Quantitative Assessment of Hand Dysfunction in Patients with Early Parkinson's Disease and Focal Hand Dystonia

Short term effects of contralateral tendon vibration on motor unit discharge rate variability and force steadiness in people with Parkinson's disease

Background

Vibration of one limb affects motor performance of the contralateral limb, and this may have clinical implications for people with lateralized motor impairments through vibration-induced increase in cortical activation, descending neural drive, or spinal excitability.

Objective

The objective of this study was to evaluate the effects of acute biceps brachii tendon vibration on force steadiness and motor unit activity in the contralateral limb of persons with Parkinson's disease.

Methods

Ten participants with mild to moderate Parkinson's disease severity performed a ramp, hold and de-ramp isometric elbow flexion at 5% of maximum voluntary contraction with the more-affected arm while vibration was applied to the distal biceps brachii tendon on the contralateral, less-affected arm. Using intramuscular fine wire electrodes, 33 MUs in the biceps brachii were recorded across three conditions (baseline, vibration, and post-vibration). Motor unit recruitment & derecruitment thresholds, discharge rates & variability, and elbow flexion force steadiness were compared between conditions with and without vibration.

Results

Coefficient of variation of force and discharge rate variability decreased 37 and 17%, respectively in post-vibration compared with baseline and vibration conditions. Although the motor unit discharge rates did not differ between conditions the total number of motor units active at rest after de-ramp were fewer in the post-vibration condition.

Conclusion

Contralateral tendon vibration reduces MU discharge rate variability and enhances force control on the more affected side in persons with Parkinson's disease.

Wuqinxi Exercise Improves Hand Dexterity in Patients with Parkinson's Disease

Objective

This study was designed to evaluate the effect of Wuqinxi after one session and 12-week intervention on hand dexterity in patients with Parkinson's disease (PD).

Methods

Forty-six elderly participants with mild-to-moderate PD were randomly assigned to the groups trained with Wuqinxi (n = 23) or stretching (n = 23). All participants practiced 60 min session of either of these exercises, 2 sessions a week for 12 weeks in standing position. The score of Purdue Pegboard Test (PPT) and time for Soda Pop Test (SPT) were performed to assess hand dexterity and motor function along assessing the 39 items of Parkinson's Disease Questionnaire before and after 12-week interventions. In addition, the PPT scores were compared before vs. after one session of either of these two exercise modes.

Results

Single session with either Wuqinxi or stretching exercise tended to improve PPT scores in PD patients. Furthermore, the improved SPT time was significant (P < 0.01) following 12-week training interventions with Wuqinxi (−1.32 ± 0.38 sec) or stretching (−0.89 ± 0.16 sec), which showed no group difference (P=0.734). However, only the participants in Wuqinxi group significantly improved the PPT scores of the dominant hand (+0.61 ± 1.34), both hand (+1.83 ± 3.13) and assemble (+2.04 ± 3.44) performance after 12-week training intervention. In parallel with improved hand dexterity and motor function, 12-week Wuqinxi training also significantly improved the patient's emotional wellbeing.

Conclusion

The Wuqinxi intervention could be safely and effectively applied to improve hand dexterity following single-session exercise or 12-week training, which were accompanied by improved quality of life in patients with mild-to-moderate PD.

Parkinsonian patients do not utilize probabilistic advance information in a grip-lift task

INTRODUCTION

Patients with Parkinson's disease (PD) are known to have decision-making impairments in tasks involving probabilistic information. How PD patients utilize task-relevant probabilistic advance information to plan and initiate common motor tasks like grasping has not yet been studied.

METHODS

PD patients (n = 15, OFF medication) and control participants repeatedly grasped and lifted an object, the weight of which could be light, medium, or heavy. Visual cues provided explicit probabilistic information about the upcoming weight at the start of each grip-lift trial. This information allows the force of the grasping fingers to be scaled predictively so that it matches the likely weight, with a suitable rate of initial force increase. Deterministic cues announced the upcoming weight with certainty in other grip-lift trials. In a weight adjustment experiment, participants associated each probabilistic cue with a specific heaviness.

RESULTS

The weight adjustment experiments showed that the probabilistic cues were understood correctly. However, PD patients utilized the probabilistic information significantly less than controls during the grip-lift task. Specifically, patients did not initiate their grasp more forcefully when probabilistic cues announced a high likelihood (66.7% probability) of a heavy weight, in contrast to controls. Thus, probabilistic cues that encouraged a more vigorous action had no effect in PD. Nevertheless, patients and controls scaled their forces appropriately when deterministic cues announced the forthcoming weights unambiguously.

CONCLUSIONS

PD patients do not invest a high movement effort to initiate a grip-lift unless the necessity of such a vigorous action initiation is decidedly clear.

Sensorimotor Control in Dystonia

This is an overview of the sensorimotor impairments in dystonia, a syndrome characterized by sustained or intermittent aberrant movement patterns leading to abnormal movements and/or postures with or without a tremulous component. Dystonia can affect the entire body or specific body regions and results from a plethora of etiologies, including subtle changes in gray and white matter in several brain regions. Research over the last 25 years addressing topics of sensorimotor control has shown functional sensorimotor impairments related to sensorimotor integration, timing, oculomotor and head control, as well as upper and lower limb control. In the context of efforts to update the classification of dystonia, sensorimotor research is highly relevant for a better understanding of the underlying pathology, and potential mechanisms contributing to global and regional dysfunction within the central nervous system. This overview of relevant research regarding sensorimotor control in humans with idiopathic dystonia attempts to frame the dysfunction with respect to what is known regarding motor control in patients and healthy individuals. We also highlight promising avenues for the future study of neuromotor control that may help to further elucidate dystonia etiology, pathology, and functional characteristics.