Features in essential tremor and the development of Parkinson's disease vs. parkinsonism

Patients with essential tremor (ET) are at higher risk to develop Parkinson's disease (PD). Recent studies suggest that propranolol (common treatment for ET) can augment pathologic expression of alpha-synuclein. We studied features associated with the development of Parkinson's disease with antecedant essential tremor (ET-PD) compared with ET-plus with parkinsonism (PK).

Retrospective case series from a tertiary movement disorders center including patients with ET and PD, found to have ET-PD or ET-plus (PK).

We analyzed two groups: (1) ET-plus (PK) (n = 33) and (2) ET-PD (n = 35). Constipation and anosmia were more common in the ET-PD group (73% and 48%) than in the ET-plus (PK) group (33% and 19%). The ET-plus (PK) group was more likely to undergo dopamine transporter (DAT) scans compared with the ET-PD group (73% vs. 34%) and less likely to receive levodopa trials (21% vs. 91%). There were no significant differences in self-reported REM sleep behavior disorders or beta-blocker use. Similar rates of depression, anxiety, cognitive complaints, and family history of tremor or PD were reported in both groups.

ET-PD and ET-plus (PK) can be clinically difficult to differentiate as they have overlapping motor and non-motor features. Beta-blocker use did not predict development of ET-PD or ET-plus (PK); however, anosmia and constipation may be helpful non-motor distinguishing features. DAT scans and levodopa trials may be valuable in clarifying the diagnoses.