Effect of subthalamic deep brain stimulation on turning kinematics and related saccadic eye movements in Parkinson disease

Background: Persons with Parkinson disease (PD) experience turning difficulty, often leading to freezing of gait and falls. Visual information plays a significant role in locomotion and turning, and while the effects of deep brain stimulation (DBS) on oculomotor function have been well documented, the effects of DBS on oculomotor function during turning and on turning itself have yet to be fully elucidated. Objective: To determine the effects of STN DBS on turning performance and related oculomotor performance in PD. Methods: Eleven subjects with PD and DBS of the subthalamic nucleus performed a seated voluntary saccade task and standing 180 degrees turns in DBS OFF and DBS ON conditions. Oculomotor data were captured using an infrared eye tracking system while segment rotations were measured using 3-D motion capture. Results: During the seated saccade task. DBS did not improve saccade amplitude or latency. DBS also did not improve gait velocity and stride length during forward walking. During turning, DBS improved turn performance (turn duration), reduced the number of saccades performed during the turns, and increased the amplitude and velocity of the saccade initiating the turn. DBS decreased the intersegmental latencies (eye-head, eye-foot, and head-trunk) but this effect was lost for eye-head and eye-foot after controlling for the duration of the first gait cycle. Conclusions: DBS significantly improves turn performance and related oculomotor performance. These findings add to the growing list of therapeutic benefits offered by DBS. (C) 2012 Elsevier Inc. All rights reserved.