Objective: This observational study was aimed at assessing anatomical correlates of Volume of Tissue Activated (VTA) by directional stimulation.

Background: Deep Brain Stimulation (DBS) of subthalamic nucleus (STN) is an effective therapy for Parkinson’s Disease (PD). Lead positioning is crucial for therapy outcome [1]. Directional DBS systems allow horizontal current steering, focusing stimulation on a preferred direction and have been shown to increase therapeutic window in acute tests [2].

Method: We retrospectively studied a series of 19 consecutive patients implanted with directional systems in the STN (electrodes Cartesia, IPG Vercise™ PC or Gevia™ -Boston Scientific, Valencia,CA) treated with chronic stimulation (minimum follow up 6 months), programmed through conventional clinical algorithm. A dedicated post-operative visualization software (Boston Scientific© Guide™ XT) was used for reconstruction of anatomy (basal ganglia) respect to electrodes position, by merging preoperative MRI and postoperative CT scan. Chronically used stimulation parameters were imported in the visualization software to calculate VTAs. Electrodes anatomical reconstructions were evaluated by two independent raters (a neurosurgeon and a neurologist), and three categories were defined according to electrode position: misplaced (MIS) (electrodes placed outside the STN), peripherical (PER) electrodes positioned near to the nucleus borders and well placed (WP) in all the other cases.

Results: Among 38 implanted leads, 5 were categorized as MIS, 12 PER (9 near to the lateral, 2 near to the medial and 1 near to the posterior border of STN), and 21 WP. Directional stimulation was used in 100% of patients (80% in both electrodes). All PER electrodes were programmed in directional mode, with VTAs oriented in the direction of the target (STN). In 4 of 5 cases of electrode misplacements VTA reached STN.

Conclusion: We found a good consistency between anatomic reconstructions of the electrode position and VTA generated by stimulations settings programmed according to clinical response; indeed, VTA was shaped to sprout toward the target area and away from surrounding structures. Directional deep brain stimulation allows to focus stimulation within STN, despite variability in electrodes position.

References: [1] Wodarg, Herzog, Reese et al., Mov Dis, 2012 [2] Steigerwald et al, Movement Disorders, 2016

« Back to 2019 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/anatomical-correlates-of-vtas-in-directional-stn-dbs/