Limb positioning and magnitude of postural tremor ratings: A study of 100 essential tremor cases

Essential tremor (ET) is a highly prevalent movement disorder. As the diagnosis is purely clinical, it is important for clinicians to develop a reliable taxonomy of signs and symptoms of ET. Here, we investigate two common clinical maneuvers for determining the presence and severity of postural tremor in ET cases: the evaluation of tremor observed when arms are held in the outstretched and wing posture positions.

Two movement disorders neurologists assessed tremor severity from videotaped neurological evaluations of 100 ET cases displaying outstretched and wing posture positions. These raters also completed a forced choice measure indicating whether upper limb tremor was more severe in the outstretched position, the wing posture position, or equivalent in the two positions.

Our raters judged tremor observed in the wing posture position to be more severe than tremor observed in the outstretched position (average ratings of 1.17 and 1.03, respectively, p's <0.05). This finding replicated across the two independent neurologists' ratings of tremor severity. Analyses of the forced choice measure revealed parallel results, with tremor observed in the wing posture position more often identified as more severe than tremor observed in the outstretched position (37.5% versus 14.5%, respectively, p < 0.05).

Our data reveal that ET cases generally display more severe upper limb tremor in the wing posture position than in the outstretched position. These findings having potential clinical and research implications, suggesting that postural tremor in ET may be more easily identified from observations of the wing posture than the outstretched position.