Dystonia, in general

Diagnosis:

This is a clinical diagnosis. There are many underlying causes

Clinical features:

Simultaneous contraction of agonist & antagonist muscles, involuntary,
Decide on primary vs. secondary
Assess for isolated dystonia or other features e.g. myoclonus, parkinsonism, peripheral neuropathy, etc
Consider:

  • EMG in atypical cases
  • EEG: if necessary to distinguish from seizures

Investigations to consider: consider as appropriate

Trial of levodopa for 2 months: rules out dopamine responsive dystonia
MRI:

  • Previous stroke: putamenal, caudate
  • Brainstem lesions: osmotic demyelination,
  • Caudate atrophy in: Huntington’s disease, neuroacanthocytosis, some GM1 gangliosidoses
  • Eye of the tiger sign or generalised atrophy: Hallervorden-Spatz disease PKAN
  • Putamenal lesions: Wilson’s disease, HIV
  • Putamenal atrophy: Glutaric aciduria
  • Symmetrical basal ganglia lesions: Leigh’s disease
  • Calcifications: Fahr’s disease
  • Thalamic lesions: Wilson’s disease, ADEM with Mycoplasma pneumoniae,
  • Tuberculoma features: TB
  • White matter disease: Krabbe’s disease, metachromatic leukodystrophy

Blood tests:

  • Blood smear: increased acanthocytes (suggests neuroacanthocytosis)

Tests for Wilson’s disease
Mycoplasma pneumoniae serology: if ADEM picture or thalamic lesions
HIV testing
Measles testing: subacute sclerosing panencephalitis SSPE
Carbon monoxide CO testing
Serum lactate, pyruvate: mitochondrial
Uric acid in young: Lesch-Nyhan disease
Glutaric acid, methylmalonic acid, very long chain fatty acids: inherited conditions
Urine amino acids
NCS/EMG:

  • Krabbe’s disease, metachromatic leukodystrophy

Genetic testing:

  • As guided by clinical features & imaging

Causes of dystonia:

Primary:

  • Hereditary, Genetic forms:
    • DYT classification
  • Other primary dystonia genetic forms
  • Sporadic

Secondary:

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