Dystonia
Dystonia is a movement disorder characterised by abnormal, repetitive movements and postures caused by involuntary, sustained or intermittent muscle contractions. It is the most common movement disorder after Parkinson's disease. Treatment depends on aetiology and distribution; botulinum toxin is first-line for focal dystonias, while deep brain stimulation of the globus pallidus interna (GPi-DBS) is a key option for generalised dystonia.
Ostatnia aktualizacja: 2026-06-07
Definition
Dystonia is a movement disorder in which involuntary muscle contractions produce abnormal postures and repetitive, often twisting movements. The contractions may be sustained or intermittent. The prevalence is approximately 16-30 per 100,000, making it the most common movement disorder after Parkinson's disease. Its pathophysiology involves dysfunction of the basal ganglia (globus pallidus, putamen, caudate nucleus) and thalamocortical circuits; loss of motor inhibition leads to co-contraction of agonist and antagonist muscles.
Classification
Dystonia is classified along several axes. By age of onset it is divided into early (typically ≤26 years) and late onset; by distribution into focal (one region), segmental (adjacent regions), multifocal and generalised (whole body). Focal dystonias are the most common form and include cervical dystonia (torticollis), blepharospasm (eyelid), oromandibular dystonia (jaw and face), laryngeal dystonia (vocal cords) and writer's cramp. Generalised dystonia is more common in children and is often genetic in origin.
Causes and Risk Factors
In primary (idiopathic) dystonia there is no underlying structural neurodegenerative disease; genetic mutations (for example TOR1A/DYT1, GCH1/DYT5) or sporadic causes are involved. Secondary dystonia may develop after traumatic brain injury, hypoxia, stroke (basal ganglia lesions), Wilson's disease (a disorder of copper metabolism), Huntington's disease, cerebral palsy, or with drugs (neuroleptics, metoclopramide, antiemetics). The late-onset form related to prolonged antipsychotic use is called tardive dystonia.
Symptoms
Symptoms vary with the region involved: involuntary, sustained or intermittent muscle contractions; abnormal postures; repetitive twisting movements; and muscle pain and fatigue due to chronic contraction. Some dystonias are task-specific (for example writer's cramp, which appears during writing). A characteristic feature is the sensory trick (geste antagoniste), in which light touch to the affected area temporarily reduces the symptoms. Cervical dystonia causes turning or tilting of the neck, blepharospasm causes eyelid closure, and oromandibular and laryngeal dystonia cause difficulty speaking.
Diagnosis
Diagnosis is primarily clinical, based on a detailed history and neurological examination. Abnormal postures, contraction patterns and the sensory trick are assessed; the Burke-Fahn-Marsden Dystonia Rating Scale provides an objective measure of severity. To investigate aetiology, brain MRI (basal ganglia lesions, characteristic signal changes in Wilson's disease), serum ceruloplasmin and 24-hour urinary copper in young-onset cases (for Wilson's disease), and genetic testing in appropriate cases are used. A trial of low-dose levodopa is performed when dopa-responsive dystonia is suspected. The differential diagnosis includes essential tremor, Parkinson's disease and psychogenic movement disorders.
Medical (Conservative) Treatment
Treatment is individualised according to aetiology and distribution. In dopa-responsive dystonia, levodopa produces marked improvement and is first-line; this entity must therefore always be excluded in paediatric dystonia. For focal dystonias, botulinum toxin injection is the first-line treatment: it is delivered to the affected muscles, takes effect within 7-14 days, lasts about 3-4 months and requires repeat injections. Oral options include anticholinergics (trihexyphenidyl), baclofen, clonazepam and the dopamine-depleting agent tetrabenazine. In tardive dystonia, reducing or switching the offending drug and tetrabenazine are used; in Wilson's disease, copper chelation is given. Physiotherapy supports stretching, postural training and preservation of range of motion.
Surgical Treatment: Deep Brain Stimulation (GPi-DBS)
In patients with generalised and selected focal/segmental dystonia who do not respond adequately to medication and botulinum toxin and whose function is markedly impaired, bilateral deep brain stimulation of the globus pallidus interna (GPi) is performed. Electrodes placed by stereotactic surgery deliver high-frequency electrical stimulation via a neurostimulator implanted under the skin, modulating abnormal basal ganglia activity and reducing contractions. The effect of DBS develops gradually over weeks to months. The best response is obtained in early-onset, genetic (DYT1-related) generalised dystonia, whereas the response in secondary dystonia is more limited. Complications include infection, haemorrhage and adjustable stimulation side effects.
Prognosis
The course of dystonia varies considerably from person to person according to type and aetiology. Focal dystonias are generally non-progressive and can be controlled for many years with botulinum toxin. In generalised dystonia, DBS can significantly improve quality of life in suitable candidates. A multidisciplinary approach (neurology, neurosurgery, physiotherapy) and regular follow-up provide the best outcomes. The treatment plan is individualised for each patient, and no outcome can be guaranteed in advance.
Źródła
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:1842-1843.
- Winn HR, ed. Youmans Neurological Surgery. 6th ed. Saunders; 2011:968-975.
- Albanese A, Bhatia K, Bressman SB, et al. Phenomenology and classification of dystonia: a consensus update. Mov Disord. 2013;28(7):863-873.
- Volkmann J, Wolters A, Kupsch A, et al. Pallidal deep brain stimulation in patients with primary generalised or segmental dystonia: 5-year follow-up of a randomised trial. Lancet Neurol. 2012;11(12):1029-1038.
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