Motor and Non-motor Features: Differences between Patients with Isolated Essential Tremor and Patients with Both Essential Tremor and Parkinson’s Disease

Abstract

BACKGROUND Patients with essential tremor (ET) who develop Parkinson's disease (PD) (i.e., ET→PD) may differ with respect to motor features (MFs) and non-motor features (NMFs) from patients with isolated ET. Few studies have assessed this issue. METHODS In this retrospective chart review, we analyzed data on MFs and NMFs of 175 patients, including 54 ET→PD and 121 ET, actively followed in the Athens University 1st Neurology Department. RESULTS Significantly more ET→PD than ET patients reported asymmetric tremor at ET onset (68.5% vs. 14.9%, p<0.001). Significantly more ET than ET→PD patients had head tremor (43.5% vs. 13.2%, p<0.001) and cerebellar signs (41.3% vs. 9.3%, p<0.001). More ET than ET→PD patients reported hearing impairment (65.3% vs. 28.3%, p<0.001) and restless legs syndrome (34.8% vs. 3.7%, p<0.001). Conversely, a larger proportion of ET→PD than ET patients reported rapid eye movement behavior disorder (51.9% vs. 10.0%, p<0.001), constipation (67.9% vs. 36.4%, p<0.001), and olfactory dysfunction (83.3% vs. 36.4%, p<0.001). DISCUSSION The subset of ET→PD patients may have distinct MFs and NMFs that should be assessed further for the possible predictive value for the emergence of PD.