Analysis of the time course of the effect of subthalamic nucleus stimulation upon hand function in Parkinson's patients.
BACKGROUND
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) as treatment for Parkinson's disease has been in use for more than a decade, yet the immediate effect of stimulation upon movement parameters is not well characterized.


OBJECTIVE
The goal of the current study is the identification of the best time point to test hand function after programming DBS devices.


METHODS
Reaction time, movement time and velocity were measured at multiple time points with a movement-sensitive glove after the deep brain stimulator had been turned on or off, during 'off medication' conditions.


RESULTS
Velocity, movement time and reaction time worsened significantly in the first 20 min after the deep brain stimulator had been turned off. A 'plateau effect' after 20 min was not observed. Initiation of stimulation led to immediate significant increases in movement time and velocity and to a lesser degree a decrease in reaction time. Patients performed more inconsistently over time after onset of stimulation compared to stimulation withdrawal. Intraoperative testing showed an immediate improvement in velocity after placement of the STN deep brain stimulator.


CONCLUSION
Movement time and velocity already reach their peak changes within 20 min after the deep brain stimulator has been reprogrammed, and therefore, this time point may be used to test the maximal clinical effect of stimulation.