Objective: To investigate dopamine-responsiveness of resting tremor in Parkinson’s disease

Background: Unlike the core Parkinson motor symptom, bradykinesia, resting tremor has a variable response to levodopa. It appears that levodopa alleviates tremor approximately in only half of all patients. However, it is unclear whether there are two distinct tremor phenotypes (dopamine-responsive and dopamine-resistant) or whether these groups are two ends of a spectrum. Furthermore, it is unclear to what extent the dopamine response of resting tremor is different from that of bradykinesia.

Methods: We performed a standardized L-Dopa challenge in 76 tremulous Parkinson patients. Clinical scores (MDS-UPDRS part III) were collected OFF and ON dopamine (200/50 mg levodopa-benserazide). In both sessions, resting tremor intensity was quantified during REST and during cognitive co-activation (COCO), using accelerometry of both arms. We calculated the distribution of dopamine-responsiveness for resting tremor and for bradykinesia.

Results: Using clinical scores, the dopamine-response of bradykinesia showed a clear normal distribution. For resting tremor, the findings were more complex: the accelerometry findings showed a normal distribution of the dopamine-response at rest, but not during cognitive co-activation. The clinical dopamine-response of resting tremor failed to show a normal distribution, and fitted the distribution during cognitive co-activation. Comparison of the extreme groups of clinically most dopamine-responsive (improvement: 73-100%; n=16) and most dopamine-resistant tremor patients (improvement: 0-10%; n=15) revealed a higher prevalence of women (62.5% vs. 20%; p<0.02) in the dopamine-responsive group, with longer disease duration (3.44y vs. 2.21y; p<0.02), lower FAB scores (16.88 vs.17.53; p<0.05), and higher prevalence of dyskinesias (50% vs. 0%; p<0.01).

Conclusions: Unlike bradykinesia, the clinical dopamine response of resting tremor is not normally distributed. This effect appears to be modulated by the presence of cognitive stress, which makes the distribution more “abnormal”. The findings suggest that the dopamine-response of resting tremor is context-dependent, which argues against a clear division of resting tremor across two phenotypes. Female gender and the presence of dyskinesias is associated with a better dopamine-response of resting tremor.

« Back to 2017 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/the-occurrence-of-dopamine-responsive-and-dopamine-resistant-resting-tremor-in-parkinsons-disease/