Essential tremor: an overdiagnosed condition?

The diagnosis of essential tremor (ET) and its differentiation from other t ypes of tremor is often difficult. In 1994 Bain et al. defined a classical phenotype by studying 20 patients with pure essential tremor and similarly affected family members in at least three generations. We assessed how many of the patients diagnosed by different neurologists at our institution as having ET conformed to this defined phenotype. We randomly selected 50 pati ents who were diagnosed with ET by any neurologist at the National Hospital for Neurology and Neurosurgery since the publication of the Bain et al. re port, and determined the number of patients who had clinical features compa tible with the phenotype that it had defined. Only 25 (50 %) of these patie nts had ET so defined. Ten patients clearly had alternative diagnoses: four had clear additional dystonia, two neuropathic tremor, two had unilateral leg tremor, one drug-induced tremor, and one sudden onset after head trauma . The remaining 15 patients also had atypical features including myoclonus (one), onset in a body part other than the arms (six), sudden onset (two), rest tremor (seven), onset after the age of 65 years (four), a family membe r with an isolated head tremor (one), or reduced armswing (two). The diagno sis of ET is overused even among experienced neurologists, and other types of tremor should be considered in atypical patients before making this diag nosis.