Motor symptoms after deep brain stimulation of the subthalamic nucleus

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 efficacy of STN-DBS on non-dopaminergic motor symptoms remains less elucidated. In this study, we have examined short- and long-term impacts of STN-DBS on the development of the postural instability and gait difficulties (PIGD) phenotype, freezing of gait (FOG), and falls.

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final examination and compared our findings to the longitudinal development of the same symptoms in a non-operated, historical reference population.

During short-term follow-up after surgery, we observed a marked improvement in mean UPDRS-motor score from 27 to 18. We also found clear improvements in tremor, bradykinesia, rigidity, and PIGD scores. However, 6-9 years after surgery, all patients had a dominating PIGD pattern of parkinsonism and 50% of the patients had developed FOG and/or had become recurrent fallers. The disease development in a group of patients with PD from the presurgery period had a similar trajectory as among the operated patients. In addition, mean annual change of both bradykinesia and PIGD scores was nearly identical in both study groups while tremor and rigidity had a significant better development in the operated patients.

We found that STN-DBS induces an acute improvement of PIGD symptoms. The following long-term development was however characterized by a marked progression of non-dopaminergic symptoms.