Clinical phenomenology of dystonia.

Dystonia is defined as a motor syndrome characterized by sustained muscle contractions, usually producing twisting and repetitive movements or abnormal postures. Dystonia can be present at rest or worsened by action. Dystonia is commonly classified according to age at onset (childhood, adolescent type, and adult type), etiology (idiopathic, and symptomatic), and distribution (focal dystonia, segmental dystonia, generalized dystonia, multifocal dystonia and hemidystonia). The different subtypes of focal and segmental dystonias may have different clinical features. Neuropsychiatric disorders may be present in dystonia.