Even though essential tremor (ET) is the most prevalent movement disorder, there has been little agreement in the neurologic literature regarding diagnostic criteria for ET. The authors attempted to determine the extent and source of agreement and disagreement among neurologists regarding diagnostic criteria for clinically definite ET. The authors designed and mailed a semistructured questionnaire to 160 neurologists who specialize in movement disorders in 24 countries. The questionnaire included three sections: a list of inclusion criteria, a list of exclusion criteria, and a List of potential clinical scenarios (for example, isolated site-specific tremor and primary orthostatic tremor). The questionnaire was completed by 98 (61%) of 160 targeted neurologists. There was greater consensus regarding features considered unnecessary inclusion criteria for clinically definite ET (extent of disability, disease duration, and positive family history) than for those considered necessary inclusion criteria (postural versus action tremor). With regard to exclusion criteria, there was some consensus in terms of the presence of Parkinson's disease, dystonia, history of hyperthyroidism or concurrent use of tremor-inducing medications, and cerebellar signs. The majority of neurologists would diagnose ET in the setting of isolated head or voice tremor. There are areas of both consensus and divergence among neurologists with regard to diagnostic criteria for ET. The choice of diagnostic criteria may vary depending on the intended use of the criteria (that is, clinical versus genetic studies). Hopefully, this study will foster further discussion to achieve a more general consensus.
