A valid performance-based test was developed to objectively assess functional capacity in patients with ET. This test would be useful in therapeutic trials, where it would provide an objective means to quantify the functional impact of tremor.

Teaching videotapes, developed to aid in the evaluation of several movement disorders, have not been used in essential tremor research. As part of the Washington Heights‐Inwood Genetic Study of Essential Tremor (WHIGET), we developed a reliable and valid tremor rating scale. Because this rating scale is currently being used by investigators at other centers, we developed a teaching videotape to aid in the consistent application of this scale. OBJECTIVE To develop a teaching videotape for a revised version of the WHIGET Tremor Rating Scale and to assess the interrater agreement among raters who used this videotape to rate tremor. METHODS The revised WHIGET Tremor Rating Scale was used to rate action tremor from 0 to 4 during six tests: arm extension, pouring, drinking, using a spoon, finger‐to‐nose, and drawing spirals. A 22‐minute teaching videotape was developed that includes a 29‐item educational section and a self‐assessment section consisting of 20 examples of tremor ratings chosen by the two WHIGET study neurologists. Eight raters, including senior movement disorder specialists, movement disorder fellows, general neurologists, and a movement disorder nurse practitioner, independently viewed the videotape and rated tremor during the self‐assessment section. Interobserver reliability was assessed with weighted kappa statistics (κw). RESULTS Eight raters each rated 20 items (160 ratings total). Total κw was 0.97 (nearly perfect agreement). Interrater reliability was as follows: κw = 0.99 (movement disorder specialists), κw = 0.98 (movement disorder fellows), and κw = 0.97 (general neurologists); all κw were nearly perfect. CONCLUSIONS This teaching videotape may be used to improve the uniform application of the revised WHIGET Tremor Rating Scale by raters with various levels of experience in movement disorders. Mov. Disord. 16:89–93, 2001. © 2001 Movement Disorder Society.

We present the clinical findings of a group of largely untreated, unselected cases of ET that would not otherwise have come to neurologic attention. The tremor was mild, often asymptomatic, and not uniformly present throughout the examination. It was rarely treated. The kinetic component of the tremor was more severe than the postural component. These clinical data further our understanding of the clinical spectrum of ET.

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Family studies of primary torsion dystonia have used the diagnostic categories of definite, probable, and possible dystonia for gene mapping and identification, but the validity of this hierarchical classification is not known. The authors assessed 147 DYT1 GAG deletion carriers and 113 blood-related noncarriers from 43 families. Only the category of definite dystonia was 100% specific. Probable dystonia, but not possible, was increased in carriers compared with noncarriers. The authors recommend that only those with definite signs of dystonia be considered affected in linkage and other genetic studies.