Stereotactic Selective Thalamotomy for Focal Dystonia with Aid of Depth Microrecording

Long-term effectiveness of selective ventralis intermedius nucleus (VIM)-ventralis oralis nucleus (VO) thalamotomy with depth microrecording for the treatment of focal dystonia was evaluated. The optimal thalamic areas for controlling focal dystonia were studied based on the electrophysiologic and anatomic data.

Stereotactic selective VIM-VO thalamotomy with depth microrecording was carried out in 8 patients with focal arm and hand dystonia and in 1 patient with cervical dystonia. Electrophysiologic data on the lateral part of thalamic VIM were studied in patients with focal dystonia. A very small and narrow therapeutic lesion was formed in the shape of a square on the sagittal plane and of an I, rotated V, Y, or inverse Y on the axial plane in the VIM-VO, which covered the kinesthetic response area topographically related to focal dystonia. Patients with arm and hand dystonia were followed up for 4.7 ± 3.0 years and 1 patient with cervical dystonia was followed up for 18.2 years.

Marked improvement of focal dystonia was shown by functional assessment using the Unified Dystonia Rating Scale. Transient dysarthria was recognized in 1 patient. The sequence of body localization of kinesthetic response in the VIM was clearly shown in patients with focal dystonia. Decreases in the amplitude and amplitude ratio of electromyography on the forearm muscles were markedly significant after VIM thalamotomy, but insignificant after VO thalamotomy immediately after VIM thalamotomy.

Marked reduction of electromyographic tonic discharges of focal dystonia was shown after VIM lesioning. Selective VIM-VO thalamotomy showed good and long-term stable effects for focal dystonia.