Essential tremor (ET) is one of the most common movement disorders and affects approximately 1% of the population worldwide. Twin and family history studies show a high heritability for essential tremor. The molecular genetic determinants of essential tremor are unknown. Some mutations have been found in ET families but have not been validated in others. The pathophysiological basis of ET remains unknown. In 2017, a task force of the International Parkinson and Movement Disorder Society proposed a new formal definition of essential tremor as a syndrome of isolated tremor of both upper limbs with a duration of at least 3 years, with or without tremor in other locations, such as head, larynx (voice tremor), or lower limbs. Defining essential tremor as a syndrome and not as a single disease, while concomitantly narrowing its phenotypic scope to increase its homogeneity, recognizes that there are multiple possible causes, which may facilitate progress in understanding the pathogenesis. Investigators aim to establish a database of longitudinal recruited ET cohort, and characterize the clinical feature, genetic basis, environmental factors and their interactions among different ET subtypes in China, identify natural history of a highly-presentative Chinese ET cohort and to discern major milestones in the disease process which indicates disease progression.

Data were collected at baseline. Information about detailed disease history, level of education, significant chronic comorbidities, physical examination, medication history, family history, living habits and toxic exposure history, which include smoking, drinking tea, alcoholic consumption, drinking coffee, exposure to pesticide or occupational solvent, history of carbon monoxide poisoning and recurrent head trauma will be recorded at baseline. For each evaluation, the same questionnaires will be conducted. A standardized neurological assessment according to the recommendation of Consensus on the construction of clinical database of Parkinson's disease and movement disorders in China.

The Essential Tremor Rating Assessment Scale (TETRAS) includes both performance and Activities of Daily Living (ADL) subscales. It is conducted for the clinical measurement of ET severity and tremor's impact on ADL. The non-motor symptoms are evaluated by Non-motor Symptom Scale (NMSS).Functional constipation was diagnosed by the Rome III diagnostic criteria. Excessive daytime sleepiness was evaluated by Epworth Sleepiness Scale (ESS). Probable rapid eye movement sleep behavior disorder (p-RBD) was diagnosed by rapid eye movement sleep behavior questionnaire-Hongkong (RBDQ-HK). Restless leg syndrome (RLS) was diagnosed with the Cambridge Hopkins Restless Leg syndrome questionnaire (CH-RLSq). Cognitive assessment was used the previously validated scale, Mini Mental State Examination (MMSE). Olfaction test was carried out by Hyposmia Rating Scale (HRS), a proportion of patients was also ascertained by Sniffin's Sticks. Depression was diagnosed by Hamilton Depression Scale (HAMD).DNA samples extracted from peripheral blood and all the ET patients will be examed by Whole Exome Sequencing or Whole-genome sequencing. All the participants are scanned by structural MRI to exclude obvious intracranial lesions and other metabolic disorders, etc.