Return of bradykinesia after subthalamic stimulation ceases: Relationship to electrode location

In 20 subjects we quantified the rate at which subthalamic nucleus deep brain stimulation effects on Parkinson's bradykinesia “washed-out” after stimulation ceased. We found that wash-out was a two-step process, consisting of an initial fast decrease in stimulation's therapeutic effect, followed by a further, slow decline. Moreover, the relative contribution of the fast and slow components differed between patients. Finally, we found that lateral stimulation caused more of the fast-decaying component, while medial stimulation caused more of the slow-decaying component. This implies the existence of at least two separate mechanisms by which subthalamic nucleus deep brain stimulation improves bradykinesia, associated with activation of spatially separate zones in the vicinity of the subthalamic nucleus.

► STN DBS wash-out is a fast decrease, followed by a further slow decline.
► The relative contributions of the fast and slow processes differ between patients.
► The fast process is associated with lateral, and the slow with medial stimulation.
► This implies there are at least two distinct physiological mechanisms of STN DBS.
► Change in neuronal oscillation with DBS might relate to slow but not fast mechanism.