Nonmotor symptoms in essential tremor: Comparison with Parkinson's disease and normal control

Recently, the definition of essential tremor (ET) has evolved to have two different meanings. One refers to classic ET, a benign mono-symptomatic disorder, and the other refers to a heterogeneous neurodegenerative disorder. The aim of this study was to categorize nonmotor symptoms according to ET phenotype, and compare them, along with autonomic function, in people with Parkinson's disease (PD) and normal controls.

We divided patients with ET into 3 subtypes according to their motor features: 23 Pure-ET, 25 Cerebellar-ET, and 12 Parkinsonism-ET. Comparisons were made between 30 PD subjects and 22 normal controls, and 60 subjects with ET. The following assessments were conducted: the Nonmotor Symptoms Scale, the Mini-Mental State Exam, Montreal Cognitive Assessment, the Montgomery-Asberg Depression Rating Scale, Neuropsychiatric Inventory Questionnaire, Beck Anxiety Inventory, the Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale and the Scales for Outcomes in Parkinson's Disease-Autonomic.

There were significant differences in the Nonmotor Symptoms Scale total scores of the ET, PD, and control groups (ET: 25.500 ± 2.346; PD: 27.960 ± 3.267;

3.328 ± 3.796.). There were no significant differences in terms of each ET phenotype. ET patients had significant cognitive dysfunction, neuropsychiatric problems including depression and have complained about significant autonomic dysfunction and excessive daytime somnolence compared to normal controls.

Patients with ET have several nonmotor symptoms similar to those of patients with PD, which have a similar impact on their quality of life. Therefore, nonmotor symptoms should be considered in the clinical evaluation and management of ET.