Intraoperative microelectrode and semi-microelectrode recording during the physiological localization of the thalamic nucleus ventral intermediate.

We review the techniques of physiological localization of the site for ventralis intermedius (Vim) thalamotomy or implantation of Vim-deep brain stimulation (DBS) for treatment of parkinsonian, essential, and intention tremor. Both microelectrode and semi-microelectrode techniques are reviewed. We believe the use of microelectrode and semi-microelectrode recordings in combination with Radiological landmarks provide the most accurate localization of the target. In addition to recording, microstimulation of subcortical structures such as Vim and thalamic nucleus ventralis caudal through the microelectrode may improve physiological identification by altering the tremor and evoking somatic sensations, respectively. Microelectrode recording provides the highest resolution picture of the target site at a cost of increased time to locate the target. We also review the relationship between thalamic neuronal firing and electromyographic activity during tremor. Implications of these results for the mechanisms for parkinsonian, essential, and intention tremors are discussed.