Objective: to evaluate the effect of tremor provocation on re-emergent tremor latency and variability.

Background: Rest and re-emergent tremor (RET) in Parkinson’s disease (PD) are known to be markedly variable. A recent study has shown that RET pause duration is inversely correlated with its amplitude.

Method: We performed a prospective observational study in 21 PD patients with RET. Evaluations were conducted by accelerometric analysis of hand movements with and without provocation by counting backwards from 100 out loud, in the OFF state. Differences in RET pause duration, tremor power at peak frequency, root mean square (RMS) and slope of return of the tremor after the pause was measured. Inter- and intra-subject variability were also calculated.

Results: RET pause duration showed a 75% decrease after provocation (p<0.001), which led to zero in 52% of cases, as compared to 9% in unprovoked measurements (p<0.001). Provocation also led to a 257% increase in tremor power (p<0.001), a 137% increase in RMS (p<0.001) and 247% increase in slope (p<0.001). A significant decrease in inter-subject variability was also observed (p=0.001).

Conclusion: Tremor provocation leads to RET amplitude increase, pause shortening, and variability decrease. Therefore, while provocation can be recommended for the evaluation of rest tremor in clinical practice, provocation might well annul its value for identifying the pause prior to re-emergent tremor.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/re-emergent-tremor-provocation/