by the Pharmaceutical Benefits Scheme (PBS) for use in cervical dystonia, blepharospasm and spasmodic dysphonia (Bledsoe et al., 2020; Sy & Fernandez, 2021). Other classifications of dystonia that are treated with off-label BoNT include upper limb dystonic tremor, upper and lower limb dystonia and orofacial dystonia. The advantages of using BoNT is the localised effect it
Invasive neuromodulation includes techniques such as ablation and deep brain stimulation (DBS) (Sy & Fernandez, 2021). Ablation refers to surgically induced scarring of the affected area of the brain that causes the dystonia, through methods such as thalamotomy and in more recent times, MRI guided high-intensity focused ultrasound (MRgFUS) (Bledsoe et al., 2020). DBS is the most commonly used invasive neurosurgical treatment for dystonia (Bledsoe et al., 2020; Pirio et al., 2017). The DBS target site most used for dystonia is the globus pallidus internus (GPi) (Bledsoe et al. 2020).
Research continues to try and better understand and treat dystonia. Over recent years, surgical treatment options for dystonia have increased due to the advances in neurosurgery (Bledsoe et al., 2020), and while both Deep Brain Stimulation (DBS) and BoTN have revolutionised dystonia treatment, they are not without their therapeutic limitations and are not suitable treatments for all patients (Galpern et al., 2014; Kilic-Berkmen et al., 2021).
Ongoing research aims to refine and increase the effectiveness of methods used to manage dystonia. By identifying similarities in the many forms of dystonia and comparing this to other movement disorders, research aims to understand more about dystonia and how to find more effective treatments (Downs et al., 2020; Galpern et al., 2014).
Due to the many types of dystonia, prognosis varies enormously. For instance, spreading of dystonia from one region to another, has a negative effect on prognosis. Other factors that affect prognosis include, the individual’s response to medications and treatment, and whether individuals experience periods of partial or complete remission from dystonic symptoms (Mainka et al., 2019). In patients with an acquired dystonia, such as drug induced dystonia or dystonia secondary to brain injury, the prognosis depends on the cause of the dystonia, the underlying pathology and available treatment options (Liow et al., 2016; van Edmond et al., 2015)
Looking forward, while effective treatment may require a combination of current therapeutic approaches, new therapies are being developed. Investigations into the effectiveness of methods such as exercise therapy, yoga, music therapy, mindfulness, transcranial electrical stimulation (TES) and transcranial magnetic stimulation (TMS) continue. Further investigation into these methods through well-designed clinical trials are necessary to evaluate their safety, effectiveness and efficacy (Galpern et al., 2014).
Dystonia continues to present as a complex disease, while its disease classification continues to evolve over time. Although dystonia is often a misunderstood disease, ongoing research and clinical trials hope to better understand disease pathophysiology and identify more efficient and effective treatment options.