Outcomes, management, and potential mechanisms of interleaving deep brain stimulation settings

Introduction: DBS is a therapeutic option for patients with Parkinson disease (PD), tremor and dystonia. In patients who experience suboptimal clinical results with conventional programming (monopolar, double monopolar or bipolar settings), interleaved pulses can sometimes be used to provide differential therapeutic benefits with the possibility of fewer side effects. Interleaving allows a clinician to define two "programs" that automatically alternate. The goal of this paper is to 1) present clinical scenarios where DBS interleaving was used across two clinics to provide improved symptom control in three patients with suboptimal results from conventional programming; 2) address the potential mechanisms of interleaving; and 3) provide practical tips on the use of interleaving. Methods: Three patients were formally compared for therapeutic benefit on interleaved and conventional parameter settings. Results: Interleaving is most likely to be useful in two clinical scenarios: 1) different contacts are beneficial for specific symptoms, but each at a different stimulation amplitude; or 2) symptoms are resolved incompletely, and further voltage increase is limited by side effects. The factors underpinning the differences in outcomes with interleaving are unknown but may be highly dependent on specific symptoms and to electrode positioning. Interleaving is a relatively new programming platform and there is no data to demonstrate long-term benefits. Conclusions: Interleaving is a tool that may augment outcomes, and possibly obviate the need for surgical revisions, although in our experience across two large centers it has been effective for only a small number of patients.