› Naranjo Adverse Drug Reaction Probability Scale
› Formal causality assessment tool for drug-adverse event relationship
› Score >=9: definite adverse drug reaction
› Score 5 to 8: probable adverse drug reaction
› Score 1 to 4: possible adverse drug reaction
› Rarely required for clinical decision-making in classic presentation
› Diagnostic-therapeutic trial
› Anticholinergic challenge as bedside scoring equivalent
› IV benztropine 2 mg or diphenhydramine 50 mg
› Resolution within 2 to 5 minutes: essentially confirms diagnosis
› Partial or no response: broaden differential urgently
› NMS severity scoring
› Levenson criteria for NMS diagnosis
› Major criteria: hyperthermia, rigidity, elevated CK
› Minor criteria: tachycardia, diaphoresis, altered consciousness
› Three major or two major plus four minor: NMS diagnosis
› Indications for MRI brain
› Atypical features
› No clear medication trigger
› Progressive or worsening dystonia
› Focal neurological deficits beyond dystonia
› Pediatric atypical presentation
› New onset movement disorder without medication exposure
› Family history of primary dystonia
› Suspected structural cause
› Posterior fossa lesion or basal ganglia abnormality
› Wilson disease suspected: basal ganglia signal change on T2
› MRI findings in drug-induced dystonia
› Expected finding: normal MRI
› Normal basal ganglia signal
› No structural lesion
› MRI not routinely indicated
› Classic drug-induced acute dystonic reaction with clear temporal medication relationship does not require MRI
› ACEP Level C: imaging reserved for atypical presentations
› CT head indications
› Atypical presentation
› Altered mental status
› Concern for hemorrhagic stroke
› Posterior fossa lesion concern
› Trauma context
› Head trauma preceding onset
› Intracranial abnormality as precipitant
› CT neck indications
› Isolated torticollis without other dystonia
› Retropharyngeal abscess exclusion
› Atlanto-axial subluxation exclusion
› CT not routinely indicated
› Classic drug-induced dystonic reaction: no CT required
› Obtain only when diagnosis is uncertain or atypical features present
› Point-of-care ultrasound role
› Limited primary role in acute dystonic reaction
› No structural muscle or vascular finding expected
› POCUS not part of standard diagnostic algorithm
› Neck ultrasound considerations
› Soft tissue swelling versus retropharyngeal pathology
› Vascular assessment if carotid dissection suspected in neck dystonia differential
› Airway ultrasound
› Subglottic airway diameter assessment
› Relevant if laryngeal dystonia prompts advanced airway planning
› Pre-intubation vocal cord and tracheal visualization
› Gastric ultrasound
› Gastric content assessment before intubation if required
› Aspiration risk stratification in obtunded patient
› Electrocardiogram indications
› QTc assessment
› Many causative antipsychotics and antiemetics prolong QTc
› QTc >500 ms: torsades de pointes risk
› Baseline ECG prior to any further antipsychotic dosing
› Arrhythmia screening
› Autonomic instability as NMS feature
› Tachyarrhythmia in serotonin syndrome
› ECG expected findings in uncomplicated dystonia
› No specific ECG pattern for acute dystonic reaction itself
› QTc may be prolonged from causative medication
› Normal ECG does not exclude drug-induced movement disorder
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