Anatomical identification of active contacts in subthalamic deep brain stimulation

BACKGROUND: Subthalamic Deep Brain Stimulation is a valid surgical procedure for the treatment of idiopathic PD, although its precise mechanism of action is still unclear; moreover, there are no conclusive data about the functional anatomy of the human subthalamic region. Identifying the location of active contacts for StnDBS can yield interesting insights on the mechanisms of action of DBS and the different role played by the anatomical structures of the subthalamic region. METHODS: Twenty-five patients operated on for bilateral StnDBS were considered. During the surgical procedure, a complete intraoperative neurophysiological study was obtained by means of semimicrorecordings and stimulations. After surgery, an MRI study confirmed the position of the electrodes; MR images were subsequently superimposed onto a stereotactic atlas by using a dedicated workstation. The coordinates relative to the tip of the electrodes and active contacts were then calculated. RESULTS: Most of the electrode tips are located inside the subthalamus or immediately ventrally to it. Of the active contacts used for chronic stimulation, 96.5% are located in a well-defined anatomical region, which includes subthalamus, zona incerta, and FF. CONCLUSIONS: Our findings seem to suggest that other structures beyond the subthalamus itself play a clinical role in symptoms control after DBS for PD.