Essential Tremor

Essential tremor (ET) is a progressive neurological disorder that is characterized by a 4- to 12-Hz kinetic tremor in the hands or head. IThis chapter focuses on the genetic form of the disease, or hereditary ET. In this disorder, patients may show signs of more widespread cerebellar involvement abnormalities referable to the basal ganglia and cognitive deficits. The tremor occurs when the hands are being used actively to perform voluntary activities such as writing, pouring, eating, and other daily activities. Patients with severe ET also have a postural tremor, which appears when the arms are held outstretched in front of the body. Tremor in ET most commonly affects the arms, but it may also affect additional regions, including the head, voice, and occasionally the trunk and lower extremities. The tremor probably originates from an abnormality in cerebellar-thalamic loops, suggesting that the disease is a cerebellar outflow disease. The etiologies of ET are both genetic and nongenetic. Differences between the genetic and nongenetic forms of the disease are not yet identified, other than a possibly younger age of onset in genetic forms of the disease.