Lesioning the thalamus for dyskinesia.

Recent advances on understanding the pallidothalamic relation lead us to perform Vim-Vo thalamotomy (combined thalamic lesion in ventralis intermedius nucleus and ventralis oralis nucleus) for cases with dyskinesia. In our recent series of thalamotomies, there are 12 cases of dyskinesia caused by various etiologies. Therefore the clinical manifestation of the involuntary movement was different in each case, including, more or less, some elements of irregular involuntary hyperkinetic movement. Stereotactic operation was performed using Leksell's apparatus aided by Surgiplan and MRI. The Vim nucleus was identified by physiological study using microelectrodes. High background activity and kinesthetic neurons are reliable indicators of Vim nucleus (but only for the lateral part). Then, selective coagulation was made by dual coagulation needles. Since the Vo nucleus is located just rostral to the Vim nucleus, the coagulation needle was turned toward the anterior part to partly cover the Vo nucleus. Thus, selective Vim-Vo thalamotomy was shown to be quite successful for the treatment of dyskinesia.