Clinical characteristics of Parkinson's disease developed from essential tremor

Background: Recent genetic and epidemiological studies have shown that there is a link between essential tremor and Parkinson's disease (PD). However, there is a lack of data about the clinical features of PD developed from essential tremor. Objective: To explore and describe the clinical characteristics of Parkinson's disease developed from essential tremor (ET-PD). Methods: Twenty-five ET-PD patients and 124 IPD controls were enrolled according to each criterion. Motor and non-motor features and dopamine transporter uptake were compared between the two groups. Results: Rest and action tremors were more severe in ET-PD patients than in IPD patients. In addition, tremor disorder of first-degree relatives occurred more frequently in the ET-PD group than in the IPD group. A comparison between cases with ET-PD and IPD was not significant for striatal dopamine transporter uptake. Among the non-motor features, sleep disorder frequency, especially rapid-eye-movement sleep behavioral disorder, were lower in patients with ET-PD than in those with IPD, and smell identification test scores were higher in patients with ET-PD than in those with IPD. The prevalence of other non-motor symptoms did not differ between the two groups. Conclusion: This is the first comparison of motor and non-motor features between ET-PD and IPD. ET-PD and IPD have different characteristic motor and non-motor features from the nosologic perspective.