The time course of the return of upper limb bradykinesia after cessation of subthalamic stimulation in Parkinson's disease.

To investigate the time span within which bradykinesia re-occurs, we registered movement parameters immediately after the termination of deep brain stimulation of the subthalamic nucleus (STN) in nine Parkinson patients with chronically implanted bilateral STN electrodes. Two repetitive movements were investigated: finger-tapping and forearm pronation-supination. When stimulation was switched off, the amplitude and velocity of the investigated movements significantly declined, but the frequency did not. The time course of this decline was modeled by an exponential function that yielded time constants between 15 and 30s. The effect of stimulation had completely disappeared within 1 min. These results suggest that it is necessary to wait at least for 1 min after the end of stimulation before performing further assessments.