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:
- Old strokes e.g. putamen
- Anoxic brain injury
- Perinatal injury
- Osmotic demyelination
- Drug induced:
- A type of tardive dyskinesia: Antipsychotics
- Levodopa
- Metoclopramide
- Others: lamivudine, cinnarizine, flunarizine, cough suppressants
- Infectious, parainfectious:
- vCJD
- Post streptococcal infection
- Mycoplasma pneumoniae
- Tuberculosis TB
- Measles subacute sclerosing panencephalitis SSPE
- Toxic:
- Degenerative:
- Multiple sclerosis
- Hereditary:
- Autosomal dominant:
- Huntington disease
- Dentatorubropallidoluysian atrophy DRPLA
- Neuroferritinopathy a.k.a. Hereditary ferritinopathy and neurodegeneration with brain iron accumulation type 2 NIBA2
- Some spinocerebellar syndromes
- Fahr disease
- Glucose transporter type I deficiency syndrome GLUT1 DS
- Autosomal recessive:
- Wilson’s disease
- Juvenile parkinsonism PARKIIN mutation
- Neurodegeneration with brain iron accumulation type 1 NBIA1 a.k.a. Pantathenate kinase associated neurodegeneration PKAN a.k.a. Pantathenate kinase PANK deficiency formerly Hallervorden-Spatz disease
- Ataxia-telangiectasia
- Vitamin E deficiency
- Metachromatic leukodystrophy
- Sphingolipidoses
- Niemann-Pick Disease
- Neuronal ceroid lipofuscinosis NCL
- Homocysteinuria
- Hartnup disease
- Organic aciduria
- Tyrosinemia
- X-linked:
- Lubag
- Lesch-Nyhan syndrome
- Rett syndrome
- Pelizaeus-Merzbacher disease
- Mitochondrial:
- Leber’s disease
- Multiple forms of inheritance:
- Leigh’s syndrome
- Neuroacanthocytosis
- Neuronal intranuclear inclusion disease
- Hemochromatosis
- Autosomal dominant:
- Dystonia-plus syndromes:
- Dopa-responsive dystonia
- Myoclous-dystonia
- Rapid-onset dystonia-parkinsonism