The primary type of tremor in essential tremor is kinetic rather than postural: cross-sectional observation of tremor phenomenology in 369 cases

Abstract

Background: Essential tremor (ET) is amongst the most commonly misdiagnosed neurological diseases. The current aim was to provide observational data on a basic characteristic of ET, namely, the relative severity of postural to kinetic tremor.

Methods: A total of 369 ET cases were enrolled in a cross-sectional study. Postural tremor scores (0-3) and kinetic tremor scores (0-3) were assigned during a standardized neurological examination.

Results: In the vast bulk of cases (~95%), kinetic tremor was more severe than postural tremor. In nearly one-in-three cases (32.8%), the kinetic tremor score was ≥ 1 points higher than the postural tremor score. Conversely, in only a few cases (~5%) was postural tremor even marginally (<1 point) more severe than kinetic tremor, and in no case was the postural tremor score ≥ 1 point higher than the kinetic tremor score. At each postural tremor score, nearly all cases had that amount of kinetic tremor or more.

Conclusion: The primary type of tremor in ET is kinetic rather than postural. Recognition of the simple, empirical features of tremor phenomenology has potential diagnostic value for practicing clinicians.

Figure 1

Kinetic tremor score by category of postural tremor (0, 0.5, 1, 1.5, 2, 2.5, 3). The top panel shows the mean kinetic tremor scores in cases with mean postural tremor score=0. The bottom panel shows the mean kinetic tremor scores in cases with a mean postural tremor score=3. The yellow background indicates cases in whom the mean kinetic tremor score was greater or equal to the mean postural tremor score. For example, among 131 cases with a mean postural tremor score=1, only 2 (1.5%) had a mean kinetic tremor score <1.