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Cerebellum. 2018 Sep 11. doi: 10.1007/s12311-018-0974-x. [Epub ahead of print]

Repeated Spiral Drawings in Essential Tremor: a Possible Limb-Based Measure of Motor Learning.

Author information

1
Department of Neurology, Clinical Motor Physiology Laboratory, Columbia University Medical Center, 710 West 168th Street, New York, NY, 10032, USA.
2
Department of Neurology, Mount Sinai Beth Israel, Icahn School of Medicine Mount Sinai, New York, NY, USA.
3
Department of Neurology, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY, USA.
4
Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT, USA.
5
Department of Chronic Disease Epidemiology, Yale School of Public Health, Yale University, New Haven, CT, USA.
6
Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, Yale University, New Haven, CT, USA.
7
Department of Neurology, Clinical Motor Physiology Laboratory, Columbia University Medical Center, 710 West 168th Street, New York, NY, 10032, USA. sp31@cumc.columbia.edu.

Abstract

To investigate changes in tremor severity over repeated spiral drawings to assess whether learning deficits can be evaluated directly in a limb in essential tremor (ET). A motor learning deficit in ET, possibly mediated by cerebellar pathways, has been established in eye-blink conditioning studies, but not paradigms measuring from an affected, tremulous limb. Computerized spiral analysis captures multiple characteristics of Archimedean spirals and quantifies performance through calculated indices. Sequential spiral drawing has recently been suggested to demonstrate improvement across trials among ET subjects. One hundred and sixty-one 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. Changes in DoS and Ampl across trials were assessed using linear regression with slope evaluations. 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. 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. DoS improved independently of Ampl, showing that DoS and Ampl are separable motor physiologic components in ET that may be independently mediated.

KEYWORDS:

Cerebellum; Computerized spiral analysis; Essential tremor; Motor learning; Movement disorders

PMID:
30206795
DOI:
10.1007/s12311-018-0974-x

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