The dystonias.

The various dystonias have been found in at least five different hereditary backgrounds. The gene responsible for one of the dystonias, idiopathic torsion dystonia (ITD), lies on chromosome 9q32-34, with flanking markers now 1-2 cM apart. Magnetic resonance imaging and computerized tomography (CT) abnormalities in the basal ganglia, especially in the putamen, are found in many secondary dystonias. Botulinum toxin therapy is proving very useful in the treatment of focal dystonias.