A comparison between rate of nonmotor symptom development in essential tremor and Parkinson’s disease

In the last decade our perspective on essential tremor (ET) as a pure motor system disorder has begun to change. By virtue of recent studies of nonmotor symptoms (NMSs) that are used to characterize Parkinson’s disease (PD), these symptoms have also been added to the definition of ET. There is increasing evidence to suggest that ET might not be as benign and monosymptomatic as we previously thought. The aim of this study was to evaluate nonmotor symptoms in ET, and to compare them with PD. We studied 37 ET and 23 PD patients. Tremor rate was evaluated using the Fahn–Tolosa–Marin tremor rating scale (FTM-TRS) in ET patients. The patients with PD were scored for motor symptoms using the unified Parkinson’s disease rating scale (UPDRS)-III and the Hoehn–Yahr scale. Cognitive functions were assessed with the Montreal Cognitive Assessment (MoCA) test. NMSs were evaluated with the nonmotor symptoms questionnaire (NMSQuest). In the ET group, the most common NMSs were forgetting things, feeling sad, nocturia, urgency, and difficulty concentrating. The mean NMSQuest score was 8.43 ± 4.14 in the ET group and 14.06 ± 5.44 in the PD group (p value <0.001). However, except for 12 items in NMSQuest, in comparing items one by one there was no statistical difference between them. The mean MoCA total score was 17.81 ± 4.56 in the ET group and 17.08 ± 4.08 in the PD group (p value 0.675). There were no significant differences in MoCA subgroup scores. Evaluation of nonmotor symptoms in ET may help us to understand this emerging definition of ET. This study contributes evidence toward this new concept.