gms | German Medical Science

Objective: While deep brain stimulation is a well-established treatment for Parkinson’s Disease, there are still multiple factors of discussion on its best performance, especially fhe value of awake DBS to guide the implantation process. Intraoperative assessment of symptom control and side effect threshold are considered the gold standard for the decision of the final trajectory. Here we focus on a retrospective analysis of prospectively collected data of intraoperative and post-operative best active contacts at one year follow up and related volume of tissue activated (VTA) models.

Methods: We analyzed 46 patients (15 female) with 92 STN leads who received STN-DBS between 2014-2018. The intraoperative best active contact was defined as the contact with the lowest current amplitude to achieve maximum therapeutic effect. To determine intraoperative stimulation location, semi-macro-test stimulation settings were applied to Guide XT software after fusion of the individual MRi and postoperative CT scan. The same procedure was repeated for the stimulation settings used one year after implantation.

Results: 96 intraoperative and 96 postoperative leads and VTAs were calculated. Average AC-PC coordinates for the best intraoperative contact were 12.4/2.9/3.1mm (lat./post./inf.) and 12.7/2.2/2mm for the one year follow up. Average vector distance was 2.4mm between intraoperative best contact and chronically used contact (range 0.2 – 7.7mm). The distance between centers of gravity of intra- versus postoperative VTAs did not show any correlation with motor outcome.

Conclusion: Our findings show a significant location difference between the best contact at intraoperative stimulation and the best active contact at one year follow up. VTA-modelling showed no correlation for the therapeutic effect and the overlap of intra- and postoperative VTAs. Since intraoperative testing is mostly limited to rigidity assessment, a more inferior/ caudal stimulation could selectively detect best rigidity control but not achieve the full scope of mobility improvement by STN-DBS. Interestingly, center of gravity for groups lied within the delineations of former published sweet spots. In view of the presented results, for the implantation procesdure of directional leads, the placement of one directional pole 1-2mm superior to the best intraoperative spot appears advisable.