Attenuation of pathological tremors by functional electrical stimulation II: Clinical evaluation

Abstract

In this study we evaluated a technique for tremor suppression with functional electrical stimulation (FES), the technical details of which were described in the previous paper. Three groups of patients were investigated: those with essential tremor, parkinsonian tremor, and cerebellar tremor associated with multiple sclerosis. In each group, tremor was attenuated by significant amounts (essential tremor: 73%; parkinsonian tremor: 62%; cerebellar tremor: 38%). These attenuations were in good accord with predictions based on the dynamic analyses and filter designs derived in the previous paper. With filters "tuned" to the lower mean tremor frequency encountered in the cerebellar patients, more attenuation was possible in this group as well. We identified some practical limitations in the clinical application of the technique in its present form. The most important was that in daily use, only one antagonist pair of muscles can realistically be controlled. At first sight, this restricts the usefulness of the system to patients with single-joint tremors. However, the concomitant use of mechanical orthoses may broaden the scope of application.

Sensory electrical stimulation for suppression of postural tremor in patients with essential tremor

“…On the other hand, electrical systems were also used for tremor suppression as Javidan, Prochazkal, and Maneski suggested functional electrical stimulation (FES) as a method for tremor suppression [12][13][14]. In these studies, electrical motor stimulation (with the intensity greater than motor threshold) was applied to the muscles acting in the direction opposite to the joint movement.…”

Closed-Loop Modulation of a Notch-Filter Stimulation Strategy for Tremor Management with a Neuroprosthesis

“…This resembled a notch filter at the selected frequency, which was selected in accordance to that expected for the different types of tremor [2,7]. However, in [7], the assumed frequency was not corrected during the experiments, which might be problematic given that the characteristics of tremor vary depending on the conditions (as the authors mentioned in the report of the experimental validation [8]). A conceptually identical strategy, but with frequency adaptation was implemented and successfully validated in a recent work [10].…”

“…Neuroprostheses (NPs) may be regarded as a special type of wearable orthoses, in which actuators are replaced by neural interfaces that stimulate the affected muscles. In [7], the authors proposed the first design of a table-mounted NP for tremor suppression, which provided a significant improvement [8] of the major types of tremor. In spite of the successful results it attained, a number of aspects should be improved to facilitate its translation into a product that improves the patients' quality of life, mainly: i) the NP should ideally be wearable system, and ii) the NP should adapt the stimulation it delivers to the ongoing characteristics of the tremor (mainly its severity).…”

Electrical stimulation for the suppression of pathological tremor

“…The alternative to application of the exoskeleton for the suppression of tremor is to use functional electrical stimulation (FES), which would eliminate or minimize this abnormality. The first FES system that was designed to suppress tremor was proposed 20 years ago [6,15]. In this system, trains of lowlevel electrical current pulses activated wrist extensor and flexor muscles, while wrist joint flexion and extension were estimated from data collected by a displacement sensor.…”