Dystonia

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)
• Acquired ^[1]
  • Drugs: dopamine antagonists
    • High-potency typical antipsychotics (e.g., haloperidol) are more likely than atypical antipsychotics to induce acute dystonia.
    • Metoclopramide
  • Neurologic disorders: Huntington disease
  • Metabolic: Wilson disease
  • Hypoxic or structural cerebral injury
  • Cerebral neoplasm
  • Infections: encephalitis, HIV
  • Psychogenic: conversion disorder
  • Toxic (e.g., cobalt)

Most cases of acute dystonia are caused by antipsychotic drugs.

Dystonia disorders are classified according to the distribution of symptoms in the body.

Focal dystonia

• 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 (geste antagonistes) with which they are able to suppress spasms (e.g., touching the affected region).

Conditions

• Spasmodic torticollis: cervical dystonia
  • Abnormal head movements or fixed head posture
  • Geste antagoniste: a voluntary maneuver that temporarily reduces the severity of dystonic postures or movements
• Blepharospasm: eye dystonia: (e.g., increased blinking or involuntary eye closure); usually bilateral, symmetrical
• Spasmodic dysphonia: laryngeal dystonia or voice dystonia
  • Voice breaks or strained voice (most common) ^[2]
  • 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)

Segmental dystonia

• Affects ≥ 2 adjacent regions of the body
• Meige syndrome: blepharospasm with oromandibular dystonia

Generalized dystonia

• Affects the trunk and at least two additional regions of the body
• Typically early onset (< 21 years of age)

Conditions

• Neuroleptic-induced acute dystonia
• Dopa-responsive dystonia (Segawa syndrome): a rare, genetic disorder with onset in childhood (< 10 years; ♀ > ♂)
  • Dystonia that responds well to treatment with levodopa
  • Parkinsonism
• Torsion dystonia (dystonia musculorum deformans): a rare, idiopathic disorder with onset in childhood ^[3]
  • Initial focal dystonia: involuntary movements of the limbs, torso, and neck
  • Progression to generalized dystonia

Other types of dystonia ^[4]

• Multifocal dystonia: affects ≥ 2 nonadjacent regions of the body
• Hemidystonia: 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. See “Extrapyramidal syndrome” for treatment of acute dystonic reactions due to antipsychotics. ^[5]

• Levodopa/carbidopa: A trial should be taken in all patients with childhood-onset dystonia to distinguish dopa-responsive dystonia from the other forms.
• Anticholinergics: (benztropine; , trihexyphenidyl) or antihistamines (diphenhydramine) ^[6]
• Periodic botulinum toxin injections: for focal dystonia ^[7]
• Deep brain stimulation
• Treatment of underlying disorder of acquired dystonia: (e.g., cessation of the causative drug)
• Supportive measures: physiotherapy, ergotherapy