Tremor suppression orthoses for parkinson’s patients: A frequency range perspective

While the majority of tremor-afflicted Parkinsonian (PD) patients suffer from rest tremors, which is not considered highly disabling, a portion of these PD patients also demonstrate action tremors that interfere with their daily lives. Two main considerations in designing an orthosis that aims at suppressing the tremor, are the frequency bands of the tremor and the joints tremor affects. Nine subjects, which included six healthy people, two PD patients with typical tremor afflictions, and a PD patient with severe tremor of not only in her fingers and wrist, but also in her elbow, participated in this study. The highly afflicted patient displayed the need for tremor suppression in action as well as when in rest. The study focuses on uncommon elbow tremors and demonstrates that, for typically afflicted patients, tremor amplitudes are comparable to healthy subjects, but the frequency distribution of the tremors are different at high levels of elbow torque. For the highly afflicted patient, both tremor amplitude and its frequency distribution are different at all levels of elbow torque. The study further investigates the tremors in two bands of frequency on both hands of the highly troubled patient before, and after medication. The two bands are those of classical Parkinsonian tremor (4-6 Hz) and physiological (or enhanced physiological) tremor (8-12 Hz). Power spectrum and tremor amplitude comparisons reveal that, for part of tremulous PD patients, both tremors coexist and, depending on the level of affliction, the designed orthosis needs to suppress tremors in both bands, even at more proximal joints, such as the elbow.