What are the causes of cervical dystonia?

Causes of Cervical Dystonia

Cervical dystonia is classified into primary (idiopathic) and secondary forms, with the majority being primary/idiopathic where no identifiable cause is found, though genetic factors, trauma, and basal ganglia dysfunction may contribute. 1, 2

Primary (Idiopathic) Cervical Dystonia

The most common form of cervical dystonia has no identifiable structural or metabolic cause 1. Primary cervical dystonia can be further subdivided:

Genetic Forms

• Familial cases with autosomal dominant inheritance patterns exist, though only a small percentage of patients have a family history 1
• NALCN gene (sodium leak channel) has shown possible association in genome-wide studies, though this requires further validation 3
• Genetic factors appear to play a role, but specific causative genes remain largely unidentified for most cases 1

Sporadic Forms

• The majority of cases are sporadic with no family history
• Pathogenesis remains obscure but may involve:
  • Impaired basal ganglia function 1
  • Sensory system dysfunction 1
  • Unknown environmental triggers

Secondary Cervical Dystonia

Secondary forms have identifiable causes and require different management approaches 2:

Structural CNS Lesions

Brainstem and cerebellar lesions are the most common structural causes, not basal ganglia as traditionally assumed 4. The distribution includes:

• Brainstem and cerebellum: Most frequent locations 4
• Cervical spinal cord: Second most common 4
• Basal ganglia: Less common than previously thought 4

Trauma-Related

Two distinct patterns exist 5:

• Acute-onset posttraumatic (within 4 weeks of trauma):

  • Markedly restricted neck mobility
  • Prominent shoulder elevation with trapezius hypertrophy
  • Absence of involuntary movements
  • Poor response to botulinum toxin
  • May represent nondystonic muscle spasm rather than true dystonia 5

• Delayed-onset posttraumatic (3 months to 1 year after trauma):

  • Clinically indistinguishable from idiopathic cervical dystonia
  • Better treatment response 5

Drug-Induced (Tardive)

• Exposure to dopamine receptor antagonists (antipsychotics) 6, 2
• Part of acute extrapyramidal syndromes
• Involves face, extraocular muscles, neck, back, and limb muscles 6

Neurodegenerative Diseases

Associated conditions include 7, 8:

• Parkinson's disease
• Multiple sclerosis
• Amyotrophic lateral sclerosis
• Essential tremor

Other Secondary Causes

• Infectious: Central nervous system infections 2
• Metabolic: Conditions affecting basal ganglia function 2
• Vascular: Cerebrovascular disease 9

Clinical Pitfalls

Cervical dystonia can present without obvious abnormal movements in rare cases, showing only pain, muscle hypertrophy, or abnormal EMG activity—these may represent prodromal or forme fruste presentations 10. This is critical because symptoms may respond to botulinum toxin even without visible dystonia.

Distinguish true dystonia from mimics 11:

• Orthopedic/rheumatologic neck diseases
• Myasthenia or ALS-related head ptosis
• Ocular torticollis
• Isolated head tremor
• Tics or chorea

The presence of sensory tricks (touching chin, back of head, or top of head temporarily ameliorates symptoms) strongly supports dystonia diagnosis 2, 11.