Walking in orthostatic tremor modulates tremor features and is characterized by impaired gait stability.

Primary orthostatic tremor (OT) is characterized by high-frequency lower-limb muscle contractions and a disabling sense of unsteadiness while standing. Patients consistently report a relief of symptoms when starting to ambulate. Here, we systematically examined and linked tremor and gait characteristics in patients with OT. Tremor and gait features were examined in nine OT patients and controls on a pressure-sensitive treadmill for one minute of walking framed by two one-minute periods of standing. Tremor characteristics were assessed by time-frequency analysis of surface EMG-recordings from four leg muscles. High-frequency tremor during standing (15.29 ± 0.17 Hz) persisted while walking but was consistently reset to higher frequencies (16.34 ± 0.25 Hz; p < 0.001). Tremor intensity was phase-dependently modulated, being predominantly observable during stance phases (p < 0.001). Tremor intensity scaled with the force applied during stepping (p < 0.001) and was linked to specific gait alterations, i.e., wide base walking (p = 0.019) and increased stride-to-stride fluctuations (p = 0.002). OT during walking persists but is reset to higher frequencies, indicating the involvement of supraspinal locomotor centers in the generation of OT rhythm. Tremor intensity is modulated during the gait cycle, pointing at specific pathways mediating the peripheral manifestation of OT. Finally, OT during walking is linked to gait alterations resembling a cerebellar and/or sensory ataxic gait disorder.

Proprioceptive muscle tendon stimulation reduces symptoms in primary orthostatic tremor.

INTRODUCTION: Primary orthostatic tremor (OT) is characterized by high-frequency lower limb muscle contractions and a disabling sense of unsteadiness while standing. To date, therapeutic options for OT are limited. Here, we examined the effects of proprioceptive leg muscle stimulation via muscle tendon vibration (MTV) on tremor and balance control in patients with primary OT. METHODS: Tremor in nine patients with primary OT was examined during four conditions: standing (1), standing with MTV on the bilateral soleus muscles (2), lying (3), and lying with MTV (4). Tremor characteristics were assessed by frequency domain analysis of surface EMG recordings from four leg muscles. Body sway was analyzed using posturographic recordings. RESULTS: During standing, all patients showed a coherent high-frequency tremor in leg muscles and body sway that was absent during lying (p < 0.001). MTV during standing did not reset tremor frequency, but resulted in a decreased tremor intensity (p < 0.001; mean reduction: 32.5 ± 7.1%) and body sway (p = 0.032; mean reduction: 37.2 ± 6.8%). MTV did not affect muscle activity during lying. Four patients further reported a noticeable relief from unsteadiness during stimulation. CONCLUSION: Proprioceptive stimulation did not reset tremor frequency consistent with the presumed central origin of OT. However, continuous MTV influenced the emergence of OT symptoms resulting in reduced tremor intensity, improved posture, and a relief from unsteadiness in half of the examined patients. These findings indicate that MTV either directly interferes with the peripheral manifestation of the central oscillatory pattern or prevents proprioceptive afferent feedback from becoming extensively synchronized at the tremor frequency.

Normative data for arm swing asymmetry: how (a)symmetrical are we?

Arm swing asymmetry during gait may be a sensitive sign for early Parkinson's disease. There is only very limited information about how much asymmetry can be considered to be physiological. To assess the normal range of arm swing asymmetry, we investigated 60 healthy subjects. The influence of age, gender, and additional mental tasks (dual-tasking) on arm swing asymmetry was assessed. Limb kinematics of 60 healthy persons in three age groups (between 40 and 75 years) were measured with an ultrasound motion capture system while subjects walked on a treadmill. Treadmill velocity was varied (3 steps) and mental loads (2 different tasks) were applied in different trials. Additionally, a group of 7 patients with early Parkinson's disease was investigated. Arm swing amplitude as well as arm swing asymmetry varied considerably in the healthy subjects. Elderly subjects swung their arms more than younger participants. Only the more demanding mental load caused a significant asymmetry, i.e., arm swing was reduced on the right side. In the patient group, asymmetry was considerably higher and even more enhanced by mental loads. Our data indicate that an asymmetry index above 50 (i.e., one side has twice the amplitude of the other) may be considered abnormal. Evaluation of arm swing asymmetry may be used as part of a test battery for early Parkinson's disease. Such testing may become even more important when disease-modifying drugs become available for Parkinson's disease.

WITHDRAWN: Treatment outcome of visual feedback training in an adult patient with habitual toe walking.

Ahead of Print article withdrawn by publisher.

Impact of tasks and users' characteristics on virtual reality performance.

A better understanding of how users perform virtual reality (VR) tasks may help build better VR interfaces. In this study, we concentrated on the compensatory behavior in VR depending on the tasks and users' characteristics. The tasks characteristics considered were display size (large display vs. desktop monitor) and tasks types (manipulation and travel). The users' characteristics studied were the visual attention abilities and users' satisfaction. Ninety-five subjects participated in the experimentation composed of two parts: the first one consisted in cognitive tests used to evaluate visual attention abilities, and the second one was based on a set of VR tasks. Our result showed that large displays positively affect on performance for some kinds of VR tasks. Moreover, this impact was linked to users' satisfaction and visual attention abilities. Indeed, users with low-level attention abilities and users who preferred the large display took more advantage of large displays. We concluded that large displays can be considered cognitive aids depending on the tasks and users' characteristics.

[A rare cause of stroke in a patient with a cardiac pacemaker]. / Etiologie rare d'accident vasculaire cérébral ischémique chez un patient ayant un stimulateur cardiaque.

The authors report the case of a 78 year old woman admitted to hospital for recurrent cerebrovascular accidents, the initial investigation of which was normal. This pacemaker patient had a displacement of the definitive ventricular pacing catheter which was positioned in the left ventricle through a patent foramen ovale. The diagnosis was suspected on clinical and echocardiographic examination and confirmed by transthoracic and transoesophageal echocardiography. In view of the risk of systemic embolism, the pacing catheter was repositioned by an endovascular approach in the right ventricle.