Attenuation of pathological tremors by functional electrical stimulation. I: Method.
In this study we explored the possibility of suppressing pathological tremors using closed-loop functional electrical stimulation (FES) to activate the tremorogenic muscles out-of-phase. A displacement signal monitored with a transducer was filtered so as to be "tuned" to the tremor frequency at the wrist or elbow. The filtered signal was used to amplitude-modulate the electrical stimulation. The design process was based on measurements of the open-loop frequency response characteristics of the forearm and hand to stimulation of the elbow and wrist flexors and extensors in a number of subjects. These data allowed us to identify closed-loop configurations, which attenuated 2-5 Hz tremors substantially, while only minimally attenuating functional movements in the 0-1 Hz range. There was a fairly delicate balance between efficacy and the risk of instability. However, designs were identified that offered enough tremor suppression and adequate immunity to muscle/load variations for the technique to be considered seriously for clinical application.
Prochazka
A
A
Division of Neuroscience, University of Alberta, Edmonton, Canada.
Elek
J
J
Javidan
M
M
D004558:Electric Stimulation; D005542:Forearm; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D009068:Movement / Q000502:physiology; D009132:Muscles / Q000502:physiology; D012016:Reference Values; D014202:Tremor / Q000503:physiopathology*