Clinical characteristics and topography of lesions in movement disorders due to thalamic lesions

Objective: To determine which thalamic subnuclei are involved in symptomati c unilateral movement disorders due to localized thalamic infarction, and t he clinical characteristics of these abnormal movements. Methods: The autho rs studied 22 patients with thalamic infarcts for their clinical presentati on and the topography of the lesions, using three-dimensional Tl-weighted M RI sequencing and stereotaxic analysis of the lesions. Results: Patients we re divided into four groups: 1) absence of abnormal involuntary movements ( AIM) (nine patients); 2) isolated dystonic posture (two patients); 3) myocl onic dystonia (five patients); and 4) tremor or myoclonus (six patients). I n patients with AIM, thalamic lesions were contralateral to the abnormal mo vements, involving the thalamogeniculate territory, centered on the ventral intermediate (Vim) and ventral caudal (Vc) nuclei. No significant differen ce in the volumes or center of mass of the lesions was found between patien ts with tremor and myoclonus and patients with dystonia, although the centr al nucleus and the internal part of the Vim nucleus were more consistently damaged in dystonic patients. Conclusion: Movement disorders related to tha lamic lesions included: 1) myoclonic dystonia with predominating myoclonus and "thalamic" hand associating dystonic posture and slow, pseudo-athetoid movements, both related to lesions in the Vim and Vc nuclei of the thalamus ; and 2) postural and action tremor, also related to lesions in the Vim, si milar to tremor associated with midbrain lesions, as a result of abnormal f unctioning of the cerebello-thalamic pathways.