Essential Tremor

Essential tremor (ET) is a progressive neurological disease characterized by a 4- to 12-Hz kinetic tremor that involves several regions of the body, including the arms and the head. Patients may have signs of more widespread cerebellar involvement abnormalities referable to the basal ganglia and cognitive deficits. There are both familial and non-familial forms of the disease, suggesting that the etiology is heterogeneous and complex. In a small number of families with apparently autosomal dominant inheritance, genetic linkage is established to regions on chromosomes 2p and 3q, but no specific susceptibility gene is identified yet. Animal models for action tremor, involving the administration of chemicals to laboratory animals, include the harmaline and the penitrem A models. Treatment of ET should be reserved for patients who experience functional disability or embarrassment. Both primidone and propranolol are superior to placebo, and there is some evidence that primidone may be more effective than propranolol. However, this needs to be studied further. The long-term tolerability of primidone may be superior; therefore, primidone is a reasonable first choice, and propranolol is the second choice. Gabapentin and benzodiazepines are alternatives, although the latter may result in sedation at the doses required to treat tremor. If the patient does not respond to medications and is significantly disabled, unilateral implantation of a deep brain thalamic stimulator is reasonable. The stimulator should be implanted in the thalamus contralateral to the more functionally disabled arm.