Etiology
- Acquired
- 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
- Psychogenic: conversion disorder
- Drugs: dopamine antagonists
Tip
Most cases of acute dystonia are caused by antipsychotic drugs.
Clinical features
- Definition: Involuntary, sustained or intermittent muscle contractions causing abnormal twisting postures or repetitive movements.
- Acute Dystonic Reaction:
- Onset: Sudden, within hours to days (typically < 4 days) of starting/increasing D2 receptor antagonists.
- Torticollis / Retrocollis: Asymmetrical neck spasm with twisting/head tilt (most common).
- Oculogyric Crisis: Involuntary, sustained upward gaze deviation. c
- Opisthotonos: Severe hyperextension and arching of the spine.
- Laryngeal Dystonia: Stridor, dyspnea (emergent airway risk).
- Focal Dystonias:
- Cervical Dystonia (Spasmodic Torticollis): Painful neck spasms; transiently relieved by tactile stimulation of face/chin (geste antagoniste / sensory trick).
- Blepharospasm: Involuntary, bilateral, sustained eye closure; provoked by bright light or stress.
- Writer’s Cramp: Task-specific dystonia limited to hand/forearm during writing.
Treatment
- Acute Dystonic Reaction:
- First-line: IV or IM Diphenhydramine OR IV or IM Benztropine (rapidly restores dopamine-acetylcholine balance).
- Second-line / Refractory: IV Benzodiazepines (e.g., Lorazepam).
- Long-term Prevention: Discontinue/reduce causative agent or switch to an SGA with low EPS liability (e.g., Quetiapine, Clozapine).
- Focal Dystonia (e.g., Cervical dystonia, Blepharospasm):
- First-line: Botulinum toxin injection into affected muscles (blocks presynaptic acetylcholine release).
- Second-line (Oral systemic agents): Oral anticholinergics (Trihexyphenidyl), Baclofen, or Clonazepam.
- Generalized / Inherited Dystonia:
- Trial of Levodopa/Carbidopa: High-yield to rule in/treat Dopa-responsive Dystonia (Segawa syndrome).
- Refractory Cases: Deep Brain Stimulation (DBS) targeting the Globus Pallidus internus (GPi).