Differential diagnosis of dystonia.

Dystonia is a movement disorder characterized by sustained muscle contractions causing twisting and repetitive movements and abnormal postures. Diagnosing dystonia may be difficult, because of variability of dystonia presentation, uncertain recognition of the specific clinical signs, wide etiological spectrum, and coexistence of other movement disorders. The major difficulties in the diagnostic assessment of primary and non-primary dystonia derive from its confusion with other movement disorders or with a psychogenic disorder. The clinical heterogeneity of dystonia and some examples of misdiagnosis are reviewed here. The movement disorders that can be most commonly taken for dystonia are tremor, Parkinson's disease, myoclonus, chorea, and tics. Given the occurrence of confounding factors, along with specific genetic and laboratory test, it is of great importance to apply a specific algorithm to recognize the clinical signs of dystonia.