Long-term follow-up of subthalamic nucleus deep brain stimulation in patients with Parkinson's disease: An analysis of survival and disability milestones

Background: Data on the long-term survival and incidence of disability milestones after subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson's disease (PD) is limited. Objectives: To estimate mortality and assess the frequency/time-to-development of disability milestones (falls, freezing, hallucinations, dementia, and institutionalization) among PD patients post STN-DBS. Methods: A longitudinal retrospective study of patients undergoing STN-DBS. For mortality, Cox proportional hazards regression analysis was performed. For disease milestones, competing risk analyses were performed and cumulative incidence functions reported. The strength of association between baselines features and event occurrence was calculated based on adjusted hazard ratios. Results: The overall mortality for the 109 patients was 16 % (62.1 +/- 21.3 months after surgery). Falls (73 %) and freezing (47 %) were both the earliest (40.4 +/- 25.4 and 39.6 +/- 28.4 months, respectively) and most frequent milestones. Dementia (34 %) and hallucinations (32 %) soon followed (56.2 +/- 21.2 and mean 60.0 +/- 20.7 months after surgery, respectively). Higher ADL scores in the OFF state and higher age at surgery were associated with falls, freezing, dementia and institutionalization. Conclusions: Long-term mortality rate is low after STN-DBS. Disease milestones occur later during the disease course, with motor milestones appearing first and at a higher frequency than cognitive ones.