Dystonia: An Overview

Abstract Dystonia is a movement disorder characterized by sustained muscle contractions which cause twisting and repetitive movements or abnormal postures. Dystonia is a feature of a heterogeneous group of disorders with various aetiologies, pathophysiology, and phenotypes. Primary dystonias include conditions in which dystonia is the only sign (e.g. DYT1/6), while in dystonia-plus syndromes further signs are present (e.g. DYT5/11); in both primary and dystonia-plus syndromes there is no secondary cause or neurodegeneration. Eleven genes have been identified as causing these disorders, and the phenotypic spectrum varies from young-onset generalized or adult-onset focal dystonia to complex clinical pictures with parkinsonism, myoclonus, or paroxysmal forms. Dystonia can also be secondary to an identified neurological condition (e.g. brain lesions, infections, use of dopamine receptor blocking drugs) or heredodegenerative, when dystonia is a feature amongst other signs of a heredodegenerative disorder (e.g. Wilson’s disease). The differential diagnosis between primary/dystonia-plus and secondary/heredodegenerative dystonia is dictated by clinical clues (age of onset, distribution, other signs), but also by supportive investigations, and is crucial for genetic counselling, prognosis and treatment. Primary dystonias plateau after some years and their distribution depends on age at onset, while heredodegenerative dystonias tend to progress and their distribution depends on the underlying condition. With regard to treatment, botulinum toxin injections are the first-line treatment for primary adult-onset craniocervical dystonia, oral treatment and deep brain stimulation of the internal segment of the globus pallidus seem to be more efficacious for young-onset generalized forms, and the treatment of secondary/heredodegenerative dystonias depends on the underlying condition.