Update on Essential Tremor.

Essential tremor is a chronic, progressive neurological disease, or perhaps a family of diseases, whose clinical characteristics place it among the disorders of involuntary movement, and more specifically, among the tremor disorders. Its underlying pathology places it within the disorders of cerebellar degeneration. Its core clinical feature, among many potential clinical features, is a 4 to 12 Hz simple kinetic tremor of the arms, which is a tremor that occurs during voluntary movements such as eating, drinking, or writing. This review summarizes current understanding of the epidemiology, health care costs, clinical features (motor features; nonmotor features; and associated embarrassment, functional disability, impaired quality of life, and caregiver burden), clinical considerations (stratification points, putative staging scheme), diagnosis (based on clinical findings and more recently, grounded in postmortem findings in the cerebellum), associations with other neurodegenerative diseases (Parkinson's disease and dementia), pathophysiology (focusing on the observed neurodegenerative changes in the cerebellar cortex), and treatment.