ABSTRACT
INTRODUCTION The basal ganglia are thought to be the primary site of neuronal dysfunction in most of the movement disorders. Although most forms of dystonia do not have clearly identifi ed pathology, focal brain lesions that produce dystonia are most commonly located in the basal ganglia or thalamic target of the basal ganglia (1,2). Even in forms of dystonia where there is evidence for cerebral cortical abnormalities, basal ganglia abnormalities have also been identifi ed (3,4). Indeed, some authors view cortical dysfunction in dystonia as a secondary consequence of basal ganglia dysfunction (5-8). Although the evidence for basal ganglia abnormalities in many forms of dystonia is convincing, there is emerging evidence that dystonia involves abnormalities in many parts of the motor system, including the cerebellum (9-11). Nevertheless, knowledge of the organization and function of basal ganglia-thalamo-cortical circuits is important to understanding the pathophysiology of dystonia.
