Objective: To evaluate the effect of horizontal current steering using a chronically implanted segmented lead and multiple independent current source technology on clinical effect and adverse effect (AE) thresholds of subthalamic nucleus (STN) deep brain stimulation (DBS) for Parkinson’s disease (PD).

Background: Optimal placement of DBS-electrodes in the dorso-lateral part of the STN to treat motor symptoms of PD is inevitably bond to a risk of current spread into the internal capsule or other adjacent structures inducing AE. The combination of a segmented electrode with multiple independent current source technology (Vercise PC, Boston Scientific, Valencia, USA) offers the possibility to control the extent and direction of current spread within the vertical and horizontal plane.

Methods: 7 PD patients eligible for STN-DBS were implanted bilaterally with segmented electrodes offering a proximal and distal ring contact and two segmented contacts in between (3 segments of 120° on two levels). The segmented contacts can either be stimulated equally together (simulating a classical ring mode) or with a flexible amount of cathodic or anodic current allowing a different horizontal shaping of the stimulation field. Effect (rigidity) and AE thresholds were evaluated using a monopolar review in medication OFF 4-9 days after implantation (and after 72 days in 2 patients) in classical ring mode as well as in directional mode (100% current through one segment or 50:50% between two adjactent segments).

Results: AE thresholds could be determined for all 14 STN. Due to stun effect after surgery we could only assess thresholds for rigidity improvement in 11 STN. In 10/11 STN at least one directional current steering setting had a greater therapeutic window (TW) compared to classical ring mode. The effect of directional current steering on the TW varied greatly between +400% to -100% (side effects before relief of rigidity) largely depending on the horizontal orientation of the electrical field vector.

Conclusions: Our preliminary data suggests that directional current steering through chronically implanted segmented electrodes allow to expand the therapeutic window in most cases compared to conventional ring mode. Double-blind studies with long-term follow up are now needed to proof advantages of this novel technology with respect to efficacy and adverse event rates of chronic subthalamic DBS.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-pilot-study-of-horizontal-current-steering-with-chronically-implanted-segmented-electrodes-for-stn-dbs-in-parkinsons-disease/