[Dystonia: concepts, classification, and physiopathology]

Since the last decades of the past century there have been several reports in the medical literature describing patients with dystonia. The clinical and phenomenological concepts of dystonic movements have been debated. Presently, dystonia is defined as a syndrome of sustained muscle contractions, frequently causing twisting and repetitive movements, or abnormal postures. Dystonia is usually classified according to three criteria: distribution, age of onset and etiology. The generalized forms often have their onset at childhood whereas the focal forms are most commonly seen in adults. Dystonic movements and postures can occur during resting or they can be precipitated by voluntary movements or by the adoption of specific posture patterns. The pathophysiologic mechanisms related to the appearance of dystonia are presently unknown. However, there are compelling evidences suggesting the involvement of some basal ganglia nuclei (e.g. putamen and globus palidus) in the development of dystonia.