Directional Leads for Deep Brain Stimulation: Technical Notes and Experiences

Abstract

Objective: Deep brain stimulation (DBS) is an approved treatment for movement disorders. Despite high precision in electrode placement, side effects do occur by current spread to adjacent fibers or nuclei. Directional leads (D-leads) are designed to adapt the volume of stimulation relative to the position within the target by horizontal and vertical current steering directions. The feasibility of implanting these new leads, possible difficulties, and complications were the focus of this study.

Material and methods: This analysis is based on 31 patients who underwent a DBS procedure with D-leads and an implantable pulse generator (IPG) capable of multiple independent current control and 31 patients who received non-D-leads with a similar IPG. While trajectory planning and most steps of the surgical procedure were identical to conventional DBS lead implantation, differences in indication, electrode handling, lead control, and complications were documented and analyzed in comparison to a control group with ring electrodes.

Results: During a consecutive series of 51 patients implanted with a DBS system, 31 patients (60.1%) were selected for implantation of D-leads and received 59 D-leads, 28 bilateral, and 3 unilateral implantations. The control group consisted of a consecutive series of a comparable time period, with 31 patients who received conventional ring electrodes. Indication of D-lead implantation was based on the anatomic conditions of the trajectory and target regions and the results of intraoperative test stimulations. In 1 patient, primary D-lead implantation on both sides was performed without any microelectrode implantation to minimize risk for hemorrhage. In the absence of an externally visible marker, the control of implant depth and of the orientation of the D-lead needs to be controlled by X-ray resulting in a longer fluoroscopy time and, therefore, higher X-ray dose compared to conventional lead implantations (415.53 vs. 328.96 Gy cm2; p = 0.09). Mean procedure duration for complete system implantation did not differ between either type of leads (ring electrodes vs. D-leads, 08:55 vs. 09:02 h:min). Surgical complications were unrelated to the type of electrode: surgical revision was necessary and successfully performed in 1 subcutaneous hematoma and 1 unilateral electrode dislocation. A rather rare complication, symptomatic idiopathic delayed-onset edema, was observed in 4 patients with D-leads. They recovered completely within 1-3 weeks, spontaneously or after short-term cortisone medication. In the control group, in a series of 31 patients (20 implanted with Medtronic 3389 lead and 11 with Boston Scientific Vercise lead), not a single problem of this kind was encountered at any time.

Conclusion: Precise positioning of D-leads is more challenging than that of conventional DBS leads. By adding an external lead marker, control of optimal lead position and orientation is enhanced. In case of supposed increased risk for hemorrhage because of vessels crossing all possible trajectories in the pre-surgical navigated simulation program, primary D-lead implantation instead of the sharper microelectrodes may be a feasible alternative and it may offer more options than ring electrodes especially in these cases. Prospective studies comparing ring-mode stimulation to directional stimulation to examine the differences of the clinical effects have been started.

Keywords: Complications; Deep brain stimulation; Directional leads; Functional neurosurgery; Movement disorder surgery.