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 mesen
cephalon, 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 r
egion and basal ganglia circuitry in the genesis of symptomatic dystonia is
discussed.