Effects of medication on turning deficits in individuals with Parkinson's disease

Abstract

Background and purpose: People with Parkinson's disease 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 Parkinson's disease.

Methods: We examined turning kinematics in 10 people with Parkinson's disease who were assessed both OFF and ON medication. For both conditions, participants were evaluated with the Unified Parkinson's Disease Rating Scale motor subscale, rated how well their medication was working on a visual analog scale, and performed straight-line walking and 180-degree in-place turns. We determined the 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 the Unified Parkinson's Disease Rating Scale scores (P = 0.02), visual analog scale ratings (P = 0.03), and walking velocity (P = 0.02). Although improvements in turning were not statistically significant, medication did reduce the time and number of steps required 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 because turning may not be effectively addressed by pharmacologic approaches. These results should be interpreted cautiously given the small sample size.

Figure 1

Onsets of yaw rotation for the head (A), trunk (B), and pelvis (C) for each individual. Onset times are expressed as a percentage of the gait cycle, with 0% representing the time of liftoff for the first step of the turn. Filled circles show values when OFF medication and open circles are ON medication. The group average OFF medication is shown with the solid vertical line and ON medication with the dashed vertical line. The dotted vertical line shows normative values previously reported for age-matched control subjects. ES = effect size, p-values are for paired t-tests comparing ON to OFF

Figure 2

Amplitudes of absolute rotation of the head (A), trunk (B), and pelvis (C) during the first stride of the turn for each individual. Filled circles show values when OFF medication and open circles are ON medication. The group average OFF medication is shown with the solid vertical line and ON medication with the dashed vertical line. The dotted vertical line shows normative values previously reported for age-matched control subjects. ES = effect size, p-values are for paired t-tests comparing ON to OFF