Pointing in the right direction: Greater motor improvements with directional versus circular subthalamic nucleus deep brain stimulation for Parkinson's disease

BackgroundDirectional deep brain stimulation (DBS) provides more precise control of current spread than conventional ring-shaped electrodes. Whether this enhanced flexibility improves motor function is unclear.ObjectiveHere we examine whether directional and circular stimulation differentially impact motor performance in patients with Parkinson's disease.MethodsMotor behaviors were assessed in 31 patients who underwent unilateral subthalamic nucleus brain stimulation surgery (SUNDIAL, NCT03353688). Eight configurations, including 6 directional contacts and their corresponding rings), were evaluated during device activation. Objective measures of motor performance related to limb dexterity, gait, and overall mobility were evaluated in a double-blind fashion in the "off" medication state versus preoperative baseline, with stimulus amplitude at the center of the therapeutic window.ResultsSignificant changes in performance were observed across each of five motor tasks between the best and worst directional contacts on a given DBS row (p < 0.001 each task). Certain stimulation directions led to functional declines versus baseline, whereas the best direction yields greater improvement than ring stimulation (p = 0.005, p = 0.001, p = 0.007, p < 0.001, respectively, across tasks). Directional DBS improves therapeutic window and side effect thresholds versus ring stimulation (0.40 ± 0.94 and 0.35 ± 0.51 mA, p < 0.001, respectively), but these variables correlated only modestly with motor performance at a given stimulation site.ConclusionsOptimized directional subthalamic nucleus DBS yields better group-level motor performance than ring stimulation, in addition to its known advantages related to tolerability. Prospective studies should evaluate whether these improvements persist over longer time intervals.