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Spiral Drawings in ET Measure Motor Learning

Cerebellum; ePub 2018 Sep 11; Kim, Luo, et al

Essential tremor (ET) subjects demonstrated less improvement than controls when drawing sequential spirals, suggesting a possible motor learning deficit in ET, here captured in an affected limb, according to a recent study. Researchers utilized computerized spiral analysis, which captures multiple characteristics of Archimedean spirals and quantifies performance through calculated indices. 161 ET and 80 age-matched control subjects drew 10 consecutive spirals on a digitizing tablet. Degree of severity (DoS)—a weighted, computational score of spiral execution that takes into account spiral shape and line smoothness, previously validated against a clinical rating scale—was calculated in both groups. Tremor amplitude (Ampl), an independent index of tremor size, measured in centimeters, was also calculated. They found:

  • Both groups demonstrated improvement in DoS across trials, but with less improvement in the ET group compared to controls.
  • Ampl demonstrated a tendency to worsen across trials in ET subjects.
  • DoS improved independently of Ampl, showing that DoS and Ampl are separable motor physiologic components in ET that may be independently mediated.
Citation:

Kim CY, Luo L, Yu Q, et al. Repeated spiral drawings in essential tremor: A possible limb-based measure of motor learning. [Published online ahead of print September 11, 2018]. Cerebellum. doi:10.1007/s12311-018-0974-x.

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