Delayed-onset hemidystonia and chorea following contralateral infarction of the posterolateral thalamus. A case report.

A 68 year-old man developed progressive hemidystonia and chorea 8 months after a contralateral thalamic stroke. The neurological examination also showed a right pyramidal syndrome without hemiparesis, a right horizontal sectoranopia, and a right hemihypesthesia for all sensory modalities. The MRI revealed infarctions in the left medial temporo-occipital lobes and left posterolateral thalamus, corresponding to the vascular territories of both the thalamo-geniculate and posterolateral choroidal arterial pedicles. The thalamic lesion involved the pulvinar, the lateral geniculate body, and the ventro-postero-lateral, dorso-lateral, posterolateral, and dorso-medial nuclei, but apparently did not extent to the ventrolateral thalamic nucleus, and the subthalamic and midbrain regions. Thalamic and striatopallidal dystonia have not a common pathophysiological mechanism. The involvement of the pulvinar nucleus and of the strategic crossing of proprioceptive, cerebellar, pyramidal, and subthalamic pathways may play a role in the genesis of the posterolateral thalamic dystonia.