Symptomatic paroxysmal hemidystonia due to a demyelinating subthalamic lesion.

We present a case of paroxysmal hemidystonia in a patient with an isolated demyelinating lesion in the subthalamic region, involving the posterior arm of the internal capsule and extending to the subthalamic nucleus and mesencephalon, possibly due to multiple sclerosis. Compared with similar reports in the literature, in our case there was a paucity of lesions, permitting a more direct clinico-anatomical correlation. The role of the subthalamic region and basal ganglia circuitry in the genesis of symptomatic dystonia is discussed.