Background Parkinson disease (PD) frequently causes difficulty turning that can lead to falls, loss of independence and diminished quality of life. Turning in tight spaces, which may be particularly impaired in PD, is an essential part of our daily lives, yet a comprehensive analysis of in-place turning has not been published. Objective The purpose of this study was to determine whether there are objective differences in turning between people with PD and unimpaired people. Methods We characterized turning in-place with kinematics and electromyographic (EMG) measures in 11 subjects with PD and 12 healthy people. We recorded kinematic data using a 3-D motion capture system in synchrony with EMG data from lower extremity muscles as participants turned 180 degrees. Those with PD were tested after overnight withdrawal of medication. Results Both groups used two distinct turning strategies. In one, the foot ipsilateral to the turning direction initiated the turn and in the other, the foot contralateral to the turning direction initiated the turn. Kinematic analysis demonstrated a cranio-caudal sequence of turning in the unimpaired group, whereas those with PD had a simultaneous onset of yaw rotation of the head, trunk, and pelvis. Thoses with PD also took longer time and more steps to complete turns. Overall lower extremity muscle activation patterns appeared similar between groups. Conclusion Differences between the groups were noted for axial control but lower extremity muscle patterns were similar. This work provides the foundation for development of new treatments for difficulty turning in PD.

Background-Bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor function in Parkinson disease (PD). However, little is known about the quantitative effects on motor behavior of unilateral STN DBS.

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We sought to determine the effect of deep brain stimulation (DBS) frequency on tremor suppression in essential tremor (ET) patients with deep brain stimulators implanted in the ventral intermediate nucleus (VIM) of the thalamus. A uniaxial accelerometer was used to measure tremor in the right upper extremity of subjects with a diagnosis of ET who had DBS electrodes implanted in the left VIM. The root-mean-square acceleration was used as the index of tremor magnitude and normalized to the OFF DBS condition. There was a highly significant inverse sigmoidal relationship between stimulation frequency and normalized tremor acceleration (X(2)/DoF = 0.42, r(2) = 0.997). Tremor acceleration had a nearly linear response to stimulation frequencies between 45 and 100 Hz with little additional benefit above 100 Hz. These findings have two important implications. Clinically, frequency of thalamic stimulation is an important variable for optimal tremor control with maximal benefit achieved with 100 to 130 Hz in most patients. Second, thalamic DBS provides tremor benefit in a graded manner and is not an all-or-nothing phenomenon.

Background and Purpose People with with Parkinson disease (PD) often have difficulty executing turns. To date, most studies of turning have examined subjects ON their anti-Parkinson medications. No studies have examined what specific aspects of turning are modified or remain unchanged when medication is administered. The purpose of this study was to determine how anti-Parkinson medications affect temporal and spatial features of turning performance in individuals with PD. Methods We examined turning kinematics in 10 people with PD who were assessed both OFF and ON medication. For both conditions, participants were evaluated with the UPDRS motor subscale, rated how well their medication was working on a visual analogue scale (VAS), performed straight-line walking and 180 degree in-place turns. We determined average walking velocity, time and number of steps to execute turns, sequence of yaw rotation onsets of the head, trunk, and pelvis during turns, and amplitudes of yaw rotation of the head, trunk, and pelvis during turns. Results Medication significantly improved UPDRS scores (p = 0.02), VAS ratings (p = 0.03), and walking velocity (p = 0.02). While improvements in turning were not statistically significant, medication did reduce the time and number of steps required to to turn, slightly increased the amplitudes of yaw rotation of the various segments, and increased the rotation of the head relative to the other segments. Medication did not improve the timing of segment rotations, which showed “en bloc” turn initiation in both the OFF and ON medication conditions. Discussion and Conclusion These results suggest that only certain aspects of turning may be responsive to anti-Parkinson medications. As such, additional rehabilitative approaches to address turning are needed, as turning may not be effectively addressed by pharmacological approaches. These results should be interpreted cautiously given the small sample size.