Physiologic changes associated with cerebellar dystonia.

Dystonia is a neurologic disorder characterized by sustained involuntary muscle contractions. Lesions responsible for unilateral secondary dystonia are confined to the putamen, caudate, globus pallidus, and thalamus. Dysfunction of these structures is suspected to play a role in both primary and secondary dystonia. Recent evidence has suggested that the cerebellum may play a role in the pathophysiology of dystonia. The role of the cerebellum in ataxia, a disorder of motor incoordination is well established. How may the cerebellum contribute to two apparently very different movement disorders? This review will discuss the idea of whether in some cases, ataxia and dystonia lie in the same clinical spectrum and whether graded perturbations in cerebellar function may explain a similar causative role for the cerebellum in these two different motor disorders. The review also proposes a model for cerebellar dystonia based on the available animal models of this disorder.