Proprioceptive muscle tendon stimulation reduces symptoms in primary orthostatic tremor
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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.
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.
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.
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.
KeywordsOrthostatic tremor Muscle tendon vibration Proprioception Tremor Body sway Unsteadiness
Conceived and designed the study: MW, CS, and RS. Performed the study: MW, CS, KM, and RS. Performed statistical analysis: MW. Wrote the paper: MW. Critical revision of the manuscript: CS, KM, and RS.
This work was supported by the German Federal Ministry of Education and Research (01EO1401).
Compliance with ethical standards
Conflicts of interest
The authors declare that they have no competing interests.
All experimental procedures were approved by the appropriate Ethics Committee.
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