Objective: To provide the first detailed systematic investigation of the phenomenon of voluntary tremor suppression in Parkinson’s disease (PD).

Background: We have observed in the clinic that a number of patients with Parkinson’s can suppress their tremor at will for brief periods, via conscious mental and muscular relaxation. Despite an abundance of research on parkinsonian tremor focussing on its description and pathophysiology, to our knowledge, the ability to consciously diminish one’s resting tremor has not yet been reported nor assessed empirically.

Methods: We recruited patients who had self-identified they could suppress their tremor via an act of will, as well as patients who self-identified they could not voluntarily suppress their tremor. We tested 37 PD patients (on-medication) presenting with rest tremor in their upper limb. Participants completed a four minute trial consisting of alternating consecutive 30 s periods of resting tremor and 30 s periods of attempted tremor suppression. A tri-axis accelerometer attached over the middle phalanx of the index finger of the hand most affected by tremor measured tremor oscillations. Following double integration of the acceleration signal, principal component analysis was used to obtain the most dominant axis of tremor displacement. Changes in tremor characteristics associated with tremor suppression were examined with Bayesian multilevel modelling. Tremor amplitude and variability, and total power were log transformed prior to analysis.

Results: During tremor suppression, we found a reduction in mean tremor amplitude of 0.37 log(mm) (95% credible interval (CI) [0.22, 0.52]), and reduced tremor variability (reduction of coefficient of variation of 9%, 95% CI [2, 15]) compared to tremor at rest. Spectral analyses of the tremor signal between 3-10 Hz revealed a decrease in total power of 0.7 W/Hz (95% CI [0.4, 1.0]) and an increase in the median frequency by 0.24 Hz (95% CI [0.16, 0.32]) during tremor suppression compared to rest. Patients reported using a variety of strategies (concentration, relaxation, breathing control) to suppress their tremor.

Conclusions: Our patients showed modulation of key tremor characteristics during tremor suppression, providing the first empirical evidence that it is possible to exert significant conscious control over parkinsonian tremor.

« Back to 2018 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/voluntary-suppression-of-parkinsons-tremor/