Author response: Deep brain stimulation in early-stage Parkinson disease: Five-year outcomes

We appreciate the interest in our research1 of subthalamic nucleus (STN) deep brain stimulation (DBS) in early-stage Parkinson disease (PD). As noted in our publication, “Participants returned to the Vanderbilt Clinical Research Center (CRC) for annual outpatient study visits at years 3, 4, and 5, undergoing evaluations similar to the day 1 assessments conducted during the initial 2-year trial.” We would like to clarify that off -therapy tremor scores were not collected in follow-up years 3, 4, or 5 because of a lack of funding. We agree that reduced dyskinesia was expected because of the long-standing history of STN DBS being a potent therapy to reduce medications, and therefore dyskinesia, in advanced-stage Parkinson disease. We are, however, unaware of any other study that has shown that STN DBS reduces the risk of polypharmacy. This is an important new finding from the pilot trial of DBS in early-stage PD,1,2 given the well-established adverse effects associated with polypharmacy in older adults.3,4 The results of this study are encouraging, and we look forward to leading the FDA-approved [IDEG050016] phase III, multicenter, clinical trial of bilateral subthalamic nucleus deep brain stimulation implanted during very early-stage Parkinson disease.