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Essential Tremor Pahwa R, Lyons KE: Essential tremor: differential diagnosis and current therapy. Am J Med 2003;115:134-42.
Essential tremor, the most common movement disorder, affects between 5 and 10 million persons in the United States in a pattern suggesting autosomal dominant inheritance. It usually affects the arms and occurs when a body part is held against gravity or during activity. Detailed tables in the article outline diagnostic criteria for essential tremor and alternative diagnoses to rule out.
Many drugs, including beta-adrenergic agonists, thyroxine, antidepressant medications, and lithium may produce postural and kinetic tremors. In most patients, alcohol will improve tremor temporarily. Because stress activates tremor, relaxation therapies such as meditation and hypnosis can reduce tremor. Although there is no cure, primidone and propranolol are first-line pharmacologic treaments. Propranolol is started at 10-60 mg daily in divided doses; most patients notice benefit at doses < 120 mg daily. Primidone, whose mechanism of action is not known, is equally as effective as propranolol. It is dosed initially at 12.5 mg at bedtime and can be gradually increased by 50 mg a week, up to 250 mg a day at bedtime. The disorder can be progressive with greater severity and wider distribution. Second-line treatments include benzodiazepines, gabapentin, topiramate, and botulinum toxin. Patients with medication-resistant disabling tremor may benefit from thalamotomy or deep brain stimulation of the thalamus.