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The concept of symptomatic or secondary dystonia, as opposed to primary or idiopathic dystonia, emerged in the medical literature as a class of dystonias of known etiology. Perinatal brain injury was the most representative cause of symptomatic dystonia. More recently, different focal brain lesions, neurodegenerations, metabolic disorders of the nervous system, and drugs and chemicals have been recognized as causes of dystonia.

As opposed to primary dystonia, secondary dystonia is considered to be “often accompanied by other neurological deficits,”1,2 to “begin suddenly at rest and occur at rest from the onset,”3 and to be associated with different known hereditary and environmental causes.4 (Table 31–1) These differential criteria are relative since there is a great clinical diversity of secondary dystonias. This chapter discusses the dystonic syndromes secondary to focal, degenerative, metabolic, or chemical insult to the nervous system as well as the pseudodystonias of organic and psychogenic origin. The main clinical characteristics of secondary dystonia, as well as clues for the differential diagnosis, are summarized in Tables 31–2 and 31–3.

Table 31–1. Etiologic Classification of Secondary Dystonia
Table 31–2. Differential Diagnosis of Symptomatic Dystonias

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