Sustained Benefits of Deep Brain Stimulation of the Subthalamic Nucleus: A Five-Year Analysis of an Implantable Neurostimulator for the Treatment of Parkinson's disease (INTREPID)

Introduction: Deep Brain Stimulation (DBS) is the preferred treatment for Parkinson's disease (PD) when medications are insufficient to control symptoms. The INTREPID study was initiated to address gaps in DBS research, particularly the need for a large, double-blind, sham-controlled, randomized clinical trial. This phase of the study aimed to evaluate the long-term effectiveness and safety of subthalamic nucleus (STN) deep brain stimulation (DBS) in an open-label study design with a 5-year follow-up.

Methods: The INTREPID 5-year follow-up study was a multicentre trial that included 191 patients with moderate to advanced PD who were implanted with the Vercise DBS system. Following a 12-week blinded phase, participants transitioned to an open-label phase and were followed for 5 years. Primary outcomes included changes in UPDRS (Unified Parkinson's Disease Rating Scale) scores, dyskinesias, quality of life measures, and safety assessments.

Results: Out of 191 participants, 137 (72%) completed the follow-up study. Significant improvements were observed in UPDRS Ill scores (medications OFF and stimulation ON), indicating a 45% improvement in motor function that was sustained over 5 years. UPDRS II scores demonstrated a 20% improvement in activities of daily living from screening. Quality of life, measured by Parkinson's Disease Questionnaire- 39 (PDQ-39), showed substantial initial improvements which gradually declined but remained above screening levels at 5 years. The most reported serious adverse event related to the device or procedure was infection, occurring in 9 subjects. No unanticipated adverse events were reported.

Conclusion : The study demonstrates that STN-DBS using the Vercise system leads to significant improvements in motor function and activities of daily living, a reduction in antiparkinsonian medication and high patient satisfaction with the treatment that was sustained over a 5-year period in patients with moderate to advanced PD.