The long-term development of non-motor problems after STN-DBS.

Objectives Stimulation of the subthalamic nucleus (STN-DBS) is an established treatment with long-term beneficial effects on motor symptoms in patients with Parkinson's disease (PD). The long-term development of non-motor problems after STN-DBS is not fully understood. In this study, we have studied how non-motor problems develop in patients with and without STN-DBS. Materials and methods We collected data from a prospectively followed cohort of patients that had been operated with STN-DBS 6–9 years before final examination and compared our findings to the longitudinal development of non-motor problems in a non-operated, comparable reference population. Results In general, the non-motor problems of advanced PD seem to develop independently of treatment with STN-DBS. We found that depressions do not worsen after STN-DBS, and the Montgomery and Aasberg Depression Rating Scale score in operated patients was substantially reduced from pre-operatively to post-operatively. Further, fatigue may represent an important unrecognized side effect of long-term stimulation, as fatigue was found to increase rapidly in operated patients already a year after surgery and continued to increase trough the 6- to 9-year follow-up. Conclusions The non-motor problems of advanced PD seem to develop independently of treatment with STN-DBS. This may influence the strategy for choice of when to perform this therapy for eligible patients.