By aetiology |
1. Primary dystonia |
|
1.1 Primary pure dystonia |
Torsion dystonia is the only clinical sign (apart from tremor) and there is no identifiable exogenous cause or other inherited or degenerative disease |
1.2 Primary plus dystonia |
Torsion dystonia is a prominent sign but is associated with another movement disorder, for example myoclonus or parkinsonism. There is no evidence of neurodegeneration. |
1.3 Primary paroxysmal dystonia |
Torsion dystonia occurs in brief episodes with normalcy in between. Three main forms are known depending on the triggering factor. |
2. Heredodegenerative dystonia |
Dystonia is a feature, among other neurological signs, of a heredodegenerative disorder, such as Wilson's disease |
3. Secondary dystonia |
Dystonia is a symptom of an identified neurological condition, such as a focal brain lesion, exposure to drugs or chemicals, e.g. dystonia because of a brain tumour, off-period dystonia in Parkinson's disease. |
By age at onset |
1. Early onset (<30 years of age) |
Usually starts in a leg or arm and frequently progresses to involve other limbs and the trunk |
2. Late onset |
Usually starts in the neck (including the larynx), the cranial muscles or one arm. Tends to remain localized with restricted progression to adjacent muscles |
By distribution of affected body parts |
1. Focal |
Single body region (e.g. writer’s cramp, blepharospasm) |
2. Segmental |
Contiguous body regions (e.g. cranial and cervical, cervical and upper limb) |
3. Multifocal |
Non-contiguous body regions (e.g. upper and lower limb, cranial and upper limb) |
4. Generalized |
Both legs and at least one other body region (usually one or both arms) |
5. Hemidystonia |
Half of the body (usually secondary to a lesion in the contralateral basal ganglia) |