- Clinical science
Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions causing involuntary movements, fixed postures, or both. The disorder may be idiopathic, hereditary, or acquired. Acquired dystonia is most commonly due to drugs (antipsychotics), metabolic disorders, cerebrovascular disease, or traumatic brain injury. Dystonia is classified according to the anatomic distribution of the symptoms into focal, multifocal, segmental, and generalized dystonia. Treatment involves pharmacologic management with levodopa or anticholinergic agents, as well as treatment of the underlying cause if possible. Focal dystonias respond well to periodic botulinum toxin injections in the affected muscle.
- Idiopathic (familial or sporadic)
- Hereditary (evidence of inherited genetic mutation)
- Drugs: dopamine antagonists
- Neurologic disorders: Huntington's disease
- Metabolic: Wilson's disease
- Hypoxic or structural cerebral injury
- Infections: encephalitis , HIV
- Psychogenic: conversion disorder
- Cerebral neoplasm
- Toxic (e.g., cobalt)
Dystonia disorders are classified according to the distribution of symptoms in the body.
- Affects a single region of the body
- The majority of cases are idiopathic.
- Onset typically in adulthood (usually > 30 years)
- Patients may have sensory tricks (gestes antagonistes) with which they are able to suppress spasms (e.g., touching the affected region).
Spasmodic torticollis: cervical dystonia
- Abnormal head movements or fixed head posture
Blepharospasm: eye dystonia
- Increased blinking or involuntary eye closure (bilateral, symmetrical)
Spasmodic dysphonia: laryngeal dystonia or voice dystonia
- Voice breaks or strained voice (most common)
- Weak, breathy voice
- Oromandibular dystonia: : involuntary movements of the tongue, jaw, and/or face (e.g., jaw clenching, jaw opening)
- Writer's dystonia: (writer's cramp): non-painful contractions of hand muscles that are provoked by specific tasks (e.g., writing)
- Spasmodic torticollis: cervical dystonia
- Affects the trunk and at least two additional regions of the body
- Typically early onset (< 21 years of age)
Dopa-responsive dystonia (Segawa syndrome): rare, genetic disorder with onset in childhood (< 10 years; ♀ > ♂)
- Dystonia that responds well to treatment with levodopa
Torsion dystonia (dystonia musculorum deformans): rare, idiopathic disorder with onset in childhood
- Initial focal dystonia: involuntary movements of the limbs, torso, and neck
- Progression to generalized dystonia
- Dopa-responsive dystonia (Segawa syndrome): rare, genetic disorder with onset in childhood (< 10 years; ♀ > ♂)
- Affects ≥ 2 nonadjacent regions of the body
- Affects the limbs of one half of the body
All treatments can be used for generalized dystonia, but botulinum toxin injections are typically reserved for focal dystonia.
- First-line: levodopa/carbidopa
- Anticholinergics ; (benztropine, trihexyphenidyl) or antihistamines (diphenhydramine)
Periodic botulinum toxin injections for focal dystonia
- Botulinum toxin injections may be considered for patients with generalized dystonia, but only to manage severe dystonia in select regions; the treatment is not widespread due to side effects associated with systemic use.
- Deep brain stimulation
- Treat underlying disorder of acquired dystonia
- Cessation of causative drug
- Supportive measures: physiotherapy, ergotherapy